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

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2011-26301

## Record

- **Collection:** Federal Register
- **Document type:** Proposed Rule
- **Published:** October 19, 2011
- **Citation:** 76 FR 64996

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2011-0085; MO 92210-0-0009]
RIN 1018-AX39
Endangered and Threatened Wildlife and Plants; Designation of Revised Critical Habitat for the Tidewater Goby

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Proposed rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), propose to revise critical habitat for the tidewater goby (
Eucyclogobius newberryi
) under the Endangered Species Act of 1973, as amended (Act). In total, approximately 12,157 acres (4,920 hectares) are being proposed for designation as critical habitat. The proposed revised critical habitat is located 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.

DATES:

We will accept comments received or postmarked on or before December 19, 2011. We must receive requests for public hearings, in writing, at one of the addresses shown in the
FOR FURTHER INFORMATION CONTACT
section by December 5, 2011.

ADDRESSES:

You may submit comments by one of the following methods:

(1)
Electronically:
Go to the Federal eRulemaking Portal:
http://www.regulations.gov.
In the Enter Keyword or ID box, enter Docket No. FWS-R8-ES-2011-0085, which is the docket number for this rulemaking.

(2)
By hard copy:
Submit by U.S. mail or hand-delivery to: Public Comments Processing, Attn: FWS-R8-ES-2011-0085
; Division of
Policy and Directives Management; U.S. Fish and Wildlife Service; 4401 N. Fairfax Drive, MS 2042-PDM; Arlington, VA 22203.

We will post all comments on
http://www.regulations.gov.
This generally means that we will post any personal information you provide us (see the Public Comments section below for more information).

FOR FURTHER INFORMATION CONTACT:

For general information, and information about the proposed 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.

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

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

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

If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Public Comments

We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available, and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning this proposed revised rule. We particularly seek comments concerning:

(1) The reasons why we should or should not designate habitat as “critical habitat” under section 4 of the Act (16 U.S.C. 1531
et seq.
), including whether there are threats to the species from human activity, the degree of which can be expected to increase due to the designation, and whether that increase in threat outweighs the benefit of designation such that the designation of critical habitat may not be prudent.

(2) Specific information on:

(a) The amount and distribution of tidewater goby habitat;

(b) Which areas that are within the geographical area occupied at the time of listing (or are currently occupied) contain features essential to the conservation of the species, should be included in the designation and why;

(c) Special management considerations or protection that may be needed for the physical or biological features essential to the conservation of the species in areas we are proposing, including managing for the potential effects of climate change; and

(d) What areas outside the geographical area occupied at the time of listing that should be included in the designation because they are essential for the conservation of the species and why.

(3) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(4) Information on the projected and reasonably likely impacts of climate change on the tidewater goby, the features essential to its conservation and the areas proposed as critical habitat.

(5) Any probable economic, national security, environmental, cultural, or other relevant impacts of designating any area that may be included in the final designation; in particular, any impacts on small entities, and the benefits of including or excluding areas that exhibit these impacts.

(6) Any information on potential threats to habitat and the feasibility of reintroduction or introduction of the tidewater goby to: Walker Creek, Bolinas Lagoon, Pomponio Creek, Waddell Creek, Salinas River, Arroyo del Cruz, Oso Flaco Lake, Arroyo Sequit, Zuma Creek, Aliso Creek, or any other areas identified for reintroduction or introduction in the recovery plan for the tidewater goby (Service 2005), and the reasons why we should or should not designate these or other unoccupied areas as critical habitat for the tidewater goby.

(7) Specifically with reference to those State Park lands under the jurisdiction of the California Department of Parks and Recreation (CDPR) that are proposed for designation, information on any areas covered by conservation or management plans that we should consider for exclusion from the designation under section 4(b)(2) of the Act.

(8) Any additional proposed critical habitat areas covered by conservation or management plans that we should consider for exclusion from the designation under section 4(b)(2) of the Act. We specifically request any information on any operative or draft habitat conservation plans for the tidewater goby that have been prepared under section 10(a)(1)(B) of the Act, or any other management or other conservation plan or agreement that benefits the tidewater goby or its primary constituent elements.

(9) Any information concerning tribal lands or trust resources that may be

impacted by this proposed revision to critical habitat.

(10) Whether our exemption under section 4(a)(3)(B) of the Act of Department of Defense land at Vandenberg Air Force Base (VAFB) in Santa Barbara County, and Marine Corps Base (MCB) Camp Pendleton in San Diego County, is or is not appropriate, and why.

(11) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the
ADDRESSES
section. We request that you send comments only by the methods described in the
ADDRESSES
section. We will post your entire comment—including your personal identifying information—on
http://www.regulations.gov.
You may request at the top of your document that we withhold personal information such as your street address, phone number, or email address from public review; however, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
http://www.regulations.gov,
or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office (see
FOR FURTHER INFORMATION CONTACT
).

Background

It is our intent to discuss only those topics directly relevant to the designation of critical habitat for the tidewater goby in this proposed rule. This proposed rule incorporates new information on tidewater goby genetics and distribution that was not available when we completed our 2008 final critical habitat designation (73 FR 5920; January 31, 2008). A summary of topics that are relevant to this proposed critical habitat designation is provided below. For more information on tidewater goby taxonomy, biology, and ecology, please refer to: the final listing rule published in the
Federal Register
on February 4, 1994 (59 FR 5494); the first and second rules proposing critical habitat published in the
Federal Register
on August 3, 1999 (64 FR 42250) and November 28, 2006 (71 FR 68914), respectively; 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). Additionally, more species information can be found in the Recovery Plan for the Tidewater Goby (Recovery Plan) (Service 2005), and in the Tidewater Goby 5-year review (Service 2007).

Species Description and Genetic/Morphological Characteristics

The tidewater goby is a small, elongate, grey-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 goby are nearly transparent with a mottled brown upper surface. Female tidewater goby develop darker colors, often black, on the body and dorsal and anal fins. Tidewater goby are 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; M. Hellmair, pers. comm. 2010).

