Endangered and Threatened Wildlife and Plants; Endangered Species Act Listing Determination for Alewife and Blueback Herring

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[Docket No. 170718681-9471-01]

RIN 0648-XF575

Endangered and Threatened Wildlife and Plants; Endangered Species Act Listing Determination for Alewife and Blueback Herring

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Notice; 12-month finding and availability of status review document.

SUMMARY:

We, NMFS, have completed a comprehensive status review under the Endangered Species Act (ESA) for alewife (

Alosa pseudoharengus

) and blueback herring (

Alosa aestivalis

). The status review identified four alewife distinct population segments (DPSs): Canada, Northern New England, Southern New England, and Mid-Atlantic. Based on the best scientific and commercial data available including the Status Review Report, we have determined that listing the alewife rangewide or as any of the identified DPSs as threatened or endangered under the ESA is not warranted at this time. The status review also identified three blueback herring DPSs: Canada/Northern New England, Mid-Atlantic, and Southern Atlantic. Based on the best scientific and commercial data available, we have determined that listing blueback herring rangewide or as any of the identified DPSs as threatened or endangered under the ESA is not warranted at this time.

DATES:

This finding was made on June 19, 2019.

ADDRESSES:

The status review document for alewife and blueback herring is available electronically at:

www.nmfs.noaa.gov/pr/species/notwarranted.htm.

You may also obtain a copy by submitting a request to the Protected Resources Division, NMFS GARFO, 55 Great Republic Drive, Gloucester, MA 01930, Attention: Alewife and Blueback Herring 12-month Finding.

FOR FURTHER INFORMATION CONTACT:

Jean Higgins, NMFS Greater Atlantic Regional Fisheries Office, 978-281-9345.

SUPPLEMENTARY INFORMATION:

Background

On August 12, 2013, we determined that listing alewife and blueback herring (collectively, “river herring”): As threatened or endangered under the Endangered Species Act (ESA) (16 U.S.C. 1531

et seq.

) was not warranted (78 FR 48943). However, we also noted that there were significant data deficiencies. In that determination, we committed to revisiting the status of both species in three to five years, a period after which ongoing scientific studies, including a river herring stock assessment update by the Atlantic States Marine Fisheries Commission (ASMFC), would be completed.

The Natural Resources Defense Council and Earthjustice (the Plaintiffs) filed suit against NMFS on February 10, 2015, in the U.S. District Court in Washington, DC, challenging our decision not to list blueback herring as threatened or endangered. The Plaintiffs also challenged our determination that the Mid-Atlantic stock complex of blueback herring is not a DPS. On March 25, 2017, the court vacated the blueback herring listing determination and remanded the listing determination to us

(Natural Resources Defense Council, Inc., et al.

v.

Samuel D. Rauch, National Marine Fisheries Services, 1:15-cv-00198 (D.D.C.)).

As part of a negotiated agreement with the Plaintiffs, we committed to publishing a revised listing determination for blueback herring by January 31, 2019; the publication date was extended by the court to June 19, 2019.

We announced the initiation of an alewife and blueback herring status review in the

Federal Register

on August 15, 2017 (82 FR 38672). At that time, we also opened a 60-day solicitation period for new scientific and commercial data on alewife and blueback herring to help ensure that we were informed by the best available scientific and commercial information.

Listing Species Under the ESA

We are responsible for determining whether species are threatened or endangered under the ESA (16 U.S.C. 1531

et seq.

). To make this determination, we first consider whether a group of organisms constitutes a “species” under section 3 of the ESA (16 U.S.C. 1532), and then consider whether the status of the species qualifies it for listing as either threatened or endangered. Section 3 of the ESA defines species to include any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature. On February 7, 1996, NMFS and the U.S. Fish and Wildlife Service (USFWS; together, the Services) adopted a policy describing what constitutes a DPS of a taxonomic species (DPS Policy; 61 FR 4722). Under the DPS Policy, we consider the following when identifying a DPS: (1) The discreteness of the population segment in relation to the remainder of the species or subspecies to which it belongs; and (2) the significance of the population segment to the species or subspecies to which it belongs.

Section 3 of the ESA further defines an endangered species as any species which is in danger of extinction throughout all or a significant portion of its range and a threatened species as one which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. Thus, we interpret an “endangered species” to be one that is presently in danger of extinction. A “threatened species,” on the other hand, is not presently in danger of extinction, but is likely to become so in the foreseeable future. In other words, the primary statutory difference between a threatened and endangered species is the timing of when a species may be in danger of extinction, either presently (endangered) or in the foreseeable future (threatened).

Section 4(a)(1) of the ESA also requires us to determine whether any species is endangered or threatened as a result of any of the following five factors: The present or threatened destruction, modification, or curtailment of its habitat or range; overutilization for commercial, recreational, scientific, or educational purposes; disease or predation; the inadequacy of existing regulatory mechanisms; or other natural or manmade factors affecting its continued existence (16 U.S.C. 1533(a)(1)(A)-(E)). Section 4(b)(1)(A) of the ESA requires us to make listing determinations based solely on the best scientific and commercial data available after conducting a review of the status of the species and after taking into account efforts being made by any state or foreign nation or political subdivision thereof to protect the species. In evaluating the efficacy of formalized domestic conservation efforts that have yet to be implemented or demonstrate effectiveness, we rely on the Services' joint

Policy on Evaluation of Conservation Efforts When Making Listing Decisions

(PECE; 68 FR 15100; March 28, 2003).

Status Review

As noted above, we had committed to revisiting the listing determination for alewife and blueback herring in the 2013 listing determination; accordingly,

although the Plaintiffs only challenged our findings related to blueback herring, we did a comprehensive status review of alewife and blueback herring. As part of the status review, we formed a status review team (SRT) composed of scientists from NMFS' Northeast Fisheries Science Center (NEFSC), USFWS, NMFS' Greater Atlantic Regional Fisheries Office, Delaware Division of Fish and Wildlife, Massachusetts Division of Marine Fisheries, New York Department of Environmental Conservation, and South Carolina Department of Natural Resources. SRT members had scientific expertise in river herring biology/ecology and/or expertise in population ecology or fisheries management. We tasked the SRT with multiple assessments for both species including the requests from the 2011 petition that NMFS list blueback herring rangewide or alternatively, as DPSs, and to provide a thorough status review for both species. First, the SRT was asked to compile and review the best available information and to assess the overall risk of extinction facing alewife and blueback herring rangewide now and in the foreseeable future. Second, the SRT was tasked with identifying any DPSs within these populations and asked to assess the risk of extinction facing each identified DPS of alewife and blueback herring now and in the foreseeable future. Third, the SRT was asked to consider whether, within the species rangewide or within any identified DPSs, a significant portion of the range may exist, and if so, whether the portion is at risk of extinction now or in the foreseeable future.

In order to complete the status review, the SRT considered a variety of scientific information from the literature, unpublished documents, and direct communications with researchers working on alewife and blueback herring, as well as technical information submitted to NMFS. Information that was not previously peer-reviewed was formally reviewed by the SRT. The SRT evaluated all factors highlighted by the petitioners as well as additional factors that may contribute to alewife and blueback herring vulnerability.

The Status Review Report for alewife and blueback herring (NMFS 2019), summarized in sections below, compiles the best available information on the status of the species as required by the ESA, provides an evaluation of the discreteness and significance of these populations in terms of the DPS Policy, and assesses the extinction risk of the species and any DPS, focusing primarily on threats related to the five statutory factors set forth above. The status review report is available electronically at the website listed in

ADDRESSES

.

The status review report underwent independent peer review as required by the Office of Management and Budget Final Information Quality Bulletin for Peer Review (M-05-03; December 16, 2004). The status review report was peer reviewed by three independent specialists selected from government, academic, and scientific communities, with expertise in biology, conservation and management, and specific knowledge of river herring and similar species. The peer reviewers were asked to evaluate the adequacy, quality, and completeness of the data considered and whether uncertainties in these data were identified and characterized in the status review report, as well as to evaluate the findings made in the “Assessment of Extinction Risk” section of the report. Peer Reviewers were also asked to identify any information missing or lacking justification, or whether information was applied incorrectly in reaching conclusions. The SRT addressed peer reviewer comments prior to finalizing the status review report. Comments received are posted online at

www.cio.noaa.gov/services_programs/prplans/IDXXX.html.

We subsequently reviewed the status review report, the cited references, and the peer review comments, and believe the status review report, upon which this 12-month finding is based, provides the best available scientific and commercial information on alewife and blueback herring. Much of the information discussed below on alewife and blueback herring biology, genetic diversity, distribution, abundance, threats, and extinction risk is attributable to the status review report. However, in making the 12-month finding determination, we have independently applied the statutory provisions of the ESA, including evaluation of the factors set forth in section 4(a)(1)(A)-(E) and our regulations regarding listing determinations (50 CFR part 424).

Description, Life History, and Ecology of the Petitioned Species

Distribution and Habitat Use

Collectively, blueback herring and alewives are known as river herring. River herring are found along the Atlantic coast of North America, from the southern Gulf of St. Lawrence, Canada to the southeastern United States (Mullen

et al.

1986, Schultz

et al.

2009). The coastal ranges of the two species overlap. Blueback herring range from Nova Scotia south to the St. Johns River, Florida, and alewives range from Labrador and Newfoundland south to North Carolina, though their occurrence in the extreme southern range is less common (Collette and Klein-MacPhee 2002, ASMFC 2009a). In Canada, river herring (often referred to as gaspereau) have been monitored at varying frequencies in the St. Croix, St. John, Gaspereau, Tusket, Margaree and Miramichi River (J. Gibson, pers. comm) and are reportedly most abundant in the Miramichi, Margaree, LaHave, Tusket, Shubenacadie and Saint John Rivers (DFO 2001). River herring are proportionally less abundant in smaller coastal rivers and streams (DFO 2001). Generally, blueback herring in Canada occur in fewer rivers than alewives and are less abundant in rivers where both species coexist (DFO 2001).

River herring are anadromous, meaning that they mature in the marine environment and then migrate up coastal rivers to estuaries and into freshwater rivers, ponds, and lake habitats to spawn (Collette and Klein-MacPhee 2002, ASMFC 2009a). In general, adult river herring are found at depths less than 328 feet (ft) (100 meters (m)) in waters along the continental shelf (Neves 1981, ASMFC 2009a, Schultz

et al.

2009).

River herring are highly migratory, pelagic, schooling species with seasonal spawning migrations cued by water temperature (Collette and Klein-MacPhee 2002, Schultz

et al.

2009). The spawning migration for alewives typically occurs when water temperatures range from 50-64 °F (10-18 °C) and for blueback herring when temperatures range from 57-77 °F (14-25 °C; Klauda

et al.

1991). Due to this temperature-dependent spawning, river herring may return to rivers to spawn as early as December or January in the southern portions and as late as July and August in the northern portions of their ranges (ASMFC 2009a; DFO 2001).

Blueback herring and alewives consume a variety of zooplankton. Blueback herring subsist chiefly on ctenophores, calanoid copepods, amphipods, mysids and other pelagic shrimps, and small fishes while at sea (Bigelow and Schroeder 1953, Brooks and Dodson 1965, Neves 1981, Stone 1986, Stone and Daborn 1987, Scott and Scott 1988, Bowman

et al.

2000). Alewives consume euphausiids, calanoid copepods, mysids, hyrperiid amphipods, chaetognaths, pteropods, decapod larvae, and salps (Edwards and Bowman, 1979, Neves 1981, Vinogradov 1984, Stone and Daborn 1987, Bowman

et al.

2000).

Little is known about their habitat preference in the marine environment; however, marine distributions of fish

are often linked to environmental variables, such as prey availability and predation, along with seascape features. Studies have shown that alewife and blueback herring distribution is linked to bottom temperature, salinity, and depth (Neves 1981, Bethoney

et al.

2014, Lynch

et al.

2015). Recent papers described marine co-occurrences of alewife and blueback herring with Atlantic herring and mackerel (Turner

et al.

2016, Turner

et al.

2017), providing further evidence, in addition to observed “bycatch” estimates (Bethoney

et al.

2014), that river herring school with Atlantic herring and mackerel. Turner

et al.

(2016) modeled associations of alewife and blueback herring, finding that alewife and blueback herring distributions overlapped with Atlantic herring (68-72 percent correct predictions) and Atlantic mackerel (57-69 percent correct predictions).

Cieri (2012) analyzed NMFS bottom trawl survey data to identify seasonal population clusters of river herring along the East Coast of the United States (N Carolina to Maine; covering the continental shelf and the U.S. Exclusive Economic Zone (EEZ)). The spring trawl survey (1968-2008 NMFS Spring Bottom Trawl Survey) indicates that river herring are widespread across the survey area (sampling locations vary by year; the spring trawl occurs from North Carolina to Nova Scotia; sampling occurs at depths ~18 m to ~300 m (~60 ft to 984 ft)). Highest occurrences during the spring were off Maine's Downeast coast (roughly from Penobscot Bay north-eastwards to the Canadian border) and areas offshore, near Cape Ann and Cape Cod in Massachusetts, and a large area between Block Island, Rhode Island, and Long Island Sound. During the summer (1948-1995 NMFS Bottom Trawl Survey), river herring occurred less frequently across the survey area, with most river herring along the New England coast north of Rhode Island, and the highest occurrences off Downeast, Maine and south of Cape Cod, Massachusetts. During the fall survey (1963-2008 NMFS bottom trawl surveys), the occurrence of river herring shifted northward, with highest occurrences north of Cape Cod, along the Maine Coast to the Bay of Fundy, and another cluster off the eastern shore of Nova Scotia.

Seasonal migrations have been observed in the marine environment as described above but are not well understood (NMFS 2012a). Hypothesized overwintering areas and migration pathways were presented at the NMFS 2012 Stock Structure workshop, but little tagging data existed at that time to confirm any one theory. The working group from the 2012 workshop was not able to determine the migration patterns and mixing patterns of alewife and blueback herring in the ocean, though they strongly suspected regional stock mixing (NMFS 2012a). Therefore, the conclusion that came out of the 2012 Stock Structure workshop was that, based on available data, the ocean phase of alewife and blueback herring was of mixed stocks.

Sparse tagging data is available to help elucidate these marine migrations of alewife and blueback herring. In 1985-1986, approximately 19,000 river herring were tagged and released in the upper Bay of Fundy, Nova Scotia (Rulifson

et al.

1987). With an overall recapture rate of 0.39, Rulifson

et al.

(1987) received returns of alewife tags from freshwater locations in Nova Scotia, and marine locations in Nova Scotia and Massachusetts; whereas, blueback herring tags were returned from freshwater locations in Maryland and North Carolina, and marine locations in Nova Scotia. The authors suspected from this recapture data that alewives and blueback herring tagged in the Bay of Fundy were of different origins, hypothesizing that alewives were likely regional fish from as far away as New England, while the blueback herring recaptures were likely not regional fish, but those of U.S. origin from the mid-Atlantic region. However, the low tag return numbers from outside of Nova Scotia (n=2) made it difficult to generalize about the natal rivers of blueback herring caught in the Bay of Fundy. More recent work with acoustic tags (n=13 alewives and n=12 blueback herring) in the Hudson River by Eakin (2017) demonstrated in-river residence times ranged from two to three weeks, with fish exiting the system three to six days post-spawn. Marine migration was also detected from four blueback herring (2 male, 2 female) showing coastal movements over a six-month period (June to November) from the Hudson River to Penobscot Bay off the coast of Maine. The study also demonstrates the potential of using acoustic tagging to tease out marine movements of alewife and blueback herring in future studies.

Landlocked Populations

Landlocked populations of alewives and blueback herring also exist. Landlocked alewife populations occur in many freshwater lakes and ponds from Canada to North Carolina as well as the Great Lakes (Rothschild 1966, Boaze and Lackey 1974). Many landlocked alewife populations occur as a result of stocking to provide a forage base for game fish species (Palkovacs

et al.

2007).

Recent efforts to assess the evolutionary origins of landlocked alewives indicate that they rapidly diverged from their anadromous cousins between 300 and 5,000 years ago and now represent a discrete life history variant of the species,

Alosa pseudoharengus

(Palkovacs

et al.

