# Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Tidewater Goby

> Briefs, arguments, decisions, and more.

URL: https://www.frixlaw.com/law-library/documents/fr%3A2013-02057

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** February 6, 2013
- **Citation:** 78 FR 8746

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2011-0085; 4500030114]
RIN 1018-AX39
Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Tidewater Goby

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Final rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service, designate critical habitat for the tidewater goby (
Eucyclogobius newberryi
) under the Endangered Species Act of 1973, as amended (Act). In total, approximately 12,156 acres (4,920 hectares) in Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Mateo, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange, and San Diego Counties, California, fall within the boundaries of the critical habitat designation.

DATES:

This rule becomes effective on March 8, 2013.

ADDRESSES:

This final rule and the associated final economic analysis are available on the Internet at
http://www.regulations.gov
at Docket No. FWS-R8-ES-2011-0085, and from the Ventura Fish and Wildlife Office Web site at
http://www.fws.gov/ventura/.
Comments and materials received, as well as supporting documentation used in preparing this final rule, are available for public inspection, by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, CA 93003; telephone 805-644-1766; facsimile 805-644-3958.

The coordinates or plot points or both from which the maps included in the regulation are generated are included in the administrative record for this critical habitat designation and are available at
http://www.fws.gov/ventura/,
at
http://www.regulations.gov
in Docket No. FWS-R8-ES-2011-0085, and at the Ventura Fish and Wildlife Office (see
FOR FURTHER INFORMATION CONTACT
). Any additional tools or supporting information that has been developed for this critical habitat designation will also be available at the Fish and Wildlife Service Web site and Field Office set out above, and may also be included in the preamble and/or at
http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT:

For general information, and information about the final designation in Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, contact Diane K. Noda, Field Supervisor, U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, CA 93003; telephone 805-644-1766; facsimile 805-644-3958. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.

For information about the final designation in Del Norte, Humboldt, and Mendocino Counties, contact Nancy Finley, Field Supervisor, U.S. Fish and Wildlife Service, Arcata Fish and Wildlife Office, 1655 Heindon Road, Arcata, CA 95521; telephone 707-822-7201; facsimile 707-822-8411.

For information about the final designation in Sonoma, Marin, and San Mateo Counties, contact Susan Moore, Field Supervisor, U.S. Fish and Wildlife Service, Sacramento Fish and Wildlife Office, 2800 Cottage Way, Suite W-2605, Sacramento, CA 95825; telephone 916-414-6600; facsimile 916-414-6712.

For information about the final designation in Orange and San Diego Counties, contact Jim Bartel, Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Service Office, 6010 Hidden Valley Road, Suite 101, Carlsbad, CA 92011; telephone 760-431-9440; facsimile 760-431-5901.

SUPPLEMENTARY INFORMATION:

Executive Summary

Why we need to publish a rule.
This is a final rule to revise the designation of critical habitat for the endangered tidewater goby. Under the Endangered Species Act of 1973, as amended (16 U.S.C. 1531
et seq.
) (Act), any species that is determined to be an endangered or threatened species requires critical habitat to be designated, to the maximum extent prudent and determinable. Designations and revisions of critical habitat can only be completed by issuing a rule. In total, approximately 12,156 acres (ac) (4,920 hectares (ha)) of critical habitat for the tidewater goby in California fall within the boundaries of the critical habitat designation.

We designated critical habitat for this species in 2000 and again in 2008. As part of a settlement agreement, we agreed to reconsider the 2008 designation. A proposed rule to revise the 2008 critical habitat designation was published in the
Federal Register
on October 19, 2011 (76 FR 64996). This constitutes our final revised designation for the tidewater goby.

We are making the following changes to the critical habitat designation.
The 2008 final critical habitat designation (73 FR 5920) consisted of 44 units in Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Mateo, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, California, totaling 10,003 ac (4,050 ha). In this final critical habitat designation, we have designated 65 critical habitat units for the tidewater goby throughout its range, including the 44 units designated in the 2008 final rule. These units are essential for the recovery of the tidewater goby as described in the Recovery Plan for the Tidewater Goby (Service 2005a; Recovery Plan).

The basis for our action.
Under the Act, we must determine critical habitat for any endangered or threatened species to the maximum extent prudent and determinable. We are required to base the designation on the best available scientific data after taking into consideration the economic impact, the impact on national security, and any other relevant impact of specifying any particular area as critical habitat. The Secretary of the Department of the Interior (Secretary) may exclude an area from critical habitat if the benefits of exclusion outweigh the benefits of designation, unless the exclusion will result in the extinction of the species.

We prepared an economic analysis.
In order to consider economic impacts, we prepared a new analysis of the economic impacts of the proposed revised critical designation. We announced the availability of the draft economic analysis (DEA) in the
Federal Register
on July 24, 2012 (77 FR 43222), allowing the public to provide comments on our analysis. We considered all comments and information received from the public during the comment period, incorporated the comments as appropriate, and have completed the final economic analysis (FEA) concurrently with this final determination. The economic analysis did not identify any areas with disproportionate costs associated with the designation, and no areas were excluded from the final designation based on economic reasons.

Peer review and public comment.
We sought comments and information from independent specialists to ensure that our critical habitat designation is based on scientifically sound data, assumptions, and analyses. We had invited these peer reviewers to comment on our specific assumptions and

conclusions in the proposed revision of the critical habitat designation. These peer reviewers generally concurred with our methods and conclusions and provided additional information, clarifications, and suggestions to improve this final rule. Information we received from peer review is incorporated in this final revised designation. We also considered all comments and information received from the public during the comment period.

Previous Federal Actions

On April 15, 2009, the Natural Resources Defense Council (NRDC) filed a lawsuit in the U.S. District Court for the Northern District of California challenging a portion of the January 31, 2008, final rule that designated 44 critical habitat units in California (73 FR 5920, January 31, 2008). The lawsuit challenged the Service's failure to include any unoccupied habitat and the exclusion of some occupied habitat from critical habitat designation, and the failure to explain why unoccupied habitat previously included in the 2000 designation was not included in the 2008 designation. In a consent decree dated December 11, 2009, the U.S. District Court: (1) Stated that the 44 critical habitat units should remain in effect; (2) stated that the final rule designating critical habitat was remanded in its entirety for reconsideration; and (3) directed the Service to promulgate a revised critical habitat rule that considers the entire geographic range of the tidewater goby and any currently unoccupied tidewater goby habitat. The consent decree requires that the Service submit proposed and final revised rules to the
Federal Register
no later than October 7, 2011, and November 27, 2012, respectively. We published a proposed revised critical habitat in the
Federal Register
on October 19, 2011 (76 FR 64996). Information on the associated draft economic analysis for the revised proposed critical habitat was published in the
Federal Register
on July 24, 2012 (77 FR 43222). At the request of the Service on November 26, 2012, the U.S. District Court granted a 60-day extension to submit the final revised rule to the
Federal Register
no later than January 26, 2013. By publishing this final revised designation we are complying with the consent decree established by the Court. For additional information on previous Federal actions please refer to the 1994 listing rule (59 FR 5494; February 4, 1994), and previous critical habitat designation (73 FR 5920; January 31, 2008).

Background

It is our intent to discuss in this final rule only those topics directly relevant to the development and designation of critical habitat for the tidewater goby under the Act (16 U.S.C. 1531
et seq.
). For more information on the biology and ecology of the tidewater goby, refer to the final listing rule published in the
Federal Register
on February 4, 1994 (59 FR 5494). For information on tidewater goby critical habitat, refer to the proposed rules to designate critical habitat for the tidewater goby published in the
Federal Register
on August 3, 1999 (64 FR 42250), November 28, 2006 (71 FR 68914), and October 19, 2011 (76 FR 64996); and the subsequent final critical habitat designations published in the
Federal Register
on November 20, 2000 (65 FR 69693), and January 31, 2008 (73 FR 5920); and to our Recovery Plan (Service 2005a), which is available from the Ventura Fish and Wildlife Office (see
ADDRESSES
section or
http://ecos.fws.gov
). Information on the associated draft economic analysis for the proposed rule to revise critical habitat was published in the
Federal Register
on July 24, 2012 (77 FR 43222).

Species Description and Genetic/Morphological Characteristics

The tidewater goby is a small, elongate, gray-brown fish rarely exceeding 2 inches (in) (5 centimeters (cm)) in length. This species possesses large pectoral fins, with the pelvic or ventral fins joined to each other beginning below the chest and belly and from below the gill cover back to just anterior of the anus. Male tidewater gobies are nearly transparent with a mottled brown upper surface. Female tidewater gobies develop darker colors, often black, on the body and dorsal and anal fins. The tidewater goby is a short-lived species; the lifespan of most individuals appears to be about 1 year (Irwin and Soltz 1984, p. 26; Swift
et al.
1989, p. 4; Hellmair 2011, p. 5).

Various genetic markers demonstrate that pronounced differences exist in the genetic structure of the tidewater goby, and that tidewater goby populations in some locations are genetically distinct. A study of mitochondrial DNA and cytochrome b (molecular material used in genetic studies) sequences from tidewater gobies that were collected at 31 locations throughout the species' geographic range has identified six major phylogeographic (historical processes that may be responsible for the current geographic distributions) units (Dawson
et al.
2001, p. 1171). These six regional units are the basis for the recovery units in the Recovery Plan (Service 2005a, p. 30), and include the following areas: (1) Tillas Slough (Smith River) in Del Norte County to Lagoon Creek in Mendocino County (North Coast (NC) Recovery Unit); (2) Salmon Creek in Sonoma County to Bennett's Slough in Monterey County (Greater Bay (GB) Recovery Unit); (3) Arroyo del Oso to Morro Bay in San Luis Obispo County (Central Coast (CC) Recovery Unit); (4) San Luis Obispo Creek in San Luis Obispo County to Rincon Creek in Santa Barbara County (Conception (CO) Recovery Unit); (5) Ventura River in Ventura County to Topanga Creek in Los Angeles County (Los Angeles-Ventura (LV) Recovery Unit); and (6) San Pedro Harbor in Los Angeles County to Los Peñasquitos Lagoon in San Diego County (South Coast (SC) Recovery Unit).

A more recent study to gather genetic distribution data for the tidewater goby used a panel of novel microsatellite loci (repeating sequences of DNA) assessed in a first-order (unbound strands of DNA) survey across its range (Earl
et al.
2010, p. 104). More specifically, Earl
et al.
(2010, p. 103) described 19 taxon-specific microsatellite loci, and assessed genetic variation across the tidewater goby's range relative to genetic subdivision. The study concluded: (1) Populations of tidewater goby in northern San Diego County form a highly divergent clade (a genetically related group) with reduced genetic variation that appears to merit status as a separate species; (2) populations along the mid-coast of California are subdivided into regional groups, which are more similar to each other than different, contrary to conclusions from previous mitochondrial sequence-based studies (Dawson
et al.
2001, p. 1176); and (3) that tidewater goby dispersal during the Pleistocene/Holocene sea level rise (approximately 7,000 years ago), followed by increased isolation during the Holocene, formed a star phylogeny (recent population formed from a common ancestor) with geographic separation in the northernmost populations and some local differentiation (Earl
et al.
2010, p. 103). Genetic diversity among populations within a species may be important to long-term persistence because it represents the raw material for adapting to differing local conditions and environmental stochasticity (Frankham 2005, p. 754).

