Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Gulf Sturgeon

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AI23

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 226

[Docket No.; I.D. 020522126-3051-02]

RIN 0648-AQ03

Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Gulf Sturgeon

AGENCY:

Fish and Wildlife Service (FWS), Interior, and National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration, Commerce.

ACTION:

Final rule.

SUMMARY:

We, FWS and NMFS, collectively “the Services,” designate critical habitat for the Gulf sturgeon (

Acipenser oxyrinchus desotoi

), a threatened species listed under the Endangered Species Act of 1973, as amended (Act). We designate 14 geographic areas among the Gulf of Mexico rivers and tributaries as critical habitat for the Gulf sturgeon. These 14 geographic areas (units) encompass approximately 2,783 river kilometers (rkm) (1,730 river miles (rmi)) and 6,042 square kilometers (km

2

) (2,333 square miles (mi

2

)) of estuarine and marine habitat.

Critical habitat identifies specific areas that are essential to the conservation of a listed species, and that may require special management considerations or protection. Section 7(a)(2) of the Act requires that each Federal agency shall, in consultation with and with the assistance of the Services, insure that any action authorized, funded or carried out by such agency is not likely to jeopardize the continued existence of an endangered or threatened species or result in the destruction or adverse modification of critical habitat. Section 4 of the Act requires us to consider economic and other relevant impacts of specifying any particular area as critical habitat. We solicited data and comments from the public on all aspects of the proposal, including data on economic and other impacts of the designation.

DATES:

The effective date of this rule is April 18, 2003.

ADDRESSES:

The complete administrative record, including comments and materials received, as well as supporting documentation, used in the preparation of this final rule are available for public inspection, by appointment, during normal business hours at the Panama City Field Office, U.S. Fish and Wildlife Service, 1601 Balboa Avenue, Panama City, Florida 32405. Copies of the final rule, economic analysis, and information regarding this critical habitat designation are available on the Internet at

http://alabama.fws.gov/gs/.

FOR FURTHER INFORMATION CONTACT:

Gail Carmody, Field Supervisor, Panama City Field Office (see

ADDRESSES

section) (telephone 850/769-0552; facsimile 850/763-2177), or Stephania Bolden, Fishery Biologist, National Oceanic and Atmospheric Administration (NOAA) Fisheries, Southeast Regional Office, 9721 Executive Center Drive North, St. Petersburg, Florida 33702 (telephone 727/570-5312; facsimile 727/570-5517). Information regarding this designation is available in alternate formats upon request.

SUPPLEMENTARY INFORMATION:

Background

The Gulf sturgeon (

Acipenser oxyrinchus (=oxyrhynchus) desotoi

), also known as the Gulf of Mexico sturgeon, is an anadromous fish (breeding in freshwater after migrating up rivers from marine and estuarine environments), inhabiting coastal rivers from Louisiana to Florida during the warmer months and overwintering in estuaries, bays, and the Gulf of Mexico. It is a nearly cylindrical primitive fish embedded with bony plates or scutes. The head ends in a hard, extended snout; the mouth is inferior and protrusible and is preceded by four conspicuous barbels. The tail (caudal fin) is distinctly asymmetrical, the upper lobe is longer than the lower lobe (heterocercal). Adults range from 1.2 to 2.4 meters (m) (4 to 8 feet (ft)) in length, with adult females larger than males. The Gulf sturgeon is distinguished from the geographically disjunct Atlantic coast subspecies (

A. o. oxyrinchus

) by its longer head, pectoral fins, and spleen (Vladykov, 1955; Wooley, 1985). King

et al.

(2001) have documented substantial divergence between

A. o. oxyrinchus

and

A. o. desotoi

using microsatellite DNA testing.

Distribution and Status

Historically, the Gulf sturgeon occurred from the Mississippi River east to Tampa Bay. Its present range extends from Lake Pontchartrain and the Pearl River system in Louisiana and Mississippi east to the Suwannee River in Florida. Sporadic occurrences have been recorded as far west as the Rio Grande River between Texas and Mexico, and as far east and south as Florida Bay (Wooley and Crateau, 1985; and Reynolds, 1993).

In the late 19th century and early 20th century, the Gulf sturgeon supported an important commercial fishery, providing eggs for caviar, flesh for smoked fish, and swim bladders for isinglass, a gelatin used in food products and glues (Huff, 1975; and Carr, 1983). Gulf sturgeon numbers declined due to overfishing throughout most of the 20th century. The decline was exacerbated by habitat loss associated with the construction of water control structures, such as dams and sills (submerged ridge or vertical wall of relatively shallow depth separating two bodies of water), mostly after 1950. In several rivers throughout the species' range, dams have severely restricted sturgeon access to historic migration routes and spawning areas (Boschung, 1976; Wooley and Crateau, 1985; and McDowall, 1988).

On September 30, 1991, we listed the Gulf sturgeon as a threatened species under the Act (16 U.S.C. 1531

et seq.

) (56 FR 49653). Other threats and potential threats identified in the listing rule included modifications to habitat associated with dredged material disposal, desnagging (removal of trees and their roots), and other navigation maintenance activities; incidental take by commercial fishermen; poor water quality associated with contamination by pesticides, heavy metals, and industrial contaminants; aquaculture and incidental or accidental introductions; and the Gulf sturgeon's slow growth and late maturation. The Gulf sturgeon listing rule and the Gulf Sturgeon Recovery/Management Plan (FWS

et al.

, 1995), which was approved by the Services and the Gulf States Marine Fisheries Commission, provide a more detailed discussion of the reasons for the species' decline and threats to surviving populations (available by request or at the FWS Internet site, see

ADDRESSES

).

The Gulf Sturgeon Recovery/Management Plan (FWS

et al.

, 1995) recommended that genetic studies be done to determine geographically distinct management units. Some work in this regard has been completed (Stabile

et al.

, 1996), but we have not formally adopted management units at this time. For purposes of this final rule, we have used the term subpopulation to subdivide the Gulf sturgeon population

based on geography, degree of connectedness, and genetic interchange (Lande and Barrowclough, 1987; and King

et al.

, 2001). Seven subpopulations are described in the “Critical Habitat Unit Descriptions” section of this rule.

Feeding Habits

Gulf sturgeon feeding habits in freshwater vary depending on the fish's life history stage (

i.e.

, young-of-the-year, juvenile, subadult, adult). Young-of-the-year Gulf sturgeon remain in freshwater feeding on aquatic invertebrates and detritus approximately 10 to 12 months after spawning occurs (Mason and Clugston, 1993; and Sulak and Clugston, 1999). Juveniles (less than 5 kg (11 lbs) are believed to forage extensively and exploit scarce food resources throughout the river, including aquatic insects (

e.g.

, mayflies and caddisflies), worms (oligochaetes), and bivalve molluscs (Huff, 1975; and Mason and Clugston, 1993). Juvenile (ages 1 to 6) Gulf sturgeon collected in the Suwannee River are trophically active (foraging) near the river mouth at the estuary, but trophically dormant (not foraging) in summer holding areas upriver—a portion of the juvenile population reside and feed year round near the river mouth at the estuary, not just in winter (K. Sulak, U.S. Geological Survey (USGS), pers. comm. 2002). In the Choctawhatchee River, juvenile (ages 1 to 6) Gulf sturgeon did not remain near the estuary at the river mouth for the entire year, instead, they were located during winter months in Choctawhatchee Bay and returned upriver to resting areas in the spring (F. Parauka, FWS, pers. comm. 2002). Subadult (age 6 to sexual maturity) and adult (sexually mature) Gulf sturgeon do not feed in freshwater (Wooley and Crateau, 1985; and Mason and Clugston, 1993).

Many reports indicate that adult and subadult Gulf sturgeon lose a substantial percentage of their body weight while in freshwater (Wooley and Crateau, 1985; Mason and Clugston, 1993; and Clugston

et al.

, 1995) and then compensate the loss during winter feeding in the estuarine and marine environments (Wooley and Crateau, 1985; and Clugston

et al.

, 1995). Gu

et al.

(2001) tested the hypothesis that subadult and adult Gulf sturgeon do not feed significantly during their annual residence in freshwater by comparing stable carbon isotope ratios of tissue samples from subadult and adult Suwannee River Gulf sturgeon and their potential freshwater and marine food sources. A large difference in isotope ratios between freshwater food sources and fish muscle tissue suggests that subadult and adult Gulf sturgeon do not feed significantly in freshwater. The isotope similarity between Gulf sturgeon and marine food resources strongly indicates that this species relies almost entirely on the marine food web for its growth (Gu

et al.

, 2001).

Once subadult and adult Gulf sturgeon leave the river, having spent at least 6 months in the river fasting, we presume that they immediately begin feeding. Upon exiting the rivers, Gulf sturgeon are found in high concentrations near their natal river mouths. Lakes and bays at the mouths of the river systems where Gulf sturgeon occur are important because they offer the first opportunity for Gulf sturgeon exiting their natal rivers to forage. Gulf sturgeon must be able to consume sufficient quantities of prey while in estuarine and marine waters to regain the weight they lose while in the river system and to maintain positive growth on a yearly basis. In addition, reproductively active Gulf sturgeon require additional food resources to obtain sufficient energy necessary for reproduction (Fox

et al.

, 2002; and D. Murie and D. Parkyn, University of Florida (UF), pers. comm. 2002).

Adult and subadult Gulf sturgeon, while in marine and estuarine habitat, are thought to forage opportunistically (Huff, 1975), primarily on benthic (bottom dwelling) invertebrates. Gut content analyses have indicated that the Gulf sturgeon's diet is predominantly amphipods, lancelets, polychaetes, gastropods, shrimp, isopods, molluscs, and crustaceans (Huff, 1975; Mason and Clugston, 1993; Carr

et al.

, 1996b; Fox

et al.

, 2000; and Fox

et al.

, 2002). Gulf sturgeon from the Suwannee River subpopulation are known to forage on brachiopods (Murie and Parkyn, pers. comm. 2002); however, this is not a documented prey item of other subpopulations. Ghost shrimp (

Lepidophthalmus louisianensis

) and the haustoriid amphipod (

Lepidactylus

spp.) are strongly suspected to be important prey for adult Gulf sturgeon over 1 m (3.3 ft) (Heard

et al.

, 2000; and Fox

et al.

, 2002). This hypothesis is based on the following evidence: (1) Gulf sturgeon have been consistently located and observed actively feeding in areas where numerous burrows similar to those occupied by ghost shrimp exist (Fox

et al.

, 2000) and in areas having a high density of ghost shrimp and haustoriid amphipods (Heard

et al.

, 2000), (2) the digestive tracts of two adult Gulf sturgeon that died during netting operations contained numerous ghost shrimp (Fox

et al.

, 2000), (3) stomach contents of a 30 kg (67 lb) sturgeon taken in the upper portion of Choctawhatchee Bay contained more than 100 individual haustoriid amphipods and 67 ghost shrimp (Heard

et al.

, 2000), and (4) approximately one-third of 157 sturgeon guts analyzed by Carr

et al.

(1996b) contained exclusively brachiopods and ghost shrimp.

Reproduction

Gulf sturgeon are long-lived, with some individuals reaching at least 42 years in age (Huff, 1975). Age at sexual maturity for females ranges from 8 to 17 years, and for males from 7 to 21 years (Huff, 1975). Gulf sturgeon eggs are demersal (they are heavy and sink to the bottom), adhesive, and vary in color from gray to brown to black (Vladykov and Greeley, 1963; Huff, 1975; and Parauka

et al.

, 1991). Chapman

et al.

(1993) estimated that mature female Gulf sturgeon weighing between 29 and 51 kg (64 and 112 lb) produce an average of 400,000 eggs. Habitat at egg collection sites consists of one or more of the following: limestone bluffs and outcroppings, cobble, limestone bedrock covered with gravel and small cobble, gravel, and sand (Marchant and Shutters, 1996; Sulak and Clugston, 1999; Heise

et al.

, 1999a; Fox

et al.

, 2000; and Craft

et al.

, 2001). On the Suwannee River, Sulak and Clugston (1999) suggest a dense matrix of gravel or cobble is likely essential for Gulf sturgeon egg adhesion and the sheltering of the yolk sac larvae, and is a habitat spawning adults apparently select. Other substrates identified as possible spawning habitat include marl (clay with substantial calcium carbonate), soapstone, or hard clay (W. Slack, Mississippi Museum of Natural Science (MMNS), pers. comm. 2002; and F. Parauka, pers. comm. 2002). Water depths at egg collection sites ranged from 1.4 to 7.9 m (4.6 to 26 ft), with temperatures ranging from 18.2 to 23.9 degrees Celsius (°C) (64.8 to 75.0 degrees Fahrenheit (°F)) (Fox

et al.

, 2000; Ross

et al.

, 2000; Craft

et al.

, 2001). Laboratory experiments indicated optimal water temperature for survival of Gulf sturgeon larvae is between 15 and 20 °C (59 and 68 °F), with low tolerance to temperatures above 25 °C (77 °F) (Chapman and Carr, 1995). Researchers hypothesize that spawning must take place where the hydrological and chemical settings are appropriate for gamete (mature reproductive cell) function, and temperature, pH, and dissolved oxygen conditions are stable and appropriate for embryonic and yolk sac larval development (Sulak and Clugston, 1999).

Sulak and Clugston (1999) suggested that sturgeon spawning activity in the Suwannee River is related to the phase

of the moon, but only after the water temperature has risen to 17 °C (62.6 °F). Other researchers however, have found little evidence of spawning associated with lunar cycles (Slack

et al.

, 1999; and Fox

et al.

, 2000). Spawning in the Suwannee River occurs during the general period of spring high water, when ionic conductivity and calcium ion concentration are most favorable for egg development and adhesion (Sulak and Clugston, 1999). Fox

et al.

(2002) found no clear pattern between timing of Gulf sturgeon entering the river and flow patterns on the Choctawhatchee River. Ross

et al.

(2001b) surmised that the high flows in early March were a cue for sturgeon to begin their upstream movement in the Pascagoula River.

Atlantic sturgeon (

A. oxyrinchus

) exhibit a long inter-spawning period, with females spawning at intervals ranging from every 3 to 5 years, and males every 1 to 5 years (Smith, 1985). It is believed that Gulf sturgeon exhibit similar spawning periodicity, as male Gulf sturgeon are capable of annual spawning, and females require more than one year between spawning events (Huff, 1975; and Fox

et al.

, 2000).

Freshwater Habitat

In the spring (March to May), most adult and subadult Gulf sturgeon return to their natal river, where sexually mature sturgeon spawn, and the population spends until October or November (6 to 8 months) in freshwater (Odenkirk, 1989; Foster, 1993; Clugston

et al.

, 1995; and Fox

et al.

, 2000). Fox

et al.

(2000) found that some individuals of the Choctawhatchee River subpopulation do not enter the river until the summer months. Gulf sturgeon migration is further discussed in the “Migration” section of this rule. During their early life history stages, sturgeon require bedrock and clean gravel or cobble substrate for eggs to adhere to and for shelter for developing larvae (Sulak and Clugston, 1998). Young-of-the-year appear to disperse widely, using extensive portions of the river as nursery habitat. They are typically found on sandbars and sand shoals over rippled bottom and in shallow, relatively open, unstructured areas. Given that the river is generally nutrient poor with low levels of total phosphorus and organic carbon, suggesting low productivity, this dispersal may be an adaptation to exploit scarce food resources (Randall and Sulak, 1999). Clugston

et al.

(1995) reported that young Gulf sturgeon in the Suwannee River, weighing between 0.3 and 2.4 kg (0.7 and 5.3 lb), remain in the vicinity of the river mouth and estuary during the winter and spring.

Adult Gulf sturgeon spawn in upper river reaches. On some river systems such as the Pascagoula River and Apalachicola River, some adult and subadult Gulf sturgeon remain near the spawning grounds throughout the summer months (Wooley and Crateau, 1985; and Ross

et al.

, 2001b), but the majority move downstream to areas referred to as summer resting or holding areas. In other rivers, most Gulf sturgeon spawn and move downstream to aggregation areas also referred to as summer resting or holding areas. A few Gulf sturgeon have been documented remaining at or near their spawning grounds throughout the winter (Wooley and Crateau, 1985; Slack

et al.