2007). Given their relatively recent divergence from anadromous populations, one plausible explanation for the existence of landlocked populations may be the construction of dams by either Native Americans or early colonial settlers that precluded the downstream migration of juvenile herring (Palkovacs

et al.

2007). Since their divergence, landlocked alewives evolved to possess significantly different mouthparts than their anadromous cousins, including narrower gapes and smaller gill raker spacings to take advantage of year round availability of smaller prey in freshwater lakes and ponds (Palkovacs

et al.

2007). Furthermore, the landlocked alewife, compared to its anadromous cousin, matures earlier, has a smaller adult body size, and reduced fecundity (Palkovacs

et al.

2007). At this time, there is no substantive information that would suggest that landlocked populations can or would revert back to an anadromous life history if they had the opportunity to do so.

The discrete life history and morphological differences between the two life history variants (anadromous and landlocked) provide substantial evidence that upon evolving to landlocked, landlocked populations become largely independent and separate from anadromous populations and occupy largely separate ecological niches (Palkovacs and Post 2008). There is the possibility that landlocked alewife and blueback herring may have the opportunity to mix with anadromous river herring during high discharge years and through dam removals that could provide passage over dams and access to historic spawning habitats restored for anadromous populations, where it did not previously exist.

A Memorandum of Understanding (MOU) between the Services regarding jurisdictional responsibilities and listing procedures under the ESA was signed August 28, 1974. This MOU states that NMFS shall have jurisdiction over species “which either (1) reside the major portion of their lifetimes in marine waters; or (2) are species which spend part of their lifetimes in estuarine waters, if the major portion of the remaining time (the time which is not spent in estuarine waters) is spent in marine waters.”

Given that landlocked populations of river herring remain in freshwater throughout their life history and are genetically divergent from the anadromous species, pursuant to the aforementioned MOU, NMFS did not include the landlocked populations of alewife and blueback herring in the review of the status of the species in 2013 (78 FR 48943) and did not include landlocked populations in this status review.

Reproduction and Growth

Overall, alewife and blueback herring are habitat generalists found over a wide variety of substrates, depths, and temperatures in freshwater lakes and ponds, river, estuaries, and the Atlantic Ocean. The substrate preferred for spawning varies greatly and can include gravel, detritus, and submerged aquatic vegetation. Alewives prefer spawning over sand or gravel bottoms (Galligan 1962), usually in quiet waters of ponds and coves (Marcy 1967, Loesch and Lund 1977). Blueback herring prefer spawning over hard substrates, where the flow is relatively swift (Loesch and Lund 1977). Nursery areas include freshwater and semi-brackish waters to fully saline waters for both species (Gahagan 2012, Turner

et al.

2014, Payne Wynne

et al.

2015).

Alewife and blueback herring are fast growing, quick to mature species with a high fecundity rate. Estimates of fecundity for alewife range from 45,800 to 400,000 eggs (Foster and Goodbred 1978, Klauda

et al.

1991, Loesch and Lund 1977). Estimates of fecundity for blueback herring range from 30,000 to 400,000 eggs (Loesch 1981, Jessop 1993). Fecundity estimates range widely based on the length and weight of the females (Schmidt and Limburg 1989) and geographic recruitment (Gainias

et al.

2015). Both species spawn three to four times throughout the spawning season (McBride

et al.

2010, Gainias

et al.

2015). Recent literature has shown that some Alosa species, including alewife, are indeterminate spawners (Hyle

et al.

2014, Gainas

et al.

2015, McBride

et al.

2016). For indeterminate spawners, the potential annual fecundity is not fixed before the onset of spawning. In these species, eggs can develop at any time during the spawning season. This is likely the case for blueback herring but more research is needed.

Incubation time depends on temperature (

i.e.,

low water temperatures results in slow development) and is estimated to take two to four days after deposit for blueback herring (Klauda

et al.

1991, Jones

et al.

1978). Incubation time for alewives takes between two to six days depending on temperature (Mansueti 1956, Jones

et al.

1978).

Population Structure

The population structure of these species has been examined using various tools, including otolith chemistry and genetics (see Population Structure section of the Status Review Report for additional information, NMFS 2019). While otolith chemistry studies focused largely on assigning fish to rivers of natal origin with some success (Gahagan

et al.

2012, Turner

et al.

2015), genetic analyses found evidence for regional structure within each species (McBride

et al.

2014, Palkovacs

et al.

2014, Hasselman

et al.

2014; Hasselman

et al.

2016; Ogburn

et al.

2017, Baetscher

et al.

2017, Reid

et al.

2018). Early genetic studies relied largely on microsatellite markers and were limited in geographic scope (see Genetic Studies section of NMFS 2019 for a detailed account); however, recent studies using single nucleotide polymorphisms (SNP) have expanded the evaluation of population structure for these species across most of their ranges.

SNPs are small genetic variations that occur in a genome. These variations are used as molecular markers in genetic research and help to overcome limitations associated with microsatellite analyses when applied to fisheries management, which includes a lack of portability across laboratories and instruments (Reid

et al.

2018).

SNPs were developed using 96 individual loci for alewife and for blueback herring by Baetscher

et al.

(2017). This study evaluated river herring samples across portions of the U.S. range for self-assignment to populations of origin and to three alewife and four blueback herring regional groupings identified by Palkovacs

et al.

(2014). While self-assignments to population of origin were lower (at around 67 percent), assignment to regional groupings was 93 percent for alewives and 96 percent for blueback herring. Structure cluster analysis showed similar results to previous regional stock structure groupings, with the addition of two additional blueback herring populations (Peticodiac and Margaree).

Recent work by Reid

et al.

(2018) built on Baetscher

et al.'

s work by increasing the geographic range and number of rivers sampled for each species, sampling across almost the entire range of these species. This study included river herring from 108 locations (genotyping over 8,000 fish) ranging from Florida to Newfoundland using SNP markers developed by Baetcher

et al.

(2017). A STRUCTURE analysis of the genetic data supported four distinct geographic groupings for alewife and five for blueback herring (STRUCTURE refers to software that is one of the most widely used population analysis tools for assessing patterns of genetic structure in samples). The study identified the following four regional groupings for alewife: (1) Canada, including: Garnish River and Otter Pond, Newfoundland to Saint John River, New Brunswick; (2) Northern New England, including: St. Croix River, ME to Merrimack River, NH; (3) Southern New England, including: Parker River, MA to Carll's River, NY; and (4) Mid Atlantic, including: Hudson River, NY to Alligator River, NC. The study also identified the following five regional groupings for blueback herring: (1) Canada/Northern New England, including: Margaree River, Nova Scotia to Kennebec River, ME; (2) Mid New England, including: Oyster River, NH to Parker River, MA; (3) Southern New England, including: Mystic River, MA to Gilbert-Stuart Pond, RI; (4) Mid Atlantic, including: Connecticut River, CT to Neuse River, NC; and (5) Southern Atlantic, including: Cape Fear River, NC to St. Johns River, FL.

Because the similarity in geographic naming of these stock complexes may make them difficult to distinguish between species, hereafter, we preface alewife regional groupings with Aw- and blueback herring regional groupings with Bb-. For example, the Mid Atlantic regional groupings of these two species would be referred to as Aw-Mid Atlantic and Bb-Mid Atlantic. We refer the reader to Figures 1 and 2 below for maps distinguishing the boundaries between stock complexes.

Self-assignment tests to these regional groups ranged from 86-92 percent for alewives and 76-95 percent for blueback herring (Reid

et al.

2018). However, self-assignment to individual rivers was low. These results indicate that at larger spatial scales, there are regions of restricted gene flow within the range-wide populations; Reid

et al.

(2018) noted that this could be driven by environmental and habitat differences. However, the results also indicate that the extent of gene flow across regional groupings was higher than previously reported by Palkovacs

et al.

(2014), especially at the borders, and that proximate rivers are usually not demographically independent due to straying behaviors. Reid

et al.

(2018) noted transitional populations present between regions, with rivers such as the Hudson and the Connecticut Rivers

acting as transition zones for alewife and blueback herring, respectively.

Genetic studies also demonstrate that stocking practices influence genetic differentiation among populations (McBride

et al.

2014, McBride

et al.

2015). McBride

et al.

(2015) used 12 microsatellite loci to evaluate the genetic structure of 16 alewife populations in Maine to determine whether past stocking influenced current populations and the genetic composition of alewives. Results showed a highly significant relationship between genetic differentiation and geographic distance among non-stocked populations, but a non-significant relationship among stocked populations (McBride

et al.

2015).

The unusual genetic groupings of river herring in Maine are likely a result of Maine's complex stocking history. Alewife populations in Maine have been subject to considerable within-basin and out-of-basin stocking for the purpose of enhancement, recolonization of extirpated populations, and stock introduction. Alewife stocking in Maine dates back at least to 1803 when alewives were reportedly moved from the Pemaquid and St. George Rivers to create a run of alewives in the Damariscotta River (Atkins and Goode 1887). These efforts were largely responsive to considerable declines in alewife populations following the construction of dams, over exploitation, and pollution. Although there has been considerable alewife stocking and relocation throughout Maine, there are very few records documenting these efforts. In contrast, considerably less stocking of alewives has occurred in Maritime Canada. This information further demonstrates that past stocking patterns influence contemporary genetic diversity, and stocking history should be taken into account when interpreting genetic groupings (Atkins and Goode 1887, McBride

et al.

2014, McBride

et al.

2015).

In summary, the best available genetic data suggest that alewife and blueback herring may be distinguished by regional groupings. Recent studies show a minimum of four stock complexes of alewife and five stock complexes of blueback herring. Transfer of river herring within-basin and out-of-basin has likely altered the genetic diversity of alewife and blueback herring observed today in several ways. First, stocked areas are most likely to have had already low populations (or local extirpation), and second, this reduced population is then stocked with a likely different genetic stock, further masking the previous population's genetics.

BILLING CODE 3510-22-P

EN19JN19.001

EN19JN19.002

BILLING CODE 3510-22-C

Straying

River herring conform to a metapopulation paradigm (

i.e.,

a group of spatially separated populations of the same species that interact at some level) with adults frequently returning to their natal rivers for spawning with straying occurring between rivers (Jones 2006; ASMFC 2009a). There have been very few studies to quantify straying rates, despite evidence of straying in the literature (Jessop 1994, Palkovacs

et al.

2014, McBride

et al.

2014, Turner and Limburg 2014, McBride

et al.

2015, Ogburn

et al.

2017). Jessop (1994) reported straying rates of 3-37 percent in the St. John River, New Brunswick. McBride

et al.

(2014) and Palkovacs

et al.

(2014) reported greater isolation by distance for alewives than for blueback herring, suggesting higher overall straying rates for blueback herring. Additionally, isolation by distance evidence from Palkovacs

et al.

(2014) and McBride

et al.

(2015), suggest that genetic exchange (straying) is more likely to happen with nearest-neighbor rivers over such distances as 100-200 kilometers (km) (62-124 miles (mi)). Straying has also been reported in other anadromous fishes, such as American shad (Jolly

et al.

2012) and striped bass (Gauthier

et al.

2013). Pess

et al.

(2014) reviewed basic life history traits of diadromous fish and hypothesized recolonization rates. Alewife and blueback herring were considered to have a moderate to strong tendency to colonize new streams (Pess

et al.

2014). Both species were considered to have the highest tendencies to colonize new streams of all the east coast diadromous fish, with blueback herring scoring slightly higher than alewife. Alewife and blueback herring were also considered to have strong tendencies to expand into habitat within existing streams; scoring higher than all other diadromous fish, except for sea lamprey.

Abundance and Trends

United States Waters

A 2017 alewife and blueback herring stock assessment update was prepared and compiled by the River Herring Stock Assessment Subcommittee, hereafter referred to as the `subcommittee,' of the ASMFC Shad and River Herring Technical Committee. Data and reports used for this assessment were obtained from Federal and state resource agencies, power generating companies, and universities.

The 2017 stock assessment followed the same methods and analyses outlined in the 2012 benchmark report (ASMFC 2012a) and updated the existing time series by adding data when available for the years 2011-2015. The subcommittee assessed the coastal stocks of alewife and blueback herring by individual rivers as well as coast-wide based on available data. As this assessment provides the most up-to-date abundance and trends data of river herring, the Status Review Report includes many excerpts from the 2017 ASMFC stock

assessment (see sections on Commercial Catch Per Unit Effort (CPUE), Run Counts, Young‐Of‐The‐Year Seine Surveys, Juvenile‐Adult Fisheries‐Independent Seine, Gillnet and Electrofishing Surveys, Juvenile and Adult Trawl Surveys, Mean Length, Maximum Age, Mean Length‐at‐Age, Repeat Spawner Frequency, Total Mortality (Z) Estimates, and Exploitation Rates) (NMFS 2019). For the full ASMFC stock assessment (including additional tables and figures), see River Herring Stock Assessment Update Volume I (

www.asmfc.org/uploads/file/59b1b81bRiverHerringStockAssessmentUpdate_Aug2017.pdf

). Of the 54 in-river stocks of river herring for which data were available, the 2017 ASMFC Stock Assessment indicates that from 2006 through 2015, 16 experienced increasing trends, two experienced decreasing trends, eight were identified as stable by the ASMFC working group, 10 experienced no discernible trend/high variability, and 18 did not have enough data to assess recent trends, including one that had no returning fish (see Table 2 in NMFS 2019; ASMFC 2017a). The coastwide meta-complex of river herring stocks on the U.S. Atlantic coast remains depleted to near historic lows. A depleted status indicates that there was evidence for declines in abundance due to a number of factors, but the relative importance of these factors in reducing river herring stocks could not be determined.

Commercial landings of river herring peaked in the late 1960s, declined rapidly through the 1970s and 1980s, and have remained at levels less than 3 percent of the peak over the past decade. Fisheries-independent surveys did not show consistent trends and were quite variable both within and among surveys. Those surveys that showed declines tended to be from areas south of Long Island. A problem with the majority of fisheries-independent surveys is that the length of their time series did not overlap with the period of peak commercial landings (

i.e.,

prior to 1970); therefore, there is no accurate way of comparing historical landings to fisheries-independent surveys. There appears to be a consensus among various assessment methodologies that exploitation has decreased. The decline in exploitation over the past decade is not surprising because river herring populations are at low levels and more restrictive regulations or moratoria have been enacted by states (See

Directed Commercial Harvest

below and State Regulations in the Status Review Report, NMFS 2019, for further detail).

Canadian Waters

The Department of Fisheries and Oceans (DFO) monitors and manages river herring runs in Canada. River herring monitoring in the Maritime region falls into two categories, rivers where abundances can be directly estimated (

e.g.,

monitoring at fishways), and rivers where information is available from the commercial fishery (Gibson

et al.

2017). River herring runs in the Miramichi River in New Brunswick and the Margaree River in Cape Breton, Nova Scotia were monitored intensively from 1983 to 2000 (DFO 2001). More recently (1997 to 2017), the Gaspereau River alewife run and harvest has been intensively monitored and managed partially in response to a 2002 fisheries management plan that had a goal of increasing spawning escapement to 400,000 adults (DFO 2007). During the period of 1970 to 2017, Billard (2017) estimated run size of alewife in the Gaspereau from 265,000 to 1.2 million. The exploitation rate for this same period ranged from 33 percent to 89 percent. Billard (2017) classified the most recent years 2015 and 2016 as having healthy escapement rates, but overexploited as a fishery. Elsewhere, river herring runs have been monitored less intensively, though harvest rates are monitored throughout Atlantic Canada through license sales, reporting requirements, and a logbook system that was enacted in 1992 (DFO 2001). At the time DFO conducted their last stock assessment in 2001, they identified river herring harvest levels as being low (relative to historical levels) and stable to low and decreasing across most rivers where data were available (DFO 2001).

With respect to the commercial harvest of river herring, reported landings of river herring peaked in 1980 at slightly less than 25.5 million lbs (11,600 metric tons (mt) and declined to less than 11 million lbs (5,000 mt) in 1996. Landings data reported through DFO indicate that river herring harvests have continued to decline through 2010.