The conclusion that the populations of the tidewater goby in the North Coast Recovery Unit formed as a result of a single recent episode of colonization of newly formed habitats is supported by McCraney
et al.
(2010, p. 3325). They compared genetic variation of 13

naturally and artificially fragmented populations of the tidewater goby in northern California, including 8 Humboldt Bay populations and 5 coastal lagoon populations (Lake Earl, Stone Lagoon, Big Lagoon, Virgin Creek, and Pudding Creek), and reached similar conclusions to Earl
et al.
(2010, p. 113). McCraney
et al.
(2010, p. 3325) also concluded that natural and artificial habitat fragmentation caused marked divergence among the tidewater goby in the North Coast populations. Their study showed that Humboldt Bay populations, due to isolation by manmade barriers, exhibited very high levels of genetic differentiation between populations, extremely low levels of genetic diversity within populations, and no migration among populations. They concluded that this pattern makes the Humboldt Bay populations of tidewater goby vulnerable to extirpation because artificial fragmentation and its resulting genetic differentiation between subpopulations, extremely low levels of genetic diversity within subpopulations, and lack of migration among the subpopulations reduces fitness and adaptive potential of a subpopulation (McCraney
et al.
2010, p. 3325). In contrast, the study found that, while coastal lagoon populations also exhibited very high levels of genetic differentiation between populations, these populations displayed substantial levels of genetic diversity within populations indicating occasional migration among lagoons (McCraney
et al.
2010, p. 3325). Populations in all coastal lagoons, with the exception of Lake Earl in Del Norte County, appear to be stable and genetically healthy (McCraney
et al.
2010, p. 3325). The Lake Earl population exhibited reduced levels of genetic diversity in comparison to similar coastal lagoon populations (McCraney
et al.
2010, p. 3324). McCraney
et al.
(2010, p. 3324) suspects that the reduced genetic diversity detected within Lake Earl is likely due to repeated population bottlenecks (reduced genetic diversity due to reduced population size) resulting from regular artificial breaching of the sandbar at the lagoon mouth.

To summarize, the conclusions from these studies are:

(1) The species can be divided into six phylogeographic units based upon genetic similarities and differences.

(2) The tidewater goby to the south of the gap between Los Angeles and Orange Counties is probably a separate species from populations to the north based on its divergent genetic makeup.

(3) Natural and anthropogenic barriers have contributed to genetic differentiation among populations.

(4) Although genetic differences occur between populations north of the Los Angeles-Orange County line, they are not as divergent as those populations further south.

(5) Some north coast populations exhibit significantly reduced genetic diversity, reduced growth potential, and reduced duration of spawning period. These populations appear to be vulnerable to extirpation.

Metapopulation Dynamics

Local populations of tidewater goby are best characterized as metapopulations (Lafferty
et al.
1999a, p. 1448; Smith,
in litt.
2012). How a metapopulation functions through time is an important factor in the conservation of the tidewater goby and thus it is an important consideration in the designation of critical habitat. As such, using information primarily from Groom
et al.
(2006, pp. 216-219, 383-384, 424-428) and Primack (2006, pp. 285-287) and elsewhere as noted below, we present the general concept of metapopulation dynamics followed by a discussion of its application to the tidewater goby.

A metapopulation, in short, is a population of populations (often referred to as subpopulations). However, because of variations in the rates of birth, death, immigration, and emigration, each population is not static over time; as such, the interplay of a metapopulation's constituent populations results in a dynamic process of metapopulation maintenance. Thus, definitions of the term
metapopulation
within the scientific literature often incorporate the dynamic interaction of subpopulations, according to Groom
et al.
(2006, p. 706) a metapopulation consists of: “A network of semi-isolated populations with some level of regular or intermittent migration and gene flow among them, in which individual populations may go extinct [become extirpated] but can then be recolonized from other populations.” The Recovery Plan also incorporates interpopulation interaction in its definition of metapopulation: “several to many subpopulations [of] tidewater goby that are close enough to one another that dispersing individuals could be exchanged” (Service 2005a, p. A-3).

Regarding this discussion, two points in particular are important to note in metapopulations: (1) Variability within subpopulations, and (2) connectivity between them through dispersing individuals. As mentioned above, subpopulations at different locations within a metapopulation vary over time. Because of intrinsic and extrinsic factors (Soulé and Simberloff 1986, pp. 27-28), some populations at given locations have high rates of growth in some years and other populations decline or even become extirpated. Yet, because subpopulations within a metapopulation are biologically connected through dispersing individuals, high-productivity subpopulations (sources) may augment the population size in low-productivity subpopulations (sinks); moreover, dispersing individuals may even recolonize extirpated areas. In this way, a metapopulation as a whole maintains a greater level of stability over time than its constituent subpopulations—in effect, metapopulation dynamics dampen the effects of variability. In addition to bolstering subpopulations or recolonizing extirpated areas, dispersing individuals are also important for maintaining gene flow between subpopulations (genetic connectivity) and thereby reducing the risk that certain alleles may be lost as a result of the extirpation of a subpopulation.

Moreover, the greater the number of constituent subpopulations within a metapopulation, the greater the likelihood the effects of variability will be attenuated in that metapopulation. In short, because of metapopulation dynamics, extirpation of a subpopulation is not necessarily permanent. This results in a situation where constituent subpopulations “blink out” and “blink on” over time. A metapopulation persists through time because the rate of extirpation in subpopulations is balanced by the rate of recolonization. As a result, occupancy of an area may change over time.

The balance discussed above is in large part dependent upon dispersal of individuals. Ultimately, when the rate of recolonization is reduced or eliminated, the effects of the threats are no longer dampened by metapopulation dynamics. In such a case, each constituent subpopulation becomes increasingly or completely independent, and extirpation of such a subpopulation is likely to be permanent.

The pattern of extirpation and recolonization observed in the tidewater goby suggests that some tidewater goby populations exhibit a metapopulation dynamic where some populations survive or remain viable by continually exchanging individuals and recolonizing after occasional extirpations (Doak and Mills 1994, p. 619). Individual populations of tidewater goby occupy coastal lagoons and estuaries that are separated from each other by land and, in most cases, are separated from the open ocean by

sandbars, or other barriers. Very few tidewater gobies have ever been captured in the marine environment (Swift
et al.
1989, p. 7), which suggests that this species rarely occurs in the open ocean. Studies of the tidewater goby suggest that some populations persist on a consistent basis, while other populations appear to experience intermittent extirpations (local extinctions) (Lafferty
et al.
1999a, p. 1452). These extirpations may result from one or a series of factors, such as the drying up of the lagoon during prolonged droughts (Lafferty
et al.
1999a, p. 1451). Some of the areas where the tidewater goby has been extirpated apparently have been recolonized by nearby populations (those within approximately 6 miles (mi) (10 kilometers (km))) (Lafferty
et al.
1999a, p. 1451; Smith,
in litt.
2012). However, genetic research has revealed tidewater gobies are capable of dispersing up to 30 mi (48 km) (Jacobs
et al.
2005, p.52).

Lafferty
et al.
(1999b, p. 618) monitored the postflood persistence of several tidewater goby populations in Santa Barbara and Los Angeles Counties after the heavy winter floods of 1995. All of the monitored populations persisted after the floods, and no significant changes in population sizes were noted (Lafferty
et al.
1999b, p. 621). However, tidewater goby apparently colonized Cañada Honda in Santa Barbara County after one flood event (Lafferty
et al.
1999b, p. 621). This suggests that flooding—where the barrier between the lagoon and the open ocean is breached and tidewater goby individuals are washed out to sea—may sometimes have a positive effect, forcing the dispersal of individuals and thereby allowing for recolonization of habitats where a tidewater goby population has become extirpated or allowing for genetic exchange between extant populations.

Historical records and survey results for several areas occupied by the tidewater goby are available (Swift
et al.
1989, pp. 18-19; Swift
et al.
1994, pp. 8-16). These studies suggest that the persistence of tidewater goby populations is related to habitat size, configuration, location, and proximity to human development. In general, the most stable and persistent tidewater goby populations tend to occur in lagoons and estuaries that are more than 2.5 ac (1 ha) in size, and that have remained relatively unaffected by human activities (Lafferty
et al.
1999a, pp. 1450-1453). Conversely, some habitats less than 2.5 ac (1 ha) in size have tidewater goby populations that persist on a regular basis, such as Cañada del Agua Caliente in Santa Barbara County (Swift
et al.
1997, p. 3). We also note that some systems that are affected or altered by human activities also have relatively large and stable populations; examples include Pismo Creek in San Luis Obispo County, the Santa Ynez River in Santa Barbara County, and the Santa Clara River in Ventura County. The best available information suggests that the lagoons and estuaries with persistent tidewater goby populations likely serve as source populations that provide individuals that colonize adjacent locations with intermittent populations (Lafferty
et al.
1999a, p. 1452). However, a rangewide metapopulation viability analysis for the tidewater goby has not been conducted; data from such a study would help inform which tidewater goby populations are source populations and which are sinks, and allow for the development of metapopulation-based recovery objectives for the species. Until data on demography and dynamics of tidewater goby metapopulations are available, the Recovery Plan for the species calls for interim objectives that emphasize consistent occupancy of habitat capable of sustaining viable tidewater goby populations (Service 2005a, p. 39).

Distribution

The known geographic range of the tidewater goby is limited to the coast of California (Eschmeyer
et al.
1983, p. 262; Swift
et al.
1989, p. 12). The species historically occurred from locations 3 mi (5 km) south of the California—Oregon border (Tillas Slough in Del Norte County) to 44 mi (71 km) north of the United States—Mexico border (Agua Hedionda Lagoon in San Diego County). The available documentation (Eschmeyer
et al.
1983, p. 262; Swift
et al.
1989, p. 12) suggests that the northernmost extent of the current geographic range has not changed over time. Tidewater goby historically occurred in Agua Hedionda Lagoon, but the site is currently considered to be unoccupied. The species' southernmost, known, currently occupied locality is the San Luis Rey River, 5 mi (8 km) north of Agua Hedionda Lagoon in San Diego County. Although the northernmost extent of the tidewater goby's range has not changed and the southernmost extent has retracted by only 5 mi (8 km), its overall distribution has become patchy and fragmented along the coast. However, as discussed above in the
Metapopulation Dynamics
section, the occupancy of an area may change overtime and, when determining occupancy of an area, we first look at the rangewide occupancy for the species and then consider potential connectivity and source areas at the subpopulation or unit level.

The tidewater goby appears to be naturally absent from several long (50 to 135 mi (80 to 217 km)) stretches of coastline lacking lagoons or estuaries, where steep topography or swift currents may prevent the tidewater goby from dispersing between adjacent locations (Swift
et al.
1989, p. 13; Earl
et al.
2010, p. 104). One such gap occurs between the Eel River in Humboldt County and the Ten Mile River in Mendocino County. A second gap exists between Davis Lake in Mendocino County and Salmon Creek in Sonoma County. Another large natural gap exists between Monterey County and Arroyo del Oso in San Luis Obispo County. Habitat loss and other anthropogenic-related factors have resulted in the tidewater goby's absence from several locations where it historically occurred; the extirpation of tidewater goby from some of these locations has expanded gaps and created additional gaps in the species' geographic distribution (Capelli 1997, p. 7). Two examples of extirpations are San Francisco Bay in San Francisco and Alameda Counties, and Redwood Creek and Freshwater Lagoon in Humboldt County.

Swift
et al.
(1989, p. 13) reported that, as of 1984, tidewater goby occurred or had been known to occur at 87 locations, including those at the extreme northern and southern end of the species' historical geographic range. An assessment of the species' distribution in 1993, using records that were limited to the area between the Monterey Peninsula in Monterey County and the United States—Mexico border, found the tidewater goby occurring at four additional sites since 1984 (Swift
et al.
1993, p. 129). Other locations have been identified since 1993, and to date the tidewater goby has been documented to have occurred at 135 locations. Of these 135 locations, 21 (16 percent) are no longer occupied by the tidewater goby.

Habitat

The lagoons, estuaries, backwater marshes, and freshwater tributaries that tidewater goby occupy are dynamic environments subject to considerable fluctuations on a seasonal and annual basis. Typically, a sandbar forms in the late spring as flow into a lagoon declines enough to allow the ocean surf to build up sand at the mouth of the lagoon. Winter rains and increased stream flows may bring in considerable sediment and dramatically affect the bottom profile and substrate composition of a lagoon or estuary. Fine mud and clay either move through the

lagoon or estuary, or settle out in the backwater marshes, while heavier sand is left behind. High flows associated with winter rains can scour out the lagoon bottom to a lower level, especially after breaching the mouth sandbar, with sand building up again after flows decline. These dynamic processes result in wetland habitats that, over time, move both up or down coast, and inland or coastward.

