Endangered and Threatened Wildlife and Plants; Revised Critical Habitat for the Tidewater Goby (Eucyclogobius newberryi, 68914-68995 [06-9291]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 71, Number 228 (Tuesday, November 28, 2006)]
[Proposed Rules]
[Pages 68914-68995]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-9291]



[[Page 68913]]

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Part II





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Revised Critical Habitat 
for the Tidewater Goby (Eucyclogobius newberryi); Proposed Rule

Federal Register / Vol. 71, No. 228 / Tuesday, November 28, 2006 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AU81


Endangered and Threatened Wildlife and Plants; Revised Critical 
Habitat for the Tidewater Goby (Eucyclogobius newberryi)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
revise currently designated critical habitat for the tidewater goby 
(Eucyclogobius newberryi) under the Endangered Species Act of 1973, as 
amended (Act). We originally designated critical habitat for the 
tidewater goby on November 20, 2000 (65 FR 69693). We are proposing to 
revise the critical habitat for the tidewater goby to a total of 
approximately 10,003 acres (ac) (4,050 hectares (ha)). This is an 
increase of approximately 8,422 ac (3,408 ha) from the currently 
designated critical habitat. In the previous rule, critical habitat was 
only designated in Orange and San Diego Counties due to uncertainty 
over the future listing status of tidewater goby populations to the 
north. 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, and Los Angeles Counties, 
California.

DATES: We will accept comments from all interested parties until 
January 29, 2007. We must receive requests for public hearings, in 
writing, at the address shown in the ADDRESSES section by January 12, 
2007.

ADDRESSES: If you wish to comment, you may submit your comments and 
materials concerning this proposal by any one of several methods:
    1. You may mail or hand-deliver written comments and information to 
Diane K. Noda, Field Supervisor, U.S. Fish and Wildlife Service, 
Ventura Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, 
CA 93003.
    2. You may send comments by electronic mail (e-mail) to 
fw8gobypch@fws.gov. Please see the Public Comments Solicited section 
below for file format and other information about electronic filing.
    3. You may fax your comments to 805/644-3958.
    4. You may go to the Federal eRulemaking Portal: https://
www.regulations.gov. Follow the instructions for submitting comments.
    Comments and materials received, as well as supporting 
documentation used in the preparation of this proposed rule, will be 
available for public inspection, by appointment, during normal business 
hours at the Ventura Fish and Wildlife Office (2493 Portola Road, Suite 
B, Ventura, CA 93003; telephone 805/644-1766).

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 
the Field Supervisor, Ventura Fish and Wildlife Office, 2493 Portola 
Road, Suite B, Ventura, CA 93003 (telephone 805/644-1766; facsimile 
805/644-3958). Persons who use a telecommunications device for the deaf 
(TDD) may call the Federal Information Relay Service (FIRS) at 800-877-
8339, 7 days a week and 24 hours a day.
    For information about the proposed designation in Del Norte, 
Humboldt, and Mendocino Counties, contact the 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 the 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).

SUPPLEMENTARY INFORMATION:

Public Comments Solicited

    We intend that any final action resulting from this proposal will 
be as accurate and as effective as possible. Therefore, comments or 
suggestions from the public, other concerned governmental agencies, the 
scientific community, industry, or any other interested party 
concerning this proposed rule are hereby solicited. Comments 
particularly are sought concerning the following issues.
    (1) The reasons any habitat should or should not be determined to 
be critical habitat as provided by section 4 of the Act (16 U.S.C. 1531 
et seq.), including whether the benefit of designation will outweigh 
any threats to the species due to designation;
    (2) Specific information on the amount and distribution of 
tidewater goby habitat, what areas should be included in the 
designation that were occupied at the time of listing that contain the 
features that are essential for the conservation of the species and 
why, and what areas not occupied at the time of listing are essential 
to 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 revised critical 
habitat;
    (4) Any foreseeable economic, national security, or other potential 
impacts resulting from the proposed revision of critical habitat and, 
in particular, any impacts on small entities;
    (5) Whether our approach to designating critical habitat could be 
improved or modified in any way to provide for greater public 
participation and understanding, or to assist us in accommodating 
public concerns and comments;
    (6) Whether our general approach to determine which localities to 
include in proposed critical habitat (44 of the 112 localities that are 
currently occupied by tidewater gobies) could be improved or modified;
    (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 goby or its primary constituent 
elements; and
    (9) Any information concerning Tribal lands or trust resources that 
may be impacted by this proposed revision to critical habitat.
    If you wish to comment, you may submit your comments and materials 
concerning this proposal by any one of several methods (see ADDRESSES). 
Internet comments may be submitted to fw8gobypch@fws.gov (please use 
ASCII file format and avoid the use of special characters or any form 
of encryption) or the Federal eRulemaking Portal: https://
www.regulations.gov. Please also include ``Attn: Tidewater goby'' in 
your e-mail subject header and your name and return address in the body 
of your message. If you do not receive a

[[Page 68915]]

confirmation from the system that we have received your Internet 
message, contact us directly by calling Chris Dellith at the Ventura 
Fish and Wildlife Office at phone number 805/644-1766. Please note that 
the Internet address fw8gobypch@fws.gov will be closed out at the 
termination of the public comment period.
    Our practice is to make comments, including names and home 
addresses of respondents, available for public review during regular 
business hours. Individual respondents may request that we withhold 
their names and/or home addresses, etc., but if you wish us to consider 
withholding this information you must state this prominently at the 
beginning of your comments. In addition, you must present rationale for 
withholding this information. This rationale must demonstrate that 
disclosure would constitute a clearly unwarranted invasion of privacy. 
Unsupported assertions will not meet this burden. In the absence of 
exceptional, documentable circumstances, this information will be 
released. We will always make submissions from organizations or 
businesses, and from individuals identifying themselves as 
representatives of or officials of organizations or businesses, 
available for public inspection in their entirety.