Species Finding

Based on the best available scientific and commercial data summarized above, we find that the alewife and blueback herring are currently considered as two taxonomically-distinct species (see Taxonomy and Distinctive Characteristics of NMFS 2019) and, therefore, meet the definition of “species” pursuant to section 3 of the ESA. Below, we evaluate whether each species warrants listing as endangered or threatened under the ESA throughout all or a significant portion of its range.

Distinct Population Segment Determination

In addition to evaluating whether each species is at risk of extinction, the SRT was asked to identify any DPSs of these species and evaluate whether such DPSs may be at risk of extinction throughout all or a significant portion of its range. As described above, the ESA's definition of “species” includes “any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature.” The DPS Policy requires the consideration of two elements: (1) The discreteness of the population segment in relation to the remainder of the species to which it belongs, and (2) the significance of the population segment to the species to which it belongs.

A population segment of a vertebrate species may be considered discrete if it satisfies either one of the following two conditions. The first condition is if the species is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Quantitative measures of genetic or morphological discontinuity may provide evidence of this separation. The second condition is if the species is delimited by international governmental boundaries within which differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist that are significant in light of section 4(a)(1)(D) of the ESA. If a population segment is found to be discrete under one or both of the above conditions, its biological and ecological significance to the taxon to which it belongs is evaluated. Factors that can be considered in evaluating significance may include, but are not limited to: (1) Persistence of the discrete population segment in an ecological setting unusual or unique for the taxon; (2) evidence that the loss of the discrete population segment would result in a significant gap in the range of a taxon; (3) evidence that the discrete population segment represents the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range; or (4) evidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics.

Evaluation of Discreteness

The SRT evaluated whether any alewife or blueback herring DPSs, including those identified by the petitioner in 2011, exist. The Status Review Report, in particular the section

on Population Structure, provides a summary of information they reviewed, including tagging and genetics data, as well as fisheries management information (NMFS 2019). As highlighted in the DPS Policy, quantitative measures of morphological discontinuity or differentiation can serve as evidence of marked separation of populations. After review of the best available information, the SRT found that genetic studies provide evidence of regional differentiation in both alewife and blueback herring by demonstrating discrete groupings at a large geographic scale. In particular, the SRT found that the study by Reid

et al.

(2018), which includes a large number of rivers across the species' ranges, provides the most comprehensive evidence of regional differentiation for these species, because STRUCTURE analyses demonstrate support for regional groupings, and because the self-assignment tests to regional groupings have high values ranging from 86-92 percent for alewife and 76-95 percent for blueback herring. The SRT found the following regional stock complexes for alewife represent discrete groupings: (1) Aw-Canada (Garnish River, Newfoundland to Saint John River, New Brunswick); (2) Aw-Northern New England (St. Croix River, ME to Merrimack River, NH); (3) Aw-Southern New England (Parker River, MA to Carlls River, NY) and; (4) Aw-Mid Atlantic (Hudson River, NY to Alligator River, NC). These four discrete groupings correspond to the stock complexes in Figure 1. In addition the SRT found the following regional stock complexes for blueback represent discrete groupings: (1) Bb-Canada/Northern New England (Margaree River, Nova Scotia to Kennebec River, ME); (2) Bb-Mid New England (Oyster River, NH to Parker River, MA); (3) Bb-Southern New England (Mystic River, MA to Gilbert-Stuart Pond, RI); (4) Bb-Mid Atlantic (Connecticut River, CT to Neuse River, NC), and; (5) Bb-Southern Atlantic (Cape Fear River, NC to St. Johns River, FL). These five discrete groupings correspond to the stock complexes shown in Figure 2.

While the SRT found that genetic information provides evidence for regional population separation and discreteness for these stock complexes (depicted in Figures 1 and 2), especially at a large spatial scale, the SRT noted some uncertainty associated with the level of discreteness of these groupings. Specifically, the high degree of admixture (mixture of two or more genetically differentiated populations) at the boundaries of each of these stock complexes, referred to earlier as transitions zones, makes separation between stocks unclear at finer spatial scales. Also spatial gaps exist where samples were not obtained or tested (

e.g.,

between the Aw-Southern New England and Aw-Mid Atlantic stock complexes, and between the Bb-Southern New England and Bb-Atlantic stock complexes) making the accuracy of these boundaries uncertain.

Additionally, the SRT noted that there is some uncertainty surrounding these groupings due to the methodology used by Reid

et al.

(2018) in the rangewide analysis where STRUCTURE was run on collection sites without binning into larger spawning habitats. For example, Black Creek, a tributary of the Hudson, was considered separate from the Hudson in the analysis even though these rivers share an estuary. Additionally, a number of small tributaries of the Connecticut River (

e.g.,

Wethersfield Cove, Mill Creek, and Mill Brook) were considered as separate independent populations.

Overall, the SRT relied upon the best available genetic information (see NMFS 2019 for complete discussion) to determine discreteness for the alewife and blueback herring. The SRT discussed but did not find evidence of physiological, ecological, behavioral factors or life history differences that would aid in further delineating discrete populations. In addition, the SRT discussed combining and/or further separating the genetic groupings outlined above, but did not find evidence to support modifying the genetic groups, despite the study limitations discussed (see above).

Evaluation of Significance

As noted above, the DPS Policy instructs that significance is evaluated in terms of the ecological and biological importance of the population segment to the species. The SRT considered the significance of each of the regional groupings (

i.e.,

stock complexes) found to be discrete. In reviewing the factors that support a finding of significance outlined above, the SRT found that the discrete groupings identified for both species are not found in areas that appear to have unique or unusual ecological settings. Although the petitioner suggested that the terrestrial ecoregions identified by The Nature Conservancy (Anderson 2003) may represent unique or unusual ecological settings for the species, the SRT found several ecoregions were not unique or unusual because they could be found within the range of more than one discrete group. For example, the Northern Appalachian/Acadian terrestrial ecoregion extends throughout both the Aw-Northern New England and Aw-Canada stock complexes. Additionally, the Northern Piedmont and North Atlantic Coastal ecoregions extended through the Bb-Mid-New England, Bb-Southern New England and into the Bb-Mid-Atlantic stock complexes. For ecoregions that existed entirely within one stock complex, the SRT found that the ecoregions appeared to have no unique or unusual bearing on the discrete grouping's biology, as the range of the group included more than one ecoregion. For example, the Chesapeake Bay Lowlands exist entirely within the range of the Aw-Mid-Atlantic stock complex; however, this range also contains a portion of the North Atlantic coast ecoregion (which spans three stock complexes). The SRT also considered whether other ecological factors, such as ocean currents or thermal regimes, existed within the boundaries of these complexes, and might point to persistence in a unique ecological setting. However, the SRT did not find that any of these stock complexes persist in a unique terrestrial ecoregions or other “ecological settings,” instead they noted that some of these stock complexes may share marine environments where oceanic features appear unique, and that terrestrial ecoregions do not align with the identified discrete stock complex boundaries.

Next, the SRT considered whether the loss of the population segments would result in significant gaps in the range of the taxa. The SRT agreed that the length of coastline or overall size of the habitat that the discrete grouping inhabited would be the greatest factor in determining whether a gap, or loss in the range, was significant to a taxon as a whole. Specifically, large gaps in the range across widespread watersheds might be difficult for either species to refill naturally (

i.e.,

through straying) and would be extremely difficult to fill through management efforts (

e.g.,

stocking).

Large gaps in the range may interfere with connectivity between populations, resulting in isolated populations that are more vulnerable to the impacts of large threats or catastrophic events (

e.g.,

storms, regional drought). Connectivity, population resilience and diversity are important when determining what constitutes a significant portion of the species' range (Waples

et al.

2007). Maintaining connectivity between genetic groups supports proper metapopulation function, in this case, anadromy. Ensuring that river herring populations are well represented across diverse habitats helps to maintain and enhance genetic variability and

population resilience (McElhany

et al.

2000). Additionally, ensuring wide geographic distribution across diverse climate and geographic regions helps to minimize risk from catastrophes (

e.g.,

droughts, floods, hurricanes, etc.; McElhany

et al.

2000). Furthermore, preventing isolation of genetic groups protects against population divergence (Allendorf and Luikart, 2007). Further, a large gap on the periphery of the range would limit the distribution of the species, similarly reducing resiliency. For example, wide distributions may provide a diversity of habitats and buffer species against widespread threats such as changing temperatures by providing more opportunities for habitat refugia. Although there is no evidence currently available to suggest that genetic differences between these stock complexes represent adaptive traits (only neutral genetic markers have been used in the current population structure analyses), the SRT also noted that significant gaps could represent a loss of genetic adaptation if these regional groupings are also linked to adaptive traits (NMFS 2019).

As noted in the Status Review Report river herring discrete stock complexes could re-colonize spatial gaps in the range. Genetic studies provide evidence of straying (see Straying above) and suggest transition zones between populations (NMFS 2019). The SRT noted that gaps in the population would most likely be filled in a step-wise fashion with fish moving in from the borders of the nearest stock complexes, but that some straying may occur mid-range as well. Because river herring exhibit straying both from nearby rivers and over larger distances (Gardner

et al.

2011, Hogg 2012, sensu Reid

et al.

2018), the SRT noted that the significance of any particular gap will be primarily a factor of the geographic scope (or size of the gap).

The SRT noted that the life history, fecundity, and straying behavior of these species could lead to having river herring within individual rivers once occupied by the “lost” stock (

i.e.,

fish recolonizing the gap in the range) rather quickly, but perhaps at low or less than sustainable levels. For the purposes of considering the loss of each discrete stock complex, the SRT defined a significant gap to be a large geographic area of the range (considering the length of coastline or size of the watershed) that was unlikely to be recolonized with self-sustaining populations within at least 10 generations (40-60 years); the upper limit of time the SRT believed that the taxon could sustain without detrimental effects from loss of connectivity.

There is debate in the literature regarding the application of assigning a general number to represent when populations are sufficiently large enough to maintain genetic variation (Allendorf and Luikart 2007). The SRT settled on a self-sustaining population of around 1,000 spawning fish annually in currently occupied rivers within the area; a number close to the population of some smaller river systems where populations are able to maintain returns (

e.g.,

Little River, MA). This metric of 1,000 fish is close to, but greater than the “500 rule” introduced by Franklin (1980) for indicating when a population may be at risk of losing genetic variability.

The SRT reviewed each of the discrete stock complexes for both species and considered the overall size of the gap that would exist as well as the likelihood that the area would be filled in by neighboring stock complexes. The SRT noted that the nearest neighboring stock complex would be most likely to colonize in a step-wise fashion at the borders of any gap. The SRT also acknowledged that strays may colonize from any stock complex, as isolation by distance evidence from Palkovacs

et al.

(2014) and McBride

et al.

(2015) suggests that genetic exchange (straying) currently happens over such distances as 100-200 km (62-124 mi). However, while this is possible, this scenario was less likely than strays colonizing from the closest stock complex.

The loss of discrete stock complexes that were large in geographic scope and, therefore, unlikely to be filled in by neighboring stock complexes were considered likely to leave a significant gap in the species' range. These findings are summarized below in Table 1.

Table 1—Summary of Significant Gap Discussion for Alewife and Blueback Herring Stock Complexes

Discrete stock complex

Estimates of geographic scope of the stock complex (watershed size (square kilometers (km

2

) (square miles mi

2

)); coastline distance (km) (mi); degrees latitude; percent of

rangewide watershed area)

Likelihood of recolonization

Loss of the stock

complex would result

in a significant gap

(yes or no)

Alewife Canada

169,000 km

2

(65,251 mi

2

); 15,200 km (9,444 mi); 7.5 degrees latitude; 35 percent

Recolonization is unlikely due to the large size of the gap and with only one neighboring complex to the south

Yes.

Alewife Northern New England

74,000 km

2

(28,572 mi

2

); 5,800 km (3,604 mi); 2.5 degrees latitude,15 percent

Recolonization across this range is unlikely due to the large size of the gap despite having neighboring complexes to the south and north beginning to recolonize bordering areas

Yes.

Alewife Southern New England

35,500 km

2

(13,707 mi

2

); 7400 km (4,598 mi); 2.5 degrees latitude; 7 percent

Recolonization is unlikely due to the large size of the gap and with only one neighboring complex to the north

Yes.

Alewife Mid-Atlantic

211,500 km

2

(81,661 mi

2

); 19,600 km (12,179 mi); 9 degrees latitude; 43 percent

Recolonization is unlikely due to the large size of the gap and with only one neighboring complex to the north

Yes.

Blueback Herring Canada/Northern New England

137,000 km

2

(52,896 mi

2

); 11,100 km (6,897 mi); 4 degrees of latitude; 26 percent

Recolonization is unlikely due to the large size of the gap and with only one neighboring complex to the south

Yes.

Blueback Herring Mid New England

12,000 km

2

(4,633 mi

2

); 311 km (193 mi); 0.5 degrees of latitude; <3 percent

Recolonization across this range is likely given the small size of the gap and because neighboring complexes can recolonize step-wise from the south and north

No.

Blueback Herring Southern New England

9,000 km

2

(3,475 mi

2

); 2,900 km (1,802 mi); 1.5 degrees of latitude; <2 percent

Recolonization across this range is likely given the small size of the gap and because neighboring complexes can recolonize step-wise from the south and north. Additionally, proximity to known river herring overwintering grounds might support further recolonization

No.

Blueback Herring Mid Atlantic

211,000 km

2

(81,468 mi

2

); 24,800 km (15,410 mi); 9 degrees of latitude; 40 percent

Recolonization across this range is unlikely due to the large size of the gap despite neighboring complexes to the south and north beginning to recolonize bordering areas

Yes.

Blueback Herring Southern Atlantic

140,000 km

2

(54,054 mi

2

); 18,300 km (11,371 mi); 7 degrees of latitude, 26 percent

Recolonization is unlikely due to the large size of the gap and with only one neighboring complex to the north

Yes.

The SRT did not find evidence that discrete population segments outlined previously represent the only surviving natural occurrence of a taxon that may be more abundant elsewhere as an introduced population outside its historic range. The SRT identified four alewife DPSs and three blueback herring DPSs. Therefore, none of the DPSs represent the only surviving natural occurrence of either alewife or blueback herring.

Finally, the SRT considered evidence to determine whether any of the discrete population segments differ markedly from other populations of the species (

i.e.,

the other identified stock complexes) in its genetic characteristics. The SRT discussed the methodology in the Reid

et al.

(2018) paper and inquired with one of the lead authors about information on the genetic diversity (

e.g.

heterozygosity among stock complexes) results from the study. The SNP markers in the Reid

et al.

(2018) paper used neutral genetic markers which do not convey adaptive traits, so the SRT was unable to find evidence that the discrete stock complexes differ markedly from other populations of the species in its genetic characteristics. The SRT also considered spawning timing, which has been shown to be heritable in steelhead and presumably could be heritable in other anadromous fish, including alewife or blueback herring. The SRT examined rangewide spawning strategies, and was not aware of differing life history strategies, such as winter and fall spawning timing in the species (as exhibited in steelhead). Alewives and blueback herring use thermal cues for spawning timing; however, this appears to be due to clinal patterns, with rivers in the southern portion of the range beginning spawning earliest in the year and the rivers at highest latitudes spawning latest in the year. Overall, the SRT did not find existing evidence to support heritable spawning timing in alewife or blueback herring.

After reviewing the significance criteria, the SRT did not find evidence to demonstrate these discrete stock complexes persist in a unique ecological setting or that they differ markedly from one another in their genetic characteristics. The SRT did find evidence that loss of the population segment would result in a significant gap in the range of the taxon for all four discrete stock complexes of alewife: Aw-Canada; Aw-Northern New England; Aw-Southern New England, and; Aw-Mid-Atlantic. In addition, the SRT also found evidence that loss of the population segment would result in a significant gap in the range of the taxon for three of the five discrete stock complexes of blueback herring: Bb-Canada/Northern New England, Bb-Mid-Atlantic, and bb-Southern Atlantic. However, due to the small size of the Bb-Mid-New England and Bb-Southern New England stock complexes and because this habitat is likely to be recolonized by blueback herring stock complexes to the north and to the south, the loss of one of these two discrete stock complexes did not represent a significant gap in the range of the taxon (which includes five discrete stock complexes across the range).