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 goby that were collected at 31 locations throughout the species' geographic range has identified six major phylogeographic units (Dawson
et al.
2001, p. 1171). These six regional units are the basis for the recovery units in the Recovery Plan (Service 2005), and include the following areas: (1) Tillas Slough (Smith River) in Del Norte County to Lagoon Creek in Mendocino County (North Coast (NC) Unit); (2) Salmon Creek in Sonoma County to Bennett's Slough in Monterey County (Greater Bay (GB) Unit); (3) Arroyo del Oso to Morro Bay in San Luis Obispo County (Central Coast (CC) Unit); (4) San Luis Obispo Creek in San Luis Obispo County to Rincon Creek in Santa Barbara County (Conception (CO) Unit); (5) Ventura River in Ventura County to Topanga Creek in Los Angeles County (Los Angeles-Ventura (LV) Unit); and (6) San Pedro Harbor in Los Angeles County to Los Peñasquitos Lagoon in San Diego County (South Coast (SC) 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 North Coast populations of the tidewater goby formed as a result of a single recent episode of colonization of newly formed habitats is supported by McCraney and Kinziger (2009, p. 30). They compared genetic variation of 13 naturally and artificially fragmented populations of the tidewater goby in northern California, including eight Humboldt Bay populations and five coastal lagoon populations, 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 man-made 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 (McCraney and Kinziger 2009, p. 37). 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 and Kinziger 2009, p. 32). Populations in all coastal lagoons, with the exception of Lake Earl in Del Norte County, appear to be stable and genetically healthy (McCraney and Kinziger 2009, p. iii). The Lake Earl population exhibited reduced levels of genetic diversity in comparison to similar coastal lagoon populations (McCraney and Kinziger 2009, p. 34). 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 lagoon mouth (McCraney and Kinziger 2009, p. 34).

The conclusions from these studies are:

(1) The tidewater goby exhibits considerable genetic diversity across its range.

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

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

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

(5) Although genetic differences occur between populations north of Los Angeles County, they are not as divergent as those populations found south of Los Angeles County.

Metapopulation Dynamics

Local populations of tidewater goby are best characterized as metapopulations (Lafferty
et al.
1999a, p. 1448). A metapopulation is defined as a population made up of a group of subpopulations interconnected through patterns of gene flow, extinction, and recolonization, and at least somewhat geographically isolated from other populations (Meffe and Carrol 1994, p. 189). Local tidewater goby populations are frequently isolated from other local populations by extensive areas of unsuitable habitat. They occupy coastal lagoons and estuaries that in most cases are separated by the open ocean. Very few tidewater goby 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 some small streams 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 (within 6 miles (mi) (10 kilometers (km))) populations (Lafferty
et al.
1999a, p. 1451). These recolonization events suggest that tidewater goby populations exhibit a metapopulation dynamic where some populations survive or remain viable by continually exchanging individuals and recolonizations after occasional extirpations (Doak and Mills 1994, p. 619).

Lafferty
et al.
(1999b, p. 618) monitored the post-flood 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 may sometimes have a positive effect by contributing to recolonization of habitats where a tidewater goby population has become extirpated.

The largest wetland habitats where the tidewater goby has been known to occur are not necessarily the most secure, as evidenced by the fact that the Santa Margarita River in San Diego County and the San Francisco Bay have lost their populations of tidewater goby. Today, the most stable locations with the largest tidewater goby populations consist of lagoons and estuaries of intermediate sizes (5 to 125 ac (2 to 50 ha)) that have remained relatively unaffected by human activities (Service 2005, p. 12). Many of the locations where tidewater goby are consistently present are likely to be “source” populations, which probably provide the colonists for locations where tidewater goby are intermittently extirpated.

Historical records and survey results for several areas occupied by tidewater goby are available (Swift
et al.
1989, pp. 18-19; Swift
et al.
1994, pp. 8-16). These documents 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 occur in lagoons and estuaries that are more than 2.47 ac (1 ha) in size, and that have remained relatively unaffected by human activities (Lafferty
et al.
1999a, pp. 1450-1453). We note, however, that some systems that are affected or altered by human activities also have relatively large and stable populations, for example, Humboldt Bay in Humboldt County, Pismo Creek in San Luis Obispo County, Santa Ynez River in Santa Barbara County, and the Santa Clara River in Ventura County. Also, some habitats less than 2.47 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). The best available information suggests that the lagoons and estuaries with persistent tidewater goby populations are likely the source of core populations that provide individuals that colonize adjacent smaller locations with intermittent populations (Lafferty
et al.
1999a, p. 1452).

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 (e.g., 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 do not currently. The species' southernmost known currently occupied locality is the San Luis Rey River, 5 mi (8 km) north of Agua Hedionda Lagoon. Although the northernmost and southernmost extent of the tidewater goby's range has not changed, its overall distribution has become patchy and fragmented along the coast.

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

occurs between the Salinas River in 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; their recent disappearance from some of these locations has created additional gaps in the species' geographic distribution (Capelli 1997, p. 7). Such locations include 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 at 135 locations within its historical range. Of these 135 locations, 23 (17 percent) are no longer occupied by the tidewater goby. Therefore, 112 locations are currently occupied (Service 2005, p. 6).

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 (pond-like) 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, 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, coastal lagoons or estuaries may be hundreds of acres in size and extend many miles inland, and may include extensive backwater marshes (Lake Earl in Del Norte County and Ten Mile River in Mendocino County). Some locations occupied by the tidewater goby, for example, 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. 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 goby have been observed in water salinities between 2 and 27 parts per thousand (ppt) (Swenson 1999, p. 31).

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) states 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.) and crayfish (
Cambaris
spp.)); (8) 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
).

Previous Federal Actions

On April 15, 2009, 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 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 (73 FR 5920, January 31, 2008). 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. 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).

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 seeks or 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) 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.

For inclusion in a critical habitat designation, the habitat within the geographical area occupied by the species at the time it was listed must contain the physical or biological features which are essential to the conservation of the species and which may require special management considerations or protection. 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), focusing on the principal biological or physical constituent elements (primary constituent elements (PCEs)) within an area that are essential to the conservation of the species (such as roost sites, nesting grounds, seasonal wetlands, water quality, tide, soil type). Primary constituent elements are the elements of physical or biological features that provide for a species' life-history processes and are essential to the conservation of the species.

Under the Act, we can 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. 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. When the best available scientific data do not demonstrate that the conservation needs of the species require such additional areas, we will not designate critical habitat in areas outside the geographical area occupied by the species. An area currently occupied by the species but that was outside the geographical area occupied by the species at the time of listing may, however, be essential for the conservation of the species and may be included in the critical habitat designation.

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 determine 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, or other unpublished materials, expert opinion, or personal knowledge.

Habitat is dynamic, and species (or habitats) may naturally shift within an area, or from one area to another, over time. Climate change will be a particular challenge for biodiversity because the addition of stressors associated with climate change to current stressors may push species beyond their ability to survive (Lovejoy and Hannah 2005, pp. 325-326). The synergistic implications of climate change and habitat fragmentation are the most threatening facet of climate change for biodiversity (Lovejoy and Hannah 2005, p. 4), because species may not be able to migrate with shifting habitats. Current climate change predictions for terrestrial areas in the Northern Hemisphere generally indicate warmer air temperatures, more intense precipitation events, and increased summer continental drying, although predictions vary for any given specific location (Field
et al.
1999, pp. 1-3; Hayhoe
et al.
2004, p. 12422; Cayan
et al.
2005, p. 6; Intergovernmental Panel on Climate Change (IPCC) 2007, p. 11; Cayan
et al.
2009, p. xi). Climate change may lead to increased frequency and duration of severe storms and droughts (McLaughlin
et al.
2002, p. 6074; Cook
et al.
2004, p. 1015; Golladay
et al.
2004, p. 504).

Furthermore, these predictions also point to a future of warmer oceans and melting glaciers and icecaps, all of which are expected to raise mean sea levels, leading to the inundation and displacement of many estuaries and lagoons. A rise in sea level will most dramatically affect those estuaries that have been confined by surrounding development that prohibits their boundaries from naturally shifting in response to inundation. Projections for sea-level rise by the year 2100 vary from 0.59 to 6.2 ft (0.18 to 1.9 m) (Raper and Braithwaite 2006, p. 311, IPCC 2007, p. 11; Rahmstorf 2007, p. 368; Herberger
et al.
2009, p. 8; Vermeer and Rahmstorf 2009, p. 21530). Paleoclimatic data suggest that the rate of future melting of the Greenland and Antarctic ice sheets and related sea level rise could be faster than currently projected (Overpeck
et al.
2006, p. 1747). Park
et al.
(1989, pp. 1-52) projected that of the salt marshes along the coast of the contiguous United

States, 30 percent would be lost with a 1.6-ft (0.5-m) sea level rise, 46 percent with a 3.3-ft (1-m) sea level rise, 52 percent with a 6.6-ft (2-m) sea level rise, and 65 percent with a 9.8-ft (3-m) sea level rise.

We cannot project directly to California the percentage of salt marsh habitat that would be lost based upon the estimates of Park
et al.
(1989, p. 1-52), who focused on the east coast and Gulf coast of the United States; however, we can anticipate that with a projected sea level rise of up to almost 6.6 ft (2 m), much of the marshlands and estuaries in the state will be lost by 2100. In addition to the inundation and displacement of estuaries/lagoons, there would be shifts in the quality of the habitats in affected coastal regions. Prior to being inundated, coastal watersheds would become saline due to saltwater intrusion into the surface and groundwater. However, predictions of climatic conditions for smaller sub-regions, such as California, remain less certain. The full effects of these changes on aquatic organisms, such as the tidewater goby, are not well known. Thus, the information currently available on the effects of global climate change is not sufficiently precise to determine what additional areas, if any, may be appropriate to include in the revised critical habitat for this species to address the effects of climate change.

Additionally, 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 required for recovery of the species. Areas that are important to the conservation of the tidewater goby, 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 ensure that 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 result in take of 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 required for tidewater goby from studies of this species' habitat, ecology, and life history as described below. Additional information can be found in the final listing rule published in the
Federal Register
on February 4, 1994 (59 FR 5494), the Tidewater Goby 5-Year Review (Service 2007), and the Recovery Plan (Service 2005). Based on our current knowledge of the life history, biology, ecology, and the habitat requirements of the species, 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 (less than 10 to 12 parts per thousand (ppt)) (Swift
et al.
1989, p. 7). 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); it has been collected in salinities as high as 42 ppt by Swift
et al.
(1989, p. 7) and at 63 ppt in McDaniel Slough, Arcata Bay, Humboldt County (G. Goldsmith pers. comm. 2011). The species' tolerance of high salinities likely enables it to withstand some exposure to the marine environment, allowing it to recolonize nearby lagoons and estuaries following flood events. However, tidewater goby 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.

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; Chamberlain and Goldsmith 2006, p. 1). Within a 2-hour period, hundreds of tidewater goby 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 goby have been detected upstream from the ocean. Chamberlain and Goldsmith (2006, p. 1) found tidewater goby 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 goby 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 goby 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 goby 3 mi (5 km) upstream from the ocean in the Santa Margarita River in San Diego County. Collectively, these data suggest the average distance tidewater goby have been detected

upstream from the ocean in medium to large rivers is approximately 3.8 mi (6.1 km). Other than a 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 stream 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 inshore 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 (about 35 ppt). 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, and increases the likelihood that adult tidewater goby, 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.

In Humboldt Bay and the Eel River estuary in Humboldt County, a large amount of salt and brackish marsh habitat was eliminated through the construction of levees and drainage channels. As a result, several of the locations occupied by 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 habitat in the Humboldt Bay-Eel River estuaries are above tidegates.

Therefore, lagoons and estuaries with relatively low salinities for suitable breeding conditions, upstream freshwater habitat for refuge, and sandbars, which creates larger areas of suitable habitat with lower salinities, are essential to the conservation of the species.

Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Diet

The tidewater goby feeds mainly on macroinvertebrates such as mysid shrimp, gammarid amphipods, ostracods, and aquatic insects such as chironomid midge larvae (Irwin and Soltz 1984, pp. 21-23; Swift
et al.
1989, p. 6; Swenson 1995, p. 87). The diets of adult and juvenile tidewater goby tend to include the same relative abundance of different invertebrate species (Swenson and McCray 1996, p. 962).

