Browse: Departments Dates Agencies
DEPARTMENT OF COMMERCE
U.S. Customs and Border Protection
CFR Citation: 50 CFR Part 226
Docket ID: [Docket No. 080730953-81003-01]
RIN ID: RIN 0648-AX04
NOTICE: Part II
DOCUMENT ACTION: Proposed rule; request for comments.
SUBJECT CATEGORY: Endangered and Threatened Wildlife and Plants: Proposed Rulemaking To Designate Critical Habitat for the Threatened Southern Distinct Population Segment of North American 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.
DOCUMENT 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 SacramentoSan 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.
SUMMARY: Commerce Department, National Oceanic and Atmospheric Administration,
SUPPLEMENTAL INFORMATION
BackgroundWe 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
[[Page 52085]]
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 decisionmaking 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 60day 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 longlived 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 1620 years of age) than males (approximately 152 cm TL and 1416 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 24 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 midApril to midJune (Emmett et al., 1991).
Spawning populations in North America have been confirmed in the Rogue (Erickson et al., 2002; Farr and
[[Page 52086]]
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 (MarchJuly) ranged from
2091,252 m\3\/s in the Sacramento River over a 10year period from
19962006 (http://waterdata.usgs.gov) and from 31260 m\3\/s in the
Rogue River over a 4year period from 20012004 (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 814 [deg]C (Moyle, 2002). In
laboratory studies, the optimal thermal range for green sturgeon
development was from 11 to 1718 [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 144216 hours, or 69 days, after fertilization (incubation temperatures ranged from 1515.7 [deg]C) and ranged from 12.615 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 56 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 (23.025.2 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 flatsurfaced substrates (slaterock 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 23 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 1516 [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 O
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 24 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 (1416 years) for males and 162 cm TL (1620 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
[[Page 52087]]
ocean; (3) summer holding (June to November) in deep pools with eddy
currents (for those that do not exhibit postspawning 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 SacramentoSan 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 (11.921.9 [deg]C; 8.832.1 ppt), experienced large
fluctuations in temperature and salinity (up to 2 [deg]C h1
and 1 practical salinity unit (PSU) h1), and occupied a
wide range of dissolved oxygen levels from 6.54 to 8.98 mg
O
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, peerreviewed 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 NMFSUSFWS 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 closelyrelated 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 postspawning 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 flatsurfaced 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 rateofchange 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 (1119 [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: 198306 m\3\/s) (Brown, 2007). Postspawning downstream
migrations are triggered by increased flows, ranging from 174417 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 1117 [deg]C
(optimal range = 1416 [deg]C) in spawning reaches for egg incubation
(MarchAugust) (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 O
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 humaninduced 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
conspecifics 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 SacramentoSan 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
O
(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 humaninduced 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 13 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 humaninduced 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
O
(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 320 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 nonnatal 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 nonnatal 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 SacramentoSan 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 GlennColusa 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 http://swr.nmfs.noaa.gov, or via 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.
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 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 4070 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 bottomtrawl fisheries records indicating that most reported locations of green sturgeon occurred inside of the 110m depth contour from 19932000, 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 longdistance migrations of up to 100 km per day (S. Lindley and M. Moser, NMFS, pers. comm. cited in BRT, 2005). These seasonal longdistance migrations are most likely driven by food resources. Some tagged individuals were observed swimming at slower speeds and spending several days within certain areas, suggesting that the individuals were feeding (S. Lindley and M. Moser, NMFS, 2008, pers. comm.).
Within the geographical area occupied (from the California/Mexico border to the Bering Sea, Alaska), the CHRT divided the coastal marine waters into 12 specific areas between estuaries or bays confirmed to be occupied by the Southern DPS. The presence of green sturgeon and Southern DPS fish within each area was based on data from tagging and tracking studies, records of fisheries captures, and NOAA Observer Program records. Tagged Southern DPS subadults and adults have been detected in coastal marine waters from Monterey Bay, CA, to Graves Harbor, AK, including the Strait of Juan de Fuca (Lindley et al., 2008). Green sturgeon bycatch data from NOAA's West Coast Groundfish Observer Program (WCGOP) support the telemetry results, showing green sturgeon occur from Monterey Bay, CA, to Cape Flattery, WA, with the greatest catch per unit effort in coastal waters from Monterey Bay to Humboldt Bay, CA (WCGOP, 2008, unpublished data). Because green sturgeon were only observed in the bottom trawl fishery, there was no data on green sturgeon bycatch off southeast Alaska, where bottom trawl fishing is prohibited. Green sturgeon have, however, been captured in bottom trawl fisheries along the coast off British Columbia. Although critical habitat cannot be designated within Canadian waters, it is important to note that several tagged Southern DPS green sturgeon have been detected off Brooks Peninsula on the northern tip of Vancouver Island, BC (Lindley et al., 2008.). Patterns of telemetry data suggest that Southern DPS fish use oversummering grounds in coastal bays and estuaries along northern California, Oregon, and Washington and overwintering grounds between Vancouver Island, BC, and southeast Alaska (Lindley et al., 2008).