, 1999; and Heise

et al.

, 1999a). Adults and subadults are not distributed uniformly throughout the river, but show a preference for these discrete areas usually located in lower and middle river reaches (Hightower

et al.

, in press). Often, these resting areas are located in close proximity to natural springs throughout the warmest months of the year, but are not located within a spring or thermal plume emanating from a spring (Clugston

et al.,

1995; Foster and Clugston, 1997; and Hightower

et al.

, in press). These resting areas are also often located in deep holes or shallow areas along straight-aways ranging from 2 to 19 m (6.6 to 62.3 ft) deep (Wooley and Crateau, 1985; Morrow

et al.

, 1998a; Ross

et al.

, 2001a and b; Craft

et al.

, 2001; and Hightower

et al.

, in press). The substrates consisted of mixtures of limestone and sand (Clugston

et al.

, 1995), sand and gravel (Wooley and Crateau, 1985; and Morrow

et al.

, 1998a), or just sandy substrate (Hightower

et al.

, in press).

River flow may serve as an environmental cue that governs both sturgeon migration and spawning (Chapman and Carr, 1995; and Ross

et al.

, 2001b). If the flow rate is too high, sturgeon in several life-history stages can be adversely affected. Data describing the sturgeon's swimming ability in the Suwannee River strongly indicates that they cannot continually swim against prevailing currents of greater than 1 to 2 m per second (3.2 to 6.6 ft per second) (K. Sulak, USGS, pers. comm. cited in Wakeford, 2001). If the flow is too strong, eggs might not be able to settle on and adhere to suitable substrate (Wooley and Crateau

et al.

, 1985). Flows that are too low can cause clumping of eggs, which leads to increased mortality from asphyxiation and fungal infection (Wooley and Crateau

et al.

, 1985). Flow velocity requirements for age 0 sturgeon may vary depending on substrate type. Chan

et al.

(1997) found that age 0 Gulf sturgeon under laboratory conditions exposed to water velocities over 12 centimeters per second (cm/s) (4.7 inches per second (in/s)) preferred a cobble substrate, but favored water velocities under 12 cm/s (4.7 in/s) and then used a variety of substrates (sand, gravel, and cobble).

Gulf sturgeon require large areas of diverse habitat that have natural variations in water flow, velocity, temperature, and turbidity (FWS

et al.

, 1995; and Wakeford, 2001). Natural surface and groundwater discharges influence a river's characteristic fluctuations in volume, depth, and velocity (Leitman

et al.

, 1993; and Albertson and Torak, 2002). Change in temperature is thought to be an important factor in initiating sturgeon migration (Wooley and Crateau, 1985; Chapman and Carr, 1995; and Foster and Clugston, 1997) (see “Migration” section for temperature ranges). Laboratory experiments indicate that Gulf sturgeon eggs, embryos, and larvae have the highest survival rates when temperatures are between 15 and 20 °C (59 and 68 °F). Mortality rates of Gulf sturgeon gametes and embryos are highest when temperatures are 25 °C (77 °F) and above (Chapman and Carr, 1995) (see “Reproduction” section for more detail). Researchers have documented temperature ranges at Gulf sturgeon resting areas between 15.3 and 33.7 °C (59.5 and 92.7 °F) with dissolved oxygen levels between 5.6 and 9.1 milligrams per liter (mg/l) (Morrow

et al.

, 1998a; and Hightower

et al.

, in press).

In comparison to other fish species, sturgeon have a limited behavioral and physiological capacity to respond to hypoxia (insufficient oxygen levels) (Secor and Niklitschek, 2001). Basal metabolism, growth, consumption, and survival are sensitive to changes in oxygen levels (Secor and Niklitschek, 2001). In laboratory experiments, young shortnose sturgeon (

A. brevirostrum

) (less than 77 days old) died at oxygen levels of 3.0 mg/l and all sturgeon died at oxygen levels of 2.0 mg/l (Jenkins

et al.

, 1993). Data concerning the temperature, oxygen, and current velocity requirements of cultured sturgeon are being collected. Researchers plan to use information gained from these laboratory experiments on hatchery-reared sturgeon to develop detailed information on water flow requirements of wild sturgeon throughout different phases of their freshwater residence (Wakeford, 2001).

Estuarine and Marine Habitat

Most subadult and adult Gulf sturgeon spend cool months (October or November through March or April) in estuarine areas, bays, or in the Gulf of Mexico (Odenkirk, 1989; Foster, 1993; Clugston

et al.

, 1995; and Fox

et al.

, 2002). Studies of subadult Gulf sturgeon (ages 4 to 7) in Choctawhatchee Bay found that 78 percent of tagged fish remained in the bay the entire winter, while 13 percent ventured into a connecting bay. Possibly the remaining 9 percent overwintered in the Gulf of Mexico (FWS, 1998). Adult Gulf sturgeon are more likely to overwinter in the Gulf of Mexico, with 45 percent of the tagged adults presumed to have left Choctawhatchee Bay and spent extended periods of time in the Gulf of Mexico (Fox and Hightower, 1998; and Fox

et al.

, 2002). In contrast, Gulf sturgeon from the Suwannee River subpopulation are known to migrate into the nearshore waters, where they remain for up to two months and then depart to unknown feeding locations in the open Gulf of Mexico (Carr

et al.

, 1996b; and Edwards

et al.

, in prep.).

Research in Choctawhatchee Bay indicates that subadult Gulf sturgeon show a preference for sandy shoreline habitats with water depths less than 3.5 m (11.5 ft) and salinity less than 6.3 parts per thousand (Parauka

et al.

, in press). Fox and Hightower (1998) found that adult Gulf sturgeon monitored in Choctawhatchee Bay use some of the same habitats as subadults. The majority of tagged fish have been located in areas lacking seagrass (Fox

et al.

, 2002; and Parauka

et al.

, in press).

Craft

et al.

(2001) found that Gulf sturgeon in Pensacola Bay appear to prefer shallow shoals 1.5 to 2.1 m (5 to 7 ft) and deep holes near passes. Unvegetated, fine to medium-grain sand habitats, such as sandbars, and intertidal and subtidal energy zones resulting in sediment sorting and a preponderance of sand support a variety of potential prey items including estuarine crustaceans, small bivalve mollusks and lancelets (Menzel, 1971; Abele and Kim, 1986; American Fisheries Society, 1989; and M. Brim, FWS, pers. comm. 2002).

Habitats used by Gulf sturgeon in the vicinity of the Mississippi Sound barrier islands tend to have a sand substrate and an average depth of 1.9 to 5.9 m (6.2 to 19.4 ft). Preliminary data from bottom samples taken in these barrier island areas show that all samples contain lancelets (

Branchiostoma

). Since lancelets are a documented prey of Gulf sturgeon, it is likely that Gulf sturgeon are feeding along the sand substrate at barrier island passes (Ross

et al.

, 2001a). Gulf of Mexico nearshore (less than 1.6 km (1 mi)) unconsolidated, fine-medium grain sand habitats, including natural inlets and passes from the Gulf to estuaries, support crustaceans such as mole crabs, sand fleas, various amphipod species, and lancelets (Menzel, 1971; Abele and Kim, 1986; American Fisheries Society, 1989; and Brim, pers. comm. 2002).

Estuary and bay unvegetated habitats have a preponderance of sandy substrates that support burrowing crustaceans, such as ghost shrimp, small crabs, various polychaete worms, and small bivalve mollusks (Menzel, 1971; Abele and Kim, 1986; American Fisheries Society, 1989; and Brim, pers. comm. 2002). Gulf sturgeon are often located in these areas, and because their known prey items are present, it is assumed that Gulf sturgeon are foraging.

Migration

Migratory behavior of the Gulf sturgeon seems influenced by sex, reproductive status, water temperature, and possibly river flow. Carr

et al.

(1996b) reported that male Gulf sturgeon initiate migration to the river earlier in spring than females. Fox

et al.

(2000) found no significant difference in the timing of river entry due to sex, but reported that males migrate further upstream than females and that ripe (in reproductive condition) males and females enter the river earlier than nonripe fish (Fox

et al.

, 2000). Most adults and subadults begin moving from estuarine and marine waters into the coastal rivers in early spring (

i.e.

, March through May) when river water temperatures range from 16.0 to 23.0 °C (60.8 to 73.4 °C) (Huff, 1975; Carr, 1983; Wooley and Crateau, 1985; Odenkirk, 1989; Clugston

et al.

, 1995; Foster and Clugston, 1997; Fox and Hightower, 1998; Sulak and Clugston, 1999; and Fox

et al.

, 2000), while others may enter the rivers during summer months (Fox

et al.

, 2000). Some research supports the theory that spring migration coincides with the general period of spring high water (Chapman and Carr, 1995; Sulak and Clugston, 1999; and Ross

et al.

, 2001b), however, observations on the Choctawhatchee River have not found a clear relationship between the timing of river entrance and flow patterns (Fox

et al.

, 2002).

Downstream migration from fresh to saltwater begins in September (at about 23°C (73.4°F)) and continues through November (Huff, 1975; Wooley and Crateau,1985; and Foster and Clugston, 1997). During the fall migration from fresh to saltwater, Gulf sturgeon may require a period of physiological acclimation to changing salinity levels, referred to as osmoregulation or staging (Wooley and Crateau, 1985). This period may be short (Fox

et al.

, 2002) as sturgeon develop an active mechanism for osmoregulation and ionic balance by age one (Altinok

et al.

, 1997). On some river systems, timing of the fall migration appears to be associated with pulses of higher river discharge (Heise

et al.

, 1999a and b; Ross

et al.

, 2000 and 2001b; and Parauka

et al.

, in press).

Sturgeon ages 1 through 6 remain in the mouth of the Suwannee River over winter. In late January through early February, young-of-the-year Gulf sturgeon migrate down river for the first time (Sulak and Clugston, 1999). Huff (1975) noted that juvenile Gulf sturgeon in the Suwannee River most likely participated in pre- and post-spawning migrations, along with the adults.

Findeis (1997) described sturgeon (Acipenseridae) as exhibiting evolutionary traits adapted for benthic cruising. Tracking observations by Sulak and Clugston (1999), Fox

et al.

(2002), and Edwards

et al.

(in prep.) support that individual fish move over an area until they encounter suitable prey type and density, at which time they forage for extended periods of time. Individual fish often remained in localized areas (less than 1 km

2

(0.4 mi

2

) for extended periods of time (greater than two weeks) and then moved rapidly to another area where localized movements occurred again (Fox

et al.

, 2002). It is unknown precisely how much benthic area is needed to sustain Gulf sturgeon health and growth, but because Gulf sturgeon have been known to travel long distances (greater than 161 km (100 mi)) during their winter feeding phase, significant resources must be necessary. These winter migrations are an important strategy for feeding and for occasional travel to non-natal rivers for possible spawning and resultant genetic interchange among subpopulations. Bays and portions of Gulf of Mexico waters adjacent to the lakes and bays near the mouths of the rivers where Gulf sturgeon occur are believed to be important for feeding and/or migrating (inter-river migrations that facilitate maintenance of the natural hierarchy of between river genetic variability).

When temperature drops occur that are associated with major cold fronts, researchers of the Escambia, Yellow, and Suwannee Rivers subpopulations have been unable to locate adult Gulf sturgeon within the bays (Craft

et al.

, 2001; and Edwards

et al.

, in prep.). They hypothesize that the drop in water temperatures associated with cold fronts disperses sturgeon to more distant foraging grounds. It is currently

unknown whether Gulf sturgeon undertake extensive offshore migrations, and further study is needed to determine whether important winter feeding habitat occurs in farther offshore areas.

Sulak and Clugston (1999) described two hypotheses regarding areas adult Gulf sturgeon may overwinter in the Gulf of Mexico in order to find abundant prey. The first hypothesis is that Gulf sturgeon spread along the coast in nearshore waters in depths less than 10 m (33 ft). The alternative hypothesis is that they migrate far offshore to the broad sedimentary plateau in deep water (40 to 100 m (131 to 328 ft)) west of the Florida Middle Grounds, where over twenty species of bottom-feeding fish congregate in the winter (Darnell and Kleypas, 1987). Available data support the first hypothesis. Evaluation of tagging data has identified several nearshore Gulf of Mexico feeding migrations, but no offshore Gulf of Mexico feeding migrations or areas. Telemetry data document that Gulf sturgeon from the Pearl River and Pascagoula River subpopulations migrate from their natal bay systems to Mississippi Sound and move along the barrier islands, with relocation of tagged individuals greatest in the passes between islands (Ross

et al.

, 2001a; and Rogillio

et al.

, 2002). Gulf sturgeon from the Choctawhatchee River, Yellow River, and Apalachicola River have been documented migrating in the nearshore Gulf of Mexico waters between Pensacola and Apalachicola Bays (Fox

et al.

, 2002; and F. Parauka, pers. comm. 2002). Telemetry data in the Gulf of Mexico usually locate sturgeon in depths of 6 m (19.8 ft) or less (Ross

et al.

, 2001a; Fox

et al.

, 2002; Rogillio

et al.

, 2002; and F. Parauka, pers. comm. 2002).

River-Specific Fidelity

Stabile

et al.

(1996) analyzed tissue from Gulf sturgeon in eight drainages along the Gulf of Mexico for genetic diversity. They noted significant differences among Gulf sturgeon stocks and suggested that they displayed region-specific affinities and may exhibit river-specific fidelity. Stabile

et al.

(1996) identified five regional or river-specific stocks (from west to east): (1) Lake Pontchartrain and Pearl River, (2) Pascagoula River, (3) Escambia and Yellow Rivers, (4) Choctawhatchee River, and (5) Apalachicola, Ochlockonee, and Suwannee Rivers.

Tagging studies suggest that Gulf sturgeon exhibit a high degree of river fidelity (Carr, 1983). From 1981 to 1993, 4,100 fish were tagged in the Apalachicola and Suwannee Rivers. Of these, 868 total fish were recaptured (FWS

et al.

1995). Of the recaptured fish, 860 fish (99 percent) were recaptured in the river of their initial collection. Eight fish moved between river systems and represented less than 1 percent (0.009) of the 868 total fish recaptured (FWS

et al.

, 1995). We have no information documenting spawning adults in non-natal rivers. Foster and Clugston (1997) noted that telemetered Gulf sturgeon in the Suwannee River returned to the same areas as the previous summer, and suggested that chemical cuing may influence distribution.

To date, biologists have documented a total of 22 Gulf sturgeon making inter-river movements from natal rivers. They are as follows: Apalachicola River to Suwannee River, six Gulf sturgeon (Carr

et al.

, 1996b); Apalachicola River to Deer Point Lake (North Bay of the St. Andrew Bay system), one fish (Wooley and Crateau, 1985); Suwannee River to Apalachicola River, three sturgeon (Carr

et al.

, 1996b; and F. Parauka, pers. comm. 2002); Choctawhatchee River to Apalachicola River, one sturgeon (F. Parauka, pers. comm. 2002); Yellow River to Choctawhatchee River, three female sturgeon (two adult, one subadult) (Craft

et al.

, 2001); Yellow River to Louisiana Estuarine area, one female sturgeon (Craft

et al.

, 2001); Escambia River to Yellow River, one mature female on spawning grounds (Craft

et al.

, 2001); Suwannee River to Ochlockonee River, one sturgeon (FWS

et al.

, 1995); Choctawhatchee River to Escambia River, one male sturgeon (Fox

et al.

, 2002); Choctawhatchee River to Escambia, one female sturgeon (Fox

et al.

, 2002); Pearl River (Bogue Chitto) to Pascagoula River, one sturgeon (Ross

et al.

, 2001b); Choctawhatchee River to Pascagoula River, one subadult sturgeon (Ross

et al.

, 2001b); and Pascagoula River to Yellow River, one sturgeon (Ross

et al.

, 2001b).

Tallman and Healey (1994) noted that observed straying rates between rivers were not the same as actual gene flow rates,

i.e.

, inter-stock movement does not equate to interstock reproduction. The gene flow is low in Gulf sturgeon stocks, with each stock exchanging less than one mature female per generation (Waldman and Wirgin, 1998).