The horizontal extent of the lentic (pondlike) wetland habitat associated with a particular tidewater goby locality varies and is affected, in part, by local precipitation patterns and topography. In coastal areas where the topography is steep and precipitation relatively low, such as areas adjacent to the Santa Ynez Mountains in Santa Barbara County, the habitats occupied by tidewater goby may be a few acres in size and only extend a few hundred feet inland from the ocean, with backwater marshes small or absent. In other coastal settings where topography is less steep and precipitation is more abundant, surface streams are larger, and coastal lagoons or estuaries may be hundreds of acres in size and extend many miles inland and may include extensive backwater marshes (for example, Lake Earl in Del Norte County and Ten Mile River in Mendocino County). Some occupied locations, such as Bennett's Slough in Monterey County, receive water from upstream areas on a year-round basis. Such locations tend to possess wetland habitats that are larger and can extend inland for several miles. Other occupied locations do not possess stream channels or tributaries that provide a considerable amount of water throughout the summer or fall months. Such locations, such as Little Pico Creek in San Luis Obispo County, tend to possess wetland habitats that extend only a short distance inland.

Reproduction

The tidewater goby has been observed to spawn in every month of the year except December (Swenson 1999, p. 107). Reproduction tends to peak in late April or May to July, and can continue into November depending on seasonal temperature and rainfall. Hellmair's (2011) findings reveal year-round reproduction for some tidewater goby populations that have high genetic diversity and restricted spawning periods for other populations with low genetic diversity. Swenson (1995, p. 31) has documented the spawning activities of adult fish or the presence of egg clutches at water temperatures between 48 and 77 degrees Fahrenheit (°F) (9 and 25 degrees Celsius (°C)). Spawning tidewater gobies have been documented to breed in water salinities between 1 and 30 parts per thousand (ppt) (Swenson 1995, p. 31, Smith,
in litt.
2012). However, tidewater gobies prefer salinities less than 10 ppt (Moyle 2002, p. 431).

Threats

The final listing rule for the tidewater goby published in 1994 (59 FR 5494; February 4, 1994) and the 5-year review (Service 2007) state that this species is threatened, or potentially threatened, by: (1) Coastal development projects that result in the loss or alteration of coastal wetland habitat; (2) water diversions and alterations of water flows upstream of coastal lagoons and estuaries that negatively impact the species' breeding and foraging activities; (3) groundwater overdrafting; (4) channelization of the rivers where the species occurs; (5) discharge of agricultural and sewage effluents; (6) cattle grazing and feral pig activity that results in increased sedimentation of coastal lagoons and riparian habitats, removal of vegetative cover, increased ambient water temperatures, and elimination of plunge pools and undercut banks utilized by the tidewater goby; (7) introduced species that prey on the tidewater goby (e.g., bass (
Micropterus
spp.), rainwater killifish (
Lucania parva
), and crayfish (
Cambarus
spp.)); (8) the inadequacy of existing regulatory mechanisms; (9) drought conditions that result in the deterioration of coastal and riparian habitats; and (10) competition with introduced species, such as the yellowfin goby (
Acanthogobius flavimanus
) and chameleon goby (
Tridentiger trigonocephalus
). Lastly, loss of genetic diversity has also been recently shown to threaten populations of tidewater goby (McCraney
et al.
2010, Hellmair 2011).

Climate Change

Our analyses under the Endangered Species Act include consideration of ongoing and projected changes in climate. The terms “climate” and “climate change” are defined by the Intergovernmental Panel on Climate Change (IPCC). “Climate” refers to the mean and variability of different types of weather conditions over time, with 30 years being a typical period for such measurements, although shorter or longer periods also may be used (IPCC 2007, p. 78). The term “climate change” thus refers to a change in the mean or variability of one or more measures of climate (e.g., temperature or precipitation) that persists for an extended period, typically decades or longer, whether the change is due to natural variability, human activity, or both (IPCC 2007, p. 78). Various types of changes in climate can have direct or indirect effects on species. These effects may be positive, neutral, or negative and they may change over time, depending on the species and other relevant considerations, such as the effects of interactions of climate with other variables (e.g., habitat fragmentation) (IPCC 2007, pp. 8-14, 18-19). In our analyses, we use our expert judgment to weigh relevant information, including uncertainty, in our consideration of various aspects of climate change.

In addition to the threats listed above, tidewater goby populations are threatened by global climate change. Sea level rise and hydrological changes associated with climate change are having and will continue to have significant effects on tidewater goby habitat over the next several decades.

Sea level rise is a result of two phenomena: thermal expansion (increased sea water temperatures) and global ice melt (Cayan
et al.
2006, p. 5, National Research Council 2012, p. 33). Between 1897 and 2006, the observed sea level rise has been approximately 2 millimeters (0.08 in) per year, or a total of 20 cm (8 in) over that period (Heberger
et al.
2009, p. 6). Older estimates projected that sea level rise along the California coast would follow a similar rate and reach 0.2-0.6 meters (m) (0.7-2 feet (ft)) by 2100 (IPCC 2007). Recent observations and models indicate that those projections were conservative and ignored some critical factors, such as melting of the Greenland and Antarctica ice sheets (Heberger
et al.
2009, p. 6; Rahmstorf 2010, p. 44). Heberger
et al.
(2009, p. 8) have updated the sea level rise projections for California to 1.0-1.4 m (3.3-4.6 ft) by 2100, while Vermeer and Rahmstorf (2009, p. 21530) calculate the sea level rise globally at 0.57-1.9 m (2.4-6.2 ft); in both cases, recent estimates were more than twice earlier projections. Combined with California's normal dramatic tidal fluctuations and coincidental storms—the severity of the latter is projected to increase with more frequent El Niño Southern Oscillations due to increasing surface water temperature (Cayan
et al.
2006, p. 17)—the effects of sea level rise are expected to result in greater coastal erosion (Scripps Institution of Oceanography 2012, p. 24) and reach farther inland than previously anticipated (Cayan
et al.
2006, pp. 48-49; Cayan
et al.
2009, p. 40).

Park
et al.
(1989, pp. 1-52) projected that, of the saltmarshes along the coast of the contiguous United States: 30 percent would be lost with a 0.5-m (1.6-

ft) sea level rise, 46 percent with a 1-m (3.3-ft) sea level rise, 52 percent with a 2-m (6.6-ft) sea level rise, and 65 percent with a 3-m (9.8-ft) sea level rise. While we cannot project directly to California from the estimates of Park
et al.
(1989, p. 1-52) who focused on the east coast and Gulf coast of the United States, we can anticipate that, with a projected global sea level rise of up to almost 2 m (6.6 ft), 46 to 65 percent of the remaining coastal saltmarshes in California would be lost by 2100. Applying Heberger
et al.'s
(2009, p. 8) more conservative estimates for California to Park
et al.'
s calculations, with a projected sea level rise of 1.0-1.4 m (3.3-4.6 ft) by 2100, somewhere between 46 and 52 percent of the coastal saltmarshes in California would be inundated.

For the tidewater goby, sea level rise estimates based on more recent projections, combined with the effects of storms and tidal fluctuations, have the potential to transform coastal lagoons into primarily saltwater bodies (Cayan
et al.
2006, pp. 34, 48-49). More severe storms that are likely to result from climate change (Cayan
et al.
2006, p. 17), especially along the northern coast of California (Cayan
et al.
2009, p. 38), combined with the higher than normal sea levels, will breach lagoon mouths more frequently from the ocean side, allowing more saltwater intrusion, altering the physical conditions of the tidewater goby's habitat (increased salinity), and disrupting the tidewater goby's normal reproduction process that requires closed lagoons and a specific range of salinities. The conversion of coastal lagoons and estuaries from brackish to primarily saltwater bodies, in addition to the inundation and breaching of sandbars, would eliminate habitat for tidewater goby in many areas. For a species that exhibits metapopulation dynamics and was listed as endangered due to past habitat loss and fragmentation of metapopulations, the projection of further habitat loss due to sea level rise raises concerns for the tidewater goby's survival over the long term.

Summary of Changes From Previously Designated Critical Habitat and 2011 Proposed Revised Critical Habitat Designation

In this section we present the differences between what was designated in the January 31, 2008, final rule (73 FR 5920), what was included in the October 19, 2011, proposed rule (76 FR 64996), and what is included in this final designation.

The 2008 final critical habitat designation (73 FR 5920, January 31, 2008) consisted of 44 units in Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Mateo, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, California, totaling 10,003 ac (4,050 ha). In this final critical habitat designation, we have designated 65 critical habitat units for the tidewater goby throughout its range, including the 44 units designated in the 2008 final rule. Of the 21 new units included in this designation, 5 units are within the geographical area occupied at the time of listing and 16 units are outside the geographical area occupied at the time of listing (Table 1). Of the 16 new units that are outside the geographical area occupied at the time of listing, 8 units are currently occupied (Table 1). These 16 units are essential for the conservation of the tidewater goby as described in the Recovery Plan (Service 2005a).

This final critical habitat designation for the tidewater goby also differs from our October 19, 2011 (76 FR 64996) proposed rule. We reviewed and considered comments from the public and peer reviewers on the proposed revised designation, and from the public on the draft economic analysis published on July 24, 2012 (77 FR 43222). As a result of comments received, our final designation differs from our proposed designation, as follows:

(1) Based on information we received in comments regarding our proposal to designate unoccupied units, we revised the language in the
Criteria Used To Identify Critical Habitat
section of this final rule to clarify our intent. In the proposed rule we stated that, “We also are proposing to designate specific areas outside the geographical area occupied by the species at the time of listing that were historically occupied, but are presently unoccupied, because such areas are essential for the conservation of the species” (p. 65004). However, we did not intend to limit the proposal to only specific areas outside the geographical area occupied by the species at the time of listing that were historically occupied. Our intent was to consider all areas that are essential for the conservation of the species and not only those that were known to be historically occupied; we were in error when we included “that were historically occupied, but are presently unoccupied” in the proposed rule. We proposed to designate six units that are outside the geographical area occupied by the species at the time of listing where the tidewater goby has not been detected historically. These units are: Pomponio Creek (SM-2), Bolinas Lagoon (MAR-5), Arroyo de la Cruz (SLO-1), Oso Flaco Lake (SLO-12), Arroyo Sequit (LA-1), and Zuma Canyon (LA-2). Subsequent to the publication of the proposed rule, tidewater gobies have been detected in Pomponio Creek (SM-2) (Rischbieter,
in litt.
2012). These units are essential for the conservation of the tidewater goby as described in the Recovery Plan (Service 2005a) and the unit descriptions below.

(2) We revised and expanded our discussion on tidewater goby metapopulation dynamics and provided a discussion on the effects of climate change on the tidewater goby and its habitat.

(3) Based on comments received from the County of Santa Barbara pertaining to unit SB-12, Arroyo Paredon Creek, we reassessed the topography of the unit as originally proposed and determined that the gradient of the upper portion of the unit was a barrier to tidewater gobies. The unit now includes approximately 3 ac (1 ha), a net decrease of approximately 1 ac (less than 1 ha) from the proposal.

Critical Habitat

Background

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features.

(a) Essential to the conservation of the species and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) of the Act would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features (1) which are essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical or biological features within an area, we focus on the principal biological or physical constituent elements (primary constituent elements that provide for a species' life-history processes, such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type) that, under the appropriate species-specific circumstances, are essential to the conservation of the species.

Under the second prong of the Act's definition of critical habitat, we designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. For example, we may determine that an area currently occupied by the species but outside the geographical area occupied at the time of listing is essential for the conservation of the species and include it in the critical habitat designation. We designate critical habitat in areas outside the geographical area occupied by a species only when a designation limited to its range would be inadequate to ensure the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the
Federal Register
on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the Recovery Plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, other unpublished materials, or experts' opinions or personal knowledge.

Habitat is dynamic, and species may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to insure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) the prohibitions of section 9 of the Act if actions occurring in these areas may affect the species. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of this species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

Physical or Biological Features

In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species at the time of listing to designate as critical habitat, we consider the physical or biological features essential to the conservation of the species and which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historical, geographical, and ecological distributions of a species.

We derive the specific physical or biological features essential to tidewater goby conservation from studies of this species' habitat, ecology, and life history as described in the Critical Habitat section of the proposed rule to revise critical habitat published in the
Federal Register
on October 19, 2011 (76 FR 64996), and in the information presented below. Additional information can be found in the final listing rule published in the
Federal Register
on February 4, 1994 (59 FR 5494), and the Recovery Plan for the tidewater goby (Service 2005a). We have determined that the tidewater goby requires the following physical or biological features:

Space for Individual and Population Growth and for Normal Behavior

Saline Aquatic Habitat

The tidewater goby occurs in lagoons, estuaries, and backwater marshes that are adjacent to the Pacific Ocean (Wang 1982, p. 14; Irwin and Soltz 1984, p. 27; Swift
et al.
1989, p. 1; Swenson 1993, p. 3; Moyle 2002, p. 431). The tidewater goby is most commonly found in waters with relatively low salinities, that is, less than 10 to 12 parts per thousand (ppt) (Swift
et al.
1989, p. 7) (see below for further details). This species can, however, tolerate a wide range of salinities and is frequently found in coastal habitats with higher salinity levels (Swift
et al.
1989, p. 7; Worcester 1992, p. 106; Swift
et al.
1997, pp. 15-22); the species has been collected in salinities as high as 42 ppt (Swift
et al.
1989, p. 7). The species' tolerance of high salinities likely enables it to withstand some exposure to the marine environment, which has a salinity of about 35 ppt, allowing it to recolonize nearby lagoons and estuaries following flood events (Swift
et al.
1989, p. 7). However, tidewater gobies have only rarely been captured in the marine environment (Swift
et al.
1989, p. 7), and they appear to enter the ocean only when flushed out of lagoons, estuaries, and river mouths by storm events or human-caused breaches of sand bars. Salinity tolerance studies indicate that larval stages are largely intolerant of high salinities whereas adult tidewater gobies can tolerate higher salinities. These findings suggest spawning in saline conditions is unlikely to be productive and that migration among subpopulations is most likely the result of adult tidewater goby movement (Kinziger,
in litt.
2012). The goal of the Recovery Plan is to preserve the diversity of habitats that occur within the range of the species, the metapopulation structure of the species, and genetic diversity (Service 2005a, p. 28).

Water Depth, Velocity, and Temperature

The tidewater goby is most commonly collected in water less than 6 ft (2 m) deep (Wang 1982, pp. 4-5; Worchester 1992, p. 53). However, recently tidewater gobies were collected in Big Lagoon in Humboldt County during the breeding season at a water depth of 15 ft (4.6 m) (Goldsmith,
in litt.
2006a). Whether use of these deeper waters is confined to this locality or is more widespread will require additional sampling at various depths and locations. The tidewater goby tends to avoid currents and concentrate in slack-water areas; this suggests it is less likely to occur in areas with a steep gradient or microhabitats that have a substantial current. At Pescadero Creek in San Mateo County, tidewater gobies were absent from portions of the flowing creek that had a surface velocity of 0.15 m per second (0.49 ft per second), and the species was instead more densely concentrated in nearby eddies with lower water velocities (Swenson 1993, p. 3). Backwater marshes may provide important refuges that reduce the likelihood that a substantial number of tidewater gobies will be flushed out of the lagoons or estuaries and into the marine environment during heavy winter floods (Lafferty
et al.
1999b, p. 619). Evidence that increased flows can eliminate the tidewater goby from a locality is suggested by the elimination of the tidewater goby from Waddell Creek in Santa Cruz County following a flood event in the winter of 1972-73 (Nelson as cited in Swift 1990, p. 2); this creek had been channelized and no longer afforded protection from high flows during flood events. Likewise, the channelization and elimination of habitat lateral to the main stream channel upstream of San Onofre Lagoon in San Diego County probably led to the flushing and extirpation of the tidewater goby from this locality during a storm in 1993 (Swift
et al.
1994, p. 22-23). The importance of backwater marshes is also highlighted by the fact that tidewater gobies in these habitats can achieve a greater size at maturity than in adjacent lagoons and creeks (Swenson 1993, pp. 6-7).

Freshwater Habitat

The tidewater goby also occurs in freshwater streams up-gradient and tributary to brackish habitats; the salinity of these freshwater streams is typically less than 0.5 ppt. The available documentation demonstrates that, in some areas, tidewater goby can occur 1.6 to 7.3 mi (2.6 to 11.7 km) upstream from the ocean environment (Irwin and Soltz 1984, p. 27; Swift
et al.
1997, p. 20; Goldsmith,
in litt.
2006b). Within a 2-hour period, hundreds of tidewater gobies have been observed to move upstream of a fixed location into areas in the Santa Ynez River 3.2 mi (5.1 km) from the ocean in Santa Barbara County (Swift
et al.
1997, p. 20). The fact that this many individuals were observed to move through an area suggests that freshwater tributaries in some riverine systems provide important habitat for individual and population growth. We have reviewed a variety of documents to determine how far tidewater gobies have been detected upstream from the ocean. Goldsmith (
in litt.
2006b) found tidewater gobies 1.6 to 2.0 mi (2.6 to 3.3 km) upstream from the ocean in the Ten Mile River in Mendocino County; Swift
et al.
(1997, p. 18) found tidewater gobies 4.6 mi (7.3 km) upstream from the ocean in the San Antonio River in Santa Barbara County; Swift
et al.
(1997, p. 20) found tidewater gobies at various distances from 3.9 to 7.3 mi (6.2 to 11.7 km) upstream from the ocean in the Santa Ynez River in Santa Barbara County; and Holland (1992, p. 9) found tidewater gobies 3 mi (5 km) upstream from the ocean in the Santa Margarita River in San Diego County. Collectively, these data suggest the average maximum distance tidewater gobies have been detected upstream from the ocean in medium to large rivers is approximately 4.0 mi (6.4 km). Other than high stream gradient, the reasons for the variation in upstream movement between one locality and another have not been determined; salinity could be an important factor. Upstream salinity levels may vary with time of year, tidal cycles, storm events, and topography. However, Swift
et al.
(1997, p. 26) indicate that gradient and lack of barriers (e.g., beaver dams, sills) are more important factors than salinity to upstream dispersal.

Sandbars

Many of the locations occupied by the tidewater goby closely correspond to stream drainages. Under natural conditions, these stream drainages and the marine environment collectively act to produce sandbars that form a barrier between the ocean and the lagoon, estuary, backwater marsh, and freshwater stream system (Habel and Armstrong 1977, p. 39). These sandbars tend to be present during the late spring, summer, and fall seasons. The presence of a sandbar can create a lower salinity level (5 to 10 ppt) in the area up gradient from the sandbar (Carpelan 1967, p. 324) than would otherwise exist if there were no sandbar. The tidewater goby is more commonly associated with these lower salinity levels than with the salinity levels that occur in the ocean or an estuary without a sandbar, that is, about 35 ppt (Swift
et al.
1989, p. 7). The formation of a sandbar also creates more habitat for aquatic organisms because water becomes ponded behind the sandbar. Artificial breaching of a sandbar tends to result in a rapid decrease in water levels, unlike natural breaching, and increases the likelihood that adult tidewater gobies, their nests, and their fry could become stranded and die, or become concentrated and subject to greater levels of predation pressure by birds or other predators. Natural breaching events tend to occur during

the late winter and early spring when tidewater goby breeding is at a low point in the reproduction cycle. Furthermore, tidewater gobies are likely able to detect storm events due to the increased inflow of fresh water that may cause a natural breaching event and swim upstream or take refuge in side channels (Lafferty
et al.
1999b, p. 619).

In Humboldt Bay and the Eel River estuary in Humboldt County, a large amount of salt and brackish marsh habitat was historically eliminated through the construction of levees and drainage channels. As a result, several of the locations occupied by the tidewater goby do not contain natural sandbars between the ocean and habitat where the species is present. Instead, manmade water control structures such as tidegates and culverts exist between tidal waters and the locations where tidewater goby occur. These tidegates have been in place for decades, and in some cases they provide habitat conditions similar to those created by the presence of a seasonal sandbar. In fact, most of the occupied tidewater goby habitats in the Humboldt Bay-Eel River estuaries are above tidegates. Other examples where large amounts of brackish marsh habitat have been lost due to construction of levees and drainage channels include the tributaries to the San Francisco Bay, Tomales Bay, Waddell Creek, Salinas River, Goleta Slough, Santa Clara River, and Mugu Lagoon.

Food

The tidewater goby feeds mainly on macroinvertebrates (for example shrimp and aquatic insects) (Irwin and Soltz 1984, p. 21-23; Swift
et al.
1989, p. 6; Swenson 1995, p. 87). The diets of adult and juvenile tidewater gobies tend to include the same relative abundance of different invertebrate species (Swenson and McCray 1996, p. 962). The nonnative New Zealand mudsnails (NZMS;
Potamopyrgus antipodarum
) have been a seasonally important component of the diet of tidewater gobies in the northcoast region (Hellmair
et al.
2011, p. 1).

Cover or Shelter

A variety of native and nonnative fish species and fish-eating bird species, such as egrets (
Egretta
spp.) and herons (e.g., great blue herons (
Ardea herodias
)), prey on tidewater gobies. Therefore, escape cover or shelter is necessary to reduce the likelihood that tidewater gobies will be preyed upon. A species' ability to persist when it is subject to predation pressure frequently depends on the presence of different features that provide a greater level of structure, which makes it more likely a prey species will avoid predation (Crowder and Cooper 1982, p. 1802; Gilinsky 1984, p. 455). At locations where the tidewater goby occurs, submerged and emergent aquatic vegetation has the potential to provide cover from predators, and provide a greater degree of habitat heterogeneity or structure that would not otherwise exist if the aquatic vegetation was absent. Stable lagoons often possess dense aquatic vegetation that frequently consists of sago pondweed (
Potamogeton pectinatus
) or widgeon grass (e.g.,
Ruppia maritima
and
R. cirrhosa
). At some locations, juvenile tidewater gobies are more prevalent in areas with at least some submergent vegetation as compared to other areas with no or little vegetation (Wang 1984, p. 16; Swenson 1994, p. 6; Trihey & Associates, Inc. 1996, p. 11). It is reasonable to assume that the presence of submerged or emergent vegetation reduces the likelihood that tidewater gobies will be preyed upon by native and nonnative species because this vegetation provides cover and increases the level of habitat heterogeneity in a way that makes it more likely that tidewater gobies will persist where they co-occur with predators.

Aquatic vegetation may provide some degree of shelter or refuge during flash flood events (Lafferty
et al.
1999b, p. 621). These refuges presumably would result because the presence of vegetation would create lower water velocities than might otherwise occur in unvegetated areas. Such refuges would be especially important to fish species that are not strong swimmers, such as the tidewater goby.

Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

The eggs of the tidewater goby are laid in burrows that are excavated by male fish. The available literature suggests that burrows most commonly occur in areas with relatively unconsolidated, clean, coarse sand (Swift
et al.
1989, p. 8), while other documents demonstrate that burrows may also occasionally occur in silt or mud (Wang 1982, p. 6). Swenson (1995, p. 148) demonstrated that tidewater gobies prefer a sandy substrate in the laboratory. Male tidewater gobies remain in the burrow to guard the eggs attached to the burrow ceiling and walls. Male tidewater gobies care for the embryos for approximately 9 to 11 days until they hatch, rarely if ever emerging from the burrow to feed (Swift
et al.
1989, p. 4). The tidewater goby larvae occupy the water column after the eggs hatch (Wang 1982, p. 15). As they mature, they occupy the bottom substrate. Worcester (1992, pp. 77-79) found that larval tidewater gobies in Pico Creek Lagoon in San Luis Obispo County tended to use the deeper portion of the lagoon, that is, depths of 29 inches (in) (73 centimeters (cm)) versus 17 in (42 cm).

Habitats Protected from Disturbance or Representative of the Historical, Geographical, and Ecological Distributions of the Species

The majority of lagoons and estuaries that currently support the tidewater goby have experienced some level of disturbance. The lagoons and estuaries that support the tidewater goby range in size from approximately 3.5 square yards (3 m
2
) of surface area to about 2,000 ac (800 ha). Most lagoons and estuaries that support the tidewater goby range from about 1.25 to 12.5 ac (0.5 to 5 ha). Surveys of tidewater goby locations and historical records indicate that size, configuration, location, and access by humans are all factors in the persistence of populations of this species (Swift
et al.
1989, p. 15, 1994, p. 26-27). Lagoons and estuaries smaller than about 5 ac (2 ha) generally have histories of extirpation or population reduction to very low levels. These small locations are also often within a mile or so of another locality from which recolonization could occur following natural episodic catastrophic events. The most stable or largest populations today are in locations of intermediate sizes, which range from 5 to 125 ac (2 to 50 ha). In many cases these intermediate-sized locations likely serve as source populations for the smaller ephemeral sites (Lafferty
et al.
1999b, p. 1452).