Based on the tagging data and the information described above regarding green sturgeon use of coastal bays and estuaries in California, Oregon, and Washington, the CHRT identified the coastal marine waters from Monterey Bay, CA, to Vancouver Island, BC, as the primary migratory/connectivity corridor for subadult and adult Southern DPS green sturgeon to migrate to and from oversummering habitats and overwintering habitats. Coastal marine waters off southeast Alaska were not considered part of the primary migratory/connectivity corridor for green sturgeon, but were recognized as an important area at the northern extent of the overwintering range, based on the detection of two tagged Southern DPS fish off Graves Harbor, AK, (S. Lindley, NMFS, and J. Israel, UC Davis, 2007, pers. comm.) and green sturgeon bycatch data along the northern coast of British Columbia (Lindley et al., 2008). For areas northwest of southeast Alaska and south of Monterey Bay, CA, data on green sturgeon occurrence include the 2006 capture of two green sturgeon of unknown DPS in bottom trawl groundfish fisheries off Kodiak Island, AK, and in the Bering Sea off Unimak Island, AK (J. Ferdinand and D. Stevenson, NMFS, 2006, pers. comm.). In coastal marine waters south of Monterey Bay, a few green sturgeon of unknown DPS have been captured off Huntington Beach and Newport (Roedel, 1941), Point Vicente (Norris, 1957), Santa Barbara, and San Pedro (R. Rasmussen, NMFS, 2006, pers. comm.). More detailed information on the specific areas within coastal marine waters can be found in the draft biological report, available at our Web site at http://swr.nmfs.noaa.gov, at the Federal eRulemaking Web site at http://www.regulations.gov, or upon request (see ADDRESSES). 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.
Special Management Considerations or Protection
Joint NMFS and USFWS regulations at 50 CFR 424.02(j) define
``special management considerations or protection'' to mean ``any methods or
[[Page 52093]]
procedures useful in protecting physical and biological features of the
environment for the conservation of listed species.'' Based on
discussions with the CHRT and consideration of the draft economic
report, a number of activities were identified that may threaten the
PCEs such that special management considerations or protection may be
required. Major categories of habitatrelated activities include: (1)
Dams; (2) water diversions; (3) dredging and disposal of dredged
material; (4) inwater construction or alterations, including channel
modifications/diking, sand and gravel mining, gravel augmentation, road
building and maintenance, forestry, grazing, agriculture, urbanization,
and other activities; (5) National Pollutant Discharge Elimination
System (NPDES) permit activities and activities generating nonpoint
source pollution; (6) power plants; (7) commercial shipping; (8)
aquaculture; (9) desalination plants; (10) proposed alternative energy
projects; (11) liquefied natural gas (LNG) projects; (12) bottom
trawling; and (13) habitat restoration. These activities may have an
effect on one or more PCE(s) via their alteration of one or more of the
following: Stream hydrology, water level and flow, water temperature,
dissolved oxygen, erosion and sediment input/transport, physical
habitat structure, vegetation, soils, nutrients and chemicals, fish
passage, and stream/estuarine/marine benthic biota and prey resources.
The CHRT identified the activities occurring within each specific area
that may necessitate special management considerations or protection
for the PCEs and these are described briefly in the following
paragraphs. These activities are documented more fully in the draft biological report.
Table 1 lists the specific areas and the river miles or area
FOR FURTHER INFORMATION CONTACT Melissa Neuman, NMFS, Southwest Region (562) 9804115 or Lisa Manning, NMFS, Office of Protected Resources (301) 7131401.
Common CFR Searches
14 CFR Part 39 40 CFR Part 52 14 CFR Part 71 33 CFR Part 165 50 CFR Part 679 47 CFR Part 73 26 CFR Part 1 40 CFR Part 180 33 CFR Part 117 50 CFR Part 17 44 CFR Part 67 50 CFR Part 648 14 CFR Part 97 40 CFR Part 63 33 CFR Part 100 50 CFR Part 622 50 CFR Part 660 44 CFR Part 65 26 CFR Part 301 39 CFR Part 111 40 CFR Part 300 6 CFR Part 5 40 CFR Part 271 47 CFR Part 64 40 CFR Parts 52 and 81 50 CFR Part 665 10 CFR Part 50 44 CFR Part 64 49 CFR Part 571 39 CFR Part 3020