Previous Federal Action

Federal action on the Gulf sturgeon began in 1982, when the fish was included as a Category 2 candidate species for listing in the FWS's vertebrate notices of review dated December 30, 1982 (47 FR 58454) and September 18, 1985 (50 FR 37958), and in the animal notice of review dated January 6, 1989 (54 FR 554). At that time, the FWS gave Category 2 designation to species for which listing as threatened or endangered was possibly appropriate, but for which additional biological information was needed to support a proposed rule. A status report on the Gulf sturgeon (Hollowell, 1980) had concluded that the fish had been reduced to a small population due to overfishing and habitat loss. In 1988, the FWS completed a report on the conservation status of the Gulf sturgeon, which recommended listing it as a threatened species (Barkuloo, 1988).

The Services jointly proposed the Gulf sturgeon for listing as a threatened species on May 2, 1990 (55 FR 18357). In that proposed rule, we stated that designation of critical habitat was not prudent due to the species” broad range and the lack of knowledge about specific areas used by the species. We published the final rule on September 30, 1991 (56 FR 49653) to add Gulf sturgeon to the list of threatened species, and included a special rule under section 4(d) of the Act to allow the take of Gulf sturgeon, in accordance with applicable State fish and wildlife conservation laws and regulations, for educational and scientific purposes, the enhancement of propagation or survival of the species, zoological exhibition, and other conservation purposes.

Section 4(a)(3)(A) of the Act requires that critical habitat be designated concurrently with a determination that a species is endangered or threatened, to the maximum extent prudent and determinable. When such a designation is not determinable at the time of final listing of a species, or if a prompt determination of endangered or threatened status is essential to the conservation of the species, section 4(b)(6)(C) of the Act provides for an additional year to promulgate a final critical habitat designation. In the final rule listing Gulf sturgeon as a threatened species, we found that a critical habitat designation may be prudent but was not determinable. We found that prompt determination of threatened status was essential to the conservation of the species and stated that we would make a final decision on designation of critical habitat by May 2, 1992. This decision, however, was not made.

On August 11, 1994, the Sierra Club Legal Defense Fund, Inc. (Fund), on behalf of the Orleans Audubon Society and Florida Wildlife Federation, gave written notice of their intent to file suit against the Department of the Interior for failure to designate critical habitat for the Gulf sturgeon within the statutory time limits established under

the Act. The Fund filed suit on October 11, 1994 (

Orleans Audubon Society

v.

Babbitt,

Civ. No. 94-3510 (E.D. La)). Following a court order on August 9, 1995, granting the Fund's motion for summary judgement, the Services published a notice of decision on critical habitat designation for the Gulf sturgeon on August 23, 1995 (60 FR 43721). We determined that critical habitat designation was not prudent based on the lack of additional conservation benefit to the species.

On September 22, 1995, the Services and the Gulf States Marine Fisheries Commission approved the Gulf Sturgeon Recovery/Management Plan (FWS

et al.

, 1995). The recovery plan established the criteria that must be met prior to the delisting of the Gulf sturgeon. The recovery plan also identified the actions that are needed to assist in the recovery of the Gulf sturgeon.

On August 12, 1996, the plaintiffs filed a motion to add the Department of Commerce as a defendant in the lawsuit. The Fund amended their complaint to challenge the August 1995 “not prudent” determination. On October 30, 1997, the court granted the plaintiffs' motion for summary judgment, with relief restricted to a remand of the “not prudent” determination to the Services, requiring that the Services publish a determination on designation of critical habitat, based on the best scientific information available. On February 27, 1998, we published a notice of decision (63 FR 9967) on critical habitat designation for the Gulf sturgeon. We again determined that lack of additional conservation benefit from critical habitat designation for this species made such designation not prudent.

On December 18, 1998, the Sierra Club sued the Services challenging the new determination not to designate critical habitat for the Gulf sturgeon (

Sierra Club

v.

U.S. Fish and Wildlife Service et al.

CA No. 98-3788 (E.D. La.)). On January 25, 2000, the Court issued an order granting our motion for summary judgment and dismissing the complaint. The Sierra Club filed an appeal and, in March 2001, the United States Court of Appeals for the 5th Circuit reversed the decision of the District Court and instructed the District Court to remand the decision to us for reconsideration (

Sierra Club

v.

U.S. Fish and Wildlife Service, 245 F.3d 434

(5th Cir. 2001)). On August 3, 2001, the District Court issued an order directing us to publish a proposed decision concerning critical habitat designation for the Gulf sturgeon by February 2, 2002, and a final decision by August 2, 2002. Negotiation with the plaintiff resulted in an agreement to submit the proposed decision to the

Federal Register

on or by May 23, 2002, and the final decision on or by February 28, 2003.

On June 6, 2002, we published a proposed rule in the

Federal Register

in which we announced our determination that designation of critical habitat was prudent, proposed designation of critical habitat for Gulf sturgeon, announced four public meetings and hearings, and requested comments on the proposal by September 23, 2002 (67 FR 39106). On August 8, 2002, we published a notice in the

Federal Register

(67 FR 51530) announcing the availability of the draft economic analysis and the extension of the comment period through October 7, 2002. We also corrected the address of a public hearing to be held in Defuniak Springs, FL on August 20, 2002. We held public meetings and public hearings on the proposed rule and draft economic analysis at four locations: Live Oak, Florida, on August 19, 2002; Defuniak Springs, Florida, on August 20, 2002; Biloxi, Mississippi, on August 21, 2002; and Kenner, Louisiana, on August 22, 2002.

Summary of Comments and Recommendations

We contacted appropriate Federal, State, and local agencies, scientific organizations, and other interested parties and invited them to comment on the proposal to designate critical habitat for the Gulf sturgeon. In addition, we published newspaper notices inviting public comment on the proposed rule and the draft economic analysis, and announced the public meetings and hearings in the following newspapers:

St. Petersburg Times,

Pensacola

News Journal,

Panama City

The News Herald,

Fort Walton

Daily News,

Crystal River

Citrus County Chronicle, Tallahassee Democrat,

and

The Gainesville Sun,

in Florida;

The Brewton Standard, Dothan Eagle, Geneva County Reaper,

and

Mobile Register,

in Alabama; Hinds County

The Clarion-Ledger

and Gulfport's

The Sun Herald,

in Mississippi; and New Orleans

The Times-Picayune

and Baton Rouge's

The Advocate

in Louisiana.

We held four public meetings and four public hearings on the proposed rule (see “Previous Federal Action” section for dates and locations). Transcripts of these hearings are available for inspection (

see

ADDRESSES

).

We received written letters or e-mails from a total of 126 parties which included 2 congressional representatives from Georgia, 10 Federal agencies, 13 State agencies, 5 county governments, 93 groups or individuals, and 3 peer reviewers. Of the 128 total responses, 29 supported the proposed rule, 2 opposed it, and the rest were neutral.

In accordance with our peer review policy published on July 1, 1994 (59 FR 34270), we solicited independent opinions from six knowledgeable individuals having expertise either with the species, with the geographic region where the species occurs, and/or familiarity with the principles of conservation biology. Three of these experts provided a written response generally supporting the designation and provided additional information that we have incorporated into the rule as appropriate. We appreciate the responses of these peer reviewers, and believe their input has improved the content of this rule.

We reviewed all comments received for substantive issues and new data regarding critical habitat and Gulf sturgeon. Some comments resulted in changes between the proposed and final designations, and those comments are discussed in the “Summary of Changes From the Proposed Rule” section of this document. Written comments and oral statements presented at the public hearings and received during the comment period are addressed in the following summary. For readers' convenience we have assigned comments to major issue categories. We have combined similar comments into single comments and responses.

Peer Review Comments

Comment 1:

Three peer reviewers recommended that additional areas be included as critical habitat, sometimes stating that the areas contain the primary constituent elements upon which Gulf sturgeon rely. Others requested inclusion based on historic use or potential use by the Gulf sturgeon in these areas. The areas requested for inclusion were St. Joseph Bay in Florida, the western portion of Lake Pontchartrain and all of Lake Maurepas in Louisiana, and the Strong River in Mississippi.

Also, twenty eight commenters recommended that additional areas be included as critical habitat, with some stating that the areas contain the primary constituent elements. Others requested inclusion based on historic use or potential use by the Gulf sturgeon in these areas. Other commenters expressed concerns that the proposed designation did not include all of the current range of the Gulf sturgeon. The areas requested for inclusion were the Ochlockonee River, Withlacoochee

River (central Florida river, not the tributary of the Suwannee River), West Bay, East Bay of St. Andrew Bay system, St. Andrew Bay, St. Joseph Bay, Tampa Bay, and the Hillsborough River in Florida; an additional Choctawhatchee River reach, Mobile Bay, Murder Creek (tributary of the Conecuh River), Alabama River, Bayou La Batre, and Perdido Bay in Mobile Bay, in Alabama; Strong River in Mississippi; the western portion of Lake Pontchartrain, Tickfaw River, Tchefuncte River, Lake Maurepas, Chandeleur Sound, in Louisiana; and the coastline from Mississippi to Tampa Bay, Florida.

Our Response:

Section 4(b)(2) of the Act directs us to designate critical habitat on the basis of the best scientific data available. However, no or insufficient data were provided to us to support inclusion of any of the above areas as critical habitat. While many of these areas may have historically supported Gulf sturgeon populations and/or may currently support populations, we cannot document that they are essential to the conservation of the Gulf sturgeon.

The definition of critical habitat in section 3(5)(A) of the Act includes “(I) specific areas within the geographic area occupied by a species, at the time it is listed in accordance with the Act, on which are found those physical or biological features (I) essential to the conservation of the species and (II) which may require special management considerations or protection; and (ii) specific areas outside the geographic area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.” By definition, essential critical habitat generally describes a subset of the area potentially containing primary constituent elements for a species. As discussed in the methods section of the proposed and this final rule, to determine areas essential for the conservation of the Gulf sturgeon, we used the best scientific data available pertaining to known habitat requirements of the species. Areas designated as critical habitat for the Gulf sturgeon are within the current known range of the species and contain one or more primary constituent elements essential for the conservation of the species. In our proposed and final designation of critical habitat, we selected essential habitat areas that currently contain populations or provide habitat components essential to the conservation of the species. During this analysis, it was determined that some areas containing one or more primary constituent elements did not represent suitable habitat or were otherwise not essential to the conservation of the species.

Comment 2:

One peer reviewer stated that the designation of critical habitat for the Chickasawhay River (Unit 2) should be expanded upstream to the beginning of the Chickasawhay River starting at the confluence of the Chunky and Okatibbee Rivers, north of Enterprise (Clarke County, Mississippi). This area contains the primary constituent elements as noted in the proposed rule, including potential spawning habitat. Research efforts conducted during spring 2002 by the University of Southern Mississippi (USM)-MMNS Gulf sturgeon research group documented the most upstream movement of a radio-tagged individual on the Chickasawhay River traveling as far upstream as the confluence of the Chunky and Okatibbee rivers. This individual was originally tagged at the mouth of the Pascagoula River during early-March 2002.

Our Response:

The area requested for inclusion would add 19 rkm (12 rmi) to the designation on the Chickasawhay River in Mississippi. However, we believe that what we proposed for the Gulf sturgeon including the portion of the Chickasawhay River proposed for designation, includes sufficient habitat to conserve the species. Accordingly, we have not made the requested change. Moreover, areas outside the critical habitat designation will continue to be subject to conservation actions that may be implemented under section 7(a)(1) and to the regulatory protections afforded by the section 7(a)(2) jeopardy standard and the section 9 take prohibitions.

Comment 3:

One peer reviewer questioned whether all Gulf sturgeon overwinter in the marine and estuarine environment and what the potential impacts on the population would be if critical habitat had a temporal component to its designation.

Our Response:

A few Gulf sturgeon have been documented remaining at or near their spawning grounds throughout the winter (Wooley and Crateau, 1985; Slack

et al.

, 1999; and Heise

et al,.

1999a). However, this is an exception to the normal behavior of adult Gulf sturgeon. During winter months, juveniles often remain in the estuary near the river mouth, but adult and sub-adults leave the riverine habitat to forage in the estuarine and marine areas. Critical habitat has no temporal boundaries, only spatial. If an area is designated as critical habitat, it receives equal protection throughout the year regardless of the presence or absence of the species.

Comment 4:

One peer reviewer and one commenter questioned our rationale for deriving seven subpopulations from the five that were proposed by Stabile

et al.

(1996).

Our Response:

We first evaluated the Gulf sturgeon in the context of its current distribution throughout the historic range to determine what portion of the range must be designated to ensure conservation of the species. We considered several factors in this evaluation: (1) Maintaining overall genetic integrity and natural rates of inter-river genetic exchange, thereby minimizing the potential for inbreeding, (2) retaining potentially important selective pressure at the margins of the species' range by protecting the eastern- and western-most subpopulations, (3) decreasing the extinction risk of a subpopulation by protecting adjacent subpopulations that can provide a rescue effect, if needed, (4) avoiding the potential for subpopulation extirpation from environmental catastrophes, and (5) protecting sufficient habitat essential to the conservation of the species.

In their analysis of Gulf sturgeon subpopulations from eight drainages along the Gulf of Mexico for genetic diversity, Stabile

et al.

(1996) identified five regional or river-specific stocks (from west to east)—(1) Lake Pontchartrain and Pearl River, (2) Pascagoula River, (3) Escambia and Yellow Rivers, (4) Choctawhatchee River, and (5) Apalachicola, Ochlockonee, and Suwannee Rivers.

All five genetic stocks are represented by the seven subpopulations occupying the critical habitat units. The number, distribution, and range of the seven Gulf sturgeon subpopulations included in these units are necessary to protect and support the extent and diversity of the species' genetic integrity and can provide a rescue effect, if needed (see “Methods” section). We believe that these seven river systems, with their associated estuarine and marine environments, represent habitat that is essential for the conservation of the Gulf sturgeon.

Comment 5:

Four commenters, including one peer reviewer, noted that the western boundary in Lake Pontchartrain (Unit 8) seemed arbitrary.

Response:

Critical habitat areas in Unit 8 provide juvenile, subadult and adult feeding, resting and passage habitat for Gulf sturgeon from the Pascagoula and Pearl Rivers subpopulations. Lake Pontchartrain is divided into eastern and western areas by the Lake Pontchartrain Causeway (a twin highway bridge supported by pilings extending 33.6 km (20.9 mi) from the north to the south). Gulf

sturgeon from the Pearl River subpopulation have been documented (by tags) to use the eastern half of Lake Pontchartrain. Researchers believe that the eastern portion of the lake provides important winter habitat for juveniles and subadults, and they have located tagged individuals in Lake Pontchartrain and have repeatedly caught untagged sturgeon between Goose Point and Point Platte, an area believed to be used for winter feeding. While Gulf sturgeon have been documented in the western portion of the Lake (generally near the mouth of small rivers), it is not known whether those sturgeon are part of the Pearl and Bogue Chitto Rivers spawning subpopulation, or if they are part of a smaller spawning subpopulation that might exist within the Tickfaw, Tangipahoa, or Tchefuncte Rivers. We, therefore, conclude that the eastern portion, but not the western portion, of Lake Pontchartrain provides essential winter habitat for the Pearl River subpopulation, as data supports inclusion of the eastern portion of Lake Pontchartrain as critical habitat. Although the Lake Pontchartrain Causeway does not restrict fish movement, it does provide an appropriate and easily identifiable boundary.

Public Comments

Issue A: General Biological Comments

Comment 6:

One commenter believes that forestry practices (

e.g.

, the use of silvicultural Best Management Practices and application of streamside management zones, to protect surface water quality during forestry operations) actively contribute to the conservation of the Gulf sturgeon by providing an important incentive for private landowners to retain forested riverine corridors adjacent to sturgeon habitat.

Our Response:

We agree that Best Management Practices when applied correctly to silvicultural activities do protect and improve the quality of surface waters and, therefore, do contribute to the conservation of the Gulf sturgeon.

Comment 7:

Some commenters questioned the basis of our statement that adult Gulf sturgeon do not feed while in freshwater.

Our Response:

As stated in the proposed and final rules (see “Feeding Habits” section), many reports indicate that subadult and adult Gulf sturgeon fast and lose between 4 and 15 percent of their total body weight while in freshwater, and then compensate the loss during winter feeding in estuarine and marine environments (Carr, 1983; Wooley and Crateau, 1985; Clugston

et al

,. 1995; Morrow

et al.

, 1998a; Heise

et al

, 1999a; Sulak and Clugston, 1999; and Ross

et al.

, 2000). Gu

et al.

(2001) tested the hypothesis that subadult and adult Gulf sturgeon do not feed significantly during their annual residence in freshwater by comparing stable carbon isotope ratios of tissue samples from subadult and adult Gulf sturgeon and their potential freshwater and marine food sources. A large difference in isotope ratios between freshwater food sources and fish muscle tissue suggests that subadult and adult Gulf sturgeon do not feed significantly in freshwater. The isotope similarity between subadult and adult Gulf sturgeon and marine food resources strongly indicates that this species relies almost entirely on the marine food web for its growth (Gu

et al.

, 2001).

Comment 8:

One commenter questioned whether fish tagging studies were limited to adults or whether they included other life stages as well.

Our Response:

Juveniles (age 1 to 6 years), subadults (age 6 years to sexual maturity), and adults (sexually mature) have been marked with different types of equipment, but primarily with T-bar tags (external) and passive integrated transponder (PIT) tags (internal). Young-of-the-year less than 20 cm (7.8 inches) tail length are too small to tag with the standard markers and therefore are exclusively pit tagged (Mike Randall, USGS, pers. comm. 2002).

Comment 9:

Four commenters had questions regarding Gulf sturgeon prey items and foraging areas.

Our Response:

As stated in the proposed rule (67 FR 39107), the diet of the Gulf sturgeon depends on its life history stage. While adults are not known to forage in freshwater, juveniles and young-of-the-year do. We have used data from stomach content analysis and telemetry studies to identify probable Gulf sturgeon foraging areas,

i.e.

, those areas with substrate that supports the known prey items, coupled with tracking data indicating sturgeon presence. We relied on two observations to conclude that subadult and adult Gulf sturgeon do not forage in freshwater: (1) Gulf sturgeon lose a substantial percentage of their body weight while in freshwater in summer and then compensate for the loss during winter, and (2) stable isotopes from sturgeon muscle tissue and their potential marine food sources are similar, while there is a large difference between muscle tissue and potential freshwater food sources. Gulf sturgeon researchers and the Services are certain that the existing data support these conclusions regarding Gulf sturgeon food items and foraging locations.

Comment 10:

Commenters wondered what we know of Gulf sturgeon's overall use of estuarine and marine waters.

Our Response:

While research indicates that Gulf sturgeon utilize estuarine and marine areas for staging, resting and foraging, researchers continue to investigate Gulf sturgeon over-wintering behavior and locale. We are not able, at this time, to readily discern the Gulf sturgeon's overall utilization of marine and estuarine areas and we look forward to evaluating additional information when it becomes available.

Comment 11:

Some commenters questioned whether we were knowledgeable of Gulf sturgeon migration routes.

Our Response:

We have identified and described Gulf sturgeon spawning migrations from coastal/marine areas to the rivers; however, inter-riverine migratory patterns are not well understood. When we could identify inter-riverine movements (mostly from telemetry data), we included appropriate inshore coastal waters in the critical habitat designation to provide protection for migrating sturgeon (

e.g.

, Unit 11). Research is ongoing to investigate Gulf sturgeon inter-riverine migrations (

e.g.

, recording broad movement patterns via satellite tags), and researchers are presently collating data to analyze Gulf-wide movements.

Issue B: Site-specific Biological Comments

Comment 12:

One commenter questioned whether any areas south of the Suwannee River in Florida were historic critical habitat for Gulf sturgeon.

Our Response:

Since this is the first critical habitat designation for the Gulf sturgeon, we presume that the commenter is asking whether areas south of the Suwannee River were of importance to the Gulf sturgeon historically. There are few reported sightings of Gulf sturgeon using rivers south of the Suwannee River, but there are historic and recent records of Gulf sturgeon in Tampa Bay and Charlotte Harbor. At one time, the Tampa Bay area produced large commercial landings of Gulf sturgeon. There have been reported Gulf sturgeon sightings in the Florida Keys during winter months. Some biologists theorize that the Suwannee River population of Gulf sturgeon may winter in the Tampa Bay and Charlotte Harbor areas; however, further research is needed in this area.

Comment 13:

Two commenters asked how we determined the upstream limit on the Suwannee River, and one commenter stated that the published literature does not report the use of the Suwannee River upstream of 230 rkm (143 rmi).

Our Response:

We received unpublished information from Gulf sturgeon experts (Ken Sulak, USGS, pers. comm. 2002; Jim Clugston, retired USGS, pers. comm. 2002) of sightings of young-of-the-year Gulf sturgeon as far upstream on the Suwannee River as to the confluence with Roaring Creek at 304 rkm (200 rmi). This is approximately 11 rkm (18 rmi) upstream of the designated critical habitat, which stops at 293 rkm (182 rmi). We believe that the area known as Big Shoals on the Suwannee River captures the upstream-most significant spawning areas and, therefore, we included upstream to this point. We have included the 0.31 rkm (0.50 rmi) of habitat upstream from Big Shoals to the confluence with Long Branch for ease of identification. It is correct that the published literature on the Suwannee River documents spawning sites no further upstream than at 230 rkm (143 rmi), but we have relied on the above unpublished literature from reliable sources to determine the upstream limit on this system.

Comment 14:

Two commenters requested that the Services omit areas adjacent to military lands from the designation under the Act's section 4(b)(2). The rationale presented included proximity to a military base that is used for military testing and training, restricting military's ability to quickly respond to training and testing due to long-lead time administrative considerations required for consultations, and reducing the number of formal consultations performed by the Services.

Our Response:

The Department of Defense (DOD) did not request that areas adjacent to military lands be excluded from critical habitat designation. In any case, we have no data indicating that these areas should be excluded. We have been successfully and efficiently conducting section 7 consultations with military bases in these critical habitat areas for over 10 years, and we intend to continue working as partners with the armed forces to uphold the Act without compromising national security. We do not foresee any impacts to military readiness as a result of the adjacent critical habitat designation.

Comment 15:

One commenter reported that unusually large fish have been taken from a fish trap on the Tennessee River near the mouth of Chickamauga Creek, above Chattanooga, Tennessee.

Our Response:

Historic information indicates that Gulf sturgeon did not venture as far inland as Tennessee, so we are fairly certain the large fish captured in the fish traps were not Gulf sturgeon. These fish may have been lake sturgeon (

A. fulvescens

) or shovelnose sturgeon (

Scaphirhynchus platorhynchus

), although these species are uncommon, particularly in east Tennessee. Paddlefish (

Polyodon spathula

), which attain weights of over 45 kg (100 lb) are found in the Tennessee River; however, additional information would be necessary to clearly identify the species involved and none was provided by the commenter.

Issue C: National Environmental Policy Act (NEPA) Compliance

Comment 16:

One commenter stated that the Services should withdraw the proposed rule pending compliance with NEPA, through preparation of an environmental assessment or an environmental impact statement (EIS). The commenter stated that FWS's position that NEPA only applies to critical habitat designations in the 10th Circuit, based upon that circuit's 1996 decision in

Catron County Bd. of Comm.

v.

USFWS

, 75 F.3d 1429, is unlawful. The commenter stated that the two exceptions to NEPA compliance identified by the 10th Circuit (

i.e.

, unavoidable conflict between NEPA and another statute or duplicative procedures provided by NEPA and a second statute) are not present in the case of critical habitat designation. The commenter stated that the proposed critical habitat rule was subject to NEPA because the effects of the designation are broader than protecting habitat. They believe that future Federal actions that are likely to adversely affect critical habitat will be prohibited. They also believe that an environmental assessment may reveal a more effective alternative to preventing extinction of the sturgeon than designating critical habitat.

Our Response:

The Services believe that in

Douglas Co.

v.

Babbitt

, 48 F.3d 1495 (9th Cir. 1995), the Court correctly interpreted the relationship between NEPA and critical habitat designation under the Act. The Ninth Circuit Court rejected the suggestion, identical to that raised by the commenter, that irreconcilable statutory conflict or duplicative statutory procedures are the only exceptions to application of NEPA to Federal actions. The Court held that the legislative history of the Act demonstrated that Congress intended to displace NEPA procedures with carefully crafted procedures specific to critical habitat designation. Further, the

Douglas County

Court held that the critical habitat mandate of the Act conflicts with NEPA in that, although the Secretary may exclude areas from critical habitat if such exclusion would be more beneficial than harmful, the Secretary has no discretion but to include areas in the designation if exclusion of such areas would result in extinction. This lack of discretion renders application of NEPA procedures (

e.g.

, consideration of broad environmental impacts, alternatives analysis) superfluous (this lack of discretion to consider broad environmental impacts was the basis for the 6th Circuit's determination that NEPA does not apply to listing decisions under the Act, in

Pacific Legal Foundation

v.

Andrus

, 657 F2d 829 (6th Cir. 1981)). The Court noted that the Act also conflicts with NEPA's demand for impact analysis, in that the Act dictates that the Secretary “shall” designate critical habitat for listed species based upon an evaluation of economic and other “relevant” impacts, which the Court interpreted as narrower than NEPA's directive. Finally, the 9th Circuit, based upon a review of precedent from several circuits including the 5th Circuit, held that an EIS is not required for actions that do not change the physical environment.

In addition, we note that Federal actions that might adversely affect critical habitat are not necessarily prohibited. Many Federal actions may adversely affect critical habitat without the effect rising to the level of destruction or adverse modification of the critical habitat. In those cases where we find that a Federal project would destroy or adversely modify critical habitat, we must identify reasonable and prudent alternatives (RPAs) to the project that would avoid the destruction or adverse modification (see “Effects of Critical Habitat Designation” section). The RPAs must be capable of being implemented in a manner consistent with the intended purpose of the action, be consistent with the action agency's legal authority and jurisdiction, and be economically and technically feasible.

Issue D: Section 7 Consultation Issues

Comment 17:

One commenter expressed concerns that the critical habitat designation will make it more difficult for fisheries managers to sample for non-endangered fish in these rivers and fears they will be required to apply for permits and provide annual reports, and that in some cases, fishery activities may be stopped due to

sampling being conducted in areas designated as critical habitat.

Our Response:

The Gulf sturgeon is a listed species and thereby protected under the Act regardless of whether or not critical habitat has been designated, therefore permits and annual reporting may be necessary if the activities being conducted for fisheries management may result in the incidental take of a Gulf sturgeon. Given that the fish has been federally protected for 10 years and fisheries management in all states throughout the Gulf sturgeon's range has proceeded unhampered, we are unclear as to the reasons for this concern. Critical habitat designation may result in required project modifications only for activities with a Federal nexus and then only if the activity were to destroy or adversely modify the primary constituent elements contained in the designated habitat (

i.e.

, prey, spawning habitat, water quality, water quantity, sediment quality, or migratory passage).

Comment 18:

One commenter questioned whether water quality issues may arise from the establishment of the critical habitat and another requested that the existing government databases be updated to reflect current water quality of southern rivers, since water quality has improved subsequent to the historic decline of the species.

Our Response:

As required under section 7 of the Act, the Environmental Protection Agency (EPA) consults with us regarding water quality standards to ensure that they are protective of endangered and threatened species. The EPA anticipates consulting with us every three years as part of its triennial review of State delegated water quality standards for Alabama, Florida, Mississippi, and Louisiana under section 303(d) of the Clean Water Act. During each review period all data relative to Gulf sturgeon and water quality will be updated and reviewed to ensure that the standards continue to be protective. The EPA recently released a new database on the water quality of the nation's rivers. This information is available on its web site (www.epa.gov). Future consultations will consider impacts to Gulf sturgeon and associated critical habitat, and will take changes in water quality into account.

Comment 19:

One commenter questioned whether the FWS provided information on flow requirements needed for critical habitat in the Apalachicola, Chattahoochee, and Flint Rivers (ACF) negotiations and whether such information was available to the public.

Our Response:

The FWS presented information about the hydrological characteristics of potential sturgeon spawning habitat on the Apalachicola River as a result of separate requests from the Georgia and Florida negotiators to the ACF Compact. This information is summarized in our response to comment 42. Our information was based on a single set of measurements at one potential spawning site, and for reasons summarized in our response to comment 41, we do not characterize this information as “flow requirements needed for critical habitat.” This information is available to the public upon request. However, the U.S. Army Corps of Engineers (USACE) is conducting more detailed surveys intended to augment and refine our initial measurements and will use these new measurements in preparing its biological assessment of the effects of Federal reservoir operations on federally-protected species and their habitats.

Comment 20:

One commenter requested that the Services withdraw their proposed critical habitat designation for the Gulf sturgeon and instead address any needs of the species in the context of the ongoing ACF Compact process.

Our Response:

The ACF Compact is a Federal law that authorizes, among other things, the States of Alabama, Florida, and Georgia, but not the Federal government, to negotiate a water allocation formula for equitably apportioning the surface waters of the ACF Basin. Under the leadership of the non-voting Federal Commissioner to the Compact, Federal agencies, including the Services, have provided technical assistance to the States' negotiators on various water management issues, including the needs of species protected under the Act. The State negotiators are not obligated to act upon any such technical assistance, and the Compact does not relieve Federal agencies, including the Services, of responsibilities under other Federal statutes or court rulings. This rule designating critical habitat fulfills our requirements under the Act and the order of the United States Court of Appeals for the Fifth Circuit.

Comment 21:

One commenter stated that by designating the Apalachicola River as critical habitat for the Gulf sturgeon, the Federal government necessarily becomes involved in the water negotiations for the ACF Compact and usurps authority from the State of Georgia to negotiate stream flows in that river basin.

Our Response:

State and Federal roles under the ACF Compact are quite distinct, as noted in our response to comment 20, and this rule in no way alters those roles. No authority is taken from the States, as the critical habitat provisions of the Act apply to Federal agencies and their actions only. Federal agencies acting in the ACF Basin are obligated to comply with sections 7 and 10 of the Act with or without an ACF Compact, and the States are solely empowered to negotiate a water allocation formula for the ACF Basin with or without designated critical habitat for the Gulf sturgeon.

Comment 22:

The USACE's Mobile District expressed concern with potential requirements to alter reservoir operations at the Jim Woodruff Lock and Dam on the Apalachicola River in Florida, in order to support minimum flow for Gulf sturgeon spawning. They are concerned that a critical habitat designation could require substantial upstream flow releases.

Our Response:

As noted in the response to comment 42, preliminary data suggest that if adjustments to reservoir operations are reasonable and prudent in the conservation of the sturgeon, such adjustments would likely occur infrequently, since it appears that flows do not limit sturgeon spawning habitat availability in most years on the Apalachicola River. Under section 7(a)(2) of the Act, Federal agencies must avoid jeopardizing the continued existence of a species or the destruction or adverse modification of designated critical habitat. During the consultation process, Federal agencies share responsibility with us for determining what operational adjustments, if any, would be reasonable and prudent for sturgeon conservation. We acknowledge that the USACE must consider its responsibilities for flood control, power generation, navigation, water quality, other fish and wildlife, etc., as well as listed species conservation, in making its operational decisions, and we appreciate the complexities of these decisions.

Comment 23:

One commenter objected to critical habitat designation because it would impede construction of any dam deemed necessary by the public for water supply, flood control, and recreation.

Our Response:

The Act's requirements regarding proposed and designated critical habitat apply only to Federal actions, such as constructing Federal reservoirs or issuing Federal permits for non-Federal reservoirs (

e.g.

, a Clean Water Act section 404 permit). For such actions, the Federal agency's responsibility is to consult with us to ensure that its actions are not likely to jeopardize the continued existence of listed species or destroy or adversely modify designated critical habitat. Reasonable and prudent alternatives to

avoid jeopardy or critical habitat destruction resulting from reservoir construction, or reasonable and prudent measures to minimize take resulting from reservoir construction, would depend entirely on the size, location, and operational plan of the reservoir and its effects on the primary constituent elements (

e.g.

, flow regime, water quality, passage). Reservoirs constructed downstream of spawning habitat would have far different and likely greater impacts than those constructed upstream of spawning habitat or on tributaries.

Comment 24:

Three commenters requested clarification and examples of specific activities that may affect essential features of the designated area, a quantitative definition or explanation of “appreciably reduce,” and information on how we intend to quantify the degree of impacts. One commenter requested that a mechanism be developed to assess the severity of the action based on the ability of the impacted area to recover as viable habitat.

Our Response:

The value of critical habitat is appreciably diminished when an action considerably reduces the capability of designated or proposed critical habitat to satisfy requirements essential to the conservation of a listed species. We continue to consult with agencies to determine the effects of an action on the primary constituent elements within the designated critical habitat by utilizing the best available scientific data. It is our intent to carefully assess each proposed project within Gulf sturgeon critical habitat and analyze how the proposed action may impact (both directly and indirectly; both temporally and spatially) those physical or biological features that were the basis for determining the habitat to be critical. As stated in the proposed rule, actions that may destroy or adversely modify Gulf sturgeon critical habitat may include, but are not limited to, dredging; dredge material disposal; channelization; in-stream mining; land uses that cause excessive turbidity or sedimentation; water impoundment; hard-bottom removal for navigation channel deepening; water diversion; dam operations; release of chemicals, biological pollutants, or heated effluents into surface water or connected groundwater via point sources or dispersed non-point sources; release of chemical or biological pollutants that accumulate in sediments; and other physical or chemical alterations of channels and passes. Note, however, that these same activities may be carried out in a way that does not destroy or adversely modify critical habitat. Such assessments are highly site and fact specific and the information about the species and its habitat is continually expanding. Therefore, whether the “appreciably diminish” threshold has been met is a consultation-specific determination.

Comment 25:

One commenter expressed concerns that the critical habitat designation will prevent maintenance dredging which is required for continued use of the Gulf Intracoastal Waterway (GIWW).

Our Response:

Gulf sturgeon migration and feeding may occur within the GIWW in some of the proposed units. As stated in the proposed rule (67 FR 39114), portions of the GIWW that consist primarily of excavated land cuts and canals have been excluded from this designation because they were not available to the species historically, and therefore, are not considered to be essential for the conservation of the species.

The GIWW requires periodic dredging by the USACE to maintain safe and adequate passage. As stated in the proposed rule (67 FR 39125), dredging is an action that may destroy or adversely modify Gulf sturgeon critical habitat. We will work closely with the USACE to identify appropriate measures to reduce dredging impacts to Gulf sturgeon critical habitat while allowing maintenance dredging to continue in the GIWW without interruption.

Issue E: Public Involvement

Comment 26:

Three commenters had questions and concerns regarding boating and sturgeon with regard to records of boat strikes on sturgeon and options for regulating boat speed. One commenter stated that critical habitat is just another way to impose restrictions and regulations on the boating public.

Our Response:

Regulating speed of boats to prevent sturgeon injury or death would be an issue related to “take” of Gulf sturgeon and not related to critical habitat. Boat speed is unlikely to have any significant effect on primary constituent elements for Gulf sturgeon.

Comment 27:

One commenter asked how anyone can be of help in our project of recovery and designation of critical habitat for the Gulf sturgeon.

Our Response:

Maintaining a natural vegetative buffer along streams and rivers, and participating in watershed conservation groups that work on protecting and restoring river and bay habitat help conserve the sturgeon's critical habitat.

Comment 28:

One commenter wondered how the critical habitat designation would raise public awareness and offer additional educational and informational benefit.

Our Response:

Critical habitat provides non-regulatory benefits to the species by informing the public (via newspaper articles, newspaper notices, public meetings, public hearings, etc.) of areas that are important for species recovery and where conservation actions would be most effective. Designation of critical habitat helps focus conservation activities for a listed species on the areas that contain the physical and biological features that are essential for conservation of that species, and alerts the public and land-managing agencies to the importance of those areas.

Issue F: Methods

Comment 29:

One commenter suggested that we have not included unoccupied habitat upstream of dams in the Apalachicola River Basin and the Hillsborough River Basin because access is not available. The commenter believes that these areas may be essential to the conservation of the species.

Our Response:

The commenter provided no data to support why these two areas may be essential. Further, we have no historic records of Gulf sturgeon using the Hillsborough River. Areas upstream of water control structures were included elsewhere because they contain the only known suitable spawning habitat for a subpopulation that shows evidence of reproduction, and therefore, were deemed essential to the conservation of the species. We believe there is sufficient habitat downstream of the Jim Woodruff Lock and Dam on the Apalachicola River to sustain a population of Gulf sturgeon. We believe that what we have designated for the Gulf sturgeon is based on the best available scientific information and includes what we consider to be essential to the conservation of the Gulf sturgeon.

Comment 30:

The Services intend to protect spawning habitats from catastrophic occurrences by including both the main stem spawning sites and at least one tributary site. One commenter asked why we included just one tributary site.

Our Response:

Each subpopulation for which critical habitat was designated had historic records of sturgeon using a mainstem river and at least one additional tributary. We included at least one tributary for relief from potentially catastrophic events. Including additional tributaries without historic records was not feasible because we have no indication that the sturgeon

would use these areas, and therefore, no evidence that they are essential to the conservation of the species. When data documented fairly recent use of additional tributaries, those tributaries were included. For example, the Pascagoula River subpopulation has sections of the Bouie River, the Leaf River, and the Chickasawhay River designated as critical habitat because data support sturgeon use.

Comment 31:

One commenter asked if any of the proposed critical habitat is in the State of Georgia.

Our Response:

No. Although the historic range of the Gulf sturgeon includes the Flint River, and possibly parts of the Chattahoochee River, we determined that none of the historic habitat in Georgia is essential to the conservation of the Gulf sturgeon.

Comment 32:

One commenter suggested that the critical habitat designation should be limited to a few specific areas within the range of the Gulf sturgeon that are most important to their continued survival (

e.g.

, spawning areas, nursery areas, summer holding areas, and fall and winter foraging areas).

Our Response:

We considered the biological basis for a more site-specific approach and concluded that it would not secure all biological features essential for the conservation of the species. The site-specific approach would neglect the importance of a migration corridor between spawning, resting, and feeding areas. Also, young-of-year and possibly juvenile sturgeon (less than 5 kg (11 lbs) (Mason and Clugston, 1993)) actively forage throughout the riverine system.

Comment 33:

One commenter requested that we discuss our rationale for not designating unoccupied areas when the Services had previously stated that unoccupied habitat would be necessary for Gulf sturgeon recovery.

Our Response:

As we stated in the proposed rule, since approval of the Recovery Plan in 1995 and our 1998 “not prudent” finding, the science of conservation biology has matured. The methods section cites numerous recent publications that contributed to our decision to select the areas we did and why they constitute habitat sufficient for the conservation of the species. We have also collected significant new biological information on this species. For example, we now have a better understanding on status of the Pearl River system subpopulation; we are confident that adult Gulf sturgeon are accessing spawning habitats above Pools Bluff Sill and Bogue Chitto Sill during high flows; spawning was confirmed in 1999 on the Pascagoula River subpopulation; usage of the Chickasawhay River, a major tributary to the Pascagoula River, was recently documented; spawning was confirmed in 2001 at five locations on the Escambia River; young-of-year have been confirmed on the Yellow River system and population estimates are 580 Gulf sturgeon 1 m (3.3 ft) or greater in size; additional suitable spawning sites were documented on the Apalachicola River in 2002; and between 1993 and 1998, additional spawning sites were confirmed on the Suwannee River population. We believe that what we have designated for the Gulf sturgeon is based on the best available scientific information and includes those areas essential to the conservation of the Gulf sturgeon.

Comment 34:

Three commenters requested that the Services provide additional detail or quantify the specific habitat requirements for each life history stage, specifically abundant prey, flow regime, water temperature, salinity, pH, oxygen content, etc.

Our Response:

We have summarized the current knowledge of the species, including life history requirements in the “Background” section of this rule. However, data are not yet available to more quantitatively express the primary constituent elements of Gulf sturgeon critical habitat. To make the critical habitat rule adaptive to increasing knowledge, we have kept the primary constituent elements general. When consultations on projects occur, biologists will use the best available science available at the time of consultation to determine whether the functions of those elements would be adversely modified by the proposed Federal action. Research is ongoing, and as those data are collected, we expect to understand better Gulf sturgeon and its life history requirements.

Comment 35:

One commenter stated that habitat is identified primarily for adults (spawning sites, resting areas, winter feeding), but not for larvae, juvenile, and subadult life stages. S/he also suggested a need to cite specific studies rather than using the term “gathered all available” data.

Our Response:

The commenter is referring to statements in the “Methods” section, which is written in general terms to explain how we decided which riverine, estuarine, and marine areas to include as critical habitat. We disagree with the commenter that the rule ignores life stages besides the adult stage. We stated in the proposed rule that we included riverine habitat from the river mouth up to and including spawning grounds to provide sufficient habitat for the riverine life stages of Gulf sturgeon. These life stages require habitat for summer resting or staging areas, juvenile feeding, entire young-of-year life cycle (including larval stages), passage throughout the river (protects all life stages), and passage into and out of estuarine habitat for adults and subadults. All of the selected areas are known to be used by Gulf sturgeon for some portion of their life cycle. Subadult and adult sturgeon use estuarine and marine areas for feeding and passage between river systems. Designation of critical habitat units in estuaries and bays adjacent to the riverine units described above would protect both passage of sturgeon to and from their feeding and spawning grounds and also the abundance of estuarine and marine prey for juvenile and adult sturgeon.

Specific references used for making our determination are cited throughout the “Background” and “Critical Habitat Unit Descriptions” sections of the proposed and final rules. A complete list of all references cited is presented in the “References Cited” section of this final rule.

Comment 36:

One commenter stated that the areas included in the proposal are those where studies have been directed toward sturgeon and that it should not be assumed that other rivers do not have critical habitat just because sturgeon have not been found in routine fishery surveys. They also stated that routine fishery surveys can and have missed the presence of sturgeon.

Our Response:

We have based our designation on the best scientific data available. However, the level of research and status surveys conducted on many subpopulations is limited. Because of the limited availability of data specific to each river system and specific to the Gulf sturgeon's use of the marine and estuarine environment, we acknowledge that habitat other than that identified in this final rule may later be found to be essential to the conservation of Gulf sturgeon. To the extent feasible, we will continue to conduct and support surveys, research, and conservation actions on the species and its habitat in areas designated and not designated as critical habitat. If additional information becomes available on the species' biology, distribution, and threats, we will evaluate the need to designate additional critical habitat, delete or reduce critical habitat, or refine the boundaries of critical habitat. Gulf sturgeon in areas not included as critical habitat will continue to receive protection under the section 7 jeopardy standard and the section 9 prohibitions on take.

Comment 37:

One commenter suggested that we clarify our use of vague terms in the proposed rule (

e.g.

, strongly suspect, believed to appear, possibly appropriate, relatively sediment free).

Our Response:

We appreciate the commenter's sentiments. However, it is seldom possible to make statements with complete or even relative certainty when describing the biological and habitat requirements of an endangered or threatened species. We have expressed ourselves as definitively as possible using the best available scientific data, recognizing the need for consultation-specific flexibility over time as new information is developed about the species and its habitat.

Comment 38:

Two commenters requested clarification of the lateral extent of the critical habitat unit descriptions in the estuarine and marine areas; clarification of our mean high water line determination, and clarification of our use of an average high water calculation over an 18.6 year period rather than using all available tidal data.

Our Response:

Regulatory jurisdiction in coastal areas is administered by the USACE and is described in 33 CFR 329.14(a)(2) as “the line on the shore reached by the plane of the mean (average) high water (MHW).” 33 CFR 329.14(a)(2) further states that when precise determination of the MHW line is necessary, it is preferable to average tidal data over a period of 18.6 years, which is a Metonic cycle,

i.e.

, the period in which new and full moon recur in the same order and on the same days as in the preceding cycle.

Issue G: Jurisdiction

Comment 39:

Three comments were received on the proposed jurisdictional responsibilities for the management of the Gulf sturgeon. Two commenters believe that FWS, instead of NMFS, should have jurisdiction in the estuarine areas, and one commenter requested clarification on the technical basis for determining areas of regulatory jurisdiction in coastal areas.

Our Response:

In 1974, a memorandum of understanding (MOU) was developed to clarify jurisdictional responsibilities for the NMFS and FWS. Section 1(a) of the 1974 MOU outlines jurisdiction by waterbody and states that all non-mammalian species, with a few exceptions not including Gulf sturgeon, that reside the major portion of their lifetime in estuarine waters shall be under the jurisdiction of the NMFS. Similarly, the FWS would have jurisdiction over species that spend the major portion of their lifetimes on land and/or in fresh water.

While the MOU does not contain specifics on jurisdictional boundaries for critical habitat, the Services have applied the standard set for listing species to this critical habitat rule—that is, NMFS will have jurisdictional responsibility for marine waters and the FWS for fresh water. In estuarine waters, the Services will consult based on their respective expertise as described in the proposed rule. Under this arrangement, the FWS will consult with the EPA since it has expertise in water quality issues, and the NMFS will consult with the USACE to maximize efficiency for the action agency when other federally protected species may be present (

e.g.

, protected sea turtles which fall under the jurisdiction of NMFS in marine and estuarine waters).

Issue H: Economic Analysis

Comment 40:

One commenter supported the two-baseline approach to the economic analysis used by the Services, and went on to suggest that the lower baseline, that identifies costs solely attributable to critical habitat designation, need not be included in the analysis to be responsive to the decision in

New Mexico Cattle Growers Association

v.

USFWS

, 248 F.3d 1277 (10th Cir. 2001). The commenter paraphrased the 10th Circuit's holding as requiring that costs resulting from the listing of a species must be considered along with the costs of critical habitat designation in determining whether the costs of such designation outweigh the benefits. The commenter went on to support the inclusion of costs associated with both jeopardy consultations and adverse modification consultations, and resulting project modification costs, in the economic analysis, stating that the full spectrum of impacts associated with the listing and critical habitat designation presents a more realistic and comprehensive understanding of probable impacts in the affected region.

Our Response:

In

New Mexico Cattle Growers Association

, the 10th Circuit ruled that the full costs of critical habitat designation must be captured in an economic analysis performed in accordance with section 4(b)(2) of the Act, and thus that costs that might be incurred co-extensively as a result of both listing and critical habitat designation must be included in the analysis. For example, projects that might modify spawning habitat of Gulf sturgeon would give rise to a consultation on both jeopardy and adverse modification grounds, and the costs of such consultations must be attributable to critical habitat designation.

Comment 41:

One commenter raised questions about impacts to Federal hydropower generation in the ACF Basin. Without specific details as to the minimum and maximum flows necessary for spawning and other flow-related habitat questions, the commenter contends “the economic ramifications of this proposal cannot be properly considered, as required by law.”

Our Response:

We agree that a meaningful assessment of economic impacts that could result from modifying the operations of the USACEs' ACF reservoirs to avoid or minimize impacts to Gulf sturgeon habitat in the Apalachicola River is not possible at this time because too many variables, such as those listed by the commenter, are unknown. Based on the limited data that are currently available about the flow rates that inundate potential spawning habitat, the FWS believes that any reasonable and prudent adjustments to ACF project operations to protect sturgeon spawning would be infrequent. As a result, the costs over time to project purposes such as hydropower would be relatively small. The basis for this preliminary determination and a brief description of the informal consultation that is underway between the USACE and the FWS about ACF project operations effects on sturgeon follows.

Possible flow-related limitations to spawning habitat in the Apalachicola River were not recognized until the spring of 2002, when project operations and unusually low basin runoff entering the fourth year of a regional drought exposed limestone outcroppings and other hard-bottom portions of the main channel. These hard-bottom areas, which likely support spawning by the small Apalachicola sub-population, are inundated during the spring months of most years by the combination of unregulated basin runoff and the USACEs' operations of the ACF reservoirs for project purposes other than the conservation of species and habitats protected under the Act. On May 2, 2002, FWS personnel surveyed a site near where sturgeon larvae were collected in 1977 (Wooley

et al.

, 1982) and 1987 (Foster

et al.

, 1988). FWS estimated the maximum discharge that would fully expose the outcropping and the minimum discharge that would fully inundate it. These estimates were 173 cubic meters per second (cms) (6,118 cubic feet per second (cfs)) and 317 cms (11,200 cfs), respectively. The minimum depth at which Gulf sturgeon eggs have been collected is 1.4 m (4.6 ft) (Fox

et

al.

, 2000). The estimated discharge corresponding to 1.4 m (4.6 ft) inundation of the bottom of the limestone shelf was 424 cms (14,970 cfs), and 612 cms (21,610 cfs) for the top of the shelf. During the March 15 to May 15 timeframe, when sturgeon spawning most likely occurs, daily average flow rates have exceeded 424 cms (14,970 cfs) and 612 cms (21,610 cfs) 87 percent and 63 percent of the time, respectively, in the 1929 to 2002 flow record of the Chattahoochee gage. March 15 to May 15 average discharge exceeds these flow rates in 97 percent and 77 percent of the years, respectively.

If flow rates between 424 cms (14,970 cfs) and 612 cms (21,610 cfs) are sufficient for successful sturgeon spawning on the Apalachicola River, any adjustments to reservoir operations that appear reasonable and prudent for sturgeon conservation would occur relatively infrequently, during the occasional years when spring-time hydrologic conditions and operations for other project purposes do not provide flows in this range. However, this flow range is based on one set of measurements at one site and relies upon the minimum depth at which eggs have been previously collected (4.6 feet); other sites with different hydrologic characteristics may support spawning and depths less than 4.6 feet may allow for successful spawning. Annual monitoring of the Apalachicola sturgeon population by net sampling shows year classes represented for all years from 1986 to 1998. In none of these years were all days in the March 15 to May 15 time frame greater than 612 cms (21,610 cfs), but all of these years had at least 11 days greater than 612 cms (21,610 cfs). In 2002, no days from March 15 to May 15 had flow greater than 612 cms (21,610 cfs). We will not know for 3 years, when year class 2002 individuals would become large enough to sample with the nets used in annual monitoring, whether the unusually low spring flows of 2002 resulted in a lost year class.

The USACE and FWS have initiated a study of sturgeon spawning habitat in the Apalachicola River that will provide a more complete relationship between flow and habitat availability than the single site measured by FWS in May 2002. The USACE will use the results of this study and other information in a biological assessment of the effects of its current operations on the sturgeon, its proposed critical habitat, and other federally-protected species. This assessment will determine whether current operations may adversely affect federally-protected species and their habitats and if so, serve to initiate formal consultation with the FWS. Until this consultation is completed, it is premature to make estimates of its economic impact, which is dependent on the results of studies that are still underway and on USACE decisions relative to reservoir operations that will weigh its responsibilities under the Act with other statutory responsibilities.

Comment 42:

One commenter stated that the economic analysis does not provide sufficient information to determine if the benefits of exclusion outweigh the benefits of inclusion of individual critical habitat units. The comment goes on to ask whether inclusion of any unit would materially affect the recovery of the Gulf Sturgeon, and requests that the Services provide a metric by which to determine whether inclusion of any unit is economically warranted.

Our Response:

Section 4(b)(2) of the Act directs that critical habitat, areas containing biological and physical features essential to the conservation of the species, shall be designated after taking into account the economic impacts and other relevant impacts of such designation. The Secretaries of the Interior and Commerce have the discretion to exclude areas from such designation if the benefits of exclusion outweigh the benefits of inclusion, unless failure to designate such areas will result in the extinction of the species concerned. This language does not establish a test of whether inclusion is “economically warranted.”

Comment 43:

One commenter suggested that uncertainty over the spatial and temporal scale that would be involved in future application of the destruction or adverse modification standard should be acknowledged, that costs could depend upon whether that standard is applied to the designated critical habitat as a whole, within individual units, or some other scale, and whether the standard would be triggered by temporary or long term impacts.

Our Response:

The Gulf sturgeon's affinity for natal river systems and the importance of every breeding unit of the species suggests that individual units or groups of units that are used by stocks or subpopulations which fulfill essential geographic distribution requirements are the appropriate scale for the analysis. The outcome of each destruction or adverse modification analysis is highly fact specific, dependent not only upon the species and designated critical habitat at issue, but also upon the particular project and its impact upon the primary constituent elements of the critical habitat. The economic analysis for this rule estimated costs of consultations on projects that the consulting Federal agencies advised were likely to be implemented in the next 10 years. Thus, the uncertainty in the analysis would be attributable to unforseen or uncertain projects and their impacts, as well as a lack of detail about each projected project, and there is no way to address this uncertainty in any non-speculative manner.

Comment 44:

The Mobile and New Orleans Districts of the USACE raised questions regarding the economic analysis' incorporation of dredging windows as potential project modifications.

Our Response:

Based on comments received from the USACE and further analysis by the Services, the economic analysis has been modified by removing dredging windows as potential project modifications that would be included in each formal consultation and omitting estimated costs of such. These changes reflect the extreme improbability that dredging windows would be recommended or adopted as a project modification to reduce impacts to critical habitat (as opposed to preventing take), given the availability of other means of protecting sturgeon or its habitat with adequate coordination and planning between the USACE and us.

Comment 45:

Several commenters expressed concerns over the potential effects of critical habitat designation on water flow regimes in the Apalachicola River, and whether needs to alter flow regimes to protect sturgeon or its habitat might impose costs by impacting hydropower or businesses and recreation dependent on existing reservoirs (

e.g.

, Lake Sidney Lanier).

Our Response:

Section 3.4 of the economic analysis has been revised to more fully discuss the factors associated with estimating economic impacts related to flow regime modifications that may emerge from consultation with the USACE as reasonable and prudent for the sturgeon and its habitat in the Apalachicola River. Conservation of listed species is one of many responsibilities the USACE must consider in operating the Apalachicola Basin reservoir projects, which are variously authorized for the purposes of flood control, hydropower, navigation, recreation, water quality, water supply, and fish and wildlife. Changing reservoir operations for sturgeon conservation could affect the degree to which the USACE is able to fulfill other project purposes; however, under normal and wet rainfall conditions, existing operations appear adequate to protect the sturgeon and its habitat. If

project operations do not release enough water, as is the case during droughts, spawning habitat may be exposed or too shallow for sturgeon to use successfully. The USACE and FWS are presently in informal consultation on the effects of ACF reservoir operations on federally-listed species, and are investigating the relationship between flow and sturgeon spawning habitat availability in the Apalachicola River. Although these studies are not yet completed, the FWS believes that project modifications for sturgeon conservation would likely represent reasonable minor adjustments to existing operations that would minimize the impacts of unavoidably adverse conditions. The economic analysis concludes that the effects of such modifications on the regional economy would be small (less than 0.1 percent).

Comment 46:

Several commenters suggested that the economic analysis did not adequately address secondary impacts of critical habitat designation on the economy on a regional scale. These commenters expressed concerns about impacts on the shipping and navigation industries and their support services, on future commercial and industrial development, and on commercial fishing, particularly shrimp fishing.

Our Response:

Section 2.1 of the economic analysis has been revised to provide more information on the current level of economic activity in the areas in or around the critical habitat designation. Specific information on State gross products and time series employment data have been added. Regional data on waterborne economic activity, including waterborne commerce, commercial fishing, recreational fishing, other water-based recreation, and hydropower generation are more fully presented. Thus, the revised economic analysis provides an appropriate economic baseline against which to evaluate the significance of section 7 costs associated with critical habitat designation.

After identifying and evaluating the activities likely to give rise to section 7 consultations and thus direct costs of critical habitat designation in section 3.2, the economic analysis discusses potential secondary impacts on the regional economy in section 3.4. Past consultations have not resulted in project changes that have affected the regional economy, including the particular activities of concern to the commenters, and no comments provided specific examples of how future consultations would result in regional economic impacts.

Waterborne commerce is unlikely to be affected by the critical habitat designation because all available evidence indicates that future operations and maintenance navigation projects will proceed without changes to timing and scope. Moreover, the frequently maintained portions of the major shipping channels located within the critical habitat designation are altered to an extent that any primary constituent elements for sturgeon that are still present in the channels are unlikely to be appreciably diminished from their current baseline by Federal actions in the channels. Portions of shipping channels that are not frequently maintained and new dredge material disposal sites likely contain one or more primary constituent elements and therefore have a higher likelihood for project modifications to be recommended.

No limitations to commercial fishing activities are expected to result from section 7 consultations pertaining to Gulf sturgeon (see Section 3.4.3 of the economic analysis).

Past consultations and available evidence do not indicate that county-wide economies or employment will be impacted by this critical habitat designation (see Section 3.4.4 of the economic analysis).

Comment 47:

One Mississippi County Commissioner expressed concern over closure of a shipping channel through Little Lake and the lower Pearl River, and its impact on commercial navigation.

Our Response:

If the shipping channel were closed, it would be attributable to litigation filed by the Tulane Environmental Law Clinic over water quality certification, and not due to sturgeon protection. Thus, no modifications were made to the economic analysis.

Comment 48:

Two commenters stated that the economic analysis should acknowledge the controversy surrounding option and existence values and the methodologies available to estimate these values. One commenter, the USACE, stated that it does not allow these values to be claimed in its economic studies “because the academic community does generally not accept the procedures used to estimate them.” The USACE went on to state that the studies presented in the economic analysis are not related to the Gulf sturgeon, the studies' methods are not discussed, and inclusion of the information adds nothing to the document.

Our Response:

The final economic analysis notes the controversy that the commenter discusses as revolving around the use of contingent valuation methodology. Therefore, the economic analysis in Section 5.2 has been revised to better explain the relevance of these values to this critical habitat designation, by including a fuller explanation of contingent valuation methodology, and adding more detail to the discussion and exhibits relating to the economic literature on valuation of natural resources such as threatened and endangered species, and the applicability of the benefits transfer methodology.

Comment 49:

Two comments stated that the economic analysis presented a flawed analytical approach in ignoring the time value of money and present values.

Our Response:

The economic analysis has been modified (see Section 4.3) to include the present value of the total estimated costs of the critical habitat designation, using 2 discount rates in order to provide a measure of sensitivity analysis. The economic analysis now also presents annualized cost estimates for the 10 year period considered for this designation.

Comment 50:

Two comments state that the economic analysis fails to meet requirements for economic analyses, including using inappropriate and archaic research techniques.

Our Response:

We believe that the methodology used is appropriate for and consistent with the analysis of economic impacts required by the Act, which does not mandate a strict cost-benefit analysis. The methodology used to produce the economic analysis has been peer-reviewed. We further believe that the research used is appropriate for the analysis required by the Act, and provides the best available scientific information available. Economic analyses are typically based on direct conversations with the action agencies regarding their expected future actions and costs.

Comment 51:

One comment stated that it is unreasonable to predict zero costs associated with project modifications attributable solely to critical habitat designation.

Our Response:

No information was provided, and none was available, regarding project modifications that would be attributable solely to critical habitat designation, as opposed to being attributed co-extensively to take of or jeopardy to the species.

Comment 52:

One comment stated that the economic analysis did not fully consider costs to the States that might arise from consultations with EPA over pollution discharge permits.

Our Response:

There is no evidence that past or future EPA projects have or

will be delayed due to consultations regarding sturgeon protection. Current EPA water quality standards take protection of endangered and threatened species and their habitat, including Gulf sturgeon, into account.

Comment 53:

One comment asserted that the economic analysis should cover at least a 20-year period.

Our Response:

To be credible, the economic analysis must estimate economic impacts based on activities that are reasonably foreseeable. The revised economic analysis does include annualized cost estimates to 10 years. It is difficult to predict the costs of consultations on activities beyond a 10-year window. Costs for section 7 consultations may increase or decrease dependent on factors other than inflation or deflation. For example, changes in requirements for development of a biological assessment may occur, or fluctuations in the cost of biologists and consultants. In order to maintain reasonable confidence in the estimated total section 7 costs, the analysis quantifies costs occurring within a ten year time frame. However, the final economic analysis does include annualized cost estimates, to the extent that these may inform the commenter's projections of costs over a 20-year period (see Section 4.3).

Comment 54:

A few commenters stated that the economic analysis may underestimate impacts on small businesses secondarily impacted by consultations with Federal agencies.

Our Response:

The courts have held that the Regulatory Flexibility Act requires an agency to perform a regulatory flexibility analysis only when a rule directly regulates them (Mid-Tex Elec. Coop, Inc. V. FERC, 773 F.2d 327 (D.C. Cir. 1985) and American Trucking Ass'ns, Inc. V. EPA, 175 F.3d 1027, 1044 (D.C. Cir. 1991)). Accordingly, the economic analysis considered the total costs that may affect small entities through section 7 of the Act. Activities likely to be impacted include those associated with operation and maintenance of navigation projects, highway bridge construction, and pipeline construction projects. The analysis found that less than one percent of these industries in the region would be affected and that it was likely that most of the costs imposed by the designation would be passed through to the Federal government as the government contracts for such services.

Issue I: Potential Impact to Commercial Shrimp Fishery

Comment 55:

Three commenters requested clarification on how designation of critical habitat would impact the commercial shrimp fishery, and if sturgeon are a bycatch of shrimping.

Our Response:

Shrimp trawling may impact both the Gulf sturgeon and its critical habitat. Shrimp trawling may directly affect Gulf sturgeon by capturing them in trawl nets. There is one documented non-lethal take of a sturgeon during testing of a Turtle Excluder Device (TED) equipped flounder trawl off Long Island, New York; the Atlantic sturgeon was approximately 1 m (3 ft) in total length, and was released alive (J. Mitchell, NOAA Fisheries, Pascagoula Laboratory, pers. comm. 2002). In addition, a single sturgeon is reported in the NOAA Fisheries shrimping bycatch database (E. Scott-Denton, NOAA Fisheries, Galveston Laboratory, pers. comm. 2002) as taken by shrimp trawling; an Atlantic sturgeon was captured off Georgia (Atlantic Ocean) in 1995. Anecdotal information indicates that while some sturgeon are taken by shrimp trawlers, many fish are alive as local researchers are often contacted so they may tag and release the fish (H. Rogillio, LADWF, pers. comm. 2002). Currently shrimp fishers report fewer sturgeon are being caught in the nets, which may reflect escapement through the TED or fewer incidents being reported. Regardless of critical habitat, the Gulf sturgeon was listed as a threatened species under the Act on September 30, 1991, and it, therefore, is protected wherever it occurs. Take of Gulf sturgeon that is not authorized (

e.g.

, through a section 7 consultation or through an incidental take permit) is unlawful.

The most likely effect of shrimp trawling on Gulf sturgeon critical habitat would be the disturbance of the benthic environment by trawling gear. This issue is being investigated at the NOAA Fisheries Galveston Laboratory. Until such time as conclusive data becomes available, any correlation between shrimp trawling and a negative effect on Gulf sturgeon critical habitat would be tenuous. While benthic molluscan and crustacean prey items favored by Gulf sturgeon could conceivably be disturbed as the shrimp trawl passes over the bottom, a possible effect of that disturbance would be to make them more susceptible to predation by Gulf sturgeon, possibly enhancing foraging opportunities. Although shrimp trawls may capture Gulf sturgeon, and the benthos within critical habitat may be disturbed, there is little to suggest that shrimp trawling significantly affects the Gulf sturgeon or its critical habitat at this time.

Issue J: Policy and Regulations

Comment 56:

One commenter stated that the proposed action serves to provide an additional layer of bureaucracy without any tangible benefits and appears to be a redundant and reaction to litigation filed against the Services in 1994 by the Sierra Club Legal Defense Fund and the Florida Wildlife Federation. Three commenters stated that the Services previously made not prudent determinations regarding critical habitat and requested additional information (data/biological factors) and detail to explain the Services change in position.

Our Response:

We had previously determined that designation of Gulf sturgeon critical habitat was not prudent given that such designation would not benefit the species based upon a view that jeopardy and adverse modification were essentially wholly overlapping standards under the Act. After the Fifth Circuit Court of Appeals rejected this interpretation, as stated in the proposed rule (67 FR 39112), we have reconsidered and found that designation will be clearly beneficial to the species. Recent research has determined and qualified numerous areas important for Gulf sturgeon spawning, resting, staging, and foraging. Many of these important areas are only utilized seasonally, and therefore not afforded the protection when the species is absent. By designating critical habitat, the Services will be able to manage impacts to those physical and biological features (primary constituent elements) that are essential to the conservation of the species regardless of the species presence or absence through the consulting mechanism under section 7 of the Act. For example, other Federal agencies will be required to consult with us on actions they carry out, fund, or authorize, to ensure that their actions will not destroy or adversely modify critical habitat. In this way, a critical habitat designation will protect areas that are necessary for the conservation of the species. It may also serve to enhance awareness within Federal agencies and the general public of the importance of Gulf sturgeon habitat and the need for special management considerations.

Summary of Changes From the Proposed Rule

Seven changes have been made from the proposed to the final rule designating Gulf sturgeon critical habitat—calculation of the total area included in designation; inclusion of identical amendments to both 50 CFR parts 17 and 226; verification of bridge

position in Unit 1; additional specifics on fish location in Unit 2; and exclusion of areas in Units 2, 8 and 9 under section 4(b)(2) of the Act.

For the proposed rule, river kilometers (and river miles) were measured with USACE mileage tables (USACE, 1985a and b), when available for a particular river reach. When not reported in the USACE mileage tables, several Geographic Information System (GIS) data layers were used to map all units and to calculate mileages, including data from NOAA, Environmental Systems Research Institute, Inc., and USGS. For the final rule, we still relied on the USACE mileage tables (USACE, 1985a and b) to calculate mileages when available for a particular river reach, but the remaining reaches were measured and mapped using the National Hydrography Dataset from the USGS at a scale of 1:100,000 (2001-2002 data set). This data layer, not available to us during the proposed rule, is available for the entire range of the mapped Gulf sturgeon critical habitat and has a higher resolution than the GIS data layers used for the proposed rule maps. Greater resolution results in the ability of the mapper to see and measure more of the rivers natural bends, thereby resulting in higher and more accurate river lengths. This change from using different data layers resulted in an additional river mileage of 259 rkm (161 rmi), which is a more accurate reflection, in reported total river kilometers and miles for all States, with no inclusion of additional areas.

In the proposed rule, we inadvertently provided different amendments to be included in 50 CFR part 17 (FWS) and part 226 (NMFS). For the final rule we are making identical amendments to both Parts. The amendment includes: (1) Maps and textual unit descriptions of all 14 critical habitat units, (2) the primary constituent elements essential for the conservation of Gulf sturgeon, and (3) a description of regulatory jurisdiction.

Below are descriptions of unit-specific changes. The changes stated below do not include those attributed to our more fine-scale mapping from the proposed rule.

Unit 1

On the Bogue Chitto River, Pike County, Mississippi, we reduced critical habitat in this river reach by approximately 3.2 km (2 mi) due to an error in what we believed to be the location of Quinn Bridge. We have documentation of a Gulf sturgeon sighting 1.6 km (1 mi) north of Quinn Bridge. In the proposed rule, we were given information that stated that Quinn Bridge was located on Mississippi (MS) Highway 570. Since the sighting was 1.6 km (1 mi) upstream of Quinn Bridge (MS Highway 570), in the proposed rule we ended the designation upstream of Quinn Bridge at Lazy Creek to encompass the fish location and to boundary at an area easily identifiable. We now know that Quinn Bridge is located along MS Highway 44 (Estes

et al.

1991), so in order to include the fish location and to boundary the designation at an area easily identifiable, we have included up to MS Highway 570 in the unit, which is the first crossing north of MS Highway 44. See “Map 1.1” to clarify locations of MS Highly 570 and MS Highway 44.

Unit 2

On the Bouie River, Forrest County, Mississippi, we received more specific information during the comment period on the location of a Gulf sturgeon captured above the gravel pits above Glendale Road in 1977. This fish was located approximately 0.80 rkm (0.50 rmi) above Glendale Road, not further upstream as originally believed. For ease of identification, we have included up to the southern-most road crossing of Interstate 59 in the unit. We have, therefore, reduced this river reach by 14.5 rkm (9.0 rmi).

In the proposed rule, we inadvertently provided different amendments to be included in 50 CFR part 17 (FWS) and part 226 (NMFS). For the final rule we are making identical amendments to both Parts. The amendment includes: (1) Maps and textual unit descriptions of all 14 critical habitat units, (2) the primary constituent elements essential for the conservation of Gulf sturgeon, and (3) a description of regulatory jurisdiction.

The Services are also excluding major shipping channels in this unit, as identified on standard navigation charts and marked by buoys, under Section 4(b)(2).

Unit 8

The Services are excluding major shipping channels, as identified on standard navigation charts and marked by buoys, under Section 4(b)(2).

Unit 9

The Services are excluding major shipping channels, as identified on standard navigation charts and marked by buoys, under Section 4(b)(2).

Critical Habitat

Critical habitat is defined in section 3(5)(A) of the Act as (I) the specific areas within the geographic area occupied by a species, at the time it is listed in accordance with the Act, on which are found those physical or biological features (I) essential to the conservation of the species and (II) that may require special management considerations or protection; and (ii) specific areas outside the geographic area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. “Conservation” is defined in section 3(3) of the Act as the use of all methods and procedures that are necessary to bring any endangered or threatened species to the point at which listing under the Act is no longer necessary.

In order for habitat to be included in a critical habitat designation, the habitat features must be “essential to the conservation of the species.”

When we designate critical habitat, we may not have the information necessary to identify all areas which are essential for the conservation of the species. Nevertheless, we are required to designate those areas we know to be critical habitat, using the best information available to us.

Within the geographic area of the species, we have designated only currently known essential areas. We will not speculate about what areas might be found to be essential if better information becomes available, or what areas may become essential over time. If the information available at the time of designation does not show that an area provides essential life cycle needs of the species, then the area will not be included in the critical habitat designation. Our regulations state that “the Secretary shall designate as critical habitat areas outside the geographic area presently occupied by the species only when a designation limited to its present range would be inadequate to ensure the conservation of the species” (50 CFR 424.12(e)). Accordingly, when the best available scientific data do not demonstrate that the conservation needs of the species require designation of critical habitat outside of occupied areas, we will not designate critical habitat in areas outside the geographic area occupied by the species.

Section 4(b)(2) of the Act requires that we take into consideration the economic impact, and any other relevant impact, of specifying any particular area as critical habitat. We may exclude areas from critical habitat designation when the benefits of exclusion outweigh the benefits of including the areas within critical habitat, provided the exclusion will not result in extinction of the species.

Methods and Criteria Used To Identify Critical Habitat

As required by section 4(b)(2) of the Act and its implementing regulations (50 CFR 424.12), this final rule is based on the best scientific information available concerning the species' present and historical range, habitat, biology, and threats. In preparing this rule, we reviewed and summarized the current information available on the Gulf sturgeon, including the physical and biological features that are essential for the conservation of the species (see “Primary Constituent Elements” section), and identified the areas containing these features. The information used includes known locations; our own site-specific species and habitat information; State-wide Geographic Information System (GIS) coverages (

e.g.

, land ownership, bathymetry (the measurement of depths of water in oceans, seas, and lakes), and estuarine substrates); the final listing rule for the Gulf sturgeon; recent biological surveys and reports; peer-reviewed literature; our recovery plan; discussions and recommendations from Gulf sturgeon experts; and information received during Gulf sturgeon recovery meetings. The Gulf Sturgeon Recovery/Management Plan (FWS

et al.

, 1995) contains valuable biological information, and it is cited throughout this document. However, the state of our knowledge regarding Gulf sturgeon biology and distribution has changed markedly since publication of the recovery plan for this species. The recovery criteria put forth in this recovery plan were deemed preliminary and may now warrant revision in light of new information. As a result of recent research and survey efforts directed towards this species, substantial portions of the biological information presented in the recovery plan are now dated or obsolete. Thus, although the recovery plan is a valuable source of information, it is not the final authority on the natural history and distribution of this species.

In the past, we had assumed, based on the information available at the time, that unoccupied habitat would be necessary for the recovery of the Gulf sturgeon. Since approval of the recovery plan in 1995 and our 1998 not prudent finding, we have collected new biological information on this species. We have analyzed what is necessary for the conservation of the Gulf sturgeon, as described above, and based on the best scientific information available at this time, we have determined that unoccupied habitat is not essential to the conservation of the Gulf sturgeon.

Determining the Scale of the Final Designation

We first evaluated the Gulf sturgeon in the context of its current distribution throughout the historic range to determine what portion of the range must be included to ensure conservation of the species. We considered several factors in this evaluation—(1) maintaining overall genetic integrity and natural rates of inter-river genetic exchange, thereby minimizing the potential for inbreeding, (2) retaining potentially important selective pressure at the margins of the species' range by protecting the eastern- and western-most subpopulations, (3) decreasing the extinction risk of a subpopulation by protecting adjacent subpopulations that can provide a rescue effect, if needed, (4) avoiding the potential for subpopulation extirpation from environmental catastrophes, and (5) protecting sufficient habitat to support conservation of the species.

The historic range of the Gulf sturgeon included nine major rivers and several smaller rivers from the Mississippi River, Louisiana, to the Suwannee River, Florida, and in marine waters of the Central and Eastern Gulf of Mexico, south to Tampa Bay (Wooley and Crateau, 1985; and FWS

et al.

, 1995). Seven of these major river systems continue to support reproducing subpopulations. These include (from west to east)—the Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee Rivers.

The Gulf Sturgeon Recovery/Management Plan (FWS

et al.

, 1995) noted the importance of identifying and maintaining genetic integrity and diversity during restoration efforts on Gulf sturgeon. A severe loss of genetic variability may lead to a decline in the fitness of a species (Soulé, 1987). Evidence suggests that peripheral subpopulations are often genetically and morphologically divergent from central subpopulations (Lesica and Allendorf, 1995). Distinct traits found in peripheral subpopulations may be crucial to the species, allowing adaptation in the face of environmental change (Lesica and Allendorf, 1995; and Allendorf

et al.

, 1997). In light of these considerations, we determined that the inclusion of stocks or subpopulations from both the eastern and the western margins of the current range were necessary to protect the potential evolutionary importance of those subpopulations (Scudder, 1989; Lesica and Allendorf, 1995; and Young and Harig, 2001).

While telemetry data indicate that Gulf sturgeon from one genetically distinct drainage occasionally enter another river and also mix during the winter months in estuarine and marine habitats, a genetic analysis of tissue samples concluded that Gulf sturgeon exhibit strong natal river fidelity, with stocks exchanging less than one mature female per generation on the average (Waldman and Wirgin, 1998). These low gene flow estimates strongly suggest that natural recolonization of extirpated subpopulations of Gulf sturgeon would proceed slowly (Waldman and Wirgin, 1998). Semi-isolated subpopulations are more vulnerable to the effects of demographic and environmental population fluctuations (Forney and Gilpin, 1989; and Wahlberg

et al.

, 1996).

Gene flow estimates are usually higher between adjacent stocks, suggesting that migrants from semi-isolated subpopulations are exchanged primarily with neighboring subpopulations (Waldman and Wirgin, 1998). The loss of any intermediate subpopulations by a single environmental catastrophe could seriously limit a species' recovery (Kautz and Cox, 2001; and Young and Harig, 2001). In light of this, we determined that it is necessary to designate as critical habitat rivers used by subpopulations evenly spaced between the western- and eastern-most limits of the current range. To ensure conservation of the species, subpopulations must be geographically located so that they can serve as sources of sturgeon emigration, albeit at a slow rate (Waldman and Wirgin, 1998), to adjacent rivers and so that they can provide a rescue effect if an adjacent subpopulation is extirpated (Brown and Kodric-Brown, 1977; Hanski and Gyllenberg, 1993; and Young and Harig, 2001).

Designating critical habitat for only a few subpopulation units, or for units not spaced in a manner that allows genetic exchange with other subpopulations, could increase the vulnerability of the species due to isolation of subpopulations. Protection of a single, isolated, minimally viable population risks the extirpation or extinction of a species as a result of harsh environmental conditions, catastrophic events, or genetic deterioration over several generations (Kautz and Cox, 2001). To reduce the risk of extinction through these processes, it is important to establish multiple protected subpopulations across the landscape (Soulé and Simberloff, 1986; and Wiens, 1996).

Because of these considerations, we reached the conclusion that this designation should include critical habitat units within the major river

systems that support the seven currently reproducing subpopulations (FWS

et al.

, 1995) and associated marine habitats. These river systems include (from west to east)—the Pearl, Pascagoula, Escambia, Yellow/Blackwater, Choctawhatchee, Apalachicola, and Suwannee Rivers. We believe that with proper protection and management, these units collectively represent habitat necessary to provide for the conservation of the species. The number, distribution, and range of Gulf sturgeon subpopulations included in these units is necessary to protect and support the extent and diversity of the species' genetic integrity and can provide a rescue effect, if needed. The Services believe that these seven river systems, with their associated estuarine and marine environments, represent habitat that is essential for the conservation of the Gulf sturgeon.

Assessing Specific Habitat Areas Essential to the Conservation of Gulf Sturgeon

Once we determined that the proper scale of the critical habitat designation should cover the area occupied by the seven reproducing subpopulations, we evaluated which habitats used by those seven subpopulations are essential to their conservation. To conduct this evaluation, we assessed the critical life history components of Gulf sturgeon as they relate to habitat. Gulf sturgeon use the rivers for spawning, larval and juvenile feeding, adult resting, and staging, and to move between the areas that support these components. Gulf sturgeon use the lower riverine, estuarine, and marine environment during winter months primarily for feeding, and more rarely, for inter-river migrations.

We then investigated what habitat types support these life history components and where these habitat areas are located. We evaluated empirical data, published and unpublished literature, and solicited the views of experts. These habitat components are described in the “Primary Constituent Elements” section of this final rule. We identified known or presumed spawning sites in each of the seven river systems. Some spawning sites have been conclusively identified; others are presumed due to the presence of suitable habitat. We identified known or presumed sites used for resting or staging. We identified areas where subadult and adult Gulf sturgeon occur during winter and are presumed to be feeding. These areas are primarily in the marine or estuarine environment; young-of-the-year and juveniles feed mostly in the riverine environment. As a component of the above identifications, we gathered all available data on locations and habitat use of marked (tagged) fish.

To determine which areas should be designated as critical habitat, we then evaluated where the necessary constituent elements of Gulf sturgeon habitat intersected with areas known to be used by both marked and unmarked fish. Detailed location data, where available, is included with each unit description in the “Critical Habitat Unit Descriptions” section of this final rule. Because most of the sturgeon species' farthest upstream movement is for spawning (Bain, 1997; and J. Hightower, USGS-Biological Resources Division, pers. comm. 2002), we have determined that the designation should include areas as far upstream as the furthest known or presumed spawning site. Therefore, in rivers where spawning sites have been confirmed, critical habitat extends upstream to a geographically identifiable point, such as a river confluence upstream of those sites. In areas where spawning sites are presumed but not confirmed, we have included river reaches that contain the appropriate substrate necessary for spawning, if those areas occur within close proximity of Gulf sturgeon historic and/or current sightings or captures, and if they are still accessible to sturgeon (

e.g.

, not entirely blocked by dams). The riverine critical habitat units include areas that continue to offer at least periodic passage of Gulf sturgeon to known and presumed spawning sites. Successful reproduction and recent recruitment have been documented in each riverine unit by eggs, larvae, and/or juveniles, or by a mixed age structure. We are proposing to protect subpopulation extirpation from a catastrophic occurrence by including up to both the main stem spawning sites and at least one tributary site.

We have included riverine habitat from the river mouth upstream to and including spawning grounds in order to provide sufficient habitat necessary for the other riverine life stages of Gulf sturgeon while they reside in the riverine habitats. Habitat necessary for these life stages includes habitat for summer resting or staging areas, juvenile feeding, entire young-of-the-year life cycle, passage throughout the river, and passage into and out of estuarine habitat. All of the selected areas are known to be used by Gulf sturgeon for some portion of their life cycle.

Subadult and adult sturgeon use estuarine and marine areas for feeding and passage between river systems. Designation of critical habitat units encompassing estuaries and bays adjacent to the riverine units discussed above will protect unobstructed passage of sturgeon from feeding areas to spawning grounds. In evaluating the estuarine and marine areas, we first reviewed where Gulf sturgeon from the seven adjacent riverine units have been documented by telemetry relocations and tag returns from incidental captures. We also considered areas for which we have Gulf sturgeon sightings and targeted and incidental capture records. When available, we reviewed habitat data (

e.g.

, bathymetry, substrate type, and community structure) associated with these estuarine and marine systems and compared these data with studies pertaining to the habitat requirements and preferences of Gulf sturgeon. We also evaluated data for evidence of critical migratory pathways between the river systems and the adjacent bays and Gulf of Mexico that allow Gulf sturgeon to travel to important feeding areas, as well as allow for the occasional travel to non-natal rivers for possible spawning and genetic interchange. Where documented inter-riverine movements have occurred, but no telemetry data exist to identify the migratory path (

e.g.

, between the Pascagoula River and Yellow River, the Pascagoula and Choctawhatchee Rivers, and between Suwannee River and Apalachicola River), we have not designated a migration route. We then assessed the Gulf sturgeon's overall use of estuarine and marine waters and delineated specific critical habitat boundaries.

Migration and feeding may take place within the GIWW in some of the units. Portions of the GIWW that consist primarily of excavated land cuts and canals have been excluded from this designation because they were not available historically, and, therefore, are not considered to be evolutionarily significant.

This final designation includes a significant portion, but not all, of the species' historic range. The fourteen critical habitat units include riverine main stems and in some cases tributaries, distributaries (a river branch flowing away from the main stem in the floodplain) and adjacent estuarine and marine areas that contain one or more of the primary constituent elements essential for the conservation of the Gulf sturgeon (see “Primary Constituent Elements” section). The omission of some historically occupied river drainages and estuarine and marine areas from this critical habitat designation does not diminish their individual or cumulative importance to the species. Rather, it is our

determination that the seven riverine units with known spawning and seven associated estuarine and marine units included in this rule include the habitats essential for the conservation of the Gulf sturgeon. With unobstructed passage in the estuarine and marine habitat, the subpopulations within the designated critical habitat units may eventually populate presently unoccupied coastal river systems or augment adjacent surviving small subpopulations.

Although the Mobile River Basin is the largest Gulf of Mexico drainage east of the Mississippi River, it has been extensively impounded and modified for navigation. Further, there have been relatively limited reports of captures and no evidence of reproduction of Gulf sturgeon from that system for many years. Gulf sturgeon have been reported from other river systems. Some of these other systems historically supported a commercial fishery (

e.g.

, Mobile River, Ochlockonee River) and some may support small reproducing subpopulations (

e.g.

, Techefuncte River, Ochlockonee River, Mobile River); however, there is no recent documented spawning and we have no evidence at this time that these systems are essential to the conservation of the species. Therefore, we have not included them as critical habitat.

The data available to us are insufficient to support a determination that Lake Maurepas, Breton and Chandeleur Sounds, the Mississippi River Delta, St. Louis, Biloxi, Mobile, Perdido, St. Andrews, St. Joseph, Ochlockonee, or Apalachee Bays are essential to the conservation of the species. Records within the majority of these bays are relatively scarce. Although some Gulf sturgeon from the seven subpopulations may occasionally use these bays for winter foraging, there are insufficient data to support these bays' regular winter use or importance and no documented spawning. Therefore, we have not included these bays in our critical habitat designation.

The amount of research and status surveys conducted on many Gulf sturgeon subpopulations is limited. Because of the limited availability of data specific to each river system and specific to the Gulf sturgeon's use of the marine environment, we are aware that habitat other than that identified in this final rule may later be found to be essential to the conservation of Gulf sturgeon. To the extent feasible, we will continue, with the assistance of other Federal, State, and private researchers, to conduct surveys, research, and conservation actions on the species and its habitat in areas designated and not designated as critical habitat. If additional information becomes available on the species' biology, distribution, and threats, we will evaluate the need to designate additional critical habitat, delete or reduce critical habitat, or refine the boundaries of critical habitat. Gulf sturgeon surviving in, or moving to rivers that are not being included as critical habitat will continue to receive protection under the section 7 of the Act including the jeopardy standard and the section 9 of the Act prohibitions on take (see “Critical Habitat” section).

Primary Constituent Elements

In accordance with sections 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas to designate as critical habitat, we are required to base critical habitat determinations on the best scientific data available and to focus on those physical and biological features (primary constituent elements) that are essential to the conservation of the species and that may require special management considerations or protection. Such requirements include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, and rearing of offspring; and habitats that are protected from disturbance or are representative of the historical geographical and ecological distribution of a species.

Based on the best available information, primary constituent elements essential for the conservation of the Gulf sturgeon include the following:

(1) Abundant food items, such as detritus, aquatic insects, worms, and/or molluscs, within riverine habitats for larval and juvenile life stages; and abundant prey items, such as amphipods, lancelets, polychaetes, gastropods, ghost shrimp, isopods, molluscs and/or crustaceans, within estuarine and marine habitats and substrates for subadult and adult life stages.

(2) Riverine spawning sites with substrates suitable for egg deposition and development, such as limestone outcrops and cut limestone banks, bedrock, large gravel or cobble beds, marl, soapstone, or hard clay;

(3) Riverine aggregation areas, also referred to as resting, holding, and staging areas, used by adult, subadult, and/or juveniles, generally, but not always, located in holes below normal riverbed depths, believed necessary for minimizing energy expenditures during fresh water residency and possibly for osmoregulatory functions;

(4) 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 in the riverine environment, including migration, breeding site selection, courtship, egg fertilization, resting, and staging, and for maintaining spawning sites in suitable condition for egg attachment, egg sheltering, resting, and larval staging;

(5) Water quality, including temperature, salinity, pH, hardness, turbidity, oxygen content, and other chemical characteristics, necessary for normal behavior, growth, and viability of all life stages;

(6) Sediment quality, including texture and other chemical characteristics, necessary for normal behavior, growth, and viability of all life stages; and

(7) Safe and unobstructed migratory pathways necessary for passage within and between riverine, estuarine, and marine habitats (

e.g.

, an unobstructed river or a dammed river that still allows for passage).

Need for Special Management Consideration or Protection

An area designated as critical habitat contains one or more of the primary constituent elements that are essential to the conservation of the species (see “Primary Constituent Elements” section), and that may require special management considerations or protection. Various activities in or adjacent to each of the critical habitat units described in this rule may affect one or more of the primary constituent elements that are found in the unit. These activities include, but are not limited to, those listed in the “Effects of Critical Habitat” section as “Federal Actions That May Affect Critical Habitat and Require Consultation.” For example, riverine spawning sites for Gulf sturgeon must be relatively sediment-free for successful egg development and may need best management practices implemented in the watershed upstream to prevent an excessive accumulation of sediment in these areas. None of the critical habitat units are presently under special management or protection provided by a legally operative plan or agreement for the conservation of the Gulf sturgeon. Therefore, we have determined that all units may require special management or protection.

Critical Habitat Designation

The areas designated as critical habitat for the Gulf sturgeon provide one or more of the primary constituent elements described above. Tables 1 and 2 summarize the location and extent of the designated critical habitat. All of the designated areas require special management considerations to ensure their contribution to the conservation of the Gulf sturgeon. The boundaries of critical habitat units are described generally below.

Table 1.—Approximate Linear Distance of the Riverine Critical Habitat Units for the Gulf Sturgeon

[Main Stems Are Listed First and Tributaries Are Indented]

Critical habitat unit—

river systems

State

River

kilometers

River

miles

1. Pearl (East, West, and all distributaries)

Louisiana/Mississippi

632

393

Bogue Chitto

163

101

2. Pascagoula

203

126

Leaf

164

102

Bouie

Mississippi

10

6

Chickasawhay

232

144

Big Black Creek

8

5

3. Escambia

Florida/

117

73

Conecuh

Alabama

127

79

Sepulga

11

7

4. Yellow

Florida/

154

96

Blackwater

Alabama

18

11

Shoal

13

8

5. Choctawhatchee

Florida/

249

155

Pea

Alabama

92

57

6. Apalachicola

Florida

254

158

Brothers

24

15

7. Suwannee

Florida

293

182

Withlacoochee

19

12

Total

2,783

1,730

Table 2.—Approximate Area of the Estuarine and Marine Critical Habitat Units for the Gulf Sturgeon

Critical habitat unit—

estuarine and marine systems

State

Kilometers

2

Miles

2

8. Lake Borgne

Louisiana/

718

277

Little Lake

Mississippi/

8

3

Lake Pontchartrain

Alabama

763

295

Lake St. Catherine

26

10

The Rigolets

13

5

Mississippi Sound

1,879

725

MS near shore Gulf

160

62

9. Pensacola Bay

Florida

381

147

10. Santa Rosa Sound

Florida

102

39

11. Near shore Gulf of Mexico

Florida

442

171

12. Choctawhatchee Bay

Florida

321

124

13. Apalachicola Bay

Florida

683

264

14. Suwannee Sound

Florida

546

211

Total

6,042

2,333

Critical Habitat Unit Descriptions

The river reaches within units 1 to 7 designated as critical habitat lie within the ordinary high water line. As defined in 33 CFR 329.11, the ordinary high water line on non-tidal rivers is the line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank; shelving; changes in the character of soil; destruction of terrestrial vegetation; the presence of litter and debris; or other appropriate means that consider the characteristics of the surrounding areas.

The downstream limit of the riverine units is the mouth of each river. The mouth is defined as rkm 0 (rmi 0). Although the interface of fresh and saltwater, referred to as the saltwater wedge, occurs within the lower-most reach of a river, for ease in delineating critical habitat units, we are defining the boundary between the riverine and estuarine units as rkm 0 (rmi 0).

Regulatory jurisdiction in coastal areas extends to the line on the shore reached by the plane of the mean (average) high water (MHW) (33 CFR 329.12(a)(2)). All bays and estuaries within units 8 to 14, therefore, lie below the MHW lines. Where precise determination of the actual location becomes necessary, it must be established by survey with reference to the available tidal datum, preferably averaged over a period of 18.6 years. Less precise methods, such as observation of the “apparent shoreline,” which is determined by reference to physical markings, lines of vegetation, may be used only where an estimate is needed of the line reached by the mean high water.

The term 72 COLREGS is defined as demarcation lines which delineate those waters upon which mariners shall comply with the International Regulations for Preventing Collisions at Sea, 1972 and those waters upon which mariners shall comply with the Inland Navigation Rules (33 CFR 80.01). The waters inside of these lines are Inland Rules waters and the waters outside the lines are COLREGS waters. These lines are defined in 33 CFR 80, and have been used for identification purposes to delineate boundary lines of the estuarine and marine habitat Units 8, 9, 11, and 12.

Unit 1. Pearl River System in St. Tammany and Washington Parishes in Louisiana and Walthall, Hancock, Pearl River, Marion, Lawrence, Simpson, Copiah, Hinds, Rankin, and Pike Counties in Mississippi

Unit 1 includes the Pearl River main stem from the spillway of the Ross Barnett Dam, Hinds and Rankin Counties, Mississippi, downstream to where the main stem river drainage discharges at its mouth joining Lake Borgne, Little Lake, or The Rigolets in Hancock County, Mississippi, and St. Tammany Parish, Louisiana. It includes the main stems of the East Pearl River, West Pearl River, West Middle River, Holmes Bayou, Wilson Slough, downstream to where these main stem river drainages discharge at the mouths of Lake Borgne, Little Lake, or The Rigolets. Unit 1 also includes the Bogue Chitto River main stem, a tributary of the Pearl River, from Mississippi State Highway 570, Pike County, Mississippi, downstream to its confluence with the West Pearl River, St. Tammany Parish, Louisiana. The lateral extent of Unit 1 is the ordinary high water line on each bank of the associated rivers and shorelines.

The majority of recent Gulf sturgeon sightings in the Pearl River drainage have occurred downstream of the Pools Bluff Sill on the Pearl River, near Bogalusa, Washington Parish, Louisiana, and downstream of the Bogue Chitto Sill on the Bogue Chitto River in St. Tammany Parish, Louisiana. Between 1992 and 1996, 257 Gulf sturgeon were captured from the Pearl River system (West Middle River, Bogue Chitto River, East Pearl River, and West Pearl River). The subpopulation was estimated at 292 fish, of which only 2 to 3 percent were adults (Morrow

et al.

, 1998b). The annual mortality rate was calculated to be 25 percent. Preliminary results from captures between 1992 and 2001 suggest a stable subpopulation of 430 fish, with approximately 300 adults (Rogillio

et al.

, 2002). These Pearl River distributaries are used for migration to spawning grounds, summer resting holes, and juvenile feeding. Gulf sturgeon have been captured in all of these distributaries and all are designated as critical habitat.

The presence of juvenile Gulf sturgeon (1 to 4 years old) in the Pearl River system indicates successful spawning at some location in the Pearl River system. It is believed that the only suitable habitat for spawning for the Pearl River subpopulation of Gulf sturgeon occurs above the sills on the Pearl River and the Bogue Chitto River with access to these areas only during high flows (Morrow

et al.

, 1996; and Morrow

et al.

, 1998a). Bedrock and limestone outcropping that are typical of Gulf sturgeon spawning areas in other systems do not occur here. However, within the Pearl drainage, spawning areas likely include soapstone, hard clay, gravel and rubble areas, and undercut banks adjacent to these substrates (W. Slack, pers. comm. 2001). Although the Pools Bluff Sill blocks upstream movement on the Pearl River during periods of low water, potential spawning sites have been identified upstream of the sill at various locations between Monticello, Lawrence County, Mississippi, and the Ross Barnett Dam spillway, Hinds and Rankin Counties, Mississippi (F. Parauka, pers. comm. 2002). Gulf sturgeon have also been recently reported as far upstream as Jackson, Hinds County, Mississippi (Morrow

et al.

, 1996; Lorio, 2000; and W. Slack, pers. comm. 2002). The Ross Barnett Dam upstream of Jackson prevents sturgeon movement further upstream at all flow conditions. Identified suitable spawning habitat, presence of juvenile fish, and documented adult captures support our inclusion of the Pearl River up to the spillway of the Ross Barnett Dam.

The Bogue Chitto Sill, located on the Bogue Chitto River near its confluence with the Pearl River, also hinders movement of Gulf sturgeon upstream of the sill except during high water flows. Suitable spawning habitat occurs within the Bogue Chitto upriver of the sill (W. Slack, pers. comm. 2001; W. Granger, FWS, pers. comm. 2002; and F. Parauka, pers. comm. 2002) and juvenile, adult and subadult Gulf sturgeon have been documented on the Bogue Chitto River as far upstream as one mile north of Quinn Bridge (Mississippi State Highway 44), McComb, Pike County, Mississippi (W. Slack pers. comm. 2001; D. Oge, Louisiana Department of Environmental Quality, pers. comm. 2002; and F. Parauka, pers. comm. 2002). We, therefore, have designated as critical habitat the main stem of the Bogue Chitto River upstream of Quinn Bridge (Mississippi State Highway 44) to Mississippi State Highway 570 for ease of identification.

Unit 2. Pascagoula River System in Forrest, Perry, Greene, George, Jackson, Clarke, Jones, and Wayne Counties, Mississippi

Unit 2 includes all of the Pascagoula River main stem and its distributaries, portions of the Bouie, Leaf, and Chickasawhay tributaries, and all of the Big Black Creek tributary. It includes the Bouie River main stem beginning on the southern-most road crossing of Interstate 59, Forrest County, Mississippi, downstream to its confluence with the Leaf River, Forrest County, Mississippi. The Leaf River main stem beginning from Mississippi State Highway 588, Jones County, Mississippi, downstream to its confluence with the Chickasawhay River, George County, Mississippi is included. The main stem of the Chickasawhay River from the mouth of Oaky Creek, Clarke County, Mississippi, downstream to its confluence with the Leaf River, George County, Mississippi is included. Unit 2 also includes Big Black Creek main stem from its confluence with Black and Red Creeks, Jackson County, Mississippi, to its confluence with the Pascagoula River, Jackson County, Mississippi. All of the main stem of the

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