While the SRT applied the “10 generations for recolonization” formula (described above), we do not find that the use of such a formula is necessary given the large geographic scope (see Table 1 column 2) of the potential gaps caused by the loss of the Aw-Canada; Aw-Northern New England; Aw-Southern New England, or; Aw-Mid-Atlantic stock complex or the Bb-Canada/Northern New England, Bb-Mid-Atlantic, or Bb-Southern Atlantic stock complex. The potential loss of any of these stock complexes would create a large gap in the range of these species creating issues with connectivity between populations, lowering the diversity of habitats that these species span, and reducing the species' ability to overcome large threats or catastrophic events. In contrast, a small gap in the range, such as either the potential loss of the Bb-Mid New England or Bb-Southern New England stock complex, may be less important to these species because their straying behavior and fecundity may allow them to regain or even maintain connectivity between neighboring stock complexes. Accordingly, based on these considerations, we agree with the SRT's findings that the loss of the Aw Canada; Aw-Northern New England; Aw-Southern New England, or; Aw-Mid-Atlantic stock complex or the Bb-Canada/Northern New England, Bb-Mid-Atlantic, or Bb-Southern Atlantic stock complex would create a significant gap in the range of these species.

The SRT relied on the best available information throughout this analysis, but noted that future information on behavior, ecology, and genetic characteristics may reveal differences significant enough to show fish to be uniquely adapted to each stock complex.

Because the following stock complexes meet both the discreteness and significance prongs, the SRT identified, and we agree with, the following DPSs for alewife (Figure 3):

• Aw-Canada DPS the range includes Garnish River, Newfoundland to Saint John River, New Brunswick;

• Aw-Northern New England DPS—the range includes St. Croix River, ME to Merrimack River, NH;

• Aw-Southern New England DPS—the range includes Parker River, MA to Carll's River, NY; and

• Aw-Mid Atlantic DPS—the range includes Hudson River, NY to Alligator River, NC.

Because the three blueback herring stock complexes meet both the discreteness and significance prongs, the SRT recommends, and we agree, with the following DPSs for blueback herring (Figure 4):

• Bb-Canada-Northern New England DPS—the range includes Margaree River, Nova Scotia to Kennebec River, ME;

• Bb-Mid Atlantic DPS—the range includes Connecticut River, CT to Neuse River, NC; and

• Bb-Southern Atlantic DPS—the range includes Cape Fear River, NC.

BILLING CODE 3510-22-P

EN19JN19.003

EN19JN19.004

BILLING CODE 3510-22-C

Assessment of Extinction Risk

Foreseeable Future

The ESA defines an endangered species as any species which is in danger of extinction throughout all or a significant portion of its range and a threatened species as any species which is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range (16 U.S.C. 1532(6) and (20)). The term “foreseeable future” is not further defined or described within the ESA. However, consistent with our past practice, we describe the “foreseeable future” on a case-by-case basis, using the best available data for the particular species, and taking into consideration factors such as the species' life history characteristics, threat projection time frames, and environmental variability. We interpret the foreseeable future as extending only so far into the future as we can reasonably determine that both the threats and the particular species' responses to those threats are likely. Because a species may be susceptible to a variety of threats for which different data are available, or which operate across different time scales, the foreseeable future is not necessarily reducible to a particular number of years.

Highly productive species with short generation times (

e.g.,

river herring) are more resilient than less productive, long-lived species, as they are quickly able to take advantage of available habitats for reproduction (Mace

et al.

2002). Species with shorter generation times, such as river herring (4 to 6 years), experience greater population variability than species with long generation times, because they maintain the capacity to replenish themselves more quickly following a period of low survival (Mace

et al.

2002). Consequently, given the high population variability among clupeids, projecting out further than a few generations could lead to considerable uncertainty in predicting the response to threats for each species.

As described below, the SRT determined that dams, water withdrawal, poor water quality, incidental catch, inadequacy of regulations, and climate change vulnerability are the main threats to both species. The SRT determined, and we agree, the foreseeable future is best defined by a 12 to 18 year time frame (

i.e.,

out to 2030-2036), or a three-generation time period, for each species for both alewife and blueback herring. This is a period in which impacts of present threats to the species could be realized in the form of noticeable population declines, as demonstrated in the available survey and fisheries data. This timeframe would allow for reliable predictions regarding the impact of current levels of mortality on the biological status of the two species.

Evaluation of Demographic Risks

In determining the extinction risk of a species, it is important to consider both the demographic risks facing the species as well as current and potential threats that may affect the species' status. To this end, a qualitative demographic analysis was conducted for the alewife and blueback herring. A demographic risk analysis is an assessment of the manifestation of past threats that have contributed to the species' current status, and it informs the consideration of the biological response of the species to present and future threats.

The approach of considering demographic risk factors to help frame the consideration of extinction risk has been used in many of our status reviews (see

http://www.nmfs.noaa.gov/pr/species

for links to these reviews). In this approach, the collective condition of individual populations is considered at the species level according to four demographic viability factors: Abundance, growth rate/productivity, spatial structure/connectivity, and diversity. These viability factors reflect concepts that are well founded in conservation biology and that individually and collectively provide strong indicators of extinction risk.

Using these concepts, the SRT evaluated demographic risks by individually assigning a risk score to each of the four demographic criteria (abundance, growth rate/productivity, spatial structure/connectivity, diversity). Qualitative reference levels with ranking scores of whole numbers from 1-5 of “

very low,”

“

low,”

“

moderate,”

“

high,”

and “

very high”

were used to describe the risk of demographic criteria. A factor (or viable population descriptor) was ranked (1)

very low

if it was unlikely that this descriptor contributed significantly to risk of extinction, either by itself or in combination with other viable population descriptors. A factor was ranked (2)

low

risk if it was unlikely that this descriptor contributed significantly to long-term or near future risk of extinction by itself, but there was some concern that it may, in combination with other viable population descriptors. A factor was ranked (3)

moderate

risk if this descriptor contributed significantly to long-term risk of extinction, but did not in itself constitute a danger of extinction in the near future. A factor was ranked (4)

high

risk if this descriptor contributed significantly to long-term risk of extinction and was likely to contribute to short-term risk of extinction in the near future, and a factor was ranked (5)

very high

risk if this descriptor by itself indicated danger of extinction in the near future.

Each SRT member scored each demographic factor individually. Each SRT member identified other demographic factors and/or threats that would work in combination with factors ranked in the higher categories to increase risk to the species. SRT members provided their expert opinions for each of the demographic risks, including considerations outlined in McElhany

et al.

(2000) and the supporting data on which it was based, and discussed their opinions with the other SRT members. SRT members were then given the opportunity to adjust their individual scores, if desired. These adjusted scores were tallied, reviewed, and then combined for an overall extinction risk determination (see below). This scoring was carried out for both species rangewide and for each DPS, and the demographic scoring summary is presented below. Here the SRT's qualitative ranking for each demographic factor is identified by rounding the mean ranking score, which is provided in parentheses. For example, a demographic factor falling between the

low

(2) and

moderate

(3) risk rankings with a mean ranking score of 2.1 will be identified as

low

(2.1), while a factor with a mean ranking score of 2.5 will be identified as

moderate

(2.5). As noted throughout this section and in the Threats Assessments section and in the corresponding sections of the Status Review Report, many of the mean ranking scores fall between

low

(2), and

moderate

(3). Only a few scores were found to be 3 or higher. As more fully explained in the Status Review Report, the SRT used a scale of whole numbers from 1 to 5 (NMFS, 2019).

Alewife

Abundance

The SRT members individually evaluated the available alewife abundance information, which is summarized in the

Abundance and Trends

section of this listing determination and additional detail can be found in the Status Review Report (NMFS 2019). Alewife abundance has declined significantly from historical levels throughout its range (ASMFC 2017a, ASMFC 2012a, Limburg and Waldman (2009).

While abundance is at or near historical lows, the recent stock assessment update reported few declining abundance trends by dataset in recent years (ASMFC 2017a). The ASMFC River Herring Stock Assessment assessed data from the last ten years (2006-2015) and reported that no run counts reflect declining trends with 11 of 29 showing increasing trends, 14 showing no trend, and four not being updated (two due to discontinuation and two due to agency recommendation to remove the rivers based on data discrepancies between observed river herring presences and fishway counts) (ASMFC 2017a and b). Because abundance is known to be highly variable from year to year for these species, in addition to the trend information, the SRT reviewed annual run count numbers and escapement information, when available, as part of its consideration of information that may inform the abundance estimates of these populations. Given the substantial number of runs with increasing trends and relatively large run counts reported in various portions of the range in recent years (in the hundreds of thousands throughout various regions) (ASMFC 2017a), there do not appear to be depensatory processes rangewide that result in low abundances such that the populations may be insufficient to support mate choice, sex-ratios, fertilization and recruitment success, reproductive or courting behaviors, foraging success, and predator avoidance behaviors. The SRT reviewed available abundance indices for each DPS (see NMFS 2019 for complete summary). The mean score calculated based on the SRT's scores for alewife rangewide (2.0), the Aw-Canada (2.0) DPS, the Aw-Northern New England (2.0) DPS, and the Aw-Southern New England DPS (2.1) all correspond to a

low

ranking, because the SRT found this factor is unlikely to contribute significantly to the risk of alewife extinction.

While abundance information is limited for alewife in the Aw-Canada DPS, data provide some indicators of population size in several rivers. Examples of data reviewed by the SRT included (but were not limited to): Gaspereau River, Nova Scotia time series (1970 to 2017) estimates that ranged from a low of 265,208 (1983) to 1.2 million (2016), (Billard 2017); St. John River, New Brunswick fixed escapement policy of 800,000 alewife released above the dam annually; and Tusket River in Nova Scotia estimated escapement for this stock in 2014-1015 in the range of 1.6 million to 2.3 million alewife.

For populations in the United States, comprehensive summaries of data that inform abundance reviewed by the SRT are available in the ASMFC State-Specific Reports (2017b).

The ASMFC Stock Assessment reports trends from select rivers along the

Atlantic Coast (see Table 1 of ASMFC 2017a); depending on sampling methods, these may be reported by species or in combination (

i.e.,

reported as just river herring). Within the Aw-Northern New England DPS, updated recent trends (2006-2015) for alewife were reported as increasing for the Androscoggin, Damariscotta, and Cocheco rivers. The ASMFC reported increasing trends for river herring as a whole from the Kennebec, Sebasticook, and Lamprey Rivers. The ASMFC also reported no trend for alewife in the Union River, stable river herring trends in the Exeter River, decreasing alewife trends in the Oyster River, no returns of river herring in the Taylor River, and unknown trends for the Winnicut River throughout this period (ASMFC 2017a).

Within the Aw-Southern New England DPS, updated recent trends (2006-2015) for alewife were reported as increasing for the Mattapoisett, Monument, Nemasket, Buckeye, and Bride Brook Rivers. The ASMFC reported stable river herring trends in the Parker and Gilbert Rivers; decreasing alewife trends in the Stony Brook and Nonquit Rivers; and no trends for alewife in the Mianus and Shetucket Rivers; and unknown trends in the Farmington and Naugatuck Rivers (ASMFC 2017a).

The Aw-Mid-Atlantic DPS abundance risk mean score corresponded to a

moderate

(2.7) ranking. Within the Aw-Mid-Atlantic DPS, updated recent trends (2006-2015) for alewife were reported as increasing for river herring in the Hudson River, no tend for alewife in the Delaware and Rappahannock Rivers, stable for alewife in the Nanticoke and Potomac Rivers, and unknown for alewife in the James, York, and Alligator Rivers (ASMFC 2017a). SRT members noted uncertainty about abundance in the Mid-Atlantic DPS, due to minimal available abundance information (with the exception of the Hudson, several rivers in Chesapeake Bay, and a few ASMFC time series). However, preliminary results from the Chesapeake Bay (Ogburn unpublished data) appear favorable, with abundance estimates in surveyed rivers in the 100,000s of fish. Recent estimates of alewife absolute abundance using hydroacoustics for the Roanoke River during 2008-2015 have ranged from 32,000 to 419,000 (Waine 2010, Hughes and Hightower 2015; McCargo 2018).

Growth Rate/Productivity

The SRT evaluated the available information on life history traits for alewife as they relate to this factor, as summarized in the Reproduction, Growth, and Demography section in the Status Review Report (NMFS 2019). Data are limited on growth rate/productivity, and there is little effort to systematically collect and standardize this type of data in most of the range of the species. The SRT considered previously discussed trends in abundance and reviewed trends in maximum age, average size-at-age, repeat spawners, and modeling results for the qualitative ranking of growth rate and productivity. ASMFC (2017a) reported alewife maximum age data indicate most runs had stable ages, and no trends appear reversed relative to the 2012 benchmark. Specifically, maximum age results showed no trends in the Androscoggin, Exeter, Cocheco, Monument, and Gilbert-Stuart Rivers; increasing trends in the Lamprey River (NH); and decreasing tends in the Nanticoke River (MD) and Chowan River (NC). Size at age results showed no trend in the Androscoggin, Cocheco (female), Lamprey, Winnicut, and Hudson Rivers; and decreasing trends in the Exeter (male), Monument, and Nanticoke Rivers. Additionally, for the Status Review Report, a population growth model (MARSS) was used for alewife rangewide. The MARSS model results show a population growth rate point estimate of 0.038, with the associated 95 percent confidence interval ranging from (0.005-0.071) (NMFS 2019).

The mean score calculated for this demographic factor based on SRT members' scores corresponds to a

low

ranking rangewide (2.1), and in each DPS (Aw-Canada DPS (2.0), Aw-Northern New England DPS (2.0), Aw-Southern New England DPS (2.1), and the Aw-Mid-Atlantic DPS (2.3)), as this factor is unlikely to contribute significantly to the risk of extinction for alewife. SRT members noted that rates of population growth for many rivers have shown growth in the past 5-10 years. Where mean age has been reduced, it is often in conjunction with recruitment of strong year classes as the populations rebuild. Some systems are beginning to have increases in age structure as older individuals persist. The SRT noted some runs in the southernmost portion of the range have not shown as strong or consistent improvement; this was reflected in the slightly higher numeric score and variability of the qualitative ranking for the growth rate of the Mid-Atlantic DPS (NMFS 2019).

Spatial Structure/Connectivity

The SRT evaluated the available information on alewife spatial structure (tagging and genetics information) summarized in the Population Structure section in the Status Review Report (NMFS 2019). Alewife range from North Carolina to Newfoundland, Canada. While the species exhibits homing, rates of straying and therefore dispersal help to buffer the species from threats related to loss of habitat and loss of spatial connectivity. The mean score calculated based on SRT members' scores corresponds to a

moderate

(2.6) ranking rangewide and for all DPSs (2.7-2.9), as this factor contributes significantly to long-term risk of extinction, but does not in itself constitute a danger of extinction in the near future. SRT members noted that habitat degradation and destruction threats related to human population growth will presumably continue to increase, and the cumulative effects will influence the species range wide. Reduced, restricted, and impacted spawning and nursery habitat will likely remain a limiting factor to population growth in many river systems.

Diversity

The SRT evaluated the available information on alewife diversity summarized in the Population Structure section in the Status Review Report (NMFS 2019). The available genetics studies indicate that there are a minimum of four genetic stock complexes rangewide and there is reproductive connectivity along a continuum rangewide. SRT members noted that, due to declines in abundance over the last several hundred years, the species has likely lost some genetic diversity, and therefore has lost some adaptive potential. This loss of diversity affects resilience, especially in the face of climate change. Additionally, SRT members determined that human activities of stocking and propagation have also contributed to reduced genetic diversity. Further, the SRT noted that stocking activities, coupled with habitat alterations (

e.g.,

in-river obstructions like dams), and reduced access to spawning and nursery habitat, may even result in the selection of characteristics in these fish that are conducive to survival in modified and dammed river systems.

The mean score calculated based on SRT members' scores corresponds to a

moderate

ranking rangewide (2.6) and in each of the DPSs (Aw-Canada (2.7), Aw-Northern New England (2.7), Aw-Southern New England (2.9) and Aw-Mid-Atlantic (2.9) DPS), as this descriptor contributes significantly to long-term risk of extinction, but does not in itself constitute a danger of extinction in the near future. Although still receiving a

moderate

ranking, SRT members noted that the Aw-Canada DPS

may have a slightly lower risk in comparison to other areas, as this DPS has a very large range and access to a wide variety of stream size and temperature regimes. Additionally, the SRT noted the Aw-Canada DPS likely experiences less active stocking (which has been suggested to negatively affect genetic diversity); therefore, the risk to genetic diversity in this DPS was ranked slightly lower.

Blueback Herring

Abundance

The SRT individually evaluated the available blueback herring abundance information, which is summarized in the Description of Population Abundance and Trends section of the Status Review Report (NMFS 2019). SRT members noted that the available information indicated blueback herring abundance had declined significantly from historical levels throughout its range. The SRT reviewed the recent ASMFC stock assessment update and available abundance indices for each DPS (NMFS 2019; ASMFC 2017a). Blueback herring abundance estimates were lower than available estimates for alewife, but recent run count estimates documented hundreds of thousands of fish in the Chowan River, Chesapeake Bay (Ogburn unpublished data), Connecticut River, various Massachusetts rivers, and rivers in Maine (ASMFC 2017b) and New Brunswick (Gibson

et al.

2017). The mean score calculated based on the SRT's scores corresponds to a

moderate

ranking rangewide (3.0) and in each DPS (Bb-Canada/Northern New England (3.0), Bb-Mid-Atlantic (3.0), and Bb-Southern Atlantic (3.0) DPSs), as this factor is contributing significantly to the blueback herring's risk of extinction, but does not in itself constitute a danger of extinction in the near future.

The SRT reviewed the best available data on blueback herring abundance in the Bb-Canada/Northern New England DPS. The SRT noted that blueback herring in the St. John River, New Brunswick are managed using a fixed escapement policy of 200,000 blueback herring moved above the dam each year; this number is not indicative of abundance, but can be viewed as a minimum when escapement targets are met. The Mactaquac time series (1999 to 2017) ranged from 192,000 to 515,000, with over 489,000 blueback herring passed upstream in 2017. Escapement estimates for the Tusket River in Nova Scotia during the period of 2014 to 2015 ranged from 200,000 to 600,000 blueback herring. As noted above for alewife, the ASMFC Stock Assessment reports trends from select rivers along the Atlantic Coast (see Table 1 of ASMFC 2017a); depending on sampling methods these may be reported by species or in combination (

i.e.,

reported as just river herring). There is little stock specific information on blueback herring in Maine. Within the U.S portion of the Bb-Canada/Northern New England DPS, the ASMFC (2017a) reported trends over 2006-2015 as increasing for river herring in the Kennebec and Sebasticook Rivers. Data reported from rivers throughout this range were also reviewed, and numbers varied widely from year to year, as expected for this species. According to the most recent stock assessment report (ASMFC 2017b), blueback herring estimates for the Kennebec and Sebasticook Rivers in Maine were over 1 million fish (reported as combined species). The state of Maine conducts an annual young-of-the-year survey for six Maine rivers (1979 to 2015). Relative abundance was near zero from 1979 to 1991, and increased gradually through 2004 before declining in recent years (ASMFC 2017a).

The SRT reviewed available abundance data for the Bb-Mid-Atlantic DPS, which ranges from Connecticut to North Carolina. The ASMFC (2017a) reported increasing blueback herring trends for the Mianus and Rappahannock Rivers; stable trends for the Connecticut River, Shetucket River, and Chowan River; no trends for the Delaware and Nanticoke Rivers; and unknown trends for the Farmington, Naugatuck, Potomac, James, York, Alligator, Scuppernog, and St. Johns Rivers. Additionally, trends for river herring were reported as increasing in the Hudson (ASMFC 2017a). Data reported from rivers throughout this range were also reviewed, and numbers varied widely from year to year as expected for this species. The SRT noted blueback herring abundance estimates ranging from 500,000-700,000 during 2013-2016 in the Choptank River; 18,000-54,000 during 2016-2017 in the Patapsco River; and 500,000-950,000 during 2013-2014 in the Marshyhope River (Ogburn unpublished data). Additionally, absolute abundance estimates of blueback herring in the Roanoake River using hydroacoustics ranged from 100,000-478,000 (Waine 2010, Hughes and Hightower 2015, McCargo 2018) across studies conducted in 2008, 2009, 2010, 2011, and 2015, with the high reported in 2015. Total blueback herring population estimates (for age 3+) in the Chowan River time series (1972 to 2015) ranged from a high of 157 million (1976) to a low of 593,693 (2007; ASMFC 2017b). The most recent estimate of blueback herring abundance in the Chowan River was 5,160,983 (2015). Commercial CPUE estimates for blueback herring in the Chowan River have declined since the 1980s.

The ASMFC (2017a) reported no trend for blueback herring in the Santee Cooper River and unknown trends for the St. Johns River. Due to limited trend information, the SRT reviewed available abundance data for the Bb-Southern Atlantic DPS, including young-of-the-year push trawl estimates from Florida (2007 to 2016); CPUE estimates from Santee-Cooper River (1969 to 2015), and minimum population size estimates from the Santee-Cooper River (1990 to 2015) (ASMFC 2017b). Minimum population size estimates from the Santee Cooper River ranged from 8,503 (1990) to 3.4 million (1996); the minimum population size was estimated at 410,000 in 2015. The SRT noted increased uncertainty for Bb-Southern Atlantic abundance risk due to the small number of available indices.

Growth Rate/Productivity

The SRT evaluated the available data for blueback herring as they relate to this factor, as summarized in the Reproduction, Growth, and Demography section in the Status Review Report (NMFS 2019). Data are limited on growth rate/productivity, and there has been limited effort to systematically collect and standardize this type of data in most of the range of the species. SRT members noted that in some populations the maximum age appears to be trending upward, and blueback herring maximum age data indicate most runs had stable ages (ASMFC 2017a). On a rangewide basis, the MARSS model (NMFS 2019) showed blueback herring population growth rates of 0.05 with a 95 percent confidence interval (−0.03 to 0.13). Also, while recent abundance trends have indicated positive growth rates, trends in demographic (maximum age) and reproductive rates (repeat spawners) are largely negative or stable; the combination of these two trends is an indicator of a potentially declining growth rate, given the paucity of high accuracy abundance data for blueback herring.

The mean score calculated based on SRT member's scores corresponds to a

moderate

ranking rangewide (2.75) and in all DPSs (Bb-Canada/Northern New England DPS (2.75), Bb-Mid-Atlantic DPS (2.88) and Bb-Southern Atlantic DPS (3.0)) as this factor is contributing significantly to the blueback herring's risk of extinction, but does not in itself constitute a danger of extinction in the

near future. The lack of available data contributed to higher uncertainty around the growth rate for blueback herring.

Spatial Structure/Connectivity

The SRT evaluated the available information on blueback herring spatial structure (tagging and genetics information), summarized in the Population Structure section in the Status Review Report (NMFS 2019). Blueback herring range from Florida to Nova Scotia, spanning 20 degrees latitude and ranging thousands of kilometers along the Atlantic Coast. While the species exhibits homing, rates of straying and the resulting dispersal help to buffer the species from threats related to loss of habitat and loss of spatial connectivity. The SRT noted, however, that blueback herring likely have longer distances between populations in comparison to alewife populations (AMFC 2017a,b), which could result in less resiliency in comparison to alewife. Additionally, depending on natal river, some blueback herring have longer migratory distances from overwintering areas, thereby exposing them to a longer duration of threats in the marine environment in comparison to alewife.

Maintaining connectivity between genetic groups supports proper metapopulation function. Ensuring that populations are well represented across a variety of river systems help to maintain and enhance population resilience and genetic variability (McElhany

et al.

2000). Blueback herring appear to have connected populations and genetic exchange with bordering populations. However, Reid

et al.

(2018) noted that the Bb-Southern Atlantic population appears to be the most distinct genetically from other populations, suggesting that gene flow and connectivity may be more limited in this DPS compared to other DPSs. Still the range of the Bb-Southern Atlantic population stretches over a wide area, and the SRT noted obstructions were more likely found farther up river in this region, providing more accessible habitat for the species.

The mean score calculated based on SRT member's scores rangewide (2.87) and in each DPS (Bb-Canada/Northern New England DPS (2.86), Bb-Mid-Atlantic DPS (2.88), and Bb-Southern Atlantic DPS (2.71)) corresponds to a

moderate

ranking rangewide, as this factor is contributing significantly to the blueback herring's risk of extinction, but does not in itself constitute a danger of extinction in the near future.

Diversity

The SRT evaluated the available information on blueback herring diversity summarized in the Population Structure section in the Status Review Report (NMFS 2019). The available genetics studies indicate that there are a minimum of five genetic stock complexes rangewide and there is evidence of reproductive connectivity along a continuum rangewide. However, blueback herring exhibit larger distances between populations when compared to alewives (ASMFC 2017a,b), thus in comparison, alewife may be better positioned to maintain genetic diversity (through mixing with bordering populations). The SRT noted that due to declines in abundance over the last several hundred years, the species has likely lost genetic diversity and therefore has lost some amount of adaptive potential. This loss of diversity affects resiliency, especially in the face of climate change. Additionally, SRT members felt that human activities of stocking and propagation have also contributed to reduced genetic diversity. The mean score calculated based on SRT member's scores correspond to a

moderate

ranking rangewide (3.1) and in each DPS (Bb-Canada/Northern New England DPS (3.14), Bb-Mid-Atlantic DPS (3.0), and Bb-Southern Atlantic DPS (3.14)), as this descriptor contributes significantly to long-term risk of extinction, but does not in itself constitute a danger of extinction in the near future.

Evaluation of Threats

Next the SRT considered whether any of the five factors (specified in section 4(a)(1) of the ESA) are contributing to the extinction risk of alewife or blueback herring. Threats considered included habitat destruction, modification, or curtailment; overutilization; disease or predation; inadequacy of existing regulatory mechanisms; and other natural or manmade threats, because these are the five factors identified in section 4(a)(1) of the ESA.

The SRT identified the following threats falling under the five factors reviewed for listing determinations (see section 4 of the Status Review Report, NMFS 2019): Climate change and variability, climate change and vulnerability, dams and other barriers, dredging/channelization, water quality, water withdrawal, directed commercial harvest, retained and discarded incidental catch (including slippage), recreational harvest, scientific research, educational use, disease, predation, inadequacy of existing regulations (international, Federal and state), competition, artificial propagation, hybrids, and landlocked populations. The SRT conducted a qualitative ranking of the severity of each of these threats to alewife and blueback herring rangewide and for each identified DPS. SRT members ranked the threats for the alewife and blueback herring at a rangewide scale and then by each DPS.

The SRT members used the “likelihood point” (Forest Ecosystem Management Assessment Team or FEMAT) method to allow individuals to express uncertainty in determining the contribution to extinction risk of each threat to the species (see Status Review Report, NMFS 2019). Each SRT member was allotted five likelihood points to rank each threat. SRT members individually ranked the severity of each threat through the allocation of these five likelihood points across five ranking criteria ranging from a score of “

very low

contribution” to “

very high

contribution.” A threat was given a rank of

very low

if it is unlikely that the threat contributes significantly to risk of extinction, either by itself or in combination with other threats. That is, it is unlikely that the threat will have population-level impacts that reduce the viability of the species. A threat was ranked as

low

contribution if it is unlikely that the threat contributes significantly to long-term or near future risk of extinction by itself, but there is some concern that it may do so, in combination with other threats. A threat was ranked as

medium

contribution if the threat contributes significantly to long-term risk of extinction, but does not in itself constitute a danger of extinction in the near future. A threat was ranked

high

contribution if the threat contributes significantly to long-term risk of extinction and is likely to contribute to short-term risk of extinction in the near future. Finally, a threat was ranked

very high

contribution if the threat by itself indicates a danger of extinction in the near future. Detailed definitions of the risk scores can be found in the Status Review Report (NMFS 2019).

The SRT also considered the ranking with respect to the interactions with other factors and threats. For example, the SRT found that threats due to the inadequacy of existing regulatory mechanisms may interact with the threat of overutilization and slow population growth rates (a demographic factor) to increase the risk extinction.

SRT members were asked to rank the effect that the threat was currently having on the extinction risk of the species. Each SRT member could allocate all five likelihood points to one

ranking criterion or distribute the likelihood points across several ranking criteria to account for any uncertainty. Each individual SRT member distributed the likelihood points as she/he deemed appropriate, with the condition that all five likelihood points had to be used for each threat. SRT members also had the option of ranking the threat as “0” to indicate that, in their opinion, there was insufficient data to assign a score, or “N/A” if in their opinion the threat was not relevant to the species either throughout its range or for individual stock complexes. When a SRT member chose either N/A (Not Applicable) or 0 (Unknown) for a threat, all five likelihood points had to be assigned to that category only.

During the group discussion, the SRT members were asked to identify other threat(s) or demographic factor(s) that were interacting with the threats or demographic factors to increase the species' extinction risk. As scores were provided by individual SRT members, each individual stated his or her expert opinion regarding each of the threats, and the supporting data on which it was based.

We summarize the threats to alewife and blueback herring below. The SRT's qualitative ranking is identified by rounding the mean ranking score, which is provided in parentheses. For example, a threat falling between the

low

(2) and

medium

(3) rankings with a mean ranking score of 2.1 will be identified as

low

(2.1), while a threat with a mean score of 2.5 will be identified as

medium

(2.5). As noted throughout this section and in the Threats Assessments sections of the Status Review Report, many of the mean ranking scores fall between

very low

(1),

low

(2), and

medium

(3); only a few scores were found to be 3 or higher. A detailed account of the rankings is provided in section 6 of the Status Review Report (NMFS 2019).

A. Habitat Destruction, Modification, or Curtailment

The SRT assessed six different factors that may contribute to destruction, modification or curtailment of habitat: Climate change and variability, climate change and vulnerability, dams and other barriers, dredging/channelization, water quality, and water withdrawal. All threats listed in this category scored in the

low

or

medium

contribution to extinction risk categories. Dams and other barriers and water withdrawal were the highest ranked alewife threats in this category. Dams and other barriers, water quality, and water withdrawal were the highest ranked blueback herring threats in this category.

Climate Change and Variability

Climate change and variability are discussed in section 4.1.1 of the Status Review Report (NMFS 2019); below we provide a summary. The SRT evaluated the available information on climate change and climate variability as summarized in the status review (NMFS 2019). River herring range from Canada through Florida in both marine and freshwater environments, and, in many of these areas, there has been reported environmental change. For example, the climate of the Northeast U.S. continental shelf (U.S. Northeast Shelf) is changing both as a result of anthropogenic climate change and natural climate variability (Hare

et al.

2016a, Hare

et al.

2016b). Ocean temperature over the last decade in the U.S. Northeast Shelf and surrounding Northwest Atlantic waters have warmed faster than the global average (Pershing

et al.

2015). New projections also suggest that this region will warm two to three times faster than the global average from a predicted northward shift in the Gulf Stream (Saba

et al.

2016). Hare

et al.

(2016a) provides a literature summary of how the climate system is changing on the U.S. Northeast Shelf; changes include a high rate of sea-level rise, as well as increases in annual precipitation and river flow, magnitude of extreme precipitation events, and magnitude and frequency of floods. NMFS (2017a) provides a literature summary of climate change drivers in the South Atlantic, which include warming ocean temperatures and sea level rise. The combination of increases in water temperature, coupled with associated changes in water composition, is believed to be one of the most significant risk drivers in the oceans and freshwater habitats in Canada (DFO 2012). Both natural climate variability and anthropogenic-forced climate change will affect river herring. For example, the species is likely to be impacted by climate change through changes in the amount of preferred marine habitat (Lynch

et al.

2015).

Changes to riverine flows and habitat due to extreme events will impact both spawning and early life stages of fish (Tommasi

et al.

2015), while migratory patterns and food availability will be two of many impacts of a changing climate on the ocean stages. As water temperatures continue to increase, river herring's coastal ranges may shrink and shift northward. A contraction of their range could result in natural or anthropogenic catastrophic events having a larger impact on the species' extinction risk.

Alewife

The SRT ranked climate change variability as

low

(2.4) rangewide and

medium

(2.5-2.7) in each DPS. The SRT noted uncertainty makes it difficult to determine the degree to which current limitations in predicting the specific changes that will occur within river herring habitat across the range may impact river herring in the foreseeable future. While mean rankings scores were close rangewide and across the DPSs, the SRT ranked the Aw-Southern New England (

medium,

2.6) and the Aw-Mid-Atlantic (

medium,

2.7) DPSs threat score for climate variability slightly higher. The SRT noted the large estuary ecosystems within the Aw-Southern New England DPS could be severely impacted by river/ocean warming and sea level rise. Additionally, rivers in this DPS are situated in areas with high population densities and with predicted population growth, which will likely decrease the amount of water available for river herring and lead to juveniles being unable to emigrate from nursery habitats. Increased impervious surfaces, as well as anthropogenic responses to rising sea levels are likely to increase flow variability in this DPS. The Aw-Mid-Atlantic DPS constitutes the southern edge of the range. It will likely be the first to see extreme riverine temperatures during spawning and juvenile phases. In addition, many of the known runs in this DPS are in larger river systems, and spawning success will likely be negatively impacted by the extreme spring flows as well as the increased summertime salt intrusions predicted to occur due to climate change.

Blueback Herring

The overall mean blueback herring rangewide score for climate change variability corresponded to a

low

(2.1) ranking rangewide and in the Bb-Canada/Northern New England DPS (

low,

2.2) and Bb-Mid-Atlantic DPS (

low,

2.1). The Bb-Southern Atlantic DPS score for climate change and variability corresponded to a

medium

(2.6) ranking. The Bb-Southern Atlantic DPS constitutes the southern edge of the range and will be the first to experience extreme riverine temperatures during spawning and juvenile phases. In addition, many of the known runs in this DPS are in larger river systems, and spawning success will likely be negatively impacted by the extreme spring flows as well as the increased summertime salt intrusions predicted to

occur due to climate change. The interacting effects of climate change with anthropogenic changes, especially in relation to temperature and flow, carry a potentially significant threat.

Climate Change and Vulnerability

Climate change and vulnerability is discussed in section 4.1.2 of the Status Review (NMFS 2019), and below we provide a summary.

Alewife

The mean scores for climate change and vulnerability for alewife rangewide corresponded to a

medium

(2.6) ranking rangewide and in each DPS (2.7-2.8). While mean ranking scores were close rangewide and across the DPSs, the SRT predicted that alewives in more southern portions of the range were at a slightly higher risk from climate change and vulnerability due to the reduced timeline of predicted impacts from this threat.

Alewife in the Aw-Mid-Atlantic DPS (

medium,

2.8) will likely be the first to see extreme riverine temperatures during spawning and juvenile phases. Additionally, fish at the edges of the range will be most impacted by changes in ocean currents due to climate change, as these fish have the longest ocean migrations to known overwintering areas. Alewife populations could expand northward, however it is unknown if expansion could occur fast enough to preserve genetic integrity of this DPS. This threat is magnified because there will be minimal opportunity to control negative climatic effects as they become more apparent.

Blueback Herring

The overall mean score for climate change and vulnerability corresponded to a

medium

(2.5) ranking rangewide and in each DPS (2.5-2.9). The SRT noted that blueback herring currently persist in warmer habitats than alewives and therefore may be more resilient to warmer temperatures. However, the largest populations of blueback herring appear to be concentrated farther south (Mid-Atlantic) than alewives, therefore the SRT expected the threats from climate change vulnerability to be greater for blueback herring than that experienced by alewives. Early life stage growth/survival and successful spawning events are temperature dependent. Increasing and irregular water temperature regimes will have large impacts at these stages. While mean ranking scores were close rangewide and across the DPSs, the SRT predicted that climate change and vulnerability threats would be greatest in the Bb-Southern Atlantic DPS (

medium,

2.9) because this region will be the first to experience extreme temperatures during spawning and juvenile phases. Numerous shifts in range and other signs of thermal stress have been observed in fish species in this region, and the same can be expected for blueback herring. Being at the southern end of the species' range, one would expect that they are already at the maximum tolerance for temperature effects. Additionally, anthropogenic responses to climate change may include construction of floodgates, berms around cities, and changes in water structures, which may further reduce access to spawning habitat. This threat is magnified because there will be minimal opportunity to control negative climatic effects as they become more apparent.

Dams and Other Barriers

Dams and other barriers are discussed in section 4.1.3 of the Status Review Report (NMFS 2019), and below we provide a summary. Dams and other barriers to upstream and downstream passage (

e.g.,

culverts, tidal and amenity barrages) can block or impede access to habitats necessary for spawning and rearing; can cause direct and indirect mortality from injuries incurred while passing over dams, through downstream passage facilities, or through hydropower turbines; and can degrade habitat features necessary to support essential river herring life history functions. As described in more detail in the Status Review Report (NMFS 2019), dams are also known to impact river herring through various mechanisms, such as habitat alteration, fish passage delays, and entrainment (injury from transport along with the flow of water) and impingement (injury related to colliding with any part of a dam; Ruggles 1980, NRC 2004). River herring can experience delayed mortality from injuries such as scale loss, lacerations, bruising, eye or fin damage, or internal hemorrhaging when passing through turbines, over spillways, and through bypasses (Amaral

et al.

2012). Man-made barriers that block or impede access to rivers throughout the entire historical range of river herring have resulted in significant losses of historical spawning habitat for river herring.

Dams and other man-made barriers have contributed to the historical and current declines in abundance of both blueback herring and alewife populations. While estimates of habitat loss over the entire range of river herring are not available, estimates from studies in Maine show that less than 5 percent of lake spawning habitat and 20 percent of river habitat remains accessible for river herring (Hall

et al.

2010). Mattocks

et al.

(2017) estimated that, due to damming, only 6.7 percent and 7.9 percent of stream habitat in the Connecticut and Merrimack Rivers, respectively, is accessible. The Merrimack and Thames-Pawtucket watersheds had the greatest losses in lake habitat due to damming, with 2.8 percent and 6.4 percent, respectively, of available habitat in 1900. Total biomass lost due to damming from 1630 to 2014 was estimated to be 7 million mt (freshwater) and 2.4 million mt (marine; Mattocks

et al.

2017).

Dams prevent access to historical spawning habitat (

e.g.,

Hall

et al.

2012, Mattocks

et al.

2016), and also alter stream continuity and impair water quality on a number of levels. Dams and other barriers often affect migration rates, influencing both upstream and downstream migration of adults and downstream migration of juveniles. Delayed migration can have serious impacts at both life stages, including impacts on the timing of forage (zooplankton availability) as well as on predator avoidance for juveniles, and preferred spawning temperatures for adults (McCord 2005). Finally, dams often have detrimental nutrient and temperature impacts on downstream river communities affecting both adult and early life stages (MEOEA 2005).

The passage solutions to get fish above dams can have a wide range of efficacy, and in some instances can be quite ineffective. Constructed fish passage also does not restore full riverine continuity or address water quality concerns. Further, both nature-like and technical fishways are engineered and built to function on flows modeled from historical records. Deviations in future flow patterns due to climate change could greatly reduce fishway efficacy.

Alewife

Because dams and other man-made barriers may result in a variety of impacts (discussed above), the overall mean score corresponded to a

medium

(2.9) threat for alewife rangewide ranking and in each of the DPSs (3.1-3.4). While the SRT noted that risks to the two species are similar in nature, there is some evidence, that, of the two river herring species, alewife are better adapted to navigating fishways (K. Sullivan, pers. comm; B.Gahagan, unpublished). Specific barriers vary across the range, and threats related to the Aw- Canada DPS include (1) head-of-tide dams that block access to freshwater habitat and (2) increased prevalence of dams and tidal barrages in

the Bay of Fundy, Minas Basin, and the St. Croix River. The SRT noted that there were limited data on barriers in this region to be able to assess the threat on alewife. A majority of SRT members spread their ranking scores to reflect greater uncertainty regarding the severity of this threat across this region.

The SRT determined that threats to alewife posed by dams and other barriers within the range of the Aw-Northern New England (

medium,

3.3) and the Aw-Southern New England (

medium,

3.4) DPS are more severe compared to those on a rangewide scale. The SRT took into account that these regions were the epicenters of colonial and industrial era dam building, and many of these structures remain in this area.

In the Aw-Northern New England DPS, the ASFMC (2017b) reports dam construction in Maine during the last century isolated many of the inland waters currently stocked with alewives. The historical significance of anadromous fish to these waters was eventually lost, and freshwater fish communities, especially recreationally important game fish, began dominating these habitats. Access to much of the river herring habitat in Maine is still blocked by dams (without upstream fish passage) and other impediments (ASFMC 2017b).

According to ASFMC (2017b), resource agencies in Maine are making progress by installing upstream and downstream fish passage facilities, especially in the Sebasticook River watershed and smaller coastal watersheds. In recent years, rock-ramp or nature-like fishways have become increasingly popular for passing river herring in Maine. In New Hampshire, restoration of diadromous fish populations began with construction of fishways in the late 1950s and continued through the early 1970s by the New Hampshire Fish and Game Department (NHFGD) in the Exeter, Lamprey, Winnicut, Oyster, and Cocheco Rivers in the Great Bay Estuary and the Taylor River in the Hampton-Seabrook Estuary. These fishways re-opened acres of freshwater spawning and nursery habitat for river herring (ASFMC 2017b).

The SRT determined that threats posed by dams and other barriers within the range of the Aw-Southern New England DPS are more severe compared to those on a rangewide scale. According to ASMFC (2017b), there are over 500 dams within the historic range of river herring in Connecticut. Access to habitat previously blocked has been restored through construction of fishways and dam removal, providing more spawning habitat to increase production. Since 1990, 11 dams have been removed and 53 fishways have been constructed throughout the state, with more projects being completed each year.

In Rhode Island, the Division of Fish and Wildlife is partnering with government agencies, NGOs, and private entities on a variety of anadromous habitat restoration projects throughout the state. Projects include constructing new fishways, culvert modifications, and dam removals to enhance spawning and nursery habitat (ASFMC 2017b). Gilbert Stuart and Nonquit Rivers river herring stocks are predominantly alewives. At Gilbert Stuart River, the Alaskan steeppass has been the primary survey site for monitoring adult river herring since 1981. Edwards (2015) reported that the fishway passed over 290,000 fish in 2000, and in recent years estimates of one thousand fish per hour have been observed. The Denil fishway at Nonquit River has been the primary survey site for monitoring adult river herring since 1999. In 1999, the fishway passed over 230,000 fish (Edwards 2015). Buckeye Brook (RI) is a free‐flowing system, and river herring migrate to Warwick Pond without obstruction (ASFMC 2017b).

Despite the aforementioned state-run fish passage solutions, the SRT determined that dams and other barriers are a more pertinent threat to the species in this DPS because alewife are typically more reliant on habitats upstream of dams for reproductive success. The SRT noted that the Aw-Southern New England DPS, like the Aw-Northern New England DPS, has many more dams located closer to the head of tide compared to the other DPSs. As a result, there is limited spawning habitat below these dams, and spawning runs are heavily influenced by management practices (

e.g.

truck and transport, fish lifts, fishway maintenance).

The average score for dams and other barriers in the Aw-Mid-Atlantic DPS (

medium,

3.1) was slightly lower than the two northern DPSs' scores. Specific barrier threats related to this DPS include the presence of man-made barriers within the historic range of river herring. While dams and other barriers to fish migration are widely distributed throughout this DPS, the SRT noted that the existing dams are generally further upstream, leaving relatively more habitat below the dams. As such, the SRT determined that barrier threats related to the Aw-Mid-Atlantic DPS are similar (and possibly less severe) compared to those considered in the rangewide analysis.

In New Jersey, restoration programs for river herring have been limited to the installation of fish ladders and occasional minor trap and transport programs or dam removal. Fish ladders have also been installed in Delaware to restore river herring runs. Twelve tidal streams located within the Delaware River/Bay watershed have fish ladders installed (eight in Delaware and four in New Jersey) at the first upstream dam to allow for river herring passage into the non-tidal impoundments above the dams.

In addition to fish passage installations, dam removal has been the focus of restoration effort is some states. In May 2016, the first dam upstream of the confluence with the Hudson River was removed from the Wynants Kill, a relatively small tributary in Troy, NY, downstream of the Federal Dam. According to ASMFC (2017b) within days of the removal, hundreds of river herring moved past the former dam location into upstream habitat. Subsequent sampling efforts yielded river herring eggs, providing evidence that river herring were actively spawning in the newly available habitat. This dam removal will provide an additional half km (0.3 mi) of spawning habitat for river herring that has not been available for 85 years (ASMFC 2017b). Similarly, Maryland DNR's Fish Passage program has completed 79 projects, reopening a total 735.5 km (457 mi) of upstream spawning habitat in Maryland since 2005.

In Pennsylvania, dam removals along with installation of fish passage have opened up 100 river miles to migratory fish. In 2000 and 2001, river herring were transported to the Conestoga River, a tributary of the Susquehanna River in Pennsylvania. The transported river herring left the Conestoga River, moved up the mainstem Susquehanna River, and were observed at the Safe Harbor Dam. Transports to the Conestoga River included 1,820 alewives in 2000.

Several states within the range of this DPS have implemented restoration programs focused on a range of solutions to fish passage. These solutions include fish passage installation, dam removal, and trap-and-transport initiatives. An abundance of available coastal and estuarine habitat and the presence of long undammed sections of major rivers within the range of this DPS led the SRT to determine that the threat of dams was slightly reduced in this region compared to other DPSs.

Blueback Herring

The overall mean score for dams and other barriers corresponded to a

medium

(3.1) threat ranking rangewide and in each DPS (2.6-3.3).

The SRT ranked the Bb-Canada/Northern New England slightly elevated (

medium,

3.3) compared to the rangewide score. Specific barrier threats related to the Bb-Canada/Northern New England DPS include (1) head-of-tide dams that block access to freshwater habitat, and (2) increased prevalence of dams and tidal barrages in the Bay of Fundy, Minas Basin, and St. Croix River. The SRT took into account that the region was one of the epicenters of colonial and industrial era dam building and that many of these structures remain in this area. According to ASFMC (2017a), dam construction in Maine during the last century isolated many of the inland waters. The historical significance of anadromous fish to these waters was eventually lost, and freshwater fish communities, especially recreationally important game fish, began dominating these habitats.

Access to much of river herring habitat in Maine is still blocked by dams without upstream fish passage and other impediments (ASFMC 2017a). The SRT took into account high mortality associated with the tidal barrages present in the Canadian portion of the range. The SRT noted that, compared to other DPSs, there are many more dams closer to the head of tide in this region. As a result, there is limited spawning habitat below these dams, and spawning runs are heavily influenced by management practices (

e.g.,

truck and transport, fish lifts, fishway maintenance).

According to ASFMC (2017a), resource agencies in Maine are making progress by installing upstream and downstream fish passage facilities, especially in the Sebasticook River watershed and smaller coastal watersheds. In recent years, rock‐ramp or nature‐like fishways have become increasingly popular for passing river herring in Maine. In Maine, blueback herring populations appear to be increasing in the upper regions of the state's watersheds (ASFMC 2017a).

The overall mean score for dams and other barriers corresponded to a

medium

(3.0) threat ranking in the Bb-Mid-Atlantic DPS, slightly lower than the rangewide score. Specific barrier threats related to this DPS include the presence of man-made barriers within the historic range of river herring. While dams and other barriers to fish migration continue to be present in states within the range of this DPS, the SRT noted that the dams that do exist in the region are further upriver, leaving a lot of blueback herring habitat below the dams. As such, the SRT determined that barrier threats related to the Bb-Mid-Atlantic DPS are similar (and possibly less severe) compared to those considered in the rangewide analysis.

Several states within the range of this DPS have implemented restoration programs focused on a range of solutions to fish passage. These solutions include fish passage installation, dam removal, and trap-and-transport initiatives.