Role of Critical Habitat in Actual Practice of Administering and 
Implementing the Act

    Attention to and protection of habitat is paramount to successful 
conservation actions. The role that designation of critical habitat 
plays in protecting habitat of listed species, however, is often 
misunderstood. As discussed in more detail below in the discussion of 
exclusions under section 4(b)(2) of the Act, there are significant 
limitations on the regulatory effect of designation under section 
7(a)(2) of the Act. In brief, (1) designation provides additional 
protection to habitat only where there is a Federal nexus; (2) the 
protection is relevant only when, in the absence of designation, 
destruction or adverse modification of the critical habitat would in 
fact take place (in other words, other statutory or regulatory 
protections, policies, or other factors relevant to agency decision-
making would not prevent the destruction or adverse modification); and 
(3) designation of critical habitat triggers the prohibition of 
destruction or adverse modification of that habitat, but it does not 
require specific actions to restore or improve habitat.
    Currently, only 476 species, or 36 percent of the 1,311 listed 
species in the United States under the jurisdiction of the Service, 
have designated critical habitat. We address the habitat needs of all 
1,311 listed species through conservation mechanisms such as listing, 
Section 7 consultations, the Section 4 recovery planning process, the 
Section 9 protective prohibitions of unauthorized take, Section 6 
funding to the States, the Section 10 incidental take permit process, 
and cooperative, nonregulatory efforts with private landowners. The 
Service believes that it is these measures that may make the difference 
between extinction and survival for many species.
    In considering potential exclusions of critical habitat proposed in 
this revision, we will evaluate the benefits of designation in light of 
Gifford Pinchot Task Force v. U.S. Fish and Wildlife Service, 378 F.3d 
1059 (9th Cir 2004) (hereinafter Gifford Pinchot). In that case, the 
Ninth Circuit invalidated the Service's regulation defining 
``destruction or adverse modification of critical habitat.'' In 
response, on December 9, 2004, the Director issued guidance to be 
considered in making section 7 adverse modification determinations. 
This proposal to revise critical habitat does not use the invalidated 
regulation in our consideration of the benefits of including areas in 
this proposed revised designation. The Service will carefully manage 
future consultations that analyze impacts to designated critical 
habitat, particularly those that appear to be resulting in an adverse 
modification determination. Such consultations will be reviewed by the 
Regional Office prior to finalizing to ensure that an adequate analysis 
has been conducted that is informed by the Director's guidance.
    On the other hand, to the extent that designation of critical 
habitat provides protection, that protection can come at significant 
social and economic cost. In addition, the mere administrative process 
of designation of critical habitat is expensive, time-consuming, and 
controversial. The current statutory framework of critical habitat, 
combined with past judicial interpretations of the statute, make 
critical habitat the subject of excessive litigation. As a result, 
critical habitat designations are driven by litigation and courts 
rather than biology, and made at a time and under a time frame that 
limits our ability to obtain and evaluate the scientific and other 
information required to make the designation most meaningful.
    In light of these circumstances, the Service believes that 
additional agency discretion would allow our focus to return to those 
actions that provide the greatest benefit to the species most in need 
of protection.

Procedural and Resource Difficulties in Designating Critical Habitat

    We have been inundated with lawsuits for our failure to designate 
critical habitat, and we face a growing number of lawsuits challenging 
critical habitat determinations once they are made. These lawsuits have 
subjected the Service to an ever-increasing series of court orders and 
court-approved settlement agreements, compliance with which now 
consumes nearly the entire listing program budget. This leaves the 
Service with little ability to prioritize its activities to direct 
scarce listing resources to the listing program actions with the most 
biologically urgent species conservation needs.
    The consequence of the critical habitat litigation activity is that 
limited listing funds are used to defend active lawsuits, to respond to 
Notices of Intent (NOIs) to sue relative to critical habitat, and to 
comply with the growing number of adverse court orders. As a result, 
listing petition responses, the Service's own proposals to list 
critically imperiled species, and final listing determinations on 
existing proposals are all significantly delayed.
    The accelerated schedules of court-ordered designations have left 
the Service with limited ability to provide for public participation or 
to ensure a defect-free rulemaking process before making decisions on 
listing and critical habitat proposals, due to the risks associated 
with noncompliance with judicially imposed deadlines. This in turn 
fosters a second round of litigation in which those who fear adverse 
impacts from critical habitat designations challenge those 
designations. The cycle of litigation appears endless, and is 
expensive, thus diverting resources from conservation actions that may 
provide relatively more benefit to imperiled species.
    The costs resulting from the designation include legal costs, the 
cost of preparation and publication of the designation, the analysis of 
the economic effects and the cost of requesting and responding to 
public comment, and in some cases the costs of compliance with the 
National Environmental Policy Act (NEPA; 42 U.S.C. 4321 et seq.). These 
costs, which are not required for many other conservation actions, 
directly reduce the funds available for direct and tangible 
conservation actions.

Background

    It is our intent to discuss only those topics directly relevant to 
the proposal

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to revise critical habitat in this rule. For more information on the 
tidewater goby, refer to the final rule listing the species, which was 
published in the Federal Register on February 4, 1994 (59 FR 5494), or 
the final rule designating critical habitat for the species in Orange 
and San Diego Counties, California, which was published in the Federal 
Register on November 20, 2000 (65 FR 69693).

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, and the pelvic or ventral fins are 
joined to each other below the chest and belly from below the gill 
cover back to just anterior of the anus. Male tidewater gobies are 
nearly transparent with a mottled brownish upper surface. Female 
tidewater gobies develop darker colors, often black, on the body and 
dorsal and anal fins. The tidewater goby is a short-lived species; the 
lifespan of most individuals appears to be about 1 year (Irwin and 
Soltz 1984, p. 26; Swift et al. 1989, p. 4).
    Various genetic markers demonstrate that pronounced differences in 
the genetic structure of tidewater gobies exist, and that tidewater 
gobies in some locations are genetically distinct. A recent study of 
mitochondrial DNA and cytochrome b (molecular material used in genetic 
studies) sequences from tidewater gobies that were collected at 31 
locations throughout the species' range identified six major 
phylogeographic (geographic differences in the evolution of a species) 
or regional groups (Dawson et al. 2001, p. 1171). These six regional 
groups include the following areas: (1) Tillas Slough (Smith River) in 
Del Norte County to Lagoon Creek in Mendocino County, i.e., the North 
Coast (NC) Unit; (2) Salmon Creek in Sonoma County to Bennett's Slough 
in Monterey County, i.e., the Greater Bay (GB) Unit; (3) Arroyo del Oso 
to Morro Bay in San Luis Obispo County, i.e., the Central Coast (CC) 
Unit; (4) San Luis Obispo Creek in San Luis Obispo County to Rincon 
Creek in Santa Barbara County, i.e., the Conception (CO) Unit; (5) 
Ventura River in Ventura County to Topanga Creek in Los Angeles County, 
i.e., the Los Angeles-Ventura (LV) Unit; and (6) San Pedro Harbor in 
Los Angeles County to Los Pe[ntilde]asquitos Lagoon in San Diego 
County, i.e., the South Coast (SC) Unit.

Metapopulation Dynamics

    Local populations of tidewater gobies are best characterized as 
metapopulations (Lafferty et al. 1999a, p. 1448). First, local goby 
populations are frequently isolated from other local populations by 
extensive areas of unsuitable habitat. Second, gobies occupy coastal 
lagoons and estuaries that in most cases are separated from each other 
by the open ocean. Very few tidewater gobies have ever been captured in 
the marine environment (Swift et al. 1989, p. 7), which suggests this 
species rarely occurs in the open ocean. Studies of the tidewater goby 
suggest that some populations persist on a consistent basis (Lafferty 
et al. 1999a, p. 1452), while other tidewater goby populations appear 
to experience intermittent extirpations. 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 tidewater gobies have been extirpated 
apparently have been recolonized when extant populations were present 
within a relatively short distance of the extirpated population (i.e., 
less than 6 miles (mi) (10 kilometers (km)). 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 may occur after occasional 
extirpations (Doak and Mills 1994, p. 619).
    Lafferty et al. (1999b) monitored the post-flood persistence of 
several tidewater goby populations in Santa Barbara and Los Angeles 
Counties during and 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). 
Tidewater gobies apparently colonized Ca[ntilde]ada Honda in Santa 
Barbara County after one flood event (Lafferty et al. 1999b, p. 621). 
This information suggests that flooding may sometimes contribute to 
recolonization of habitats where a tidewater goby population has become 
extirpated.
    The largest wetland habitats where tidewater gobies have 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 
majority of the most stable and largest tidewater goby populations 
consist of lagoons and estuaries of intermediate sizes, i.e., 5 to 125 
ac (2 to 50 ha) that have remained relatively unaffected by human 
activities (Service 2005, p. 12). Many of the localities where 
tidewater gobies are consistently present may be ``source'' 
populations, and such locations may provide the colonists for 
localities that intermittently lose their tidewater goby populations.
    Historical records and survey results for several localities 
occupied by the tidewater goby are available (e.g., Swift et al. 1989, 
pp. 18-19; Swift et al. 1994, pp. 8-16). These documents suggest 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 the 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 (e.g., 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 (Swift et al. 1997, p. 
3; Keegan 2006, p. 8). The best available information suggests that the 
lagoons and estuaries that have persistent populations are likely the 
core populations that provide the individuals that colonize adjacent, 
smaller localities that have ephemeral tidewater goby 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 localities that extended 
from 3 mi (5 km) south of the California--Oregon border (i.e., Tillas 
Slough in Del Norte County) to 44 mi (71 km) north of the United 
States--Mexico border (i.e., 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 the northernmost locality that forms one 
end of the historical and current geographic range of the tidewater 
goby has not changed over time. Tidewater gobies do not currently occur 
in Agua Hedionda Lagoon, and the species' southernmost known locality 
currently is located in Cockleburr Canyon 9.2 mi (14.8 km) north of 
Agua Hedionda Lagoon. Although the northernmost and southernmost extent 
of the goby's range has not changed much over time, the

[[Page 68917]]

goby's overall population has become patchy and fragmented along the 
coast.
    Tidewater gobies appear to be naturally absent from several large 
(50 to 135 mi (80 to 217 km)) stretches of coastline where lagoons or 
estuaries are absent, and steep topography or swift currents may 
prevent tidewater gobies from dispersing between adjacent localities 
(Swift et al. 1989, p. 13). One such gap in lagoons and estuaries 
occurs between the Eel River in Humboldt County and the Ten Mile River 
in Mendocino County. A second gap exists between Lagoon Creek 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 now 
being absent from several locations where it historically occurred; 
their recent disappearance from specific locations has created smaller, 
artificial gaps in the species' geographic distribution (Capelli 1997, 
p. 7). Such locations include Buena Vista Lagoon and Agua Hedionda 
Lagoon in San Diego County, Calleguas Creek/Mugu Lagoon in Ventura 
County, 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 
gobies occurred, or had been known to occur, at 87 localities; these 
localities included 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 tidewater gobies occurring at four 
additional localities (Swift et al. 1993, p. 129). Other goby 
localities have been identified since 1993, and currently tidewater 
gobies have been documented at 135 localities within the historical 
geographic range of the species (Service 2005, p. 6). Of these 135 
localities, 23 (17 percent) are no longer known to be occupied by 
tidewater gobies. Therefore, 112 localities are currently occupied.

Habitat

    The lagoons, estuaries, backwater marshes, and freshwater 
tributaries that tidewater gobies occupy are dynamic environments that 
are subject to considerable fluctuations on a seasonal and annual 
basis. In a typical year, the formation of a sandbar occurs in the late 
spring as flow into a lagoon declines enough to allow the ocean surf to 
build up the sandbar at the mouth of the lagoon. Winter rains and 
subsequently 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 moves through the lagoon 
or estuary or settles out in backwater marshes, while heavier sand is 
left in the lagoon or estuary. High flows associated with winter rains 
can scour out the lagoon bottom to lower levels, with sand building up 
again after flows decline. These dynamic processes result in wetland 
habitats that, over time, move both laterally and up- or down-gradient 
relative to stationary features that exist outside the flood zone 
(e.g., roads or buildings).
    The horizontal extent of the lentic (pond-like) wetland habitat 
associated with a particular tidewater goby locality varies on a site-
specific basis, and is affected in part by local precipitation patterns 
and topography. In coastal areas where the topography is steep and 
precipitation is relatively low (e.g., areas adjacent to the Santa Ynez 
Mountains in Santa Barbara County), the habitats occupied by tidewater 
gobies may be a few acres in size, only extend a few hundred feet 
inland from the ocean, and backwater marshes may be small or absent. In 
other coastal settings where precipitation is more abundant: (1) 
Topography is less steep and surface streams are larger; (2) coastal 
lagoons or estuaries may be hundreds of acres in size and extend many 
miles inland; and (3) extensive backwater marshes may be present (e.g., 
Lake Earl in Del Norte County and Ten Mile River in Mendocino County).
    Some localities occupied by tidewater gobies receive surface or 
ground water from upstream areas on a year-round basis. Such localities 
(e.g., Bennett's Slough in Monterey County) tend to possess wetland 
habitats that are larger and can extend inland for several hundred feet 
or even 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 (e.g., Little Pico Creek in 
San Luis Obispo County) tend to possess wetland habitats that only 
extend a short distance inland from the ocean (i.e., 290 ft (88 m)).

Reproduction

    Tidewater gobies have been observed spawning 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 spawning behavior in adult fish and the presence of egg 
clutches at water temperatures between 48 and 77 degrees Fahrenheit (F) 
(9 and 25 degrees Celsius (C)). Spawning tidewater gobies have been 
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 that was published in 
1994 (59 FR 5494) 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 tidewater gobies; (7) introduced species that prey on the 
tidewater goby (e.g., bass (Micropterus spp.) and crayfish (Cambaris 
spp.)); (8) the inadequacy of existing regulatory mechanisms; (9) 
drought conditions that result in the deterioration of coastal and 
riparian habitats; and (10) competition with introduced species such as 
the yellowfin goby (Acanthogobius flavimanus) and chameleon goby 
(Tridentiger trigonocephalus).

Previous Federal Actions

    On February 4, 1994, the tidewater goby was listed as endangered 
throughout its entire range (59 FR 5494). We did not designate critical 
habitat at the time we listed this species because we found that 
critical habitat for the tidewater goby was not then determinable.
    On September 18, 1998, the Natural Resources Defense Council, Inc., 
filed a lawsuit in Federal District Court in California against the 
United States Department of the Interior, et al., for failure to 
designate critical habitat for the tidewater goby. On April 5, 1999, 
Judge Carlos R. Moreno ordered that the ``Service publish a proposed 
critical habitat designation for the tidewater goby in 120 days' 
(Natural Resources Defense Council, Inc. v. United States

[[Page 68918]]

Department of the Interior et al. CV 98-7596 ).
    On June 24, 1999, we published a proposed rule to: (1) Delist 
populations of the tidewater goby in areas north of Orange and San 
Diego Counties, and (2) retain the tidewater goby populations in Orange 
and San Diego Counties as an endangered distinct population segment 
based on our re-evaluation of the species' status throughout its range 
(64 FR 33816). The Service proposed delisting northern populations of 
tidewater gobies because there were more populations in the north than 
were known at the time of listing, and it was believed that the threats 
to the northern populations may have been less severe and that the 
ability of tidewater gobies to recolonize sites may have been greater 
than previously thought.
    On August 3, 1999, we proposed critical habitat for the tidewater 
goby in Orange and San Diego Counties (64 FR 42250); we did not propose 
critical habitat for this species throughout the rest of its geographic 
range in 1999 because we believed that the tidewater goby populations 
north of Orange County did not warrant listing under the Act, and had 
proposed to delist the species north of Orange County; therefore there 
were no areas essential to the conservation of the tidewater goby north 
of Orange County. On November 20, 2000, the Service designated critical 
habitat for the tidewater goby in Orange and San Diego Counties (65 FR 
69693). The critical habitat designation consisted of 10 coastal stream 
segments that collectively measured 9 linear mi (14.5 km) in length.
    On November 7, 2002, we withdrew our proposal to delist the 
tidewater goby in areas north of Orange County (67 FR 67803) based in 
large part on comments from the public, the scientific community, 
industry, and other concerned government agencies and new information, 
received after the publication of the proposed rule, that indicated 
that the reasons for delisting may have been in error. Therefore, the 
tidewater goby has remained listed as an endangered species throughout 
its historical geographic range since 1994.
    On August 31, 2001, Cabrillo Power L.L.C. (Cabrillo) filed a 
lawsuit in the U.S. District Court for the Southern District of 
California challenging a portion of the November 20, 2000, final rule 
that designated the 10 critical habitat units in Orange and San Diego 
Counties. Specifically, Cabrillo objected to the critical habitat unit 
involving Agua Hedionda Lagoon and Creek. In a consent decree dated 
February 27, 2003, the U.S. District Court: (1) Agreed to vacate the 
critical habitat designation involving Agua Hedionda Lagoon and Creek; 
(2) stated the nine other critical habitat units should remain in 
effect; (3) stated the final rule designating critical habitat was 
remanded in its entirety for reconsideration; and (4) 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 revised rules to the Federal Register no 
later than November 15, 2006, and November 1, 2007, respectively.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as--(i) the 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by a 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 which are necessary to 
bring any endangered species 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 prohibition against destruction or adverse modification of 
critical habitat with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 requires consultation on 
Federal actions that are 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 government or public access to private lands. Section 7 is a 
purely protective measure and does not require implementation of 
restoration, recovery, or enhancement measures.
    To be included in a critical habitat designation, the habitat 
within the area occupied by the species must first have features that 
are essential to the conservation of the species. Critical habitat 
designations identify, to the extent known using the best scientific 
data available, habitat areas that provide essential life cycle needs 
of the species (i.e., areas on which are found the primary constituent 
elements (PCEs), as defined at 50 CFR 424.12(b)).
    Habitat occupied at the time of listing may be included in critical 
habitat only if the essential features thereon may require special 
management considerations or protection. Thus, we do not include areas 
where existing management is sufficient to conserve the species. (As 
discussed below, such areas may also be excluded from critical habitat 
pursuant to section 4(b)(2)). Areas outside of the geographic area 
occupied by the species at the time of listing may only be included in 
critical habitat if they are essential for the conservation of the 
species. Accordingly, when the best available scientific data do not 
demonstrate that the conservation needs of the species require 
additional areas, we will not designate critical habitat in areas 
outside the geographical area occupied by the species at the time of 
listing. An area currently occupied by the species that was not known 
to be occupied at the time of listing will likely, but not always, be 
essential to the conservation of the species and, therefore, typically 
included in the critical habitat designation.
    The Service's Policy on Information Standards Under the Endangered 
Species Act, published in the Federal Register on July 1, 1994 (59 FR 
34271), and Section 515 of the Treasury and General Government 
Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658) 
and the associated Information Quality Guidelines issued by the 
Service, provide criteria, establish procedures, and provide guidance 
to ensure that decisions made by the Service represent the best 
scientific data available. They require Service 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 
determining which areas are critical habitat, a primary source of 
information is generally the listing package for the species. 
Additional information sources include the

[[Page 68919]]

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 and expert opinion or personal knowledge. All information is 
used in accordance with the provisions of Section 515 of the Treasury 
and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 
106-554; H.R. 5658) and the associated Information Quality Guidelines 
issued by the Service.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific data available. Habitat is often 
dynamic, and species may move from one area to another over time. 
Furthermore, we recognize that designation of critical habitat may not 
include all of the habitat areas that may eventually be determined to 
be necessary for the recovery of the species. For these reasons, 
critical habitat designations do not signal that habitat outside the 
designation is unimportant or may not be required for recovery.
    Areas that support populations, but are outside the critical 
habitat designation, will continue to be subject to conservation 
actions implemented under section 7(a)(1) of the Act and to the 
regulatory protections afforded by the section 7(a)(2) jeopardy 
standard, as determined on the basis of the best available information 
at the time of the action. Federally funded or permitted projects 
affecting listed species outside their designated critical habitat 
areas may still result in jeopardy findings in some cases. 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, or 
other species conservation planning efforts if new information 
available to these planning efforts calls for a different outcome.

Methods

    As required by section 4(b)(2) of the Act, we use the best 
scientific data available in determining areas that contain the 
features that are essential to the conservation of the tidewater goby. 
The sources of data used in identifying critical habitat include 
information in our files regarding habitat requirements of this 
species, and the data sources mentioned in the published final rule 
that resulted in the designation of critical habitat in Orange and San 
Diego Counties (65 FR 69693). We also reviewed available information in 
reports submitted during section 7 consultations and by biologists 
holding section 10(a)(1)(A) recovery permits; information contained 
within the recently completed and peer reviewed tidewater goby recovery 
plan (Service 2005) that does not appear elsewhere; research published 
in peer-reviewed articles and presented in academic theses and agency 
reports; and regional Geographic Information System (GIS) coverages. We 
also solicited information from knowledgeable experts that have worked 
with the tidewater goby.

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to propose as critical 
habitat within areas occupied by the species at the time of listing, we 
consider those physical and biological features that are essential to 
the conservation of the species and that may require special management 
considerations or protection. These include, but are not limited to, 
space for individual and population growth and for normal behavior; 
food, water, air, light, minerals, or other nutritional or 
physiological requirements; cover or shelter; sites for breeding, 
reproduction, and rearing (or development) of offspring; and habitats 
that are protected from disturbance or are representative of the 
historical geographical and ecological distributions of a species.
    The specific primary constituent elements required for the 
tidewater goby are derived from the biological needs of the tidewater 
goby as described in the Background section of this proposal and the 
following text.

Space for Individual and Population Growth and for Normal Behavior

Saline Aquatic Habitat
    Tidewater gobies occur 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). Tidewater gobies are most commonly found in waters with 
relatively low salinities, i.e., less than 10-12 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). The species has been collected in salinities 
as high as 42 ppt (Swift et al. 1989, p. 7). The species' tolerance of 
high salinities likely enables it to withstand some exposure to the 
marine environment, allowing it to recolonize nearby lagoons and 
estuaries following flood events. However, tidewater gobies have only 
rarely been captured in the marine environment (Swift et al. 1989, p. 
7), and they appear to enter the ocean only when flushed out of 
lagoons, estuaries, and river mouths by storm events.
Water Depth, Velocity, and Temperature
    Tidewater gobies are most commonly collected in water less than 6 
ft (2 m) deep (Wang 1982, pp. 4-5; Worchester 1992, p. 53). However, 
recently tidewater gobies were collected in Big Lagoon in Humboldt 
County during the breeding season at a water depth of 15 ft (4.6 m) 
(Goldsmith 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 at various locations.
    Tidewater gobies tend 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 that have a substantial current. At 
Pescadero Creek in San Mateo County, tidewater gobies were absent from 
portions of the flowing creek that had a surface velocity of 0.15 m 
(0.49 ft per second), and the species was instead more densely 
concentrated in nearby eddies with lower water velocities (Swenson 
1993, p. 3).
    Backwater marshes, including lateral sloughs, are likely to be 
important to tidewater gobies for multiple reasons. Flood waters with 
increased water velocities can have a negative effect on tidewater 
gobies (Irwin and Soltz 1984, p. 27), and backwater marshes may provide 
important refuges that reduce the likelihood that tidewater gobies 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 gobies from a 
locality is suggested by the elimination of tidewater gobies 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 gobies from this locality during a storm in 1993 (Swift et 
al. 1994, p. 22-23). The importance of backwater marshes is also 
highlighted by the fact that tidewater gobies in these habitats can 
achieve a greater size than in adjacent lagoons and creeks (Swenson 
1993, pp. 6-7).

[[Page 68920]]

Because the number of eggs produced per female increases as female size 
increases (Swift et al. 1989, p. 9), it is likely that females in the 
backwater marshes can produce a proportionally greater number of young 
fry that allow a population to persist.
    Tidewater gobies have been documented in habitats with water 
temperatures that range from 46 to 77 degrees F (8 to 25 degrees C) 
(Irwin and Soltz 1984, Tables 3 and 4; Swift et al. 1989, p. 1).
Freshwater Habitat
    Tidewater gobies also occur in freshwater streams upgradient 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 gobies 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).
    Hundreds of tidewater gobies have been observed to move upstream of 
a fixed location into areas in the Santa Ynez River 3.2 mi (5.1 km) 
from the ocean in Santa Barbara County (Swift et al. 1997, p. 20). The 
fact that this many individuals were observed to move through an area 
within a 2-hour period suggests that freshwater tributaries in some 
riverine systems provide important space for individual and population 
growth.
    We have reviewed a variety of documents to determine how far 
tidewater gobies have been detected upstream from the ocean. 
Chamberlain and Goldsmith (2006, p. 1) found tidewater gobies 1.6-2.0 
mi (2.6-3.3 km) upstream from the ocean in the Ten Mile River in 
Mendocino County; Swift et al. (1997, p. 18) found tidewater gobies 4.6 
mi (7.3 km) upstream from the ocean in the San Antonio River in Santa 
Barbara County; Swift et al. (1997, p. 20) found tidewater gobies at 
various distances from 3.9 to 7.3 mi (6.2 to 11.7 km) upstream from the 
ocean in the Santa Ynez River in Santa Barbara County; and Holland 
(1992, p. 9) found tidewater gobies 3 mi (5 km) upstream from the ocean 
in the Santa Margarita River in San Diego County. Collectively, these 
data suggest the average distance tidewater gobies have been detected 
upstream from the ocean in medium to large rivers is approximately 3.8 
mi (6.1 km). Although the reasons for the variation in up-stream 
movement between one locality and another have not been determined, 
salinity is likely an important factor. Upstream salinity levels may 
vary with time of year, tidal cycles, storm events, and topography.
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 (i.e., 5 to 10 ppt) in the area upgradient from the 
sandbar (Carpelan 1967, p. 324) than would otherwise exist if there 
were no sandbar. Tidewater gobies are more commonly associated with 
these lower salinity levels than with the salinity levels that occur in 
the ocean or an estuary without a sandbar, i.e., about 35 ppt. The 
formation of a sandbar also creates a larger area 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 gobies, their nests, and 
their fry could become stranded and die, or become concentrated and 
subject to greater levels of predation pressure by birds or other 
predators.
    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 localities occupied by the tidewater goby do not contain natural 
sandbars between the ocean and habitat where the species is present. 
Instead, manmade water control structures, such as tidegates and 
culverts, exist between tidal waters and the locations where tidewater 
gobies occur. These tidegates have been in place for decades, and in 
some cases, they provide habitat conditions similar to those created by 
the presence of a seasonal sandbar. In fact, most of the occupied 
tidewater goby habitats in the Humboldt Bay-Eel River estuaries are 
above tidegates.

Food

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

Cover or Shelter

    A variety of native and nonnative fish species and fish-eating bird 
species such as egrets (Egretta spp.) and herons (e.g., great blue 
herons (Ardea herodias)) prey on tidewater gobies, and escape cover or 
shelter is necessary to reduce the likelihood that tidewater gobies 
will be preyed upon.
    A species' ability to persist when it is subject to predation 
pressure frequently depends on the presence of features that provide 
cover from predators, or the presence of a heterogeneous habitat that 
provides a greater level of structure which makes it more likely a prey 
species will avoid predation (Crowder and Cooper 1982, p. 1802; 
Gilinsky 1984, p. 455).
    At locations where tidewater gobies occur, submerged and emergent 
aquatic vegetation has the potential to provide cover from predators, 
and provide a greater degree of habitat heterogeneity or structure that 
would not otherwise exist if the aquatic vegetation was absent. Stable 
lagoons often possess dense aquatic vegetation that frequently consists 
of sago pondweed (Potamogeton pectinatus) or widgeon grass (e.g., 
Ruppia maritima and R. cirrhosa). At some locations, juvenile tidewater 
gobies are more prevalent in areas with at least some submergent 
vegetation as compared to other areas with no or little vegetation 
(Wang 1984, p. 16; Swenson 1994, p. 6; Trihey & Associates, Inc. 1996, 
p. 11). We believe it is reasonable to assume that the presence of 
submerged or emergent vegetation reduces the likelihood that tidewater 
gobies will be preyed upon by native and nonnative species because this 
vegetation provides cover and increases the level of habitat 
heterogeneity in a way that makes it more likely that tidewater gobies 
will persist where they co-occur with predators.
    Aquatic vegetation may provide some degree of shelter or refuge 
during flash flood events (Lafferty et al. 1999b, p. 621). These 
refuges presumably would result because the presence of vegetation 
would create lower water velocities than might otherwise occur in 
unvegetated areas. Such refuges would be especially important to fish 
species that are not strong swimmers, such as the tidewater goby.

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

    The eggs of the tidewater goby are laid in burrows that are 
excavated by male

[[Page 68921]]

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

Primary Constituent Elements for the Tidewater Goby

    Pursuant to our regulations, we are required to identify the known 
physical and biological features (PCEs) essential to the conservation 
of the tidewater goby. All of the areas proposed as revised critical 
habitat for the tidewater goby are within the species' historical 
geographic range and contain sufficient PCEs to support at least one 
life history function.
    Based on our current knowledge of the life history, biology, and 
ecology of the tidewater goby and the requirements of the habitat to 
sustain the essential life history functions of this species, we have 
determined that the PCEs for the tidewater goby are:
    (1) Persistent, shallow (in the range of about 0.1-2 m), still-to-
slow-moving, aquatic habitat most commonly ranging in salinity from 
less than 0.5 ppt to about 10-12 ppt, which provides adequate space for 
normal behavior and individual and population growth;
    (2) Substrates (e.g., sand, silt, mud) suitable for the 
construction of burrows for reproduction;
    (3) Submerged and emergent aquatic vegetation, such as Potamogeton 
pectinatus and Ruppia maritima, that provides protection from 
predators; and
    (4) 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.
    Although the previous rule included a PCE on the prey species the 
tidewater goby may use as food, tidewater gobies are generalists and 
prey on a wide diversity of invertebrate species that are readily 
available wherever gobies occur. Therefore, we have not included prey 
as a PCE in this revised rule.
    This proposed revised designation is designed for the conservation 
of areas supporting PCEs that exist at coastal lagoons, estuaries, 
backwater marshes, and associated freshwater tributaries, and that are 
necessary to support the life history functions which were the basis 
for the proposal. Because not all life history functions require all 
the PCEs, not all proposed revised critical habitat will contain all 
the PCEs. The presence of PCE 4 at a given location will, in general, 
only be applicable to locations where a sandbar forms due to natural 
processes.
    Units are proposed for revised designation based on sufficient PCEs 
being present to support the life processes of the species. Some lands 
contain all PCEs and support multiple life processes. Some lands 
contain only a portion of the PCEs necessary to support the particular 
use of that habitat.

Criteria Used To Identify Critical Habitat

    As required by section 4(b)(1)(A) of the Act, we use the best 
scientific data and information available in determining areas that 
contain the features that are essential to the conservation and habitat 
requirements of the tidewater goby. These include research published in 
peer-reviewed articles and presented in academic theses and agency 
reports; information submitted during section 7 consultations and by 
biologists holding section 10(a)(1)(A) recovery permits; information 
that is contained within the recently completed recovery plan for the 
tidewater goby that does not appear elsewhere; and regional Geographic 
Information System (GIS) coverages. We also solicited information from 
knowledgeable biologists that have worked with the tidewater goby.
    The process we use in this proposed rule to identify the features 
that are essential to the conservation of the tidewater goby reflects a 
complete assessment of the current, best scientific data available. 
Based on this assessment, we developed criteria for identifying 
critical habitat units (see below). By applying these criteria to the 
112 localities known to be currently occupied by gobies, we identified 
44 (39 percent) that we are proposing to designate as revised critical 
habitat. In general, we are proposing these 44 units as critical 
habitat because they support the conservation of the species in that 
these units are representative of the distribution of the goby occupied 
at the time of listing; some units are occupied by source populations, 
such that they support other habitats with gobies; and proposed units 
reflect the diversity of the species and its habitats which it 
currently occupies. In this rule, we have also attempted to describe, 
in a more explicit manner, the features that we use to determine the 
lateral and upstream extent of the critical habitat unit boundaries.
    The criteria for identifying critical habitat units include:
    (a) Areas known to be occupied at the time of listing and that 
possess one or more PCEs such that the area supports one or more of the 
tidewater goby's life processes. We determined which areas were 
occupied at the time of listing from information in two papers on goby 
occurrence (Swift et al. 1989, p. 13; Swift et al. 1993, p. 129), both 
of which were used in the preparation of the final listing rule for the 
goby;
    (b) Areas that are currently occupied but were not known to be 
occupied at the time of listing that are determined to be essential to 
the conservation of the species;
    (c) Areas that are representative of the distribution of the 
tidewater goby throughout the entire geographic range known to be 
occupied at the time of listing including those with unique ecological 
characteristics (e.g., large open bays in Humboldt County vs. small, 
routinely closed lagoons in Santa Barbara County) with the goal of 
maintaining the full range of the habitat variability and genetic and 
morphological adaptation in the species; and
    (d) Areas that allow for the continued existence of viable 
metapopulations (as defined in the ``Background'' section) under 
varying environmental conditions (e.g., drought). These areas include 
those that presumably serve as source populations or those that provide 
important connectivity between source populations.
    No areas that are currently unoccupied were found to be essential 
to the conservation of the species.
    For the purposes of this proposed rule, we assume that source 
populations are those where tidewater gobies have been observed or 
collected on a regular basis, and therefore are more likely to provide 
the individuals that disperse and recolonize localities where the 
species periodically disappears. Locations that provide connectivity 
between source populations are those locations that exist between 
source populations that are likely to act as

[[Page 68922]]

``stepping stones'' between more isolated populations, and contribute 
to metapopulation persistence. Locations that possess unique ecological 
characteristics are those that represent the full range of 
environmental variability where the tidewater goby has evolved, and 
therefore are likely to promote the adaptation of the species to 
different environmental conditions. For example, some of these habitats 
would include locations that reflect different environmental conditions 
in southern and northern California (e.g. smaller habitats that occur 
in a more arid environment vs. large habitats that occur in areas with 
abundant rainfall). Genetic or morphological variability was used to 
support the inclusion of locations where we assume that this 
variability may play a role in positively affecting the species' 
conservation over time. For additional information on any of the above 
definitions, please refer back to the ``Background'' section in this 
proposed rule.
    The conservation of a broad range of environmental, morphological, 
and genetic diversity that is present at the various locations is an 
important consideration in determining locations that are important for 
the conservation of the species. For example, a population's ability to 
successfully adapt to changing environmental conditions is a function 
of the heterozygosity, 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: (a) Identifying areas 
that represent the species and genetic diversity, and (b) 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).
    After determining the occupied localities necessary for the 
conservation of the tidewater goby by applying criteria ``a'' through 
``d'' above, the boundary of each critical habitat unit was mapped. 
Unit boundaries were based on several factors including species 
occurrence data that demonstrated where tidewater gobies have been 
observed, the presence of barriers and stream gradients that limit 
tidewater goby movements, and the presence and extent of the aquatic 
habitat required by tidewater gobies.
    The lateral extent of each critical habitat unit was delineated, in 
part, using existing digital data. To determine the lateral boundaries 
of each proposed critical habitat unit, we most frequently relied on 
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); 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) 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 the PCE's 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 proposed critical habitat unit 
where insufficient NWI data was available.
    The precise location where tidewater goby habitat occurs at a 
particular locality may vary on a daily, seasonal, and annual basis, 
i.e., the habitats occupied by tidewater gobies exist in a dynam