Endangered and threatened species: Findings on petitions, etc.— Fluvial arctic grayling,

[Federal Register: April 24, 2007 (Volume 72, Number 78)]

[Proposed Rules]

[Page 20305-20314]

From the Federal Register Online via GPO Access [wais.access.gpo.gov]

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; Revised 12-Month Finding for Upper Missouri River Distinct Population Segment of Fluvial Arctic Grayling

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of revised 12-month finding.

SUMMARY: We, the Fish and Wildlife Service (Service), announce our revised 12-month finding on a petition to list the upper Missouri River Distinct Population Segment (DPS) of fluvial Arctic grayling (Thymallus arcticus) as threatened or endangered under the Endangered Species Act of 1973, as amended (Act). After a review of the best available scientific and commercial information, we find that fluvial Arctic grayling of the upper Missouri River does not constitute a species, subspecies, or distinct population segment under the Act. Therefore, we find that the petition to list the upper Missouri River DPS of fluvial Arctic grayling is not warranted, and we withdraw the fluvial Arctic grayling from the candidate list. The Service continues to seek new information on the taxonomy, biology, ecology, and status of fluvial Arctic grayling and to support cooperative conservation of fluvial Arctic grayling in the upper Missouri River system.

DATES: This finding was made on April 24, 2007.

ADDRESSES: The complete file for this finding is available for inspection, by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Montana Field Office, 585 Shepard Way, Helena, MT 59601; telephone (406) 449-5225. Submit new information, materials, comments, or questions concerning this species to us at this address (Attention: Arctic grayling).

FOR FURTHER INFORMATION CONTACT: Mark Wilson, Field Supervisor, Montana Field Office, at the address and telephone listed above.

SUPPLEMENTARY INFORMATION:

Species Information

Description

The Arctic grayling (Thymallus arcticus) belongs to the family Salmonidae (salmon, trout, charr, whitefishes), subfamily Thymallinae (graylings), and is represented by a single genus, Thymallus, which contains three other recognized species in addition to T. arcticus (Scott and Crossman 1973, pp. 301-302; Behnke 2002, pp. 327-331). Arctic grayling have elongate, laterally compressed bodies with deeply forked tails, and adults typically average 254 to 330 millimeters (10 to 13 inches) in length. Coloration varies from silvery or iridescent blue and lavender, to dark blue (Behnke 2002, pp. 327-328). During the spawning period, the colors darken and the males become more brilliantly colored than the females. A prominent morphological feature of Arctic grayling is the sail-like dorsal fin, which is large and vividly colored with rows of orange to bright green spots, and often has an orange border. Dark spots are often evident on the body towards the head (Behnke 2002, pp. 327-328).

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Distribution

Arctic grayling have a primarily holarctic distribution and are native to Arctic Ocean drainages of northwestern Canada and Alaska, from the Peace, Saskatchewan, and Athabasca River drainages in Alberta eastward to Hudson Bay and westward to the Bering Straits and eastern Siberia and northern Eurasia (Scott and Crossman 1973, pp. 301-302). Arctic grayling also are native to Pacific coast drainages of Alaska and Canada as far south as the Stikine River in British Columbia (Scott and Crossman 1973, pp. 301-302; Nelson and Paetz 1991, pp. 253-256; Behnke 2002, pp. 327-331). Arctic grayling generally occur throughout their native range though the species is extirpated in some locations (Michigan) and has experienced local range contraction in others (e.g., Peace-Willison watershed in British Columbia (Blackman et al. (1990, pp. 15, 17, 34), portions of Alberta (Alberta Sustainable Resource Development (2005; pp. iv, 5-18), and Montana).

In North America, two populations of Arctic grayling, believed to have been isolated by Pleistocene glaciations, have been recorded outside of Canada and Alaska (Vincent 1962, pp. 23-31). One population was found in streams and rivers of the Great Lakes region of northern Michigan, but those grayling were extirpated in the 1930s (Hubbs and Lagler 1949, p. 44; Scott and Crossman 1973, p. 301). The second population historically inhabited watersheds in the upper Missouri River basin upstream of Great Falls, Montana (Figure 1). BILLING CODE 4310-55-P

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Genetic data indicate Arctic grayling native to the Missouri River system were most likely isolated geographically from Hudson Bay and Arctic Ocean drainages by the onset of Wisconsin glaciation approximately 70,000 years ago (Redenbach and Taylor 1999, p. 32). Arctic grayling native to the upper Missouri River system are genetically diverged from Arctic grayling in the northern part of the species' range (Lynch and Vyse 1979, pp. 268-270, 275; Everett 1986, pp. 15-16, 79-80; Redenbach and Taylor 1999, pp. 23, 28-29, 32-33; reviewed by Leary 2005, pp. 1-3; reviewed by Campton 2006, pp. 5-6), and appear to be most closely related evolutionarily to populations in the Fond du Lac area of northeastern Saskatchewan, Canada (Stamford and Taylor 2004, p. 1538). Genetic divergence happens when two or more genetic characteristics that have occurred naturally over time are passed from one generation to subsequent generations. Arctic grayling in the upper Missouri River basin are commonly referred to as ``Montana grayling'' and have been variously categorized as a separate species (Thymallus montanas; Scott and Crossman 1973, p. 301) or subspecies (T. arcticus montanus; Williams et al. 1989, p. 4), but these designations are of uncertain validity (Scott and Crossman 1973, p. 301) and not widely accepted (Kaya 1990, pp. 3-4; Integrated Taxonomic Information System 2006). The lack of accepted subspecific designations is based on morphological similarity among disjunct populations (Kaya 1990, p. 4).

Arctic grayling in the upper Missouri River basin currently represent the southern extent of the species' range (Scott and Crossman 1973, pp. 301-302), and both migratory, river-dwelling (fluvial) and lake-dwelling (adfluvial and lacustrine) populations are native to the upper Missouri River. For simplicity, the term ``adfluvial'' will be used to refer to all Arctic grayling populations associated with lakes or reservoirs. The migratory, stream- and river-dwelling form of Arctic grayling native to the upper Missouri River is hereafter referred to as ``fluvial'' Arctic grayling of the upper Missouri River.

Arctic Grayling Distribution in the Upper Missouri River Basin

Fluvial Arctic grayling reside in the Big Hole River and the lower reaches of connected tributaries (see Figure 1 above). Adfluvial Arctic grayling native to the upper Missouri River system are known to reside in the Red Rock Lakes system, in the upper reaches of the Beaverhead River within the Centennial Valley, Montana (Vincent 1962, p. 120; see Figure 1 above). An indigenous Arctic grayling population exhibiting adfluvial characteristics also is present in the Madison River upstream from Ennis Reservoir (see Figure 1 above). The adfluvial characteristics expressed by the Madison River-Ennis Reservoir population may reflect recent divergence away from the presumed ancestral fluvial form resulting from the construction of Ennis Dam (Kaya 1990, p. 33; Kaya 1992a, p. 53). A few adfluvial populations found in small lakes within the Big Hole River system (in particular Miner and Mussigbrod Lakes; see Figure 1 above) