Endangered and Threatened Wildlife and Plants: Proposed Rulemaking To Designate Critical Habitat for the Threatened Southern Distinct Population Segment of North American Green Sturgeon, 52084-52110 [E8-20632]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 73, Number 174 (Monday, September 8, 2008)]
[Proposed Rules]
[Pages 52084-52110]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-20632]



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Part II





Department of Commerce





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National Oceanic and Atmospheric Administration



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50 CFR Part 226



Endangered and Threatened Wildlife and Plants: Proposed Rulemaking To 
Designate Critical Habitat for the Threatened Southern Distinct 
Population Segment of North American Green Sturgeon; Proposed Rule

Federal Register / Vol. 73, No. 174 / Monday, September 8, 2008 / 
Proposed Rules

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 226

[Docket No. 080730953-81003-01]
RIN 0648-AX04


Endangered and Threatened Wildlife and Plants: Proposed 
Rulemaking To Designate Critical Habitat for the Threatened Southern 
Distinct Population Segment of North American Green Sturgeon

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

ACTION: Proposed rule; request for comments.

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SUMMARY: We, the National Marine Fisheries Service (NMFS), propose to 
designate critical habitat for the threatened Southern distinct 
population segment of North American green sturgeon (Southern DPS of 
green sturgeon) pursuant to section 4 of the Endangered Species Act 
(ESA). Specific areas proposed for designation include: coastal U.S. 
marine waters within 110 meters (m) depth from Monterey Bay, California 
(including Monterey Bay), north to Cape Flattery, Washington, including 
the Strait of Juan de Fuca, Washington, to its United States boundary; 
the Sacramento River, lower Feather River, and lower Yuba River in 
California; the Sacramento-San Joaquin Delta and Suisun, San Pablo, and 
San Francisco bays in California; the lower Columbia River estuary; and 
certain coastal bays and estuaries in California (Humboldt Bay), Oregon 
(Coos Bay, Winchester Bay, and Yaquina Bay), and Washington (Willapa 
Bay and Grays Harbor). The areas proposed for designation comprise 
approximately 325 miles (524 km) of freshwater river habitat, 1,058 
square miles (2,739 sq km) of estuarine habitat, 11,927 square miles 
(30,890 sq km) of marine habitat, and 136 square miles (352 sq km) of 
habitat within the Yolo and Sutter bypasses (Sacramento River, CA).
    We propose to exclude the following areas from designation because 
the benefits of exclusion outweigh the benefits of inclusion and 
exclusion will not result in the extinction of the species: coastal 
U.S. marine waters within 110 m depth from the California/Mexico border 
north to Monterey Bay, CA, and from the Alaska/Canada border northwest 
to the Bering Strait; and certain coastal bays and estuaries in 
California (Tomales Bay, Elkhorn Slough, Noyo Harbor, and the estuaries 
to the head of the tide in the Eel and Klamath/Trinity rivers), Oregon 
(Tillamook Bay and the estuaries to the head of the tide in the Rogue, 
Siuslaw, and Alsea rivers), and Washington (Puget Sound). The areas 
excluded from the proposed designation comprise approximately 1,057 
square miles (2,738 sq km) of estuarine habitat and 396,917 square 
miles (1,028,015 sq km) of marine habitat.
    We acknowledge that there may be costs incurred by those planning 
to undertake activities in certain areas, in particular Coo Bay, OR, or 
other areas along the lower Columbia River estuary, as a result of this 
proposed critical habitat designation for the Southern DPS of green 
sturgeon that were not captured in our draft economic report. These 
activities include, but are not limited to, liquefied natural gas (LNG) 
projects, hydropower activities, and alternative energy projects. We 
solicit comment on what these additional costs might be and will 
consider any additional information received in developing our final 
determination to designate or exclude areas from critical habitat for 
the Southern DPS of green sturgeon.

DATES: Comments on this proposed rule to designate critical habitat 
must be received by no later than 5 p.m. Pacific Standard Time on 
November 7, 2008. A public hearing will be held promptly if any person 
so requests by October 23, 2008. Notice of the date, location, and time 
of any such hearing will be published in the Federal Register not less 
than 15 days before the hearing is held.

ADDRESSES: You may submit comments on the proposed rule, identified by 
RIN 0648-AX04, by any one of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal: https://
www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 1-562-980-4027, Attention: Melissa Neuman.
     Mail: Submit written information to Chief, Protected 
Resources Division, Southwest Region, National Marine Fisheries 
Service, 650 Capitol Mall, Sacramento, CA 95814-4706.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All Personal Identifying Information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit Confidential Business Information or 
otherwise sensitive or protected information. NMFS will accept 
anonymous comments (please enter N/A in the required fields if you wish 
to remain anonymous). Attachments to electronic comments will be 
accepted in Microsoft Word, Excel, WordPerfect, or Adobe PDF file 
formats only.
    Reference materials regarding this determination can be obtained 
via the Internet at: https://www.nmfs.noaa.gov or by submitting a 
request to the Assistant Regional Administrator, Protected Resources 
Division, Southwest Region, NMFS, 501 West Ocean Blvd., Suite 4200, 
Long Beach, CA 90802-4213.

FOR FURTHER INFORMATION CONTACT: Melissa Neuman, NMFS, Southwest Region 
(562) 980-4115 or Lisa Manning, NMFS, Office of Protected Resources 
(301) 713-1401.

SUPPLEMENTARY INFORMATION:

Background

    We determined that the Southern DPS of green sturgeon is likely to 
become endangered in the foreseeable future throughout all or a 
significant portion of its range and listed the species as threatened 
under the Endangered Species Act (ESA) on April 7, 2006 (71 FR 17757).
    Section 4(b)(2) of the ESA requires us to designate critical 
habitat for threatened and endangered species ``on the basis of the 
best scientific data available and after taking into consideration the 
economic impact, impact on national security, and any other relevant 
impact, of specifying any particular area as critical habitat.'' This 
section grants the Secretary [of Commerce] discretion to exclude any 
area from critical habitat if he determines ``the benefits of such 
exclusion outweigh the benefits of specifying such area as part of the 
critical habitat.'' The Secretary may not exclude an area if it ``will 
result in the extinction of the species.''
    The ESA defines critical habitat under Section 3(5)(A) as:

    ``(i) the specific areas within the geographical area occupied 
by the species, at the time it is listed * * *, on which are found 
those physical or biological features (I) essential to the 
conservation of the species and (II) which may require special 
management considerations or protection; and
    (ii) specific areas outside the geographical area occupied by 
the species at the time it is listed * * * upon a determination by 
the Secretary that such areas are essential for the conservation of 
the species.''

    Once critical habitat is designated, section 7 of the ESA requires 
Federal

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agencies to ensure they do not fund, authorize, or carry out any 
actions that will destroy or adversely modify that habitat. This 
requirement is in addition to the ESA section 7 requirement that 
Federal agencies ensure their actions do not jeopardize the continued 
existence of listed species.
    When the final rule to list the Southern DPS of green sturgeon was 
published on April 7, 2006, we solicited from the public information 
that would inform the decision-making process for designating critical 
habitat for the species. Specifically, we requested information 
regarding: (1) Green sturgeon spawning habitat within the range of the 
Southern DPS that was present in the past, but may have been lost over 
time; (2) biological or other relevant data concerning any threats to 
the Southern DPS of green sturgeon; (3) quantitative evaluations 
describing the quality and extent of freshwater and marine habitats 
(occupied currently or occupied in the past, but no longer occupied) 
for juvenile and adult green sturgeon as well as information on areas 
that may qualify as critical habitat in California for the Southern 
DPS; (4) activities that could be affected by an ESA critical habitat 
designation; and (5) the economic costs and benefits of additional 
requirements of management measures likely to result from the 
designation. No substantive additional comments, beyond those that had 
been received during prior solicitations for information, were 
received.
    The timeline for completing the proposed critical habitat 
designation described in this Federal Register document was established 
pursuant to a settlement agreement. On April 17, 2007, the Center for 
Biological Diversity (CBD) filed a 60-day notice of intent to sue the 
Secretary of Commerce and NMFS for failing to designate critical 
habitat and establish protective regulations for the Southern DPS of 
green sturgeon, as required by the ESA. Pursuant to the settlement 
agreement reached between the parties, we agreed to make a 
determination on a proposed critical habitat designation for the 
Southern DPS of green sturgeon by April 30, 2008, and a final 
designation by April 30, 2009, which were later extended to September 
2, 2008 and June 30, 2009, respectively.
    In developing this proposed rule, we evaluated the best available 
information regarding green sturgeon distribution and habitat 
requirements, as well as threats to the species. In the Final Rule to 
list the Southern DPS as threatened under the ESA (71 FR 17757; April 
7, 2006), we identified seven extinction risk factors, including: (1) 
Concentration of spawning into one spawning river, increasing the risk 
of catastrophic extinction; (2) loss of spawning habitat in the upper 
Sacramento and Feather rivers due to migration barriers; (3) a general 
lack of population data, but suspected small population size; (4) 
entrainment by water project operations; (5) potentially limiting or 
lethal water temperatures; (6) commercial and recreational fisheries 
harvest; and (7) toxins and exotic species. This document describes the 
proposed critical habitat designation, including supporting information 
on green sturgeon biology, distribution, and habitat use, and the 
methods used to develop the proposed designation.

Green Sturgeon Natural History

    In the following sections, we describe the natural history of green 
sturgeon as it relates to the habitat needs of this species. The green 
sturgeon is an anadromous fish species that is long-lived and the most 
marine oriented sturgeon species in the family Acipenseridae. The North 
American form of green sturgeon (Acipenser medirostris; hereafter, 
``green sturgeon'') is related to the Asian form (A. mikadoi, also 
called Sakhalin sturgeon), but is most likely a different species 
(Artyukhin et al., 2007). Green sturgeon is one of two sturgeon species 
occurring on the U.S. west coast, the other being white sturgeon 
(Acipenser transmontanus). Adults can reach up to 270 cm in total 
length (TL) and 175 kg in weight (Moyle, 2002); however, adults greater 
than 2 m TL and 90 kg in weight are not common (Skinner, 1972). Females 
are larger and older (approximately 162 cm TL and 16-20 years of age) 
than males (approximately 152 cm TL and 14-16 years of age) upon 
reaching reproductive maturity (Van Eenennaam et al., 2006). Maximum 
ages most likely range from 60 to 70 years or older (Emmett et al., 
1991). Until recently, few studies have focused on green sturgeon due 
to its low abundance and low commercial value compared to white 
sturgeon.
    Green sturgeon range from the Bering Sea, Alaska, to 
Ense[ntilde]ada, Mexico. A few green sturgeon have been observed off 
the southern California coast, including fish less than 100 cm TL 
(Fitch and Lavenberg, 1971, cited in Moyle et al., 1995; Fitch and 
Schultz, 1978, cited in Moyle et al., 1995). Green sturgeon abundance 
increases north of Point Conception, CA (Moyle et al., 1995). Green 
sturgeon occupy freshwater rivers from the Sacramento River up through 
British Columbia (Moyle, 2002), but spawning has been confirmed in only 
three rivers, the Rogue River in Oregon and the Klamath and Sacramento 
rivers in California. Based on genetic analyses and spawning site 
fidelity (Adams et al., 2002; Israel et al., 2004), NMFS has determined 
green sturgeon are comprised of at least two distinct population 
segments (DPSs): (1) A Northern DPS consisting of populations 
originating from coastal watersheds northward of and including the Eel 
River (i.e., the Klamath and Rogue rivers) (``Northern DPS''); and (2) 
a southern DPS consisting of populations originating from coastal 
watersheds south of the Eel River, with the only known spawning 
population in the Sacramento River (``Southern DPS''). The Northern DPS 
and Southern DPS are distinguished based on genetic data and spawning 
locations, but their distributions outside of natal waters generally 
overlap with one another (Chadwick, 1959; Miller, 1972; CDFG, 2002; 
Israel et al., 2004; Moser and Lindley, 2007; Erickson and Hightower, 
2007; Lindley et al., 2008.). Both Northern DPS and Southern DPS green 
sturgeon occupy coastal estuaries and coastal marine waters from 
southern California to Alaska, including Humboldt Bay, the lower 
Columbia river estuary, Willapa Bay, Grays Harbor, and coastal waters 
between Vancouver Island, BC, and southeast Alaska (Israel et al., 
2004; Moser and Lindley, 2007; Lindley et al., 2008). Thus, green 
sturgeon observed in coastal bays, estuaries, and coastal marine waters 
outside of natal rivers may belong to either DPS. However, the Northern 
DPS of green sturgeon is not classified as a listed species under the 
ESA. Tagging or genetics data are needed to determine to which DPS an 
individual fish belongs. The distribution of green sturgeon, and 
specifically of the Southern DPS, is described in detail under the 
section titled ``Geographical Areas Occupied by the Species and 
Specific Areas within the Geographical Areas Occupied.''

Spawning

    Spawning frequency is not well known, but the best information 
suggests adult green sturgeon spawn every 2-4 years (Lindley and Moser, 
NMFS, 2004, pers. comm., cited in 70 FR 17386, April 6, 2005; Erickson 
and Webb, 2007). Beginning in late February, adult green sturgeon 
migrate from the ocean into fresh water to begin their spawning 
migrations (Moyle et al., 1995). Spawning occurs from March to July, 
with peak activity from mid-April to mid-June (Emmett et al., 1991). 
Spawning populations in North America have been confirmed in the Rogue 
(Erickson et al., 2002; Farr and

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Kern, 2005), Klamath, and Sacramento Rivers (Moyle et al., 1992; CDFG, 
2002). Klamath and Rogue River populations appear to spawn within 100 
miles (161 km) of the ocean, whereas spawning on the mainstem 
Sacramento River has been documented over 240 miles (391 km) upstream, 
both downstream and upstream of Red Bluff Diversion Dam (RBDD) (Brown, 
2007). Spawning most likely occurs in fast, deep water (> 3 m deep) 
over substrates ranging from clean sand to bedrock, with preferences 
for cobble substrates (Emmett et al., 1991; Moyle et al., 1995). Green 
sturgeon females produce 59,000 to 242,000 eggs, with fecundity 
increasing with fish length and age (Van Eenennaam et al., 2006). Green 
sturgeon eggs are the largest of any sturgeon species, ranging from 
4.04 to 4.66 mm in diameter, and have a thin chorionic layer (Van 
Eenennaam et al., 2001; Van Eenennaam et al., 2006). Eggs are broadcast 
spawned and likely adhere to substrates or settle into crevices of 
river bedrock or under gravel (Deng, 2000; Van Eenennaam et al., 2001; 
Deng et al., 2002). Van Eenennaam et al. (2001) reported that green 
sturgeon eggs have weak adhesiveness, but have since retracted that 
statement, noting instead that green sturgeon eggs are quite adhesive 
within a few minutes after release from the female (Van Eenennaam, UC 
Davis, 2008, pers. comm.). Optimum flow and temperature requirements 
for spawning and incubation are unclear, but spawning success in most 
sturgeons is related to these factors (Detlaff et al., 1993). Average 
monthly water flow during the spawning season (March-July) ranged from 
209-1,252 m\3\/s in the Sacramento River over a 10-year period from 
1996-2006 (https://waterdata.usgs.gov) and from 31-260 m\3\/s in the 
Rogue River over a 4-year period from 2001-2004 (Erickson and Webb, 
2007). Spawning may be triggered by small increases in water flow 
(Schaffter, 1997; Brown, 2007). Adult sturgeon occur in the Sacramento 
River when temperatures are between 8-14 [deg]C (Moyle, 2002). In 
laboratory studies, the optimal thermal range for green sturgeon 
development was from 11 to 17-18 [deg]C, and temperatures >= 23 [deg]C 
were lethal to embryos (Van Eenennaam et al., 2005).

Development of Early Life Stages

    Green sturgeon embryos have poor swimming ability and exhibit a 
strong drive to remain in contact with structure, preferring cover and 
dark habitats to open bottom and illuminated habitats in laboratory 
experiments (Kynard et al., 2005). In these experiments, early embryos 
made no effort to swim, suggesting embryos remain in spawning areas to 
develop (Kynard et al., 2005). Newly emerged green sturgeon larvae in 
the laboratory hatched 144-216 hours, or 6-9 days, after fertilization 
(incubation temperatures ranged from 15-15.7 [deg]C) and ranged from 
12.6-15 mm in length (Van Eenennaam et al., 2001; Deng et al., 2002). 
Unlike other acipenserids, newly hatched larvae did not swim up toward 
the water surface within the first 5 days post hatch (dph), but 
remained in clumps near the bottom. By 5-6 dph, larvae exhibited 
nocturnal behavior, remaining clumped near the bottom during the day 
and actively swimming at night (Van Eenennaam et al., 2001; Deng et 
al., 2002). Upon onset of feeding at 10 dph (23.0-25.2 mm length) (Deng 
et al., 2002), larvae are believed to initiate downstream migration 
from spawning areas, staying close to the bottom and periodically 
interrupting downstream movement with upstream foraging bouts (Kynard 
et al., 2005).
    Little is known about larval rearing habitat and requirements. 
Temperatures of 15 [deg]C are believed to be optimal for larval growth, 
whereas temperatures below 11 [deg]C or above 19 [deg]C may be 
detrimental for growth (Cech et al., 2000, cited in COSEWIC, 2004). 
Substrate may also affect growth and foraging behavior. Larvae reared 
on flat-surfaced substrates (slate-rock and glass) had higher specific 
growth rates than larvae reared on cobble or sand, most likely due to 
lower foraging effectiveness and greater activity levels in cobble and 
sand substrates (Nguyen and Crocker, 2007). Larvae complete 
metamorphosis to the juvenile stage at 45 dph, when fish range from 
62.5 to 94.4 mm in length (Deng et al., 2002).
    Juveniles continue to grow rapidly, reaching 300 mm in length in 
one year and over 600 mm within 2-3 years (based on Klamath River fish; 
Nakamoto et al., 1995). Laboratory experiments indicate juveniles may 
occupy fresh to brackish water at any age, but are able to completely 
transition to salt water at around 1.5 years in age (about 533 dph; 
mean TL of 75.2 plus or minus 0.7 cm) (Allen and Cech, 2007). Early 
juveniles at 100 and 170 dph tolerated prolonged exposure to saltwater, 
but experienced decreased growth and activity levels and, in some 
cases, mortality for individuals at 100 dph (Allen and Cech, 2007). 
These results were consistent with the Nakamoto et al. (1995) study 
indicating that juveniles rear in fresh and estuarine waters before 
dispersing into salt water at about 1 to 4 years in age (about 300 to 
750 mm in length). Early juveniles also exhibit nocturnal behavior in 
all activities and initiate directed downstream movement in the fall, 
most likely to migrate to wintering habitats (Kynard et al., 2005). 
Juvenile green sturgeon prefer temperatures of 15-16 [deg]C with an 
upper limit of 19 [deg]C, beyond which swimming performance may 
decrease and cellular stress may occur (Mayfield and Cech, 2004; Allen 
et al., 2006). Laboratory measurements of oxygen consumption by 
juveniles ranged from 61.78 plus or minus 4.65 mg O2 
hr-1 kg-1 to 76.06 plus or minus 7.63 mg 
O2 hr-1 kg-1, with a trend of 
increasing oxygen consumption with increasing body mass (Allen and 
Cech, 2006). Studies on juvenile feeding in San Pablo Bay, Suisun Bay, 
and the Sacramento-San Joaquin Delta identified prey items of shrimp 
(Neomysis awatchensis, Crangon franciscorum), amphipods (Corophium 
spp., Photis californica), isopods (Synidotea laticauda), clams (Macoma 
spp.), annelid worms, and unidentified crabs and fishes (Ganssle, 1966; 
Radtke, 1966).

Adults and Subadults

    To distinguish among different life stages, we used the following 
definitions. Adults are sexually mature fish, subadults are sexually 
immature fish that have entered into coastal marine waters (usually at 
3 years of age), and juveniles are fish that have not yet made their 
first entry into marine waters. Green sturgeon spend a large portion of 
their lives in coastal marine waters as subadults and adults between 
spawning episodes. Subadult male and female green sturgeon spend at 
least approximately 6 and 10 years, respectively, at sea before 
reaching reproductive maturity and returning to freshwater to spawn for 
the first time (Nakamoto et al., 1995). Adult green sturgeon spend as 
many as 2-4 years at sea between spawning events (Lindley and Moser, 
NMFS, pers. comm., cited in 70 FR 17386, April 6, 2005; Erickson and 
Webb, 2007). The average length at maturity for green sturgeon is 
estimated to be 152 cm TL (14-16 years) for males and 162 cm TL (16-20 
years) for females in the Klamath River (Van Eenennaam et al., 2006), 
and 145 cm TL for males and 166 cm TL for females in the Rogue River 
(Erickson and Webb, 2007). The maximum size of subadults is 
approximately 167 cm TL (Erickson and Webb, 2007).
    Adults typically begin their upstream spawning migration in the 
spring and either migrate downstream after spawning, or reside within 
the river over the summer. In the Klamath River, tagged adults 
exhibited four movement patterns: (1) Upstream spawning migration; (2) 
spring outmigration to the

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ocean; (3) summer holding (June to November) in deep pools with eddy 
currents (for those that do not exhibit post-spawning spring 
outmigration); and (4) outmigration after summer holding (Benson et 
al., 2007). Use of summer holding sites has also been observed in the 
Rogue River (Erickson et al., 2002) and in the Sacramento River (R. 
Corwin, U.S. Bureau of Reclamation (USBR), 2008, pers. comm.). Deep 
holding pools greater than 5 m in depth are believed to be important 
for spawning as well as for summer holding (R. Corwin, USBR, and B. 
Poytress, USFWS, 2008, pers. comm). Winter outmigration from the 
Klamath and Rogue rivers was initiated when temperatures dropped to 10-
12 [deg]C or below 10 [deg]C, and when discharge increased to greater 
than 100 m\3\/s (Erickson et al., 2002; Benson et al., 2007). In the 
Sacramento River, tagged adult green sturgeon were present through 
November and December, before moving downstream with increased winter 
flows (M. Thomas, UC Davis, and R. Corwin, USBR, 2008, pers. comm.). 
Subadults may also migrate upstream into the natal rivers, but for 
unknown purposes. Adults and subadults also occupy the San Francisco, 
San Pablo, and Suisun bays and the Sacramento-San Joaquin Delta 
adjacent to the Sacramento River in the summer months (although some 
individuals that remain in the river until late fall/early winter 
migrate through the bays and Delta during their winter outmigration), 
during which time they are likely feeding and optimizing growth (Kelly 
et al., 2007; Moser and Lindley, 2007).
    Outside of their natal waters, adult and subadult green sturgeon 
inhabit coastal marine habitats from the Bering Sea to southern 
California, primarily occupying waters within 110 meters (m) depth 
(Erickson and Hightower, 2007). Tagged subadults and adults have been 
documented to make sustained coastal migrations of up to 100 km per day 
(S. Lindley and M. Moser, NMFS, pers. comm., cited in BRT, 2005), but 
may also reside in aggregation/feeding areas in coastal marine waters 
for several days at a time (S. Lindley and M. Moser, NMFS, 2008, pers. 
comm.). There is evidence that green sturgeon inhabit certain estuaries 
on the northern California, Oregon, and Washington coasts during the 
summer, and inhabit coastal marine waters along the central California 
coast and between Vancouver Island, British Columbia, and southeast 
Alaska over the winter (Lindley et al., 2008). Green sturgeon likely 
inhabit these estuarine and marine waters to feed and to optimize 
growth (Moser and Lindley, 2007). Particularly large aggregations of 
green sturgeon occur in the Columbia River estuary and Washington 
estuaries and include green sturgeon from all known spawning 
populations (Moser and Lindley, 2007). Although adult and subadult 
green sturgeon occur in coastal marine waters as far north as the 
Bering Sea, green sturgeon have not been observed in freshwater rivers 
or coastal bays and estuaries in Alaska.
    Within bays and estuaries, adults and subadults inhabit a wide 
range of environmental conditions. Adults and subadults in Willapa Bay 
and the San Francisco Bay Estuary occurred over the entire temperature 
and salinity range (11.9-21.9 [deg]C; 8.8-32.1 ppt), experienced large 
fluctuations in temperature and salinity (up to 2 [deg]C h-1 
and 1 practical salinity unit (PSU) h-1), and occupied a 
wide range of dissolved oxygen levels from 6.54 to 8.98 mg 
O2/l (Kelly et al., 2007; Moser and Lindley, 2007). Tagged 
adults and subadults in the San Francisco Bay Estuary occupied shallow 
depths during directional movements but stayed close to the bottom 
during non-directional movements, presumably because they were foraging 
(Kelly et al., 2007). Similar to freshwater rivers, winter outmigration 
from Willapa Bay was initiated when water temperatures dropped below 10 
[deg]C (Moser and Lindley, 2007).
    Adult and subadult green sturgeon in the Columbia River estuary, 
Willapa Bay, and Grays Harbor feed on crangonid shrimp, burrowing 
thalassinidean shrimp (primarily the burrowing ghost shrimp (Neotrypaea 
californiensis), but possibly other related species), amphipods, clams, 
juvenile Dungeness crab (Cancer magister), anchovies, sand lances 
(Ammodytes hexapterus), lingcod (Ophiodon elongatus), and other 
unidentified fishes (P. Foley, unpublished data cited in Moyle et al., 
1995; C. Tracy, minutes to USFWS meeting, cited in Moyle et al., 1995; 
O. Langness, WDFW, pers. comm., cited in Moser and Lindley, 2007; 
Dumbauld et al., 2008). Burrowing ghost shrimp made up about 50 percent 
of the stomach contents of green sturgeon sampled in 2003 (Dumbauld et 
al., 2008). Subadults and adults feeding in bays and estuaries may be 
exposed to contaminants that may affect their growth and reproduction. 
Studies on white sturgeon in estuaries indicate that the 
bioaccumulation of pesticides and other contaminants adversely affects 
growth and reproductive development and may result in decreased 
reproductive success (Fairey et al., 1997; Foster et al., 2001a; Foster 
et al., 2001b; Kruse and Scarnecchia, 2002; Feist et al., 2005; 
Greenfield et al., 2005). Green sturgeon are believed to experience 
similar risks from contaminants (70 FR 17386, April 6, 2005).

Methods and Criteria Used to Identify Critical Habitat

    In the following sections, we describe the relevant definitions and 
requirements in the ESA and our implementing regulations and the key 
methods and criteria used to prepare this proposed critical habitat 
designation. In accordance with section 4(b)(2) of the ESA and our 
implementing regulations (50 CFR 424.12(a)), this proposed rule is 
based on the best scientific information available concerning the 
Southern DPS's present and historical range, habitat, and biology, as 
well as threats to its habitat. In preparing this rule, we reviewed and 
summarized current information on the green sturgeon, including recent 
biological surveys and reports, peer-reviewed literature, NMFS status 
reviews for green sturgeon (Moyle et al., 1992; Adams et al., 2002; 
BRT, 2005), and the proposed and final listing rules for the green 
sturgeon (70 FR 17386, April 6, 2005; 71 FR 17757, April 7, 2006).
    To assist with the evaluation of critical habitat, we convened a 
critical habitat review team (CHRT) of nine Federal biologists from 
NMFS, the U.S. Fish and Wildlife Service (USFWS), and the USBR with 
experience in green sturgeon biology, consultations, and management, or 
experience in the critical habitat designation process. The CHRT used 
the best available scientific and commercial data and their best 
professional judgment to: (1) Verify the geographical area occupied by 
the Southern DPS at the time of listing; (2) identify the physical and 
biological features essential to the conservation of the species; (3) 
identify specific areas within the occupied area containing those 
essential physical and biological features; (4) verify whether the 
essential features within each specific area may need special 
management considerations or protection and identify activities that 
may affect these essential features; (5) evaluate the conservation 
value of each specific area; and (6) determine if any unoccupied areas 
are essential to the conservation of the Southern DPS. The CHRT's 
evaluation and conclusions are described in detail in the following 
sections.

[[Page 52088]]

Physical or Biological Features Essential for Conservation

    Joint NMFS-USFWS regulations, at 50 CFR 424.12(b), state that in 
determining what areas are critical habitat, the agencies ``shall 
consider those physical and biological features that are essential to 
the conservation of a given species and that may require special 
management considerations or protection.'' Features to consider may 
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, rearing of 
offspring, germination, or seed dispersal; and generally; (5) Habitats 
that are protected from disturbance or are representative of the 
historic geographical and ecological distributions of a species.'' The 
regulations also require the agencies to ``focus on the principal 
biological or physical constituent elements'' (hereafter referred to as 
``Primary Constituent Elements'' or PCEs) within the specific areas 
considered for designation that are essential to conservation of the 
species, which ``may include, but are not limited to, the following: * 
* * spawning sites, feeding sites, seasonal wetland or dryland, water 
quality or quantity, * * * geological formation, vegetation type, tide, 
and specific soil types.''
    The CHRT recognized that the different systems occupied by green 
sturgeon at specific stages of their life cycle serve distinct purposes 
and thus may contain different PCEs. Based on the best available 
scientific information, the CHRT identified PCEs for freshwater 
riverine systems, estuarine areas, and nearshore marine waters.
    The specific PCEs essential for the conservation of the Southern 
DPS in freshwater riverine systems include:
    (1) Food resources. Abundant prey items for larval, juvenile, 
subadult, and adult life stages. Although the CHRT lacked specific data 
on food resources for green sturgeon within freshwater riverine 
systems, juvenile green sturgeon most likely feed on fly larvae (based 
on nutritional studies on the closely-related white sturgeon) (J. 
Stuart, NMFS, 2008, pers. comm.). Food resources are important for 
juvenile foraging, growth, and development during their downstream 
migration to the Delta and bays. In addition, subadult and adult green 
sturgeon may forage during their downstream post-spawning migration, 
while holding within deep pools (Erickson et al., 2002), or on non-
spawning migrations within freshwater rivers. Subadult and adult green 
sturgeon in freshwater rivers most likely feed on benthic prey species 
similar to those fed on in bays and estuaries, including shrimp, clams, 
and benthic fishes (Moyle et al., 1995; Erickson et al., 2002; Moser 
and Lindley, 2007; Dumbauld et al., 2008).
    (2) Substrate type or size (i.e., structural features of 
substrates). Substrates suitable for egg deposition and development 
(e.g., bedrock sills and shelves, cobble and gravel, or hard clean 
sand, with interstices or irregular surfaces to ``collect'' eggs and 
provide protection from predators, and free of excessive silt and 
debris that could smother eggs during incubation), larval development 
(e.g., substrates with interstices or voids providing refuge from 
predators and from high flow conditions), and subadults and adults 
(e.g., substrates for holding and spawning). For example, spawning is 
believed to occur over substrates ranging from clean sand to bedrock, 
with preferences for cobble (Emmett et al., 1991; Moyle et al., 1995). 
Eggs likely adhere to substrates, or settle into crevices between 
substrates (Deng, 2000; Van Eenennaam et al., 2001; Deng et al., 2002). 
Both embryos and larvae exhibited a strong affinity for benthic 
structure during laboratory studies (Van Eenennaam et al., 2001; Deng 
et al., 2002; Kynard et al., 2005), and may seek refuge within 
crevices, but use flat-surfaced substrates for foraging (Nguyen and 
Crocker, 2007). For more details, see the sections on ``Spawning'' and 
``Development of early life stages''.
    (3) Water flow. A flow regime (i.e., the magnitude, frequency, 
duration, seasonality, and rate-of-change of fresh water discharge over 
time) necessary for normal behavior, growth, and survival of all life 
stages. Such a flow regime should include stable and sufficient water 
flow rates in spawning and rearing reaches to maintain water 
temperatures within the optimal range for egg, larval, and juvenile 
survival and development (11-19 [deg]C) (Cech et al., 2000, cited in 
COSEWIC, 2004; Mayfield and Cech, 2004; Van Eenennaam et al., 2005; 
Allen et al., 2006). Sufficient flow is needed to reduce the incidence 
of fungal infestations of the eggs (Deng et al., 2002; Parsley et al., 
2002). In addition, sufficient flow is needed to flush silt and debris 
from cobble, gravel, and other substrate surfaces to prevent crevices 
from being filled in (and potentially suffocating the eggs; Deng et 
al., 2002) and to maintain surfaces for feeding (Nguyen and Crocker, 
2007). Successful migration of adult green sturgeon to and from 
spawning grounds is also dependent on sufficient water flow. As stated 
in the subsection titled ``Spawning'', spawning success is most 
certainly associated with water flow and water temperature. Spawning in 
the Sacramento River is believed to be triggered by increases in water 
flow to about 400 m\3\/s (average daily water flow during spawning 
months: 198-306 m\3\/s) (Brown, 2007). Post-spawning downstream 
migrations are triggered by increased flows, ranging from 174-417 m\3\/
s in the late summer (Vogel, 2005) and greater than 100 m\3\/s in the 
winter (Erickson et al., 2002; Benson et al., 2007; M. Thomas and R. 
Corwin, USBR, 2008, pers. comm.).
    (4) Water quality. Water quality, including temperature, salinity, 
oxygen content, and other chemical characteristics, necessary for 
normal behavior, growth, and viability of all life stages (see sections 
on ``Development of early life stages'' and ``Adults and subadults''). 
Suitable water temperatures would include: Stable water temperatures 
within spawning reaches (wide fluctuations could increase egg mortality 
or deformities in developing embryos); temperatures within 11-17 [deg]C 
(optimal range = 14-16 [deg]C) in spawning reaches for egg incubation 
(March-August) (Van Eenennaam et al., 2005); temperatures below 20 
[deg]C for larval development (Werner et al., 2007); and temperatures 
below 24 [deg]C for juveniles (Mayfield and Cech, 2004; Allen et al., 
2006a). Suitable salinity levels range from fresh water (< 3 parts per 
thousand (ppt)) for larvae and early juveniles (about 100 dph) to 
brackish water (10 ppt) for juveniles prior to their transition to salt 
water. Prolonged exposure to higher salinities may result in decreased 
growth and activity levels and even mortality (Allen and Cech, 2007). 
Adequate levels of dissolved oxygen are needed to support oxygen 
consumption by fish in their early life stages (ranging from 61.78 to 
76.06 mg O2 hr-\1\ kg-\1\ for 
juveniles) (Allen and Cech, 2007). Suitable water quality would also 
include water containing acceptably low levels of contaminants (i.e., 
pesticides, organochlorines, elevated levels of heavy metals, etc.; 
acceptably low levels would be determined by NMFS on a case-by-case 
basis) that may disrupt normal development of embryonic, larval, and 
juvenile stages of green sturgeon. Water with acceptably low levels of 
such contaminants would protect green sturgeon from adverse impacts on 
growth, reproductive development, and reproductive success (e.g., 
reduced egg size and abnormal gonadal development) likely to result

[[Page 52089]]

from exposure to contaminants (Fairey et al., 1997; Foster et al., 
2001a; Foster et al., 2001b; Kruse and Scarnecchia, 2002; Feist et al., 
2005; Greenfield et al., 2005).
    (5) Migratory corridor. A migratory pathway necessary for the safe 
and timely passage of Southern DPS fish within riverine habitats and 
between riverine and estuarine habitats (e.g., an unobstructed river or 
dammed river that still allows for safe and timely passage). We define 
safe and timely passage to mean that human-induced impediments, either 
physical, chemical or biological, do not alter the migratory behavior 
of the fish such that its survival or the overall viability of the 
species is compromised (e.g., an impediment that compromises the 
ability of fish to reach their spawning habitat in time to encounter 
con-specifics and reproduce). Unimpeded migratory corridors are 
necessary for adult green sturgeon to migrate to and from spawning 
habitats, and for larval and juvenile green sturgeon to migrate 
downstream from spawning/rearing habitats within freshwater rivers to 
rearing habitats within the estuaries.
    (6) Water depth. Deep (>= 5 m) holding pools for both upstream and 
downstream holding of adult or subadult fish, with adequate water 
quality and flow to maintain the physiological needs of the holding 
adult or subadult fish (see section titled Adults and Subadults). Deep 
pools of >= 5 m depth with high associated turbulence and upwelling are 
critical for adult green sturgeon spawning and for summer holding 
within the Sacramento River (R. Corwin, USBR, and B. Poytress, USFWS, 
2008, pers. comm.). Adult green sturgeon in the Klamath and Rogue 
rivers also occupy deep holding pools for extended periods of time, 
presumably for feeding, energy conservation, and/or refuge from high 
water temperatures (Erickson et al., 2002; Benson et al., 2007).
    (7) Sediment quality. Sediment quality (i.e., chemical 
characteristics) necessary for normal behavior, growth, and viability 
of all life stages. This includes sediments free of elevated levels of 
contaminants (e.g., selenium, polyaromatic hydrocarbons (PAHs), and 
organochlorine pesticides) that may adversely affect green sturgeon. 
Based on studies of white sturgeon, bioaccumulation of contaminants 
from feeding on benthic species may adversely affect the growth, 
reproductive development, and reproductive success of green sturgeon 
(see section titled Adult and Subadults).
    The specific PCEs essential for the conservation of the Southern 
DPS in estuarine areas include:
    (1) Food resources. Abundant prey items within estuarine habitats 
and substrates for juvenile, subadult, and adult life stages. As 
described previously (see Green Sturgeon Natural History), prey species 
for juvenile, subadult, and adult green sturgeon within bays and 
estuaries primarily consist of benthic invertebrates and fishes, 
including crangonid shrimp, burrowing thalassinidean shrimp 
(particularly the burrowing ghost shrimp), amphipods, isopods, clams, 
annelid worms, crabs, sand lances, and anchovies. These prey species 
are critical for the rearing, foraging, growth, and development of 
juvenile, subadult, and adult green sturgeon within the bays and 
estuaries.
    (2) Water flow. Within bays and estuaries adjacent to the 
Sacramento River (i.e., the Sacramento-San Joaquin Delta and the 
Suisun, San Pablo, and San Francisco bays), sufficient flow into the 
bay and estuary to allow adults to successfully orient to the incoming 
flow and migrate upstream to spawning grounds. Sufficient flows are 
needed to attract adult green sturgeon to the Sacramento River to 
initiate the upstream spawning migration (Kohlhorst et al., 1991, cited 
in CDFG, 2002; J. Stuart, NMFS, 2008, pers. comm.).
    (3) Water quality. Water quality, including temperature, salinity, 
oxygen content, and other chemical characteristics, necessary for 
normal behavior, growth, and viability of all life stages. Suitable 
water temperatures for juvenile green sturgeon should be below 24 
[deg]C. At temperatures above 24 [deg]C, juvenile green sturgeon 
exhibit decreased swimming performance (Mayfield and Cech, 2004) and 
increased cellular stress (Allen et al., 2006). Suitable salinities 
range from brackish water (10 ppt) to salt water (33 ppt). Juveniles 
transitioning from brackish to salt water can tolerate prolonged 
exposure to salt water salinities, but may exhibit decreased growth and 
activity levels (Allen and Cech, 2007), whereas subadults and adults 
tolerate a wide range of salinities (Kelly et al., 2007). Subadult and 
adult green sturgeon occupy a wide range of dissolved oxygen levels, 
but may need a minimum dissolved oxygen level of at least 6.54 mg 
O2/l (Kelly et al., 2007; Moser and Lindley, 2007). As 
described above, adequate levels of dissolved oxygen are also required 
to support oxygen consumption by juveniles (ranging from 61.78 to 76.06 
mg O2 hr-\1\ kg-\1\) (Allen and Cech, 
2007). Suitable water quality also includes water with acceptably low 
levels of contaminants (e.g., pesticides, organochlorines, elevated 
levels of heavy metals; acceptable low levels as determined by NMFS on 
a case-by-case basis) that may disrupt the normal development of 
juvenile life stages, or the growth, survival, or reproduction of 
subadult or adult stages.
    (4) Migratory corridor. A migratory pathway necessary for the safe 
and timely passage of Southern DPS fish within estuarine habitats and 
between estuarine and riverine or marine habitats. We define safe and 
timely passage to mean that human-induced impediments, either physical, 
chemical or biological, do not alter the migratory behavior of the fish 
such that its survival or the overall viability of the species is 
compromised (e.g., an impediment that compromises the ability of fish 
to reach thermal refugia by the time they enter a particular life 
stage). Within the bays and estuaries adjacent to the Sacramento River, 
unimpeded passage is needed for juvenile green sturgeon to migrate from 
the river to the bays and estuaries and eventually out into the ocean. 
Passage within the bays and the Delta is also critical for adults and 
subadults for feeding and summer holding, as well as to access the 
Sacramento River for their upstream spawning migrations and to make 
their outmigration back into the ocean. Within bays and estuaries 
outside of the Delta and the Suisun, San Pablo, and San Francisco bays, 
unimpeded passage is necessary for adult and subadult green sturgeon to 
access feeding areas, holding areas, and thermal refugia, and to ensure 
passage back out into the ocean.
    (5) Water depth. A diversity of depths necessary for shelter, 
foraging, and migration of juvenile, subadult, and adult life stages. 
Subadult and adult green sturgeon occupy a diversity of depths within 
bays and estuaries for feeding and migration. Tagged adults and 
subadults within the San Francisco Bay estuary primarily occupied 
waters over shallow depths of less than 10 m, either swimming near the 
surface or foraging along the bottom (Kelly et al., 2007). In a study 
of juvenile green sturgeon in the Delta, relatively large numbers of 
juveniles were captured primarily in shallow waters from 1-3 meters 
deep, indicating juveniles may require even shallower depths for 
rearing and foraging (Radtke, 1966). Thus, a diversity of depths is 
important to support different life stages and habitat uses for green 
sturgeon within estuarine areas.

[[Page 52090]]

    (6) Sediment quality. Sediment quality (i.e., chemical 
characteristics) necessary for normal behavior, growth, and viability 
of all life stages. This includes sediments free of elevated levels of 
contaminants (e.g., selenium, PAHs, and organochlorine pesticides) that 
can cause adverse effects on all life stages of green sturgeon (see 
description of ``Sediment quality'' for riverine habitats above).
    The specific PCEs essential for the conservation of the Southern 
DPS in coastal marine areas include:
    (1) Migratory corridor. A migratory pathway necessary for the safe 
and timely passage of Southern DPS fish within marine and between 
estuarine and marine habitats. We define safe and timely passage to 
mean that human-induced impediments, either physical, chemical or 
biological, do not alter the migratory behavior of the fish such that 
its survival or the overall viability of the species is compromised 
(e.g., an impediment that compromises the ability of fish to reach 
abundant prey resources during the summer months in Northwest Pacific 
estuaries). Subadult and adult green sturgeon spend the majority of 
their time in marine and estuarine waters outside of their natal 
rivers. Unimpeded passage within coastal marine waters is critical for 
subadult and adult green sturgeon to access oversummering habitats 
within coastal bays and estuaries and overwintering habitat within 
coastal waters between Vancouver Island, BC, and southeast Alaska. 
Access to and unimpeded movement within these areas is also necessary 
for green sturgeon to forage for prey and make lengthy migrations 
necessary to reach other foraging areas (Lindley et al., 2008). Passage 
is also necessary for subadults and adults to migrate back to San 
Francisco Bay and to the Sacramento River for spawning.
    (2) Water quality. Coastal marine waters with adequate dissolved 
oxygen levels and acceptably low levels of contaminants (e.g., 
pesticides, organochlorines, heavy metals that may disrupt the normal 
behavior, growth, and viability of subadult and adult green sturgeon). 
Based on studies of tagged subadult and adult green sturgeon in the San 
Francisco Bay estuary, CA, and Willapa Bay, WA, subadults and adults 
may need a minimum dissolved oxygen level of at least 6.54 mg 
O2/l (Kelly et al., 2007; Moser and Lindley, 2007). As 
described above, exposure to and bioaccumulation of contaminants may 
adversely affect the growth, reproductive development, and reproductive 
success of subadult and adult green sturgeon. Thus, waters with 
acceptably low levels of such contaminants (as determined by NMFS on a 
case-by-case basis) are required for the normal development of green 
sturgeon for optimal survival and spawning success.
    (3) Food resources. Abundant prey items for subadults and adults, 
which may include benthic invertebrates and fishes. Green sturgeon 
spend more than half their lives in coastal marine and estuarine 
waters, spending from 3-20 years at a time out at sea. Abundant food 
resources are important to support subadults and adults over long-
distance migrations, and may be one of the factors attracting green 
sturgeon to habitats far to the north (off the coast of Vancouver 
Island and Alaska) and to the south (Monterey Bay, CA, and off the 
coast of southern California) of their natal habitat. Although the CHRT 
lacked direct evidence, prey species likely include benthic 
invertebrates and fishes similar to those fed upon by green sturgeon in 
bays and estuaries (e.g., shrimp, clams, crabs, anchovies, sand lances) 
(see section on ``Adults and subadults'').

Geographical Area Occupied by the Species and Specific Areas Within the 
Geographical Area Occupied

    One of the first steps in the critical habitat designation process 
is to define the geographical area occupied by the species at the time 
of listing. The CHRT relied on data from tagging and tracking studies, 
genetic analyses, field observations, records of fisheries take and 
incidental take (e.g., in water diversion activities), and 
opportunistic sightings to provide information on the current range and 
distribution of green sturgeon and of the Southern DPS. The range of 
green sturgeon extends from the Bering Sea, Alaska, to Ense[ntilde]ada, 
Mexico. Within this range, Southern DPS fish are confirmed to occur 
from Graves Harbor, Alaska, to Monterey Bay, California (Lindley et 
al., 2008; S. Lindley and M. Moser, NMFS, 2008, unpublished data), 
based on telemetry data and genetic analyses. Green sturgeon have been 
observed northwest of Graves Harbor, AK, and south of Monterey Bay, CA, 
but have not been identified as belonging to either the Northern or 
Southern DPS. The CHRT concluded that there are no barriers or habitat 
conditions preventing Southern DPS fish detected in Monterey Bay, CA, 
or off Graves Harbor, AK, from moving further south or further north, 
and that the green sturgeon observed in these areas could belong to 
either the Northern DPS or the Southern DPS. Based on this reasoning, 
the geographical area occupied by the Southern DPS was defined as the 
entire range occupied by green sturgeon (i.e., from the Bering Sea, AK, 
to Ense[ntilde]ada, Mexico), encompassing all areas where the presence 
of Southern DPS fish has been confirmed, as well as areas where the 
presence of Southern DPS fish is likely (based on the presence of 
confirmed Northern DPS fish or green sturgeon of unknown DPS).
    Areas outside of the United States cannot be designated as critical 
habitat (50 CFR 424.12(h)). Thus, the occupied geographical area under 
consideration for this designation is limited to areas from the Bering 
Sea, AK, to the California/Mexico border, excluding Canadian waters. 
For freshwater rivers, the CHRT concluded that green sturgeon of each 
DPS are likely to occur throughout their natal river systems, but, 
within non-natal river systems, are likely to be limited to the 
estuaries and would not occur upstream of the head of the tide. For the 
purposes of our evaluation of critical habitat, we defined all green 
sturgeon observed upstream of the head of the tide in freshwater rivers 
south of the Eel River (i.e., the Sacramento River and its tributaries) 
as belonging to the Southern DPS, and all green sturgeon observed 
upstream of the head of the tide in freshwater rivers north of and 
including the Eel River as belonging to the Northern DPS. Thus, for 
freshwater rivers north of and including the Eel River, the areas 
upstream of the head of the tide were not considered part of the 
geographical area occupied by the Southern DPS.
    The CHRT then identified ``specific areas'' within the geographical 
area occupied. To be eligible for designation as critical habitat under 
the ESA, each specific area must contain at least one PCE that may 
require special management considerations or protection. For each 
specific occupied area, the CHRT noted whether the presence of Southern 
DPS green sturgeon is confirmed or likely (based on the presence of 
Northern DPS fish or green sturgeon of unknown DPS) and verified that 
each area contained one or more PCE(s) that may require special 
management considerations or protection. The following paragraphs 
provide a brief description of the presence and distribution of 
Southern DPS green sturgeon within each area and summarize the CHRT's 
methods for delineating the specific areas.

Freshwater Rivers, Bypasses, and the Delta

    Green sturgeon occupy several freshwater river systems from the 
Sacramento River, CA, north to British Columbia, Canada (Moyle, 2002). 
As

[[Page 52091]]

described in the previous section, Southern DPS green sturgeon occur 
throughout their natal river systems (i.e., the Sacramento River, lower 
Feather River, and lower Yuba River), but are believed to be restricted 
to the estuaries in non-natal river systems (i.e., north of and 
including the Eel River). The CHRT defined the specific areas in the 
Sacramento, Feather, and Yuba rivers in California to include riverine 
habitat from the river mouth upstream to and including the furthest 
known site of historic and/or current sighting or capture of green 
sturgeon, as long as the site is still accessible. The specific areas 
were extended upstream to a geographically identifiable point. The 
riverine specific areas include areas that offer at least periodic 
passage of Southern DPS fish to upstream sites and include sufficient 
habitat necessary for each riverine life stage (e.g., spawning, egg 
incubation, larval rearing, juvenile feeding, passage throughout the 
river, and/or passage into and out of estuarine or marine habitat).
    The CHRT delineated specific areas where Southern DPS green 
sturgeon occur, including: the Sacramento River, the Yolo and Sutter 
bypasses, the lower Feather River, and the lower Yuba River. The CHRT 
also delineated a specific area in the Sacramento-San Joaquin Delta. 
The mainstem Sacramento River is the only area where spawning by 
Southern DPS green sturgeon has been confirmed and where all life 
stages of the Southern DPS are supported. Beginning in March and 
through early summer, adult green sturgeon migrate as far upstream as 
the Keswick Dam (rkm 486) to spawn (Brown, 2007). Spawning has been 
confirmed by the collection of larvae and juveniles at the RBDD and the 
Glenn-Colusa Irrigation District (GCID) (CDFG, 2002; Brown, 2007) and 
by the collection of green sturgeon eggs downstream of the RBDD (Brown, 
2007; B. Poytress, USFWS, 2008, pers. comm.). The Sacramento River 
provides important spawning, holding, and migratory habitat for adults 
and important rearing, feeding, and migratory habitat for larvae and 
juveniles. The Yolo and Sutter bypasses adjacent to the lower 
Sacramento River also serve as important migratory corridors for 
Southern DPS adults, subadults, and juveniles on their upstream or 
downstream migration and provide a high macroinvertebrate forage base 
that may support green sturgeon feeding. Southern DPS adults occupy the 
lower Feather River up to Oroville Dam (rkm 116) and the lower Yuba 
River up to Daguerre Dam (rkm 19). Based on observations of Southern 
DPS adults occurring right up to the dams and of spawning behavior by 
adults on the Feather River, spawning may have occurred historically in 
the lower Feather River and, to a lesser extent, in the lower Yuba 
River. However, no green sturgeon eggs, larvae, or juveniles have ever 
been collected within these rivers. Further downstream, the Sacramento-
San Joaquin Delta provides important rearing, feeding, and migratory 
habitat for juveniles, which occur throughout the Delta in all months 
of the year. Subadults and adults also occur throughout the Delta to 
feed, grow, and prepare for their outmigration to the ocean. The draft 
biological report provides more detailed information on each specific 
area, including a description of the PCEs present, special management 
considerations or protection that may be needed, and the presence and 
distribution of Southern DPS green sturgeon. The draft biological 
report is available upon request (see ADDRESSES), via our Web site at 
https://swr.nmfs.noaa.gov, or via the Federal eRulemaking Web site at 
https://www.regulations.gov. For additional discussion of the special 
management considerations or protection that may be needed for the 
PCEs, please see also the description of ``Special management 
considerations or protection'' below.

Bays and Estuaries

    Southern DPS green sturgeon occupy coastal bays and estuaries from 
Monterey Bay, CA, to Puget Sound, WA. In the Central Valley, CA, 
juvenile, subadult, and adult life stages occur throughout the Suisun, 
San Pablo, and San Francisco bays. These bays support the rearing, 
feeding, and growth of juveniles prior to their first entry into marine 
waters. The bays also serve as important feeding, rearing, and 
migratory habitat for subadult and adult Southern DPS green sturgeon.
    Outside of their natal system, subadult and adult Southern DPS fish 
occupy coastal bays and estuaries in California, Oregon, and 
Washington, including estuarine waters at the mouths of non- natal 
rivers. Subadult and adult Southern DPS green sturgeon have been 
confirmed to occupy the following coastal bays and estuaries: Monterey 
Bay, CA; Humboldt Bay, CA; Coos Bay, OR; Winchester Bay, OR; the lower 
Columbia River estuary; Willapa Bay, WA; Grays Harbor, WA; and Puget 
Sound, WA (Chadwick, 1959; Miller, 1972; Lindley et al., 2008; Pinnix, 
2008; S. Lindley and M. Moser, NMFS, 2008, unpublished data). The 
presence of Southern DPS green sturgeon is likely (based on limited 
records of confirmed Northern DPS fish or green sturgeon of unknown 
DPS), but not confirmed within the following coastal bays and 
estuaries: Elkhorn Slough, CA; Tomales Bay, CA; Noyo Harbor, CA; Eel 
River estuary, CA; Klamath/Trinity River estuary, CA; Rogue River 
estuary, OR; Siuslaw River estuary, OR; Alsea River estuary, OR; 
Yaquina Bay, OR; and Tillamook Bay, OR (Emmett et al., 1991; Moyle et 
al., 1992; Adams et al., 2002; Erickson et al., 2002; Yoklavich et al., 
2002; Farr and Kern, 2005).
    Subadult and adult green sturgeon are believed to occupy coastal 
bays and estuaries outside of their natal waters for feeding, 
optimization of growth, and thermal refugia (Moser and Lindley, 2007; 
Lindley et al., 2008). Occupied coastal bays and estuaries north of San 
Francisco Bay, CA, contain oversummering habitats for subadults and 
adults, whereas coastal bays and estuaries south of San Francisco Bay, 
CA, are believed to contain overwintering habitats (Lindley et al., 
2008). The largest concentrations of green sturgeon, including Southern 
DPS fish, occur within the lower Columbia River estuary, Willapa Bay, 
and Grays Harbor (Emmett et al., 1991; Adams et al., 2002; WDFW and 
ODFW, 2002; Israel and May, 2006; Moser and Lindley, 2007; Lindley et 
al., 2008). Large numbers of green sturgeon also occur within 
Winchester Bay, Coos Bay, and Humboldt Bay (Moyle et al., 1992; Rien et 
al., 2000; Farr et al., 2001; Adams et al., 2002; Farr and Rien, 2002, 
2003; Farr and Kern, 2004, 2005; Israel and May, 2006; Lindley et al., 
2008; Pinnix, 2008). Smaller numbers of green sturgeon occur in Tomales 
Bay, CA (Moyle et al., 1992), Yaquina Bay (Emmett et al., 1991; Rien et 
al., 2000; Farr et al., 2001; Farr and Rien, 2002, 2003; Farr and Kern, 
2004, 2005), and Puget Sound, WA (S. Lindley and M. Moser, NMFS, 2008, 
unpublished data). Based on limited available data, green sturgeon 
presence is believed to be rare in the following bays and estuaries: 
Elkhorn Slough, CA; Noyo Harbor, CA; Siuslaw River estuary, OR; Alsea 
River estuary, OR; and Tillamook Bay, OR (Emmett et al., 1991; Moyle et 
al., 1992; Rien et al., 2000; Farr et al., 2001; Farr and Rien, 2002; 
Yoklavich et al., 2002; Farr and Rien, 2003; Farr and Kern, 2004, 
2005). Green sturgeon are present in the estuaries of the Eel River, 
Klamath/Trinity rivers, and Rogue River, but are believed to most 
likely belong to the Northern DPS. This is based on the fact that the 
Eel, Klamath/Trinity, and Rogue rivers are spawning rivers for the 
Northern DPS and that, to

[[Page 52092]]

date, no tagged Southern DPS subadults or adults have been detected in 
the estuaries of the three rivers, although Southern DPS fish have been 
observed in coastal marine waters just outside the mouth of the Klamath 
River (S. Lindley, NMFS, 2008, pers. comm.).
    The CHRT included all coastal bays and estuaries for which there 
was evidence to confirm the presence of green sturgeon, noting where 
there were confirmed Southern DPS fish, confirmed Northern DPS fish, or 
confirmed green sturgeon of unknown DPS. As stated in the previous 
section, based on our definitions for the Northern DPS and Southern 
DPS, any green sturgeon observed upstream of the head of the tide in 
freshwater rivers north of and including the Eel River were assigned to 
the Northern DPS. Thus, areas upstream of the head of the tide on these 
rivers were not included as part of the occupied specific areas for the 
Southern DPS. Each specific area was defined to extend from the mouth 
of the bay or estuary upstream to the head of the tide. The boundary at 
the mouth of each bay or estuary was defined by the COLREGS demarcation 
line. COLREGS demarcation lines delineate ``those waters upon which 
mariners shall comply with the International Regulations for Preventing 
Collisions at Sea, 1972 (72 COLREGS) and those waters upon which 
mariners shall comply with the Inland Navigation Rules'' (33 CFR 
80.01). Waters inside of the 72 COLREGS lines are Inland Rules waters 
and waters outside of the 72 COLREGS lines are COLREGS waters. The 
draft biological report provides additional information for each 
specific area. For a copy of the report, see ADDRESSES, our Web site at 
https://swr.nmfs.noaa.gov, or the Federal eRulemaking Web site at http:/
/www.regulations.gov. For additional discussion of the special 
management considerations or protection that may be needed for the 
PCEs, please see also the description of ``Special management 
considerations or protection'' below.

Coastal Marine Waters

    Subadult and adult green sturgeon spend most of their time in 
coastal marine and estuarine waters. The best available data indicate 
coastal marine waters are important for seasonal migrations from 
southern California to Alaska to reach distant foraging and aggregation 
areas. Green sturgeon occur primarily within the 110 m depth bathymetry 
(Erickson and Hightower, 2007). Green sturgeon tagged in the Rogue 
River and tracked in marine waters typically occupied the water column 
at 40-70 m depth, but made rapid vertical ascents to or near the 
surface, for reasons yet unknown (Erickson and Hightower, 2007). Green 
sturgeon use of waters < 110 m depth was confirmed by coastal Oregon 
and Washington bottom-trawl fisheries records indicating that most 
reported locations of green sturgeon occurred inside of the 110-m depth 
contour from 1993-2000, despite the fact that most of the fishing 
effort occurred in water deeper than 110 m (Erickson and Hightower, 
2007).
    Based on tagging studies of both Southern and Northern DPS fish, 
green sturgeon spend a large part of their time in coastal marine 
waters migrating between coastal bays and estuaries, including 
sustained long-distance m