Water Depth, Velocity, and Temperature

The tidewater goby is most commonly collected in water less than 6 feet (ft) (2 meters (m)) deep (Wang 1982, pp. 4-5; Worchester 1992, p. 53). However, tidewater goby were recently collected in Big Lagoon in Humboldt County during the breeding season at a water depth of 15 ft (4.6 m) (Goldsmith 2006a, p. 1). 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 they are less likely to occur in areas with a steep gradient or microhabitats with a substantial current. At Pescadero Creek in San Mateo County, tidewater goby 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 were instead more densely concentrated in nearby eddies with lower water velocities (Swenson 1993, p. 3).

Backwater marshes, including lateral sloughs, are likely to be important to the tidewater goby for multiple reasons. Flood waters with increased water velocities can have a negative effect on the tidewater goby (Irwin and Soltz 1984, p. 27), and backwater marshes may provide important refuges that reduce the likelihood that tidewater goby will be flushed out of the lagoons or estuaries and into the marine environment during heavy winter floods (Lafferty
et al.
1999a, p. 619). Evidence that increased flows can eliminate tidewater goby from a locality is suggested by the extirpation of 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 tidewater goby from this locality during a storm in 1993 (Swift
et al.
1994, pp. 22-23). The importance of backwater marshes is also highlighted by the fact that tidewater goby in these habitats can achieve a greater size than in adjacent lagoons and creeks (Swenson 1993, pp. 6-7).

Therefore, lagoons and estuaries with a variety of aquatic macroinvertebrates providing food for tidewater goby as well as backwater marshes, including lateral sloughs, which are used as refuge during storm events and sandbar breaches, are essential to the conservation of the species.

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 goby. A species' ability to persist when it is subject to predation pressure frequently depends on the presence of escape cover or shelter, heterogeneous features that provide a greater level of structure to make it more likely to avoid predation (Crowder and Cooper 1982, p. 1802; Gilinsky 1984, p. 455). At locations where the tidewater goby occurs, submerged and emergent aquatic vegetation can create habitat heterogeneity and structure to provide a greater degree of cover from predators than would exist without it. Stable lagoons often possess dense aquatic vegetation, including sago pondweed (
Potamogeton pectinatus
) or widgeon grass (e.g.,
Ruppia maritima
and
R. cirrhosa
). At some locations, juvenile tidewater goby are more prevalent in areas with at least some submergent vegetation compared to areas with little or no vegetation (Wang 1984, p. 16; Swenson 1994, p. 6; Trihey & Associates, Inc. 1996, p. 11). The presence of submerged or emergent vegetation appears to reduce the likelihood that tidewater goby will be preyed upon. Aquatic vegetation also may provide some degree of shelter or refuge during flash flood events (Lafferty
et al.
1999b, p. 621) by lowering water velocity compared to unvegetated areas. Such refuges would

be especially important to fish species, such as tidewater goby, that are not strong swimmers. Therefore, lagoons and estuaries with submerged and emerged vegetation, which provide protection from predators and provide refuge during flood events, are essential to the conservation of the species.

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

The eggs of the tidewater goby are laid in burrows excavated by male fish. Burrows most commonly occur in areas with relatively unconsolidated, clean, coarse sand (Swift
et al.
1989, p. 8), and in silt or mud (Wang 1982, p. 6). Swenson (1995, p. 148) demonstrated that tidewater goby prefer a sandy substrate in the laboratory. Male tidewater goby remain in the burrow to guard the eggs attached to the burrow ceiling and walls, and care for the embryos for approximately 9 to 11 days until they hatch. They rarely, if ever, emerge 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), then move to the bottom substrate as they mature. Worcester (1992, pp. 77-79) found that larval tidewater goby in Pico Creek Lagoon in San Luis Obispo County tended to use the deeper portion of the lagoon at a depth of 29 in (73 cm), which is considerably deeper than the depth level of 17 in (42 cm) where they were not detected. Therefore, lagoons and estuaries with relatively unconsolidated, clean, coarse sand, and silt or mud, which provide for breeding, are essential to the conservation of the species.

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

The majority of lagoons, estuaries, and coastal streams that currently support the tidewater goby have experienced some level of disturbance. These range in size from approximately 31.5 square feet (3 m
2
) of surface area to about 2,000 acres (ac) (800 hectares (ha)). Most lagoons and estuaries that support tidewater goby range from about 1.25 to 12.5 ac (0.5 to 5 ha). Surveys of tidewater goby locations and historic 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; Swift
et al.
1994, pp. 26-27). Lagoons and estuaries smaller than about 5 ac (2 ha) generally exhibit patterns of extirpation or population reduction and subsequent recolonization to very low levels. Many of the records for smaller locations, less than about 1 ac (0.4 ha), include one or a few large individuals with no evidence of reproduction. These small locations are also often within a mile or so of another locality from which recolonization could occur following catastrophic events, such as drought or artificial breaching of the lagoon.

The largest locations are not necessarily the most secure, such as the San Francisco Bay or the Santa Margarita River, which have lost their populations of tidewater goby. However, an exception is Lake Tolowa, Del Norte County, which is several thousand acres in size and has had a continuous presence of tidewater goby. 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, the tidewater goby populations in these intermediate sized locations likely serve as source populations for the smaller ephemeral sites (Lafferty
et al.
1999b, p. 1452). Therefore, lagoons and estuaries that range in size from small to large are important for maintaining the metapopulation dynamics and are essential to the conservation of the species.

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 tidewater goby in areas within the geographical area occupied by the species at the time of listing, focusing on the features' primary constituent elements. We consider primary constituent elements to be the elements of the physical or biological features that provide for a species' life-history processes and, under the appropriate circumstances, 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 (and its components) specific to tidewater goby are:

(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 ranging in salinity from 0.5 ppt to about 12 ppt, which provides adequate space for normal behavior and individual and population growth that contain:

(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 which 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 tidewater goby. Threats identified in the final listing rule for the tidewater goby include: (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 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 (e.g., bass, crayfish); (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 proposed 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,
i.e.,
“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, crayfish)” and “competition with introduced species such as the yellowfin goby and chameleon goby” into one category,
i.e.,
“introduced species that prey on, or compete with, the tidewater goby (e.g., yellowfin goby, bass, and crayfish).” 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 exhibits a pattern of occupancy and extirpation throughout its range. 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. A more detailed discussion of threats to the tidewater goby can be found in the final listing rule (59 FR 5494, March 7, 1994), and the final Recovery Plan (Service 2005, pp. 16-19).

We find that the components of the PCE present within all the areas we are proposing to designate 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 2005, 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 3 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 adverse modification of tidewater goby habitat due to dredging, draining, and filling of lagoons and estuaries. Additional management actions should be taken to restore historic 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) Measures should be developed and implemented 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 within current or enhanced parameters. Measures should prevent further increase in 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, for example, use of pumping and other water control structures to regulate water levels, to provide conditions during the summer and fall, when reproduction is at its highest and freshwater inflow is at its lowest.

(6) Implement measures to prevent further degradation of water quality resulting from agricultural runoff and effluent, municipal run-off, 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 that prevent further increases in the abundance and distribution of nonnative species.

Criteria Used To Identify Critical Habitat

As required by section 4(b)(1)(A) of the Act, we use the best scientific and commercial data available to designate critical habitat. We review available information pertaining to the habitat requirements of the species. In accordance with the Act and its implementing regulation at 50 CFR 424.12(e), we consider whether designating additional areas—outside those currently occupied as well as those occupied at the time of listing—are necessary to ensure the conservation of the species. We are proposing to designate critical habitat in areas within the geographical area occupied by the species at the time of listing in 1994. 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.

In proposing revised critical habitat for the tidewater goby, we made extensive use of the information in the Recovery Plan (Service 2005), and incorporated the recovery goals and strategy identified in the Recovery Plan in the development of our proposed revised designation. We also reviewed other relevant information, including peer-reviewed journal articles, unpublished reports and materials (e.g., 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 revised critical habitat rule (71 FR 68914; November 28, 2006), the 2008 final revised critical habitat rule (73 FR 5920; January 31, 2008), the 5-year review for the tidewater goby (Service 2007), and regional databases and GIS coverages, for example, California Natural Diversity Database, and National Wetlands Inventory maps. We analyzed this information to determine historical occupancy, occupancy at the time of listing, and current occupancy, and to develop criteria for identifying: (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 catastrophic events, and preserving genetic diversity (Service 2005, 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 Recovery Plan, we developed the following 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 thus delineates the specific areas that meet the definition of critical habitat:

(1) Areas that allow for the conservation of viable metapopulations (as defined in the Background section above) under varying environmental conditions, for example, drought. These areas include those that presumably 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 three or more consecutive years based on survey data and published reports. We believe these 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. We have also included other populations within each metapopulation in addition to source populations in the event that the source population is extirpated due to a catastrophic event such as a major flood or drought.

(2) 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 identified locations that provide connectivity as those within 6 mi (10 km) of another occupied location.

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

(1) The Recovery Plan states that, to minimize the chance of local extirpations resulting in extinction of a broader metapopulation (see Background section) and resultant loss of its unique genetic traits, introduction and reintroduction of the tidewater goby into suitable habitat is necessary to recover the species (Service 2005, p. 29);

(2) There has been considerable loss and degradation 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; 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.

One example of the need to propose additional sites that are 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 proposed for introduction or reintroduction, habitat would require some restoration, for example, facilitation of a natural breaching regime, exotic predator management, or freshwater inflow enhancement. For areas outside the geographical area occupied at the time of listing, those meeting the criteria below are proposed for designation in this revised 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 (as defined in the Background section above) under varying environmental conditions, for example, drought. Areas that are currently occupied may include those that presumably support source populations (e.g., Malibu Lagoon).

(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 identified locations that provide connectivity as those within 6 mi (10 km) of another occupied location.

(3) Additional areas that may be more isolated but may represent unique adaptations to local features (habitat variability, hydrology, microclimate).

We did not propose to designate any unoccupied areas that are highly degraded or fragmented and not likely restorable. Such areas provide little or no long-term conservation value, and are not essential for the conservation of the species.

By applying these 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 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 2, below, for the occupancy status of each of the 65 proposed critical habitat units.

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 goby 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 PCEs 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, and 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 goby are known to move upstream from the ocean (3.8 mi (6.1 km)), (2) the presence of barriers, such as culverts that may prevent tidewater goby 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 goby from swimming upstream or can act as a barrier that makes it less likely tidewater goby 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 revisions to critical habitat boundaries for this proposed rule, we made every effort to avoid developed areas, such as lands covered by buildings, pavement, and other structures, because such lands lack the physical or biological features 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 revised critical habitat are excluded by text in this proposed rule. Therefore, if the critical habitat is finalized as proposed, a Federal action involving these lands would not trigger section 7 consultation with respect to critical habitat and the requirement of no adverse modification, unless the specific action may affect the physical or biological features in the adjacent critical habitat.

We are proposing for designation of critical habitat lands that we have determined are within the geographical area occupied by the species at the time of listing and contain those physical or biological features necessary 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 proposed for designation based on one or more components of the PCE being present to support tidewater goby life-history processes. Some units contain all of the identified elements of physical or biological features and support multiple life-history processes. Some units contain only some elements necessary to support the tidewater goby, but nevertheless provide the physical or biological features essential to the conservation of the species.

Summary of Changes From Previously Designated Critical Habitat

On January 31, 2008, we designated 44 coastal stream segments in Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Mateo, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, California, totaling approximately 10,003 ac (4,053 ha) (73 FR 5920). We are proposing to revise this designation to a total of approximately 12,157 ac (4,920 ha) consisting of 65 critical habitat units. This is an increase of approximately 2,154 ac (867 ha) from the currently designated critical habitat. As a result of the additional units, some of the unit names have changed. In this section we present the differences between what was designated in 2008 and what is included in this proposed designation.

(1) Our analysis of new and updated information received since the 2008 critical habitat designation (73 FR 5920) resulted in the identification of areas meeting the definition of critical habitat that differ from the areas identified in 2008. We added and revised areas that meet the definition of critical habitat. Based on our current knowledge of the status and distribution of the species and life history requirements, we believe that including in this proposed rule some areas that were not previously identified as meeting the definition of critical habitat better supports the overall survival and conservation objectives for the species.

(2) We added information related to the genetics of the species rangewide and new distribution data that have become available to us following our 2008 designation (see Background section above).

As a result of the above, we are proposing to designate 12,157 ac (4,920 ha) as critical habitat in this revised rule (Table 1). The lands proposed for designation as critical habitat include areas 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.

Table 1—A Comparison of the Areas (in Acres and Hectares) Identified as Meeting the Definition of Critical Habitat for Tidewater Goby in the 2008 Final Critical Habitat Designation and This 2011 Proposed Revised Critical Habitat Designation

Unit

Name

2008
Acres
Hectares
2011
Acres
Hectares

Del Norte County

DN-1
Tillas Slough (Smith River)
0
0
21
8

DN-2
Lake Earl/Lake Tolowa
2,682
1,085
2,683
1,086

Totals

2,682
1,085
2,704
1,094

Humboldt County

HUM-1
Stone Lagoon
586
237
653
264

HUM-2
Big Lagoon
1,505
609
1,529
619

HUM-3
Humboldt Bay
1,478
598
839
339

HUM-4
Eel River
268
109
39
15

Totals

3,837
1,553
3,060
1,237

Mendocino County

MEN-1
Ten Mile River
218
88
73
30

MEN-2
Virgin Creek
11
4
4
2

MEN-3
Pudding Creek
23
9
17
7

MEN-4
Davis Lake and Manchester State Park Ponds
24
10
29
12

Totals

276
112
123
51

Sonoma County

SON-1
Salmon Creek
100
41
108
44

Totals

100
41
108
44

Marin County

MAR-1
Estero Americano
295
120
465
188

MAR-2
Estero de San Antonio
178
72
285
115

MAR-3
Walker Creek
0
0
118
48

MAR-4
Lagunitas (Papermill) Creek
849
344
998
405

MAR-5
Bolinas Lagoon
0
0
1,114
451

MAR-6
Rodeo Lagoon
40
16
40
16

Totals

1,362
551
3,020
1,223

San Mateo County

SM-1
San Gregorio Creek
39
16
45
18

SM-2
Pomponio Creek
0
0
7
3

SM-3
Pescadero-Butano Creek
218
88
245
99

SM-4
Bean Hollow Creek (Arroyo de Los Frijoles)
10
4
10
4

Totals

267
108
307
124

Santa Cruz County

SC-1
Waddell Creek
0
0
75
30

SC-2
Scott Creek
0
0
74
30

SC-3
Laguna Creek
26
11
26
11

SC-4
Baldwin Creek
17
7
27
11

SC-5
Moore Creek
0
0
15
6

SC-6
Corcoran Lagoon
32
12
28
11

SC-7
Aptos Creek
3
1
9
4

SC-8
Pajaro River
176
71
215
87

Totals

254
103
469
190

Monterey County

MN-1
Bennett Slough
155
63
167
68

MN-2
Salinas River
0
0
466
189

Totals

155
63
633
257

San Luis Obispo County

SLO-1
Arroyo de la Cruz
0
0
33
13

SLO-2
Arroyo del Corral
5
2
5
3

SLO-3
Oak Knoll Creek (Arroyo Laguna)
3
1
5
3

SLO-4
Little Pico Creek
2
1
9
4

SLO-5
San Simeon Creek
16
7
17
7

SLO-6
Villa Creek
5
2
15
7

SLO-7
San Geronimo Creek
1
1
1
1

SLO-8
Toro Creek
0
0
9
4

SLO-9
Los Osos Creek
0
0
73
30

SLO-10
San Luis Obispo Creek
0
0
31
12

SLO-11
Pismo Creek
18
8
20
9

SLO-12
Oso Flaco Lake
0
0
171
69

Totals

50
20
389
162

Santa Barbara County

SB-1
Santa Maria River
468
189
474
192

SB-2
Cañada de las Agujas
1
1
1
1

SB-3
Cañada de Santa Anita
3
1
3
1

SB-4
Cañada de Alegria
1
1
2
1

SB-5
Cañada del Agua Caliente
1
1
1
1

SB-6
Gaviota Creek
9
4
11
5

SB-7
Arroyo Hondo
0
0
1
1

SB-8
Winchester/Bell Canyon
6
3
6
3

SB-9
Goleta Slough
0
0
190
76

SB-10
Arroyo Burro
2
1
3
1

SB-11
Mission Creek-Laguna Channel
14
6
7
3

SB-12
Arroyo Paredon
0
0
4
3

Totals

505
204
703
288

Ventura County

VEN-1
Ventura River
51
20
50
21

VEN-2
Santa Clara River
350
142
322
130

VEN-3
J Street Drain-Ormond Lagoon
45
18
121
49

VEN-4
Big Sycamore Canyon
0
0
1
1

Totals

446
180
495
201

Los Angeles County

LA-1
Arroyo Sequit
0
0
1
1

LA-2
Zuma Canyon
0
0
5
2

LA-3
Malibu Lagoon
64
27
64
27

LA-4
Topanga Creek
5
2
6
2

Totals

69
29
76
32

Orange County

OR-1
Aliso Creek
0
0
14
5

Totals

0
0
14
5

San Diego

SAN-1
San Luis Rey River
0
0
56
23

Totals

0
0
56
23

Grand Totals

10,003
4,053
12,157
4,920

Note:
Area sizes may not sum due to rounding.

Proposed Revised Critical Habitat Designation

We are proposing 65 units as critical habitat for the tidewater goby. The critical habitat areas we describe below constitute our current best assessment of areas that meet the definition of critical habitat for the tidewater goby. The 65 areas we propose as revised critical habitat are listed in Table 2, which shows the occupancy status of the units.

Table 2—Occupancy of Tidewater Goby by Proposed Revised Critical Habitat Units

Unit
Name

Within the geographical area
occupied at time of listing?

Currently occupied?

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
No
No.

MAR-6
Rodeo Lagoon
Yes
Yes.

SM-1
San Gregorio Creek
Yes
Yes.

SM-2
Pomponio Creek
No
No.

SM-3
Pescadero-Butano Creek
Yes
Yes.

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

SC-1
Waddell Creek
Yes
No.

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
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
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 del 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
No
No.

LA-2
Zuma Canyon
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.

Table 3 below provides the approximate area, by unit and landownership, proposed for revised designation of critical habitat for the tidewater goby.

Table 3—Critical Habitat Units Proposed for the Tidewater Goby (in Acres and Hectares) 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
State
Local
Private

Total
1

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)
1,4

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)
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)
1,4

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)
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)
34(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 del 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)
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)
2(1)
4(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)
1,3,4

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)
2,906(1,177)
12,157(4,920)

Note:
Area sizes may not sum due to rounding.

1
Area estimates in ac (ha) reflect the entire area within the proposed revised 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 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 1a, or 1b.
3. Channelization of habitats where the species occurs affecting the PCE 1a, 1b, or 1c.
4. Non-point 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 proposed revised 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 1-3 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 (21 ac (8 ha))

This unit is located in Del Norte County, approximately 3.0 mi (4.8 km) west of the community of Smith River. The unit encompasses approximately 21 ac (8.0 ha), and consists entirely of private lands. DN-1 is located 8.0 mi (12.8 km) north of Lake Earl/Lake Tolowa (DN-2), which is also the next nearest extant population. DN-1 was occupied at the time of listing. This unit has the northernmost tidewater goby population rangewide. DN-1 will support the recovery of the tidewater goby population along this portion of the coast. This unit is important for maintaining the tidewater goby metapopulation in the region, and may play an important role in dispersal northwards and extending the range of the tidewater goby. This could prove critical 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 3. 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 (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 encompasses approximately 2,683 ac (1,086 ha), and 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 population. DN-2 was occupied at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region.

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, 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 multi-year cycle, tidewater goby may persist and breed anywhere within the lagoon.

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 3. 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 (653 ac (264 ha))

This unit is located in Humboldt County, approximately 11 mi (18 km) north of the City of Trinidad. The unit encompasses approximately 653 ac (264 ha), and 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 population. HUM-1 was occupied at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region. HUM-1 will also support the recovery of tidewater goby populations along this portion of the coast.

Of special concern is the threat to Stone Lagoon from the potential for accidental introduction of New Zealand mud snails (NZMS;
Potamopyrgus antipodarum
) from nearby Big Lagoon (HUM-2) and Freshwater Lagoon (not proposed as critical habitat), which are currently infested with NZMS. NZMS have spread throughout the western United States since becoming established in Idaho and Montana approximately 25 years ago. Once in a new habitat, NZMS typically have explosive population growth. Their large population numbers can drastically alter natural ecosystems with the NZMS competing with native species. Recreational fishing and boating occurs at Stone, Big, and Freshwater Lagoons. Introduction of NZMS to Stone Lagoon is likely to occur through foot traffic and boat launching from the two infested lagoons. Additional threats include the accidental introduction of other exotic aquatic species from outside the local area, including quagga mussels (
Dreissena rostriformis
) and zebra mussels (
Dreissena polymorpha
), which may also drastically alter the natural ecosystem of Stone Lagoon.

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 3. 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 (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 encompasses approximately 1,529 ac (619 ha), and 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 population. HUM-2 was occupied at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region. HUM-2 will also support the recovery of tidewater goby populations along this portion of the coast.

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 population for each year (Kinziger, pers. comm. 2010). Results indicate that, in 2008, the tidewater goby population was approximately 21,000 individuals. In 2009, the population was approximately 1.7 to 3.4 million individuals in the cove. In 2010, the population was approximately 30,000 individuals in the same cove. Based on the results of this research, which estimated that the population 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 population in northern California. The results of the study also reflect how variable tidewater goby population 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 3. 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 (839 ac (339 ha))

This unit is located in Humboldt County, within an approximate 8-mi (13-km) radius to the north, south, and east of the City of Eureka. The unit encompasses approximately 839 ac (339 ha), and 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 population. HUM-3 was occupied at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region. HUM-3 will also support the recovery of tidewater goby populations along this portion of the coast. This population 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 population 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 human-made structures along the eastern edge of Humboldt Bay, which collectively mimic, on a much reduced scale, habitats largely lost through past management practices. 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 tidewater goby have been documented, as well as portions of those channels contiguous to, upchannel or downchannel, occupied habitat. We have not proposed Humboldt Bay proper in critical habitat, nor have we proposed major channels substantially subject to daily tidal fluctuations, as tidewater goby are not known to breed there. Similarly, we have not proposed 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. Recently, significant restoration efforts directed primarily at salmonid recovery have occurred, or are anticipated to occur, within areas proposed as critical habitat. The effects of these salmonid restoration efforts to tidewater goby are unknown, and will likely vary with their design features and location.

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 3. 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 (39 ac (15 ha))

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 populations have been found in isolated populations in severely and artificially fragmented habitats, which are often found behind tidegates, culverts, and other man-made structures. In Humboldt Bay (HUM-3), McCraney
et al.
(2010, p. 3315) found that artificial fragmentation reduced dispersal and gene flow in these populations. The same may be true for the Eel River estuary populations with isolated populations that are genetically distinct from each other. Therefore, until additional information is available regarding population genetics, distribution, and other parameters, we recommend that these two areas, the Eel River North Area (Subunit-4a) and the Eel River South Area (Subunit-4b), be considered distinct from each other. Artificially fragmented habitats in the Eel River estuary may have genetically isolated or weakened populations of tidewater goby, as has been identified in Humboldt Bay (HUM-3) (McCraney
et al.
2010, p. 3315). Current and proposed estuarine restoration projects in the Eel River estuary may improve dispersal of tidewater goby, increase genetic diversity, and aid in recovery of the species in these locations as well.

Subunit-4a (Eel River North Area)

Subunit-4a encompasses approximately 16 ac (6 ha), and consists of 5 ac (2 ha) of State lands and 11 ac (4 ha) of private lands. Subunit-4a is located 18.4 mi (29.7 km) south of Humboldt Bay (HUM-3), which is also the nearest extant population. This subunit is essential for the conservation of the species 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. The

Eel River delta includes a large, complex estuary with a network of diked and natural slough channels with suitable tidewater goby habitat. The Eel River delta contains many small unsurveyed slough channels and other backwater areas that provide suitable habitat for tidewater goby, but it also contains larger channels open to direct tidal influence that do not provide suitable habitat and are not included in this subunit. This subunit consists of backwater channels and immediately adjacent marsh contiguous to the known occupied habitat.

This unit is subject to infrequent, yet severe, flooding from the nearby Eel River proper. The major flood event of 1964 (“Christmas Flood”), and other major floods during the past century, may have severely altered habitat in most channels, including those currently occupied. Tidewater goby may have survived the flood and resulting loss of habitat in the refugia provided in upper channels and swales. Alternatively, the species may have been extirpated at the Eel River delta during those severe events, and become reestablished through recolonization by individuals from Humboldt Bay populations (HUM-3). Of particular importance, the Eel River location is at the north end of one of the largest natural geographic gaps in the tidewater goby's geographic range. The gap extends to the Ten Mile River (Mendocino County) to the south, representing a coastline distance in excess of 135 mi (217 km).

Although no tidewater goby surveys are known to have occurred in the Eel River estuary prior to listing, we considered this area to be unoccupied by the species until the Service discovered a new population of tidewater goby in the Eel River estuary during surveys in 2004 (Goldsmith 2006b, p. 1). Although Subunit-4a was not considered occupied at the time of listing, it does possess the PCE that could support tidewater goby. On an intermittent basis, Subunit-4a 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.

Subunit-4b (Eel River South Area)

Subunit-4b encompasses approximately 23 ac (9 ha), and consists entirely of private lands. Subunit-4b is located 18.4 mi (29.7 km) south of Humboldt Bay (HUM-3), which is also the nearest extant population. This subunit is essential for the conservation of the species 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. The Southern Eel River delta includes a large complex estuary with a network of diked and natural slough channels, and other backwater areas that provide suitable habitat for tidewater goby. It also contains larger channels open to direct tidal influence that do not provide suitable habitat and are not included in this unit. This unit consists of backwater channels and immediately adjacent marsh contiguous to the known occupied habitat.

This unit is subject to infrequent, yet severe, flooding from the nearby Eel River proper. The major flood event of 1964 (“Christmas Flood”), and other major floods during the past century, may have severely altered habitat in most channels, including those currently occupied. Tidewater goby may have survived the flood and resulting loss of habitat in the refugia provided in upper channels and swales. Alternatively, the species may have been extirpated at the Eel River delta during those severe events, and become reestablished through recolonization by individuals from Humboldt Bay populations (HUM-3). Of particular importance, the Eel River location is at the north end of one of the largest natural geographic gaps in the tidewater goby's geographic range. The gap extends to the Ten Mile River (Mendocino County) to the south, representing a coastline distance in excess of 135 mi (217 km).

Although no tidewater goby surveys are known to have occurred in the Eel River estuary prior to listing, we considered this area to be unoccupied by the species until the Service discovered a new population of tidewater goby in the Eel River estuary during surveys in 2004 (Goldsmith 2006b, p. 1). Although Subunit-4b was not considered occupied at the time of listing, it does possess the PCE that could support tidewater goby. On an intermittent basis, Subunit-4b 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.

MEN-1: Ten Mile River (73 ac (30 ha))

This unit is located in Mendocino County, approximately 9.0 mi (14.5 km) north of the Town of Fort Bragg. The unit encompasses approximately 73 ac (30 ha), and consists of 17 ac (7 ha) of State lands and 56 ac (23 ha) of private lands. MEN-1 is located 5.6 mi (8.9 km) north of the Virgin Creek (MEN-2), which is also the nearest extant population. MEN-1 was occupied by tidewater goby at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region. Furthermore, this unit is the largest block of habitat along the coast of Mendocino County, and is the first location on the southern end of one of the longest stretches of unsuitable habitat in the species' range (previously described under HUM-4). Thus, this unit is important to connect populations within Mendocino County. South of Ten Mile River, only three other small isolated locations (MEN-2, 3, 4) occupied by tidewater goby are known to exist across the more than 100 miles of rugged coastline between MEN-1 and SON-1 in south coastal Sonoma County.

On an intermittent basis, MEN-1 possesses a sandbar across the mouth of the lagoon or estuary during 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 3. 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.

MEN-2: Virgin Creek (4 ac (2 ha))

This unit is located in Mendocino County, approximately 3.5 mi (5.6 km) north of the Town of Fort Bragg. The unit encompasses approximately 4 ac (2 ha), and consists of 2 ac (1 ha) of State lands and 2 ac (1 ha) of private lands. MEN-2 is located 1.2 mi (2.0 km) north of Pudding Creek (MEN-3), which is also the nearest extant population. MEN-2 was occupied by tidewater goby

at the time of listing. The tidewater goby population in this unit is likely a source population for this region, and is therefore important for maintaining the metapopulation in this region. On an intermittent basis, MEN-2 possesses a sandbar across the mouth of the lagoon or estuary during 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 3. 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.

MEN-3: Pudding Creek (17 ac (7 ha))

This unit is located in Mendocino County, approximately 2.5 mi (4.0 km) north of the town of Fort Bragg. The unit encompasses approximately 17 ac (7 ha), and consists of 10 ac (4 ha) of State lands, 1 ac (1 ha) of local lands, and 6 ac (2 ha) of private lands. MEN-3 is located 1.2 mi (2.0 km) south of Virgin Creek (MEN-2), which is also the nearest extant population. MEN-3 was occupied by the tidewater goby at the time of listing. This unit allows for connectivity between tidewater goby source populations, and thereby supports gene flow and metapopulation dynamics in this region. On an intermittent basis, MEN-3 possesses a sandbar across the mouth of the lagoon or estuary during 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 3. 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.

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

This unit is located in Mendocino County, approximately 1.2 mi (1.9 ha) west of the community of Manchester. The unit encompasses approximately 29 ac (12 ha), and consists entirely of State lands. MEN-4 is located 32.4 mi (52.2 km

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2011-26301. Public record. Not legal advice.