Primary Constituent Elements for Tidewater Goby

Under the Act and its implementing regulations, we are required to identify the physical or biological features essential to the conservation of the tidewater goby within the geographical area occupied at the time of listing, focusing on the features' primary constituent elements. We consider primary constituent elements to be the elements of physical or biological features that provide for a species' life-history processes that are essential to the conservation of the species.

Based on our current knowledge of the physical or biological features and habitat characteristics required to sustain the species' life-history processes, we determine that the primary constituent element (PCE) specific to the tidewater goby is:

(1) Persistent, shallow (in the range of approximately 0.3 to 6.6 ft (0.1 to 2 m)),

still-to-slow-moving lagoons, estuaries, and coastal streams with salinity up to 12 ppt, which provide adequate space for normal behavior and individual and population growth that contain one or more of the following:

(a) Substrates (e.g., sand, silt, mud) suitable for the construction of burrows for reproduction;

(b) Submerged and emergent aquatic vegetation, such as
Potamogeton pectinatus, Ruppia maritima,

Typha latifolia,
and
Scirpus
spp., that provides protection from predators and high flow events; or

(c) Presence of a sandbar(s) across the mouth of a lagoon or estuary during the late spring, summer, and fall that closes or partially closes the lagoon or estuary, thereby providing relatively stable water levels and salinity.

Special Management Considerations or Protection

When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain features that are essential to the conservation of the species and which may require special management considerations or protection. Special management considerations or protection may be necessary to eliminate or reduce the magnitude of threats that affect the physical or biological features essential to the conservation of the tidewater goby. Threats identified in the final listing rule for the tidewater goby include:

(1) Coastal development projects, including proposed restoration projects that involve elimination of backwaters and loss or alteration of coastal wetland habitat, which may be crucial for flood refuge for the tidewater goby;

(2) water diversions and alterations of water flows upstream of coastal lagoons and estuaries that negatively impact the species' breeding and foraging habitat and activities;

(3) groundwater overdrafting that results in reduction of flows and negatively impacts the species' breeding and foraging habitat and activities;

(4) channelization of habitats where the species occurs that removes or reduces quality of habitat;

(5) discharge of agricultural and sewage effluents;

(6) cattle grazing and feral pig activity that result in increased sedimentation of coastal lagoons and riparian habitats, remove vegetative cover, increase ambient water temperatures, and eliminate plunge pools and collapsed undercut banks utilized by the tidewater goby;

(7) introduced species that prey on the tidewater goby (such as bass, rainwater killifish, African clawed frogs);

(8) the inadequacy of existing regulatory mechanisms;

(9) drought conditions that result in the deterioration of coastal and riparian habitats; and

(10) competition with introduced species, such as the yellowfin goby and chameleon goby.

For the purposes of this final rule, we have combined the “water diversions and alterations of water flows upstream of coastal lagoons and estuaries that negatively impact the species' breeding and foraging activities” threats category with “drought conditions” and “groundwater overdrafting,” along with the addition of artificial breaching of sandbars, into one threat category. The combined category is referred to as “water diversions, alterations of water flows, artificial sandbar breaching, and groundwater overdrafting that negatively impact the species' breeding and foraging activities.” Similarly, we have combined the two threat categories of “introduced species that prey on the tidewater goby (e.g., bass, African clawed frogs)” and “competition with introduced species such as the yellowfin goby and chameleon goby” into one category called, “introduced species that prey on, or compete with, the tidewater goby (for example, yellowfin goby, and bass).” We also recognize that where special management may be necessary, regulatory mechanisms may need to be added or amended by local, State, or Federal governmental entities if sufficient management is not achievable through voluntary mechanisms.

The tidewater goby's distribution reflects a pattern of occupancy and extirpation. The species requires refugia under drought conditions and places to recolonize under wetter conditions; otherwise, the tidewater goby would be relegated to existing only within those few lagoons and estuaries large enough to support it during periods of drought. If the suitable localities that are occupied during periods of normal precipitation cease to function as tidewater goby habitat due to modification or destruction while the localities are unoccupied, the metapopulation dynamics may be disrupted and the species may not be able to respond by recolonizing unoccupied localities under favorable conditions. The tidewater goby is facing numerous threats, including habitat loss from multiple sources, habitat fragmentation due to the loss of “stepping stone” localities between subpopulations, predation and nonnative competitors, alterations to hydrology (sandbar breaching, channelization, for example), changes in water quality, stochastic events such as drought, and the growing and inevitable impact of sea level rise. While some of these threats can singly have a substantial impact on individual tidewater goby subpopulations, in most cases it is the combined impact that is a threat to the species, especially in light of global climate change. A more detailed discussion of threats to the tidewater goby can be found in the final listing rule (59 FR 5494, February 4, 1994), and the final Recovery Plan (Service 2005a, pp. 16-19).

We find that the components of the PCE present within all the areas we are designating as critical habitat may require special management considerations or protection due to threats to the tidewater goby or its habitat. Using current information provided in the Recovery Plan (Service 2005a, Appendix E) and other information in our files, we have identified the components of the PCE that may require special management considerations or protection from known threats within each of the critical habitat units (see Critical Habitat Designation and Table 2 below for a unit-by-unit description). Some of the special management actions that may be needed for essential features of tidewater goby habitat are briefly summarized below.

(1) Implement measures to avoid, minimize or mitigate direct and indirect loss and modification of tidewater goby habitat due to dredging, draining, and filling of lagoons and estuaries. Additional management actions should be taken to restore historical tidewater goby locations and potential habitats as opportunities become available to eliminate, minimize, or mitigate the effects of existing structures and past activities that have destroyed or degraded tidewater goby habitat.

(2) Develop and implement measures to minimize the adverse effects due to channelization that can eliminate crucial backwater habitats or other flood refuges.

(3) Implement measures, such as best management practices, for managing excessive sedimentation in tidewater goby habitat. Measures should be implemented to control sedimentation in tidewater goby habitat due to cattle grazing, development, channel modification, recreational activity, and agricultural practices.

(4) Implement measures to prevent further decrease in freshwater inflow, water depth, and surface area within

tidewater goby habitat due to dams, water diversions, and groundwater pumping.

(5) Implement measures to avoid anthropogenic breaching of lagoons and use of pumping and other water control structures to regulate water levels, to maintain suitable habitat conditions during the summer and fall when tidewater goby reproduction is at its highest and freshwater inflow is at its lowest.

(6) Implement measures to improve water quality degraded as a result of agricultural runoff and effluent, municipal runoff, golf course runoff, sewage treatment effluent, cattle grazing, development, oil spills, oil field runoff, toxic waste, and gray-water dumping. Also, measures should be implemented to prevent further degradation of the water quality due to dikes, tidal gates, and other impedances to the natural freshwater/saltwater interface that alter the salinity regime in some of the tidewater goby habitats.

(7) Implement measures to control the abundance and distribution of nonnative species.

(8) Implement measures to restore genetic diversity within populations where the natural metapopulation dynamic will be unable to do so.

Criteria Used To Identify Critical Habitat

As required by section 4(b)(2) of the Act, we used the best scientific and commercial data available to designate critical habitat. We reviewed available information pertaining to the habitat requirements of this species. In accordance with the Act and its implementing regulation at 50 CFR 424.12(e), we considered whether designating areas outside those currently occupied as well as those occupied at the time of listing are essential to ensure the conservation of the species. We are designating critical habitat in areas within the geographical area occupied by the species at the time of listing in 1994. We also are designating specific areas outside the geographical area occupied by the species at the time of listing because such areas are essential for the conservation of the species.

In revising critical habitat for the tidewater goby, we made extensive use of the information in the Recovery Plan (Service 2005a), and incorporated the recovery goals and strategy identified in the Recovery Plan for the development of our revised designation. We also reviewed other relevant information, including peer-reviewed journal articles, unpublished reports and materials (for example, survey results and expert opinions), the final listing rule (59 FR 5494; February 4, 1994), the 2000 final critical habitat rule (65 FR 69693; November 20, 2000), the 2006 proposed critical habitat rule (71 FR 68914; November 28, 2006), the 2008 final critical habitat rule (73 FR 5920; January 31, 2008), the 2011 proposed critical habitat rule (76 FR 64996; October 19, 2011), the 5-year review for the tidewater goby (Service 2007), and regional databases and GIS coverages, for example, the California Natural Diversity Database, and National Wetlands Inventory maps. We analyzed this information to identify: (1) Specific areas within the geographical area occupied at the time of listing that contain the physical or biological features essential to the conservation of the tidewater goby and which may require special management considerations or protection, and (2) criteria for specific areas outside the geographical area occupied at the time of listing that are essential for the conservation of the tidewater goby.

The Recovery Plan focuses on preserving the diversity of tidewater goby habitats throughout the range of the species, preserving the natural processes of recolonization and population exchange (metapopulation dynamics) that enable recovery following natural episodic catastrophic events, and preserving genetic diversity (Service 2005a, p. 28). The conservation of the environmental, morphological, and genetic diversity across the range of the species is an important consideration in determining specific areas on which are found the physical or biological features essential to the conservation of the species and other specific areas that are essential for the conservation of the tidewater goby. For example, a population's ability to successfully adapt to changing environmental conditions is a function of the population size and genetic variation of the individuals at a given location (Reed and Frankham 2003, p. 233).

Local adaptations to different environmental conditions and morphological differences are likely linked to genetic variations among populations. These features may in turn be best protected by: (1) Identifying areas that represent the range of environmental, genetic, and morphological diversity; and (2) maximizing within these areas the protection of contiguous environmental gradients across which selection and migration can interact to maintain population viability and (adaptive) genetic diversity (Moritz 2002, p. 238). The Recovery Plan subdivides the geographical distribution of the tidewater goby into 6 recovery units, encompassing a total of 26 subunits defined according to genetic differentiation and geomorphology. We considered the conservation of the tidewater goby in each of the recovery units and subunits, as well as the species as a whole, in our analysis.

Based on the information and recommendations in the Recovery Plan, we developed a conservation framework and criteria to identify the specific circumstances under which the presence of the components of the PCE within the geographical area occupied by the species at the time of listing provides the physical or biological features essential to the conservation of the tidewater goby, and additionally what areas outside the geographical area occupied at the time of listing are essential for the conservation of the species.

Areas Within the Geographical Area Occupied at the Time of Listing

Within the geographical area occupied at the time of listing, the specific areas meeting the criteria below are designated as critical habitat in this final rule because they provide the physical or biological features essential to the conservation of the tidewater goby.

(1) Areas that support source populations (populations where local reproductive success is greater than local mortality (Meffe and Carroll 1994, p. 187)). For the purposes of this designation, we identified areas supporting source populations as those that are currently occupied and have been consistently occupied for 3 or more consecutive years based on survey data and published reports. Source populations are more likely to be capable of maintaining populations over many years and are, therefore, capable of providing individuals to recruit into surrounding subpopulations.

(2) Areas that support subpopulations within each metapopulation in addition to source populations in the event that the source population is extirpated due to a natural episodic catastrophic event such as a major flood or drought.

(3) Areas that provide connectivity between metapopulations. These areas are likely to act as “stepping stones” between more isolated populations, and thereby contribute to metapopulation persistence and genetic exchange. For the purposes of this designation, we generally identified locations that provide connectivity as those within approximately 6 mi (10 km) of another location. However, we included a few locations that exceeded 6 mi but were

within the maximum dispersal distance as determined through genetic research (Jacobs
et al.
2005, p. 52) where there were no other locations with suitable habitat in that portion of the coast.

Areas Outside the Geographical Area Occupied at the Time of Listing

We have determined that the specific areas within the geographical area occupied at the time of listing alone are not sufficient to meet the recovery goals for the species because:

(1) The Recovery Plan recommends a targeted program of introduction and reintroduction of tidewater gobies into suitable habitat to minimize the chance of local extirpations resulting in extinction of a broader metapopulation (see the
Metapopulation Dynamics
section, above, for details) and resultant loss of its unique genetic traits (Service 2005a, p. 29);

(2) There has been loss and degradation (see the
Threats
section, above, for details) of habitat throughout the species' range since the time of listing;

(3) We anticipate a further loss of habitat in the future due to sea-level rise resulting from climate change (see the
Climate Change
section, above, for details); and

(4) The species needs habitat areas that are arranged spatially in a way that will maintain connectivity and allow dispersal within and between units (see the
Metapopulation Dynamics
section, above, for details).