In Connecticut, the largest blueback herring run has historically been found in the Connecticut River. Between 1849 and 1955, anadromous fish had no access above the Holyoke Dam, in Holyoke, Massachusetts. Today, the Connecticut River blueback herring population size below the Holyoke Dam is unknown, and there are insufficient historical data to make an estimate. However, according to ASFMC (2017a), there continues to be stable juvenile blueback herring production in recent years with index values comparable to values produced with passage of several hundred thousand of fish at the lift despite the lack of adults passed at the Holyoke Dam. It is unknown as to whether or not the peak values of passage at the Holyoke Dam are a sustainable population for the Connecticut River above the Holyoke Dam, since there is not enough historical population data.

The SRT ranked the threat of dams in Bb-Southern Atlantic DPS as a

medium

(2.6), with a slightly lower score than the rangewide and other DPS scores. An abundance of available coastal and estuarine habitat and the presence of long undammed sections of major rivers within the range of this DPS led the SRT to rank the mean score lower. Specific barrier threats related to this DPS include habitat loss and alterations occurring in tributaries of Winyah Bay, the Santee-Cooper River system, and the Savannah River. The SRT noted that dams in this region are often very high in river systems and in many cases are not likely to block an abundance of blueback herring habitat. The SRT also considered this threat somewhat mitigated in this DPS by the ability of blueback herring to use successfully lotic spawning habitats such as those found below dams. The SRT added that alterations to flow regimes and thermal effects of dams are still of concern, and these concerns may grow in importance with climate change.

Documented impacts of past flow manipulations support the SRT's assessment. In 1938, a large diversion project to move water from the Santee River to the Cooper River was initiated. The project resulted in the construction of the Wilson Dam for flood control on Santee River at km 143, which created Lake Marion, and the construction of Pinopolis Dam at km 77 on the Cooper River, which is a hydroelectric facility with a navigation lock. According to Cooke and Coale (1996), large numbers of blueback herring that utilized the Cooper River before rediversion, switched to the Santee River after rediversion.

Dredging and Habitat Alteration

Dredging and habitat alteration are discussed in section 4.1.4 of the Status Review Report (NMFS 2019), and below we provide a summary.

Wetlands provide migratory corridors and spawning habitat for river herring. The combination of incremental losses of wetland habitat, changes in hydrology, and inputs of nutrients and chemicals over time, can be extremely harmful, resulting in diseases and declines in the abundance and quality of habitat. Wetland loss is a cumulative impact that results from activities related to dredging/dredge spoil placement, port development, marinas, solid waste disposal, ocean disposal, and marine mining. In the late 1970s and early 1980s, the United States was losing wetlands at an estimated rate of 300,000 acres (1,214 square kilometer (km

2

)) per year. The Clean Water Act and state wetland protection programs helped decrease wetland losses to 117,000 acres (473 km

2

) per year between 1985 and 1995. Estimates of total wetland loss vary according to the different agencies. The U.S. Department of Agriculture attributes 57 percent of wetland loss to development, 20 percent to agriculture, 13 percent to creation of deepwater habitat, and 10 percent to forest land, rangeland, and other uses. Of the wetlands lost between 1985 and 1995, the USFWS estimates that 79 percent of wetlands were lost to upland agriculture. Urban development and other types of land use activities were responsible for 6 percent and 15 percent of wetland loss, respectively.

Similar to dams, dredging has affected historical spawning and nursery habitats. Maintenance dredging continues to reduce available habitat, negatively affect water quality, and s change river flows. Although regulated through Federal and state permitting, dredging and shoreline hardening associated with estuary/coastline development are not likely to decrease in spatial extent or scope through the next century. Both practices reduce wetland and nearshore habitats, impacting nursery habitats for river herring, including the macrophytes and

natural streamflow important to nearshore ecosystem health.

Alewife

The SRT ranked the threat of dredging/channelization rangewide and in each DPS as

low

(1.5-1.7). The SRT ranked the threat of dredging in the Aw-Mid-Atlantic DPS (

low,

1.7) to be at slightly higher risk compared to other DPSs. The increased volume of industrial activity and growing number of dredge projects in the Aw-Mid-Atlantic DPS may pose a greater risk to alewife compared to other regions. This DPS encompasses several hundred miles of dredged river channels, as well as the ports of New York and New Jersey, Baltimore Harbor, the Hudson and Delaware Rivers, and the Chesapeake Bay, all of which are subject to regular dredging.

Blueback Herring

The SRT ranked the threat of dredging/channelization as

low

(2.0-2.3) rangewide and in each DPS. For the same reasons stated above for the Aw-Mid-Atlantic DPS, the SRT ranked the threat of dredging slightly higher in the Bb-Mid-Atlantic DPS (

low,

2.3) compared to the blueback herring rangewide and other DPS scores.

Water Quality

Risks associated with changes to water quality are discussed in section 4.1.5 of the Status Review (NMFS 2019), and below we provide a summary.

Nutrient enrichment has become a major cumulative problem for many coastal waters. Nutrient loading results from the individual activities of coastal development, marinas and recreational boating, sewage treatment and disposal, industrial wastewater and solid waste disposal, ocean disposal, agriculture, and aquaculture. Excess nutrients from land-based activities accumulate in the soil, pollute the atmosphere, and groundwater, and move into streams and coastal waters. Nutrient inputs have a direct effect on water quality. For example, nutrient enrichment can stimulate growth of phytoplankton that consumes oxygen when they decay, which can lead to low dissolved oxygen that may result in fish kills (Correll 1987, Tuttle

et al.

1987, Klauda

et al.

1991b); this condition is known as eutrophication.

From the 1950s to the present, increased nutrient loading has made hypoxic conditions more prevalent (Officer

et al.

1984, Mackiernan 1987, Jordan

et al.

1992, Kemp

et al.

1992, Cooper and Brush 1993, Secor and Gunderson 1998). Hypoxia is most likely caused by eutrophication, due mostly to non-point source pollution (

e.g.,

industrial fertilizers used in agriculture) and point source pollution (

e.g.,

urban sewage). In addition to the direct cumulative effects incurred by development activities, inshore and coastal habitats are also threatened by persistent increases in certain chemical discharges. The combination of incremental losses of wetland habitat, changes in hydrology from dams and other barriers, and nutrient and chemical inputs produced over time can be extremely harmful to marine and estuarine biota, including river herring, and can result in diseases and declines in the abundance and quality of the affected resources.

Poor water quality is an important threat in some parts of the species' range. While the large scale acute water quality issues that fueled the creation of the EPA and enactment Clean Water Act have, in many areas, been remedied, the wide impacts of increasing urbanization on the eastern coast of the United States has led to widespread deleterious conditions (

e.g.,

perennial hypoxic and anoxic areas in estuaries and nurseries, eutrophication of freshwater systems, invasive plants and eutrophication altering spawning habitat). Siltation—resulting from erosional land use practices as well as natural disturbances such as hurricanes and/or flood events reduces survival of aquatic vegetation and impacts streamflow. Additionally, climate variability may increase sedimentation in natal rivers, contributing to poorer water quality. These types of effects, often from non-point sources, occur over entire landscapes and are often more difficult to detect, measure, test, and remedy.

Alewife

The overall mean score for water quality corresponded to a

medium

(2.8) ranking rangewide and in each DPS (2.7-3.2). The threat from poor water quality was slightly elevated in the Aw-Mid-Atlantic DPS (

medium

3.2) compared to the rangewide ranking. Many of the major estuaries in the Aw-Mid-Atlantic DPS have documented water quality issues. This DPS also has many growing population centers, and anthropogenic threats are predicted to increase in the foreseeable future. Similar to climate change and variability, the interactions between anthropogenic change and climate change are likely to have severe detrimental effects on water quality, especially water temperature, in regions at the edge of the species' tolerance.

Blueback Herring

The overall mean score for water quality corresponded to a

medium (2.9)

ranking rangewide and in each DPS (2.9-3.2). For the same reasons stated above for the Aw-Mid-Atlantic DPS, the threat of water quality was slightly elevated in the Bb-Mid-Atlantic DPS (

medium,

3.2) compared to the rangewide ranking.

Water Withdrawal/Outfall (Physical)

Water withdrawal facilities and toxic and thermal discharges have also been identified as a threat that is impacting river herring. This threat is discussed in section 4.1.6 of the Status Review Report (NMFS 2019), and below we provide a summary of impacts to river herring.

Water withdrawal facilities impact natural streamflow and result in impingement/entrainment mortality of river herring. Disrupting streamflow can influence migratory timing as well as water quality downstream of the facility. Additionally, water withdrawal (for agriculture or other human activities) degrades or destroys habitat for river herring and poses a significant threat to their survival, especially when coupled with other threats. The threat is likely to increase alongside coastal population growth, which, in conjunction with climate change effects, will likely result in reduced base flows. Water withdrawals and reduced flows can disrupt connectivity between habitats and cause ontogenetic shifts in life history. For alewives and blueback herring to be successful, adults must be able to immigrate to nursery areas, spawn, and then emigrate. Juveniles should have adequate flow to emigrate volitionally. In this way, withdrawals act much like dams and other barriers, even though their effects are less obviously visible.

Alewife

The overall mean score for water withdrawal corresponded to a

medium

(3.2) ranking for alewife rangewide and in each DPS (2.8-3.3). The threat of water withdrawal was slightly reduced in the Aw-Canada DPS (

medium,

2.8) compared to the rangewide ranking. Human population density and the resulting anthropogenic effects on water quality (including animal husbandry and agriculture) and the demands for water withdrawals/diversions are likely less of a threat to the species in this DPS compared to rangewide average.

Because of the lower human population density in the Aw-Northern New England DPS (

medium,

3.0) and corresponding demands on water

resources, there is a diminished risk related to water withdrawals for the species in this region compared to the rangewide average. However, the presence of numerous head-of-tide-dams, where emigration is related to fall flows/water levels from head ponds, remains a threat.

The threat of water withdrawal was slightly elevated in the Aw-Southern New England (

medium,

3.3) DPS compared to the rangewide ranking. Water withdrawal may be higher in the Aw-Southern New England DPS than in other areas due to high population density. Water withdrawal can lead to reduced stream flow, and the water storage capacities of impoundments can further affect temporal variability of stream flow. Similar to populations further north, populations here face an increased risk from artificially manipulated water levels in head ponds, where summer and fall emigration is dependent on adequate stream flows. As water transfers/withdrawals increase in the future, this threat will increase.

The threat of water withdrawal in the Aw-Mid-Atlantic DPS (

medium,

3.2) was similar to the rangewide score for alewife. The SRT noted predicted high population growth rate in this region. Demand for water and anthropogenic pressures will likely increase, resulting in reduced stream flows, which affect juvenile emigration and survival.

Blueback Herring

The overall mean score for water quality corresponded to a

medium

(2.9) ranking for blueback herring rangewide and in each DPS (2.8-2.9). Because of the lower human population density in the Bb-Canada/Northern New England DPS (

medium,

2.8) and corresponding demands on water resources, there is a diminished risk to the species as compared to the rangewide average. Human population density and the resulting anthropogenic effects on water quality (including animal husbandry and agriculture) and the demands and for water withdrawals/diversions are likely less of a threat to the species in this DPS compared to the rangewide average. The threat ranking for water withdrawal in the Bb-Mid-Atlantic DPS (

medium,

2.9) was similar to the rangewide score. The SRT noted that predicted population growth rate in this region will drive future demand for water. As anthropogenic pressures increase, it will negatively affect water quality (hypoxia, eutrophication) in most major estuaries. Further, the interactions between anthropogenic change and climate change are likely to severely affect water quality in portions of the species' range where water quality is already impaired. The threat ranking for water withdrawal in the Bb-Southern DPS (

medium,

2.9) was similar to the rangewide score. The SRT noted that utility water intake may be a larger issue in the Bb-Southern Atlantic DPS compared to water withdrawals rangewide.

B. Overutilization

The SRT assessed five different factors that may contribute to the overutilization of alewife: Directed commercial harvest, retained and discarded incidental catch (including slippage), recreational harvest, scientific research and educational harvest. Although ranked separately, the SRT's assessments for scientific research and educational harvest are discussed in combination below due to the limited information and similarity in overall rankings for these factors.

Directed Commercial Harvest

This threat is discussed in sections 4.2.1 of the Status Review Report (NMFS 2019). Below, we provide a summary of impacts on river herring.

Information on river herring fisheries in the United States was gathered largely from the ASMFC's benchmark assessment of river herring stocks of the U.S. Atlantic Coast from Maine through Florida (ASMFC 2012) and the River Herring Stock Assessment update (ASMFC 2017a). The ASMFC (2017a) report provides an update to the 2012 benchmark assessment of river herring. Both documents were prepared by the River Herring Stock Assessment Subcommittee (SAS) of the ASMFC's Shad and Herring Technical Committee (TC).

Domestic commercial landings of river herring were presented in the stock assessment update by state and by gear from 1887 to 2015 where available (ASMFC 2017a). Landings of alewife and blueback herring were collectively classified as “river herring” by most states. Only a few states had species-specific information recorded for a limited range of years. Commercial landings records were available for each state since 1887, except for Florida and the Potomac River Fisheries Commission (PRFC), which began recording landings in 1929 and 1960, respectively. It is important to note that historical landings presented in the stock assessment do not include all landings for all states over the entire period and are likely underestimates, particularly for the first third of the time series, because not all river landings were reported (ASMFC 2012, ASMFC 2017a).

During 1887 to 1938, reported commercial landings of river herring along the Atlantic Coast averaged approximately 30.5 million lbs (13,835 mt) per year. The majority of river herring landed by commercial fisheries in these early years are attributed to the mid-Atlantic region (NY to VA). The dominance of the mid-Atlantic region is, in part, due to the apparent bias in the spatial coverage of the reported landings. During this early period, landings were predominately from Maryland, North Carolina, Virginia, and Massachusetts (overall, harvest is likely underestimated because landings were not recorded consistently during this time.) Virginia made up approximately half of the commercial landings from 1929 until the 1970s, and the majority of Virginia's landings came from the Chesapeake Bay, the Potomac River, the York River, and offshore harvest.

Severe declines in landings began coast-wide in the early 1970s and, where still allowed, domestic landings are now a fraction of what they were at their peak, having remained at persistently low levels since the mid-1990s. Moratoria were enacted in Massachusetts (commercial and recreational in 2005), Rhode Island (commercial and recreational in 2006), Connecticut (commercial and recreational in 2002), Virginia (for waters flowing into North Carolina in 2007), and North Carolina (commercial and recreational in 2007). As of January 1, 2012, river herring fisheries in states or jurisdictions without an approved sustainable fisheries management plan, as required under ASMFC Amendment 2 to the Shad and River Herring Fishery Management Plan, were closed. (Note as anadromous alosines of the east coast, shad, alewife, and blueback herring are managed under the same Fisheries Management Plan; ASMFC 1987). As a result, prohibitions on harvest (commercial or recreational) were extended to New Jersey, Delaware, Pennsylvania, Maryland, DC, Virginia, Georgia and Florida (ASMFC 2012, ASMFC 2017a,b).

The ASMFC stock assessment committee calculated in-river exploitation rates of the spawning runs for five rivers (Damariscotta River (ME—alewife), Union River (ME—alewife), Monument River (MA—both species combined), Mattapoisett River (MA—alewife), and Nemasket River (MA—alewife)) by dividing in-river harvest by total run size (escapement plus harvest) for a given year (ASMFC 2012). Exploitation rates were highest (range: 0.53 to 0.98) in the Damariscotta River and Union River prior to 1985, while the exploitation was lowest (range: 0.26

to 0.68) in the Monument River. In Massachusetts, exploitation rates of both species in the Monument River and of alewives in the Mattapoisett River and Nemasket River were variable (average = 0.16) and, except for the Nemasket River, declined generally through 2005 until the moratorium was imposed. Exploitation rates of alewives in the Damariscotta River were low (<0.05) during the period from 1993 to 2000, but they increased steadily through 2004 and remained greater than 0.34 through 2008. Exploitation in the Damariscotta River dropped to 0.15 in 2009 to 2010. In-river exploitation of alewives has continued to decline in the Damariscotta River, with the lowest levels occurring in the last five years (2011-2015), with the exception of very low values that occurred in the 1990s (due to lack of harvest) (ASMFC 2017a). Exploitation rates of alewives in the Union River declined through 2005 but have remained above 0.50 since 2007 (ASMFC 2012). In-river exploitation of alewives has remained relatively stable in the Union River, but it did decline to the lowest level of the time series (2010-2015) in the terminal year of the update. Exploitation has essentially ceased on other rivers assessed during the benchmark due to moratoria (MA rivers) (ASMFC 2017a).