One example of the need to designate areas outside the geographical area occupied at the time of listing is where distances between areas occupied at the time of listing may make it difficult for tidewater goby to disperse from one area to the next. Another example is to help prevent the extirpation of a metapopulation in which only one or two occupied sites remain. These areas that are outside the geographical area occupied at the time of listing include locations that are currently occupied and, in a few cases, ones that were historically occupied. In some unoccupied areas, the habitat would require some management: For example, restoration of a natural breaching regime, exotic predator management, or freshwater inflow enhancement.

Therefore, for areas outside the geographical area occupied at the time of listing, those meeting the criteria below are designated as critical habitat in this final rule because they are essential for the conservation of the species.

(1) Areas of aquatic habitat in coastal lagoons and estuaries with still-to-slow-moving water that allow for the conservation of viable metapopulations under varying environmental conditions, such as, for example, drought.

(2) Areas that provide connectivity between source populations or may provide connectivity in the future. These areas are likely to act as “stepping stones” between more isolated populations, and thereby contribute to metapopulation persistence and genetic exchange. For the purposes of this designation, we generally identified locations that provide connectivity as those within approximately 6 mi (10 km) of another location.

(3) Additional areas that may be more isolated but may represent unique adaptations to local features (habitat variability, hydrology, microclimate). For example, the Eel River (HUM-4) is essential for the conservation of tidewater goby because it possesses ecological characteristics that are important in maintaining the species' ability to adapt to changing environments, including the ability to disperse into higher channels and marsh habitat during severe flood events.

By applying the two sets of criteria to the 26 recovery subunits described in the Recovery Plan, we have identified 45 critical habitat units within the geographical area occupied by the species at the time of listing that we have determined contain the physical or biological features essential to the conservation of the tidewater goby and which may require special management considerations or protection, and 20 critical habitat units outside the geographical area occupied by the species at the time of listing that we have determined are essential for the conservation of the species. Please see Table 1, below, for the occupancy status of each of the 65 critical habitat units.

As emphasized throughout this rule and the Recovery Plan, the conservation of the tidewater goby is dependent on maintaining the metapopulation dynamics of the species, and we have therefore designated all those locations that we determined are essential for achieving that goal. In order to maintain metapopulation dynamics, we have determined that some locations where tidewater gobies have never been found or have not been found in recent years are essential for the conservation of the species. It should be noted, however, that some subpopulations within a metapopulation tend to decline or disappear periodically due to events such as drought and severe flooding, but then reappear or increase in abundance during more optimal conditions. However, surveys to determine the presence or absence of tidewater gobies are not usually conducted every year, and therefore the presence of tidewater gobies may have been missed. For example, tidewater gobies were known to occur in the San Luis Rey River in 1958. However, the river has only been surveyed five times in the last 65 years since 1958, and tidewater gobies were found in 2010.

As discussed previously, a metapopulation is generally considered to consist of several distinct but related subpopulations that are within dispersal distance of each other. Although the individual subpopulations may sometimes disappear, the metapopulation as a whole is often stable because immigrants from one population (which may, for example, be experiencing a population boom) are likely to re-colonize habitat which has been left open by the extirpation of another population as long as the habitat still remains. They may also emigrate to a small population and rescue that population from extirpation. In a metapopulation dynamic, connectivity of source populations is crucial, and locations considered unoccupied may serve this purpose. Although no single tidewater goby subpopulation may be able to guarantee the long-term survival of this species, the combined effect of many sporadically connected subpopulations may. Therefore, although a particular location may not be occupied at one point in time, or even for long periods of time, that location may be important for maintaining the connectivity between subpopulations, and hence contribute to the species' overall survival and conservation. For example, although tidewater gobies have not been detected in Arroyo del la Cruz, it is within dispersal distance of Arroyo del Corral, which is considered currently to be occupied in critical habitat. Arroyo de la Cruz is located approximately 2.0 mi (3.2 km) north of the Arroyo de Corral. Arroyo de la Cruz provides habitat for tidewater gobies that disperse from Arroyo del Corral, which may serve to decrease the risk of extirpation of this metapopulation through stochastic events. Arroyo de la Cruz is one of two locations with suitable habitat within the Central Coast Recovery Subunit (CC 1), as described in the Recovery Plan. Therefore, although tidewater gobies have not been detected at Arroyo de la Cruz, we consider this area to be essential to the conservation of the species because it contributes to ensuring the viability of the metapopulation because if the subpopulation within the Arroyo de

Corral unit (SLO-2) is extirpated, the entire metapopulation would be lost.

The process of making exclusions under Section 4(b)(2) considers the extent to which habitat restoration would be necessary to support the species in areas currently unoccupied. Where restoration is not likely due to cost or other factors, the benefits in terms of conservation value may not be as strong. Restoration activities would benefit all of the critical habitat units in this designation, and some form of restoration will be necessary to support the successful reintroduction or recolonization of the tidewater goby in the units that are unoccupied. For example, some of the unoccupied locations need improvements to water quality, barrier removal, exotic species management (e.g., Walker Creek, Salinas River, Arroyo de la Cruz, Oso Flaco Lake, etc.). However, designation of critical habitat does not mandate restoration or management of any areas. However, we determined it is feasible to restore all of the unoccupied habitat designated in this rule to the point where it can support gobies and we avoided designating unoccupied areas that are highly degraded or fragmented and not likely restorable (e.g., Los Angeles River, Mugu Lagoon). Such areas provide little or no long-term conservation value, and are not essential for the conservation of the species.

Mapping

After determining the lagoons and estuaries necessary for the conservation of the tidewater goby by applying criteria outlined above, the boundaries of each critical habitat unit were mapped. Unit boundaries were based on several factors, including species occurrence data that demonstrated where tidewater gobies have been observed, the presence of barriers and stream gradients that limit tidewater goby movements, and the presence and extent of the essential physical or biological features.

The geographic extent of each critical habitat unit was delineated, in part, using existing digital data. To determine the lateral boundaries of each critical habitat unit, we most frequently relied on the Pacific Institute global climate change model and National Wetland Inventory (NWI) maps that were prepared by the Service in 2006. The NWI maps are based on the Cowardin classification system (Cowardin
et al.
1979, pp. 1-103). The Service has adopted this classification system as its official standard to describe wetland and deepwater habitats. Specifically, the following wetland types based on Cowardin (1979, p. 5) were used to delineate unit boundaries: Lake, Estuarine and Marine Deepwater, Estuarine and Marine Wetland, Freshwater Pond, Freshwater Emergent Wetland, Freshwater Forested/Shrub Wetland, and Riverine. These wetland types have, or are likely to have, components of the PCE at various times throughout the year, depending on the season and environmental factors such as storm or drought events. In some cases, we used existing anthropogenic structures, such as concrete or riprap channel linings that occur within wetland habitat types, to delineate the lateral boundaries of units. To a lesser extent, we also used aerial imagery from the National Agricultural Imagery Program (NAIP) to delineate the lateral boundaries of a critical habitat unit where insufficient NWI data were available.

The precise location of tidewater goby habitat at a particular locality may vary on a daily, seasonal, and annual basis; the habitats occupied by tidewater goby exist in a dynamic environment that varies over time. For example, the size and lateral extent of a coastal lagoon or estuary varies with daily tide cycles. Flood events may also change the precise location where surface water exists within a given lagoon, estuary, backwater marsh, or freshwater tributary. Therefore, it is appropriate to delineate each critical habitat unit to encompass the entire area that may be occupied by tidewater goby on a daily, seasonal, or annual basis. This was accomplished by using the boundaries delineated on the NWI maps to determine the lateral extent of each unit.

The delineation of the farthest upstream extent of a particular critical habitat unit was determined using one of four features that include:

(1) The average distance that tidewater gobies are known to move upstream from the ocean (4.0 mi (6.4 km)),

(2) the presence of barriers, such as culverts that may prevent tidewater gobies from moving upstream,

(3) the presence of a vertical drop, for example more than 4 to 8 in (10 to 20 cm) high, or steep gradient that precludes tidewater gobies from swimming upstream or can act as a barrier that makes it less likely tidewater gobies will be able to swim upstream (Swift
et al.
1997, p. 20)), or

(4) limited surface water in the tributary up-gradient from the lagoon or estuary.

Each of the above features describes a barrier to upstream movement; therefore, the upstream extent of a particular unit was determined by whichever barrier was identified first through the mapping process regardless of whether or not components of the PCE were still present above it.

When determining critical habitat boundaries within this final rule, we made every effort to avoid including developed areas such as lands covered by bridges, docks, and other structures because such lands cannot provide habitat for the tidewater goby. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed lands. Any such lands inadvertently left inside critical habitat boundaries shown on the maps of this final rule have been excluded by text in the rule and are not designated as critical habitat. Therefore, a Federal action involving these lands will not trigger section 7 consultation with respect to critical habitat and the requirement of no adverse modification unless the specific action may affect adjacent critical habitat.

The critical habitat designation is defined by the map or maps, as modified by any accompanying regulatory text, presented at the end of this document in the rule portion. We include more detailed information on the boundaries of the critical habitat designation in the preamble of this document. We will make the coordinates or plot points or both on which each map is based available to the public on
http://www.regulations.gov
at Docket No. FWS-R8-ES-2011-0085, on our Internet sites at
http://www.fws.gov/ventura/,
and at the field office responsible for the designation (see
FOR FURTHER INFORMATION CONTACT
above).

We are designating as critical habitat lands that we have determined are within the geographical area occupied at the time of listing and contain sufficient physical or biological features to support life-history processes essential to the conservation of the species, and lands outside of the geographical area occupied at the time of listing that we have determined are essential for the conservation of tidewater goby.

Units within the geographical area occupied at the time of listing are designated based on sufficient elements of physical or biological features being present to support tidewater goby life processes. Some units contain all of the identified elements of physical or biological features and support multiple life processes. Some units contain only some elements of the physical or biological features necessary to support the tidewater goby's particular use of that habitat.

Final Critical Habitat Designation

We are designating 65 units as critical habitat for tidewater goby (see Table 1 below). The critical habitat areas described below constitute our best assessment at this time of areas that meet the definition of critical habitat.

Table 1—Occupancy of Tidewater Goby by Designated Critical Habitat Units

Unit
Name
Within the geographical area occupied at time of listing?

Currently occupied
1

DN-1
Tillas Slough (Smith River)
Yes
Yes.

DN-2
Lake Earl/Lake Tolowa
Yes
Yes.

HUM-1
Stone Lagoon
Yes
Yes.

HUM-2
Big Lagoon
Yes
Yes.

HUM-3
Humboldt Bay
Yes
Yes.

HUM-4
Eel River
No
Yes.

MEN-1
Ten Mile River
Yes
Yes.

MEN-2
Virgin Creek
Yes
Yes.

MEN-3
Pudding Creek
Yes
Yes.

MEN-4
Davis Lake and Manchester State Park Ponds
Yes
Yes.

SON-1
Salmon Creek
Yes
Yes.

MAR-1
Estero Americano
Yes
Yes.

MAR-2
Estero de San Antonio
Yes
Yes.

MAR-3
Walker Creek
No
No.

MAR-4
Lagunitas (Papermill) Creek
No
Yes.

MAR-5

Bolinas Lagoon
2

No
No.

MAR-6
Rodeo Lagoon
Yes
Yes.

SM-1
San Gregorio Creek
Yes
Yes.

SM-2
Pomponio Creek
No
Yes.

SM-3
Pescadero-Butano Creek
Yes
Yes.

SM-4
Bean Hollow Creek (Arroyo de Los Frijoles)
Yes
Yes.

SC-1
Waddell Creek
Yes
Yes.

SC-2
Scott Creek
No
Yes.

SC-3
Laguna Creek
Yes
Yes.

SC-4
Baldwin Creek
Yes
Yes.

SC-5
Moore Creek
Yes
Yes.

SC-6
Corcoran Lagoon
Yes
Yes.

SC-7
Aptos Creek
Yes
Yes.

SC-8
Pajaro River
Yes
Yes.

MN-1
Bennett Slough
Yes
Yes.

MN-2
Salinas River
No
No.

SLO-1

Arroyo de la Cruz
2

No
No.

SLO-2
Arroyo del Corral
Yes
Yes.

SLO-3
Oak Knoll Creek (Arroyo Laguna)
Yes
Yes.

SLO-4
Little Pico Creek
Yes
Yes.

SLO-5
San Simeon Creek
Yes
Yes.

SLO-6
Villa Creek
Yes
Yes.

SLO-7
San Geronimo Creek
Yes
Yes.

SLO-8
Toro Creek
Yes
Yes.

SLO-9
Los Osos Creek
No
Yes.

SLO-10
San Luis Obispo Creek
Yes
Yes.

SLO-11
Pismo Creek
Yes
Yes.

SLO-12

Oso Flaco Lake
2

No
No.

SB-1
Santa Maria River
Yes
Yes.

SB-2
Cañada de las Agujas
Yes
Yes.

SB-3
Cañada de Santa Anita
Yes
Yes.

SB-4
Cañada de Alegria
Yes
Yes.

SB-5
Cañada de Agua Caliente
Yes
Yes.

SB-6
Gaviota Creek
Yes
Yes.

SB-7
Arroyo Hondo
No
Yes.

SB-8
Winchester-Bell Canyon
Yes
Yes.

SB-9
Goleta Slough
No
Yes.

SB-10
Arroyo Burro
No
Yes.

SB-11
Mission Creek-Laguna Channel
Yes
Yes.

SB-12
Arroyo Paredon
No
Yes.

VEN-1
Ventura River
Yes
Yes.

VEN-2
Santa Clara River
Yes
Yes.

VEN-3
J Street Drain-Ormond Lagoon
Yes
Yes.

VEN-4
Big Sycamore Canyon
No
Yes.

LA-1

Arroyo Sequit
2

No
No.

LA-2

Zuma Creek
2

No
No.

LA-3
Malibu Lagoon
Yes
Yes.

LA-4
Topanga Creek
No
Yes.

OR-1
Aliso Creek
No
No.

SAN-1
San Luis Rey River
No
Yes.

1
Based on the Recovery Plan and subsequent survey information where available.

2
Tidewater gobies have never been recorded from this location; however, regularly scheduled monitoring of these subpopulations has not been conducted.

The approximate area of each critical habitat unit is shown in Table 2.

Table 2—Critical Habitat Units Designated for the Tidewater Goby and Known Threats That May Require Special Management Considerations or Protection of the Essential Physical or Biological Features for Units Within the Geographical Area Occupied by the Species at the Time of Listing

Unit name

Federal
ac (ha)

State
ac (ha)

Local
ac (ha)

Private
ac (ha)

Total
1
ac (ha)

Known threats that may require special management considerations or protection of the essential features
2

DN-1: Tillas Slough (Smith River)
0 (0)
0 (0)
0 (0)
21 (8)
21 (8)
2, 3, 5

DN-2: Lake Earl/Lake Tolowa
0 (0)
2,335 (945)
0 (0)
348 (141)
2,683 (1,086)
1, 2, 4

HUM-1: Stone Lagoon
0 (0)
653 (264)
0 (0)
0 (0)
653 (264)
4

HUM-2: Big Lagoon
0 (0)
1,527 (618)
0 (0)
2 (1)
1,529 (619)
2, 4

HUM-3: Humboldt Bay
652 (264)
61 (24)
45 (18)
81 (33)
839 (339)
1, 3, 4, 5

HUM-4: Eel River
0 (0)
5 (2)
0 (0)
34 (13)
39 (15)
N/A

MEN-1: Ten Mile River
0 (0)
17 (7)
0 (0)
56 (23)
73 (30)
4

MEN-2: Virgin Creek
0 (0)
2 (1)
0 (0)
2 (1)
4 (2)
1, 4

MEN-3: Pudding Creek
0 (0)
10 (4)
1 (1)
6 (2)
17 (7)
1, 2, 4

MEN-4: Davis Lake and Manchester State Park Ponds
0 (0)
29 (12)
0 (0)
0 (0)
29 (12)
4

SON-1: Salmon Creek
0 (0)
47 (19)
14 (6)
47 (19)
108 (44)
1, 2, 4, 5

MAR-1: Estero Americano
0 (0)
0 (0)
0 (0)
465 (188)
465 (188)
1, 4, 5

MAR-2: Estero De San Antonio
0 (0)
0 (0)
0 (0)
285 (115)
285 (115)
1, 2, 4, 5

MAR-3: Walker Creek
0 (0)
9 (4)
0 (0)
109 (44)
118 (48)
N/A

MAR-4: Lagunitas (Papermill) Creek
318 (129)
459 (186)
0 (0)
221 (90)
998 (405)
N/A

MAR-5: Bolinas Lagoon
29 (12)
0 (0)
1,048 (424)
37 (15)
1,114 (451)
N/A

MAR-6: Rodeo Lagoon
40 (16)
0 (0)
0 (0)
0 (0)
40 (16)
1

SM-1: San Gregorio Creek
0 (0)
33 (13)
0 (0)
12 (5)
45 (18)
1, 3

SM-2: Pomponio Creek
0 (0)
1 (1)
0 (0)
6 (2)
7 (3)
N/A

SM-3: Pescadero-Butano Creek
0 (0)
241 (97)
0 (0)
4 (2)
245 (99)
1, 3, 4

SM-4: Bean Hollow Creek (Arroyo de Los Frijoles)
0 (0)
3 (1)
0 (0)
7 (3)
10 (4)
1, 2

SC-1: Waddell Creek
0 (0)
39 (16)
0 (0)
36 (14)
75 (30)
2, 3, 4

SC-2: Scott Creek
0 (0)
66 (27)
6 (2)
2 (1)
74 (30)
N/A

SC-3: Laguna Creek
0 (0)
26 (11)
0 (0)
0 (0)
26 (11)
2, 4

SC-4: Baldwin Creek
0 (0)
27 (11)
0 (0)
0 (0)
27 (11)
2, 4

SC-5: Moore Creek
15 (6)
0 (0)
0 (0)
0 (0)
15 (6)
2, 4

SC-6: Corcoran Lagoon
0 (0)
1 (1)
6 (2)
21 (8)
28 (11)
1, 4

SC-7: Aptos Creek
0 (0)
9 (4)
0 (0)
0 (0)
9 (4)
1, 3, 4

SC-8: Pajaro River
0 (0)
158 (64)
11 (4)
46 (19)
215 (87)
1, 3, 4

MN-1: Bennett Slough
0 (0)
108 (44)
5 (2)
54 (22)
167 (68)
1, 2, 3, 4

MN-2: Salinas River
195 (79)
33 (13)
1 (1)
237 (96)
466 (189)
N/A

SLO-1: Arroyo de la Cruz
0 (0)
25 (10)
0 (0)
8 (3)
33 (13)
N/A

SLO-2: Arroyo del Corral
0 (0)
4 (2)
0 (0)
1 (1)
5 (3)
1, 5

SLO-3: Oak Knoll Creek (Arroyo Laguna)
0 (0)
4 (2)
0 (0)
1 (1)
5 (3)
1, 3

SLO-4: Little Pico Creek
0 (0)
2 (1)
0 (0)
7 (3)
9 (4)
5

SLO-5: San Simeon Creek
0 (0)
17 (7)
0 (0)
0 (0)
17 (7)
2, 4, 5

SLO-6: Villa Creek
0 (0)
14 (6)
0 (0)
1 (1)
15 (7)
1, 2, 4, 5

SLO-7: San Geronimo Creek
0 (0)
1 (1)
0 (0)
0 (0)
1 (1)
5

SLO-8: Toro Creek
0 (0)
1 (1)
0 (0)
8 (3)
9 (4)
2, 3, 4

SLO-9: Los Osos Creek
0 (0)
62 (25)
1 (1)
10 (4)
73 (30)
N/A

SLO-10: San Luis Obispo Creek
0 (0)
0 (0)
3 (1)
28 (11)
31 (12)
1, 2, 3, 4

SLO-11: Pismo Creek
0 (0)
14 (6)
1 (1)
5 (2)
20 (9)
1, 3, 4

SLO-12: Oso Flaco Lake
0 (0)
165 (67)
0 (0)
6 (2)
171 (69)
N/A

SB-1: Santa Maria River
0 (0)
0 (0)
42 (17)
432 (174)
474 (192)
1, 2, 4, 5

SB-2: Cañada de las Agujas
0 (0)
0 (0)
0 (0)
1 (1)
1 (1)
1, 4

SB-3: Cañada de Santa Anita
0 (0)
0 (0)
0 (0)
3 (1)
3 (1)
4

SB-4: Cañada de Alegria
0 (0)
0 (0)
0 (0)
2 (1)
2 (1)
1, 2, 4, 5

SB-5: Cañada de Agua Caliente
0 (0)
0 (0)
0 (0)
1 (1)
1 (1)
1, 4

SB-6: Gaviota Creek
0 (0)
10 (4)
0 (0)
1 (1)
11 (5)
1, 3, 4, 5

SB-7: Arroyo Hondo
0 (0)
0 (0)
0 (0)
1 (1)
1 (1)
N/A

SB-8: Winchester-Bell Canyon
0 (0)
0 (0)
1 (1)
5 (2)
6 (3)
2, 4

SB-9: Goleta Slough
0 (0)
0 (0)
164 (66)
26 (10)
190 (76)
N/A

SB-10: Arroyo Burro
0 (0)
0 (0)
3 (1)
0 (0)
3 (1)
N/A

SB-11: Mission Creek-Laguna Channel
0 (0)
3 (1)
4 (2)
0 (0)
7 (3)
1, 3, 4

SB-12: Arroyo Paredon
0 (0)
1 (1)
1 (1)
1 (1)
3 (3)
N/A

VEN-1: Ventura River
0 (0)
25 (10)
16 (7)
9 (4)
50 (20)
1, 2, 3, 4

VEN-2: Santa Clara River
0 (0)
199 (80)
14 (6)
110 (44)
323 (130)
1, 2, 3, 4

VEN-3: J Street Drain-Ormond Lagoon
0 (0)
5 (2)
49 (20)
67 (27)
121 (49)
1, 2, 3, 4

VEN-4: Big Sycamore Canyon
0 (0)
1 (1)
0 (0)
0 (0)
1 (1)
N/A

LA-1: Arroyo Sequit
0 (0)
1 (1)
0 (0)
0 (0)
1 (1)
N/A

LA-2: Zuma Canyon
0 (0)
0 (0)
5 (2)
0 (0)
5 (2)
N/A

LA-3: Malibu Lagoon
0 (0)
41 (17)
1 (1)
22 (9)
64 (27)
1, 2, 3, 4

LA-4: Topanga Creek
0 (0)
4 (1)
0 (0)
2 (1)
6 (2)
N/A

OR-1: Aliso Creek
0 (0)
0 (0)
8 (3)
6 (2)
14 (5)
N/A

SAN-1: San Luis Rey River
0 (0)
3 (1)
49 (20)
4 (2)
56 (23)
N/A

Total
1

1,249 (506)
6,501 (2,636)
1,501 (611)
2,905 (1,177)
12,156 (4,920)

Note:
Area sizes may not sum due to rounding.

1
Area estimates in ac (ha) reflect the entire area within the critical habitat unit boundaries. Area estimates are rounded to the nearest whole integer that is equal to or greater than 1.

2
Codes of known threats that may require special management considerations or protection of the essential physical or biological features are as follows:

1. Coastal development projects that result in the loss or alteration of coastal wetland habitat affecting the PCE components 1a, 1b, or 1c.
2. Water diversions, alterations of water flows, and groundwater overdrafting upstream of coastal lagoons and estuaries that negatively impact the species' breeding and foraging activities and the PCE components 1a or 1b.
3. Channelization of habitats where the species occurs affecting the PCE components 1a, 1b, or 1c.
4. Nonpoint- and point-source pollution or discharge of agricultural and sewage effluents that are likely to impact the species' health or breeding and foraging activities and the PCE.
5. Cattle grazing that results in increased sedimentation of coastal lagoons and riparian habitats, removes vegetative cover, increases ambient water temperatures, and eliminates plunge pools and undercut banks utilized by tidewater goby affecting the PCE.
N/A—Not applicable because location is outside the geographical area occupied by the species at the time of listing.

We present brief descriptions of all units, and reasons why they meet the definition of critical habitat for tidewater goby, below. The first two or three letters in the code for each critical habitat unit description reflect the county where the unit occurs: DN = Del Norte, HUM = Humboldt, MEN = Mendocino, SON = Sonoma, MAR = Marin, SM = San Mateo, SC = Santa Cruz, MN = Monterey, SLO = San Luis Obispo, SB = Santa Barbara, VEN = Ventura, LA = Los Angeles, OR = Orange, and SAN = San Diego. In Tables 1 and 2 above, these units are listed in sequential order from north to south. For the purposes of this document, the term “local ownership” refers to land owned or managed by a city, county, or municipal government entity.

DN-1: Tillas Slough

DN-1 consists of 21 ac (8 ha) of private lands. This unit is located in Del Norte County, approximately 3.0 mi (4.8 km) west of the community of Smith River and 8.0 mi (12.8 km) north of Lake Earl/Lake Tolowa (DN-2), which is also the next nearest extant subpopulation.

DN-1 was occupied at the time of listing. This unit supports the northernmost tidewater goby subpopulation. DN-1 will support the recovery of the tidewater goby subpopulation within the North Coast Recovery Unit. This unit is important for maintaining the tidewater goby metapopulation in the region, and plays an important role in dispersal of the tidewater goby, which could prove vital if certain factors, such as climate change, adversely impact the tidewater goby habitat locally or to the south. A culvert that serves as a grade control structure, which mutes the tide cycle, provides relatively stable water levels in this unit (PCE 1c). PCE 1a and 1b occur throughout the unit, although their precise location during any particular time period may change in response to seasonal fluctuations in precipitation and tidal inundation. The physical or biological features essential to the conservation of the species in this unit may require special management considerations or protection to address threats described in Table 2. Please see
Special Management Considerations or Protection
section of this rule for a discussion of the threats to tidewater goby habitat and potential management considerations.

DN-2: Lake Earl/Lake Tolowa

DN-2 consists of 2,683 ac (1,086 ha). This unit is located in Del Norte County, approximately 3 mi (4.8 km) north of the town of Crescent City. The unit consists of 2,335 ac (945 ha) of State lands and 348 ac (140 ha) of private lands. This unit includes two contiguous lagoons (Lake Tolowa and Lake Earl), referred to collectively as Lake Earl. DN-2 is located 8.0 mi (12.8 km) south of (DN-1), which is also the nearest extant subpopulation.

DN-2 was occupied at the time of listing. The tidewater goby subpopulation in DN-2 is likely a source population, which is important in maintaining metapopulation dynamics, and hence the long-term viability, of the North Coast Recovery Unit.

DN-2 is representative of extensive coastal lagoons and bays north of Cape Mendocino formed over uplifting Holocene sediments on broad flat coastal benches. These coastal benches include an intricate network of estuaries and other channels that are features essential to the conservation of the tidewater goby because they provide refugia during seasonal floods and breeding habitat through the full range of drought cycles. The water level and salinity within the lagoon varies seasonally and annually in response to: (a) Periods of high precipitation or drought within its watershed; (b) the timing, duration, and frequency of breaching events; (c) the water level in the lagoon at the time of breaching; and (d) ocean tidal cycles during and immediately following a breach. As a result of natural and human-induced environmental changes, including artificial breaching, maximum water depth within Lake Earl/Lake Tolowa varies during an annual cycle from less than 5 ft (1.5 m) deep to more than 10 ft (3 m) deep. The distribution of tidewater goby and the PCE within Lake Earl/Lake Tolowa changes in response to these dynamic short-term habitat conditions; over a multiyear cycle, tidewater goby may persist and breed anywhere within the lagoon. McCraney
et al.
(2010) indicate that artificial breaching activities may be reducing genetic diversity in this subpopulation by repeated bottlenecking.

On an intermittent basis, DN-2 possesses a sandbar across the mouth of the lagoon or estuary during the majority of the late spring, summer, and fall that closes or partially closes the lagoon or estuary, and thereby provides relatively stable conditions during those times (PCE 1c). PCE 1a and 1b occur throughout the unit, although their precise location during any particular time period may change in response to seasonal fluctuations in precipitation and tidal inundation. The physical or biological features essential to the conservation of the species in this unit may require special management considerations or protection to address threats described in Table 2. Please see
Special Management Considerations or Protection
section of this rule for a discussion of the threats to tidewater goby habitat and potential management considerations.

HUM-1: Stone Lagoon

HUM-1 consists of 653 ac (264 ha). This unit is located in Humboldt County, approximately 11 mi (18 km) north of the City of Trinidad. The unit consists entirely of State lands. HUM-1 is located 3.1 mi (5.0 km) north of Big Lagoon (HUM-2), which is also the nearest extant subpopulation.

HUM-1 was occupied at the time of listing. The tidewater goby subpopulation in HUM-1 is likely a source population, which is important in maintaining metapopulation dynamics, and hence the long-term viability, of the North Coast Recovery Unit.

On an intermittent basis, HUM-1 possesses a sandbar across the mouth of the lagoon or estuary during the majority of the late spring, summer, and fall that closes or partially closes the lagoon or estuary, and thereby provides relatively stable conditions (PCE 1c). PCE 1a and 1b occur throughout the unit, although their precise location during any particular time period may change in response to seasonal fluctuations in precipitation and tidal inundation. The physical or biological features essential to the conservation of the species in this unit may require special management considerations or protection to address threats described in Table 2. Please see
Special Management Considerations or Protection
section of this rule for a discussion of the threats to tidewater goby habitat and potential management considerations.

HUM-2: Big Lagoon

HUM-2 consists of 1,529 ac (619 ha). This unit is located in Humboldt County, approximately 7 mi (11 km) north of the City of Trinidad. The unit consists of 1,527 ac (618 ha) of State lands and 2 ac (1 ha) of private lands. HUM-2 is located 3.1 mi (5.0 km) south of Stone Lagoon (HUM-1), which is also the nearest extant subpopulation.

HUM-2 was occupied at the time of listing. The tidewater goby subpopulation in HUM-2 is likely a source population, which is important in maintaining metapopulation dynamics, and hence the long-term viability, of the North Coast Recovery Unit.

Mark and recapture surveys for tidewater goby were conducted by Humboldt State University in a large cove near the State Park boat ramp in Big Lagoon during the fall of 2008, 2009, and 2010, to estimate the minimum tidewater goby subpopulation for each year (Hellmair 2011, p. 47). Results indicate that, in 2008, the tidewater goby subpopulation was approximately 21,000 individuals. In 2009, the subpopulation was approximately 1.7 to 3.4 million individuals in the cove. In 2010, the subpopulation was approximately 30,000 individuals in the same cove. Based on the results of this research, which estimated that the subpopulation fluctuated between 21,000 and 1.7-3.4 million individuals, and the relatively large size of the lagoon, Big Lagoon likely has the largest and most robust tidewater goby subpopulation in northern California. The results of the study also reflect how variable tidewater goby subpopulation numbers can be from year to year in a given location.

On an intermittent basis, HUM-2 possesses a sandbar across the mouth of the lagoon or estuary during the majority of the late spring, summer, and fall that closes or partially closes the lagoon or estuary, and thereby provides relatively stable conditions during those times (PCE 1c). PCE 1a and 1b occur throughout the unit, although their precise location during any particular time period may change in response to seasonal fluctuations in precipitation and tidal inundation. The physical or biological features essential to the conservation of the species in this unit may require special management considerations or protection to address threats described in Table 2. Please see
Special Management Considerations or Protection
section of this rule for a discussion of the threats to tidewater goby habitat and potential management considerations.

HUM-3: Humboldt Bay

HUM-3 consists of 839 ac (339 ha). This unit is located in Humboldt County, within an approximate 8-mi (13-km) radius to the north, south, and west of the City of Eureka. The unit consists of 652 ac (264 ha) of Federal lands, 61 ac (24 ha) of State lands, 45 ac (18 ha) of local lands, and 81 ac (33 ha) of private lands. HUM-3 is located 18.4 mi (29.7 km) north of the Eel River (HUM-4), which is also the nearest extant subpopulation. HUM-3 was

occupied at the time of listing. The tidewater goby subpopulation in HUM-3 is likely a source population, which is important in maintaining the metapopulation dynamics, and hence the long-term viability, of the North Coast Recovery Unit. This subpopulation may provide essential demographic and genetic support to HUM-4, especially after periods of extreme floods, for example, after the 1964 “Christmas Flood,” when the subpopulation of tidewater goby at the Eel River estuary may have been extirpated.

Humboldt Bay and its adjacent marshes and estuaries are a complex mixture of natural and human-made aquatic features that have experienced many decades of human-induced changes. These changes include the construction of levees, tidegates, culverts, and other water control structures, and extensive dredging of sandbars. Surrounding the Bay itself is a generally broad bench historically dominated by mudflats, tidal marshes, estuarine channels, and brackish marshes. Substantial portions of these habitats were converted to agricultural, urban, and industrial uses in recent history, resulting in the loss of as much as 10,000 ac (4,047 ha) of potentially suitable tidewater goby habitat. This critical habitat unit consists of a complex of interconnected estuary channels and tidegates along the eastern edge of Humboldt Bay, which collectively mimic, on a much-reduced scale, suitable habitat for tidewater goby. Many of these channels and marshes are themselves the result of changes to historical habitats, and depend on specific, yet generally undocumented, management activities, such as dredging or sandbar breaches, for their continued function.

To address the dynamic variability of these habitats resulting from seasonal and inter-annual precipitation differences, we have included both the actual known locations where the tidewater goby has been documented, as well as portions of those channels contiguous to, and upchannel or downchannel from, occupied habitat. We have not designated Humboldt Bay proper as critical habitat, nor have we proposed major channels subject to substantial daily tidal fluctuations, as tidewater gobies are not known to breed there. Similarly, we have not designated channels that are discontiguous with occupied habitat, nor have we included intervening marsh or agricultural lands that may occasionally be flooded during severe winter storm events.

Based on several recent surveys, we have found that the precise locations of tidewater goby use within the channel complex during any particular year may change in response to variations in precipitation and channel hydrology. We anticipate that the persistence of the tidewater goby source population within this unit may require protection of lagoons and estuaries that are not occupied every year, but collectively support a source population through an interconnected complex of channels and shallow water habitats. That is, any of the several known occupied locations within a channel complex may be used by tidewater goby during various years in response to dynamic habitat conditions during seasonal, annual, and longer term climatic cycles, such as drought.

PCE 1c (a sandbar(s) across the mouth of a lagoon or estuary) is not likely to occur within this unit because a navigable, dredged channel with a permanent open connection to the ocean is maintained on a regular basis. PCE 1a and 1b occur throughout the unit, although their precise location during any particular time period may change in response to seasonal fluctuations in precipitation and tidal inundation. The physical or biological features essential to the conservation of the species in this unit may require special management considerations or protection to address threats described in Table 2. Please see
Special Management Considerations or Protection
section of this rule for a discussion of the threats to tidewater goby habitat and potential management considerations.

HUM-4: Eel River

This unit is located in Humboldt County, approximately 4.0 mi (6.5 ha) northwest of the City of Ferndale. The unit consists of two subunits, totaling 5 ac (2 ha) of State lands and 34 ac (13 ha) of private lands.

Both subunits are outside the geographical area occupied by the species at the time of listing but are now occupied. The Eel River estuary is similar to Humboldt Bay (HUM-3) in that tidewater goby subpopulations have been found in isolated populations in severely and artificially fragmented habitats, which are often found behind tidegates, culverts, and other manmade structures. In Humboldt Bay (HUM-3), McCraney
et al.
(2010, p. 3315) found that artificial fragmentation reduced dispersal and gene flow in these subpopulations. The same may be true for the Eel River estuary subpopulations with isolated populations that are genetically distinct from each other. Therefore, until additional information is available regarding population genetics, distribution, and other parameters, we consider these two areas, the Eel River North Area (Subunit-4a) and the Eel River South Area (Subunit-4b), to be distinct from each other. Artificially fragmented habitats in the Eel River estuary may have genetically isolated or weakened populations of tid

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2013-02057. Public record. Not legal advice.