The coastwide index of relative exploitation also declined following a peak in the late 1980s and has remained fairly stable over the past decade. In all model runs except for one, exploitation rates coastwide declined. Exploitation rates estimated from the statistical catch-at-age model for blueback herring in the Chowan River (see Status of River Herring in North Carolina in the ASMFC 2017b stock assessment) also showed a slight declining trend from 1999 to 2007, at which time a moratorium was instituted.

There appears to be a consensus that exploitation has decreased in recent times. The stock assessment indicates that the decline in exploitation over the past decade is not surprising because river herring populations are at low levels and more restrictive regulations or moratoria have been enacted by states (ASMFC 2017a).

Fisheries in Canada for river herring are regulated through limited seasons, gears, and licenses. Licenses may cover different gear types; however, few new licenses have been issued since 1993 (DFO 2001). River-specific management plans include closures and restrictions. River herring used locally for bait in other fisheries are not accounted for in river-specific management plans (DFO 2001). DFO estimated river herring landings at just under 25.5 million lbs (11,577 mt) in 1980, 23.1 million lbs (10,487 mt) in 1988, and 11 million lbs (4,994 mt) in 1996 (DFO 2001). The largest river herring fisheries in Canadian waters occur in the Bay of Fundy, southern Gulf of Maine, New Brunswick, and in the Saint John and Miramichi Rivers where annual harvest estimates often exceed 2.2 million lbs (1,000 mt) (DFO 2001).

There is little directed effort on river herring across the Northwest Atlantic. Foreign fleet landings of river herring (reported as alewife and blueback shad) are available through the Northwest Atlantic Fisheries Organization (NAFO). Offshore exploitation of river herring and shad (generally <190 millimeters (mm) (7.5 inches) in length) by foreign fleets began in the late 1960s and landings peaked at about 80 million lbs (36,320 mt) in 1969 (ASMFC 2017a). After the Fishery Conservation and Management Act of 1976 (16 U.S.C. 1801

et seq.

), later retitled the Magnuson Fishery and Conservation and Management Act, and the formation of the Fishery Conservation Zone in 1977, foreign allocation of river herring (to both foreign vessels and joint venture vessels) between 1977 and 1980 was 1.1 million lbs (499 mt). The foreign allocation was reduced to 220,000 lbs (100 mt) in 1981 because of the condition of the river herring resource. In 1985, a bycatch cap of no more than 0.25 percent of total catch was enacted for the foreign fishery. The cap was exceeded once in 1987, and this shut down the foreign mackerel fishery. In 1991, amendment 4 to the Atlantic Mackerel, squid and butterfish fisheries management plan added area restrictions to exclude foreign vessels from within 20 miles (32.2 km) of shore for two reasons: (1) In response to the increased occurrence of river herring bycatch closer to shore and (2) to promote increased fishing opportunities for the domestic mackerel fleet (50 CFR part 611.50; ASMFC 2012). There have been no reported landings by foreign fleets since 1990 (ASMFC 2012, ASMFC 2017). From 1991 to 2015, the only reported catch in Areas 5 and 6 was from the United States.

Alewife

The overall mean score for alewife directed harvest corresponded to a

low

(1.7) ranking rangewide and for all DPS (1.2-2.1). Overutilization for commercial purposes was once considered one of the primary threats to alewife and blueback herring populations. Significant declines have been documented throughout much of the range for both species due to historic fishing pressure and other threats. Directed harvest does still occur in several states (see State Regulations in the Status Review Report for Maine, New Hampshire, New York, the Potomac River Fisheries Commission/District of Columbia, North Carolina, and South Carolina (NMFS 2019), and the fishing occurs during migration to spawning grounds. Amendment 2 to the ASMFC Shad and River Herring Interstate Fishery Management Plan requires states to have a sustainable fishery management plan (SFMP) for each river with a river herring fishery (beginning in 2012). SFMPs must be reviewed by the ASMFC Shad and River Herring Technical Committee for adequate sustainability measures and approved by the ASMFC Management Board. Monitoring is required on all harvested runs in the U.S. Overall, SRT members found that the current directed harvest was well regulated and occurred only on stocks that have demonstrated sustainability.

The threat ranking for directed commercial harvest was higher in the Aw-Canada DPS (

low,

2.1) compared to the rangewide ranking and other DPSs (1.2-1.7). SRT members noted increased uncertainty related to directed harvest levels within Canada. Gibson

et al.

(2017) indicated high annual removal rates where recorded or reported. Additionally, Gibson

et al.

(2017) indicated that previous reporting and collection methods do not provide consistent and accurate information, increasing concern and uncertainty for this threat. Finally, the Department of Fisheries and Oceans still allows some fishing on mixed stocks in Canadian waters, which makes managing impacts to individual populations more difficult.

The threat ranking for directed commercial harvest was slightly higher in the Aw-Northern New England DPS (

low,

1.7) compared to the rangewide ranking. Maine and New Hampshire currently have approved ASMFC sustainable fishing management plans within this DPS. The SRT noted uncertainty related to lack of publicly available commercial harvest data for Maine due to confidentiality; therefore, the total removals and removal rates by river system are largely unknown.

The threat ranking for directed commercial harvest was lower in the Aw-Southern New England DPS (

low,

1.2) compared to the rangewide ranking. There is currently no directed commercial harvest conducted within the Aw-Southern New England DPS. The Nemasket River, in southern Massachusetts, has an ASMFC approved SFMP, but no harvest has occurred to date, largely due to variability in run strength. SRT members noted

uncertainty related to whether further directed harvest of alewife would be permitted within the Aw-Southern New England DPS in the foreseeable future.

The threat ranking for directed commercial harvest was lower in the Aw-Mid-Atlantic DPS (

low,

1.6) compared to the rangewide ranking. New York is the only state to have an approved ASMFC sustainable fishing management plan within this DPS.

Blueback Herring

For the same reasons stated above for alewife, the overall mean score for blueback herring directed harvest corresponded to a

low

(1.8) ranking rangewide and for all DPS (1.5-1.9). The threat ranking for directed commercial harvest was slightly higher in the Bb-Canada/Northern New England DPS (

low,

1.9) compared to the rangewide ranking, for the same reasons stated above for the Aw-Canada and the Aw-Northern New England DPSs including the lack of publicly available commercial harvest data for Maine. Likewise, for the same reason stated above for the Aw-Mid-Atlantic DPS ranking, this threat ranked in the

low

(1.6) category for the Bb-Mid-Atlantic DPS.

Retained and Discarded Incidental Catch (Including Slippage)

River herring are caught incidentally at sea in Federal fisheries targeting other species such as Atlantic herring, squid, and mackerel. In this section, we refer to several terms: Retained incidental catch, discarded incidental catch, slippage and bycatch. Retained incidental catch is the capture and mortality of a non-targeted species. Discarded incidental catch is the portion of the non-targeted catch brought on board and then returned to sea. Slippage is a term used to describe a process in which a boat does not bring the entire catch on board and releases part of the catch into the water, thereby potentially biasing estimates of retained and discarded incidental catch. Bycatch, under National Standard 9, refers to fish that are harvested in a fishery, but that are not sold or kept for personal use (50 CFR part 600).

The magnitude of this ocean catch is highly uncertain because of the short time series of incidental data, underreporting, and a lack of observer coverage. In addition, there are limited data on the stock composition of the incidentally caught fish and, thus, no way to partition estimates of bycatch among river systems. With no estimates of coastwide or regional stock complex abundances, it is also difficult to assess the significance of these removals on the overall population or segments of it (ASMFC 2017a).

Because bycatch occurs in marine waters, and alewife and blueback herring stock complexes overlap in their distribution in the ocean, the retained and discarded incidental catch occurs on a mixed stock complex fishery (that is, there is no “oceanic” stock of alewife or blueback herring, the alewife and blueback herring in the ocean come from all of the stock complexes described herein). Recent studies have also shown that alewife and blueback herring incidentally caught in a number of statistical areas were from several genetic stock complexes (Hasselman

et al.

2016, Palkovacs unpublished). This finding increases the probability that alewife and blueback herring are being exploited from populations that do not meet sustainable harvest requirements approved through the ASMFC.

Several studies estimated river herring retained and discarded incidental catch (Cieri

et al.

2008, Wigley

et al.

2009, Lessard and Bryan 2011). The discard and incidental catch estimates from these studies cannot be directly compared, as they used different ratio estimators based on data from the Northeast Fishery Observer Program (NEFOP), as well as different information to quantity total catch estimates. Cieri

et al.

(2008) estimated the kept (

i.e.,

landed) portion of river herring incidental catch in the Atlantic herring fishery with an estimated average annual landed river herring catch of approximately 71,290 lbs (32.4 mt) for 2005-2007, and the corresponding coefficient of variation (CV) was 0.56. Cournane

et al.

(2012) extended this analysis with additional years of data. Further work is needed to elucidate how the incidental catch of river herring in the directed Atlantic herring fishery compares to total incidental catch across all fisheries. Since this analysis only quantified kept river herring in the Atlantic herring fishery, it underestimates the total catch (kept and discarded) of river herring across all fishing fleets. Wigley

et al.

(2009) quantified river herring discards across fishing fleets that had sufficient observer coverage from July 2007-August 2008 with an estimated approximately 105,820 lbs (48 mt) discarded during the 12 months (July 2007 to August 2008); the estimated precision was low (149 percent CV). This analysis estimated only river herring discards (in contrast to total incidental catch), and noted that midwater trawl fleets generally retained river herring while otter trawls typically discarded river herring.

Lessard and Bryan (2011) estimated an average incidental catch of river herring and American shad of 3.3 million lbs (1,498 mt)/yr from 2000-2008. Lessard and Bryan (2011) analyzed NEFOP data at the haul level; however, the sampling unit for the NEFOP database is at the trip level. Within each gear and region, all data, including those from high volume fisheries, appeared to be aggregated across years from 2000 through 2008. However, substantial changes in NEFOP sampling methodology for high volume fisheries were implemented in 2005, limiting the interpretability of estimates from these fleets in prior years. The total number of tows from the fishing vessel trip report (VTR) database was used as the raising factor to estimate total incidental catch. The use of effort without standardization makes the implicit assumption that effort is constant across all tows within a gear type, potentially resulting in a biased effort metric. In contrast, the total kept weight of all species is used as the raising factor in standardized bycatch reporting methodology (SBRM). SBRM is a methodology to assess the amount and type of bycatch in a fishery. When quantifying incidental catch across multiple fleets, total kept weight of all species is an appropriate surrogate for effective fishing power because it is likely that no trips will exhibit the same attributes. Lessard and Bryan (2011) also did not provide precision estimates, which are imperative for estimation of incidental catch.

The stock assessment update (ASMFC 2017a, b) presents the total incidental catch of river herring updated through 2015 following methods described in the benchmark assessment. These methods were developed during Amendment 14 to the Atlantic Mackerel, Squid and Butterfish (MSB) Fishery Management Plan, which includes measures to address incidental catch of river herring and shads (ASMFC 2017a). The stock assessment update presents the total incidental catch estimates by species.

From 2005 to 2015, the total annual incidental catch of alewife ranged from 36.5-531.7 m (80,469-1,172,198 lbs) in New England and 10.9-295.0 mt (24,030-650,364 lbs) in the Mid-Atlantic region (ASMFC 2017a). The dominant gear varied across years between paired midwater trawls and bottom trawls (ASMFC 2017a). Corresponding estimates of precision exhibited substantial inter-annual variation and ranged from 0-10.6 across gears and regions. Between 2005 and 2015, total annual blueback herring incidental catch ranged from 8.2-186.6 mt

(18,078-411,383 lbs) in New England and 1.4-388.3 mt (3,086-856,055 lbs) in the Mid-Atlantic region (ASMFC 2017a). Across years, paired and single midwater trawls exhibited the greatest blueback herring incidental catches (ASMFC 2017a). Corresponding precision estimates ranged from 0-3.6.

The temporal distribution of incidental catch was summarized by quarter and fishing region for the most recent 10-year period (2005 to 2015). River herring catches occurred primarily in midwater trawls (62 percent, of which 48 percent were from paired midwater trawls and the rest from single midwater trawls), followed by small mesh bottom trawls (24 percent). Catches of river herring in gillnets were negligible. Across gear types, catches of river herring were greater in New England (56 percent) than in the Mid-Atlantic (37 percent). The percentages of midwater trawl catches of river herring were similar between New England (31.3 percent) and the Mid-Atlantic region (30.5 percent). However, catches in New England small mesh bottom trawls were almost three times higher (27 percent) than those from the Mid-Atlantic (10 percent). Overall, the highest quarterly catches of river herring occurred in midwater trawls during Quarter 1 in the Mid-Atlantic (28 percent), followed by catches in New England during Quarter 4 (12 percent) (ASMFC 2017). Quarterly catches in small mesh bottom trawls were highest in New England during Quarter 1 (9 percent) and totaled 5 to 7 percent during each of the other three quarters (ASMFC 2017a). The New England and Mid-Atlantic Fishery Management Councils have adopted measures for the Atlantic herring and mackerel fisheries intended to decrease incidental catch and bycatch of alewife and blueback herring.

Partitioning incidental bycatch in U.S. waters to river of origin or proposed stock complex is an ongoing area of research. Using the 15 microsatellites previously identified (Palkovacs

et al.

2014), Hasselman

et al.

(2016) applied genetic stock identification (GSI) to determine potential regional stock composition of river herring bycatch from the New England Atlantic herring fishery (2012-2013). GSI is a biological tool to determine the composition of mixed stocks and the origin of individual fish. Results showed assignment of over 70 percent to the Aw-Southern New England stock complex for alewife and 78 percent assignment to the Bb-Mid-Atlantic stock complex for blueback herring. The study also gives a marine spatial snapshot of stock complexes in the NOAA statistical areas sampled during 2012-2013, though the authors noted extreme inter-annual variability in both the magnitude and composition of incidental catch, demonstrating that marine distributions for both species are highly dynamic from year to year.

Retained and discarded incidental catch (including slippage) is likely negatively affecting some river herring populations. Slippage was defined as catch that is discarded prior to it being brought aboard a vessel and/or prior to making it available for sampling and inspection by a NOAA-approved observer. The SRT noted that historical declines in river herring abundance were not likely driven by incidental catch, but because of current depleted abundances, incidental catch may impede population growth. As with all of the threats, the true magnitude of incidental catch remains largely unknown because there is no estimate of rangewide abundance. While some monitoring of incidental catch does occur in the Atlantic herring and mackerel fisheries, it has been estimated that monitored fisheries may only constitute half the discards in a given year (Wigley 2009). Further, the contribution of slippage also remains unknown because it is not currently reported.

Alewife

Based on the best available information, noted above, the SRT concluded that the threat from incidental catch corresponded to a

medium

(2.5) contribution to extinction risk to alewife rangewide and in the Aw-Canada DPS (2.7), the Aw-Northern New England DPS (2.4), the Aw-Southern New England DPS (2.7), and the Aw-Mid-Atlantic DPS (2.5). However, the SRT noted the highest uncertainty around the contribution of incidental catch to extinction (expressed in variability and range of scores; see NMFS 2019), due to uncertainties around the estimates of exploitation, future monitoring coverage, and future use of bycatch avoidance programs.

Incidental catch data available from the herring and mackerel fisheries for the years 2012-2015 (Palkovacs, unpublished) showed large proportions of Aw-Mid-Atlantic and Aw-Southern New England alewife captured by mid-water trawl and small mesh bottom trawl in the Atlantic herring/mackerel fisheries compared to other DPSs. Aw-Northern New England alewife made up a minimal amount of indirect catch (Palkovacs, unpublished). Much of the incidental catch from these fisheries was concentrated around Block Island Sound, which is located closest to the Aw-Mid-Atlantic DPS. SRT members noted that the results presented by Palkovacs are representative of the bycatch samples i

This text is long and has been trimmed here. Open the source document for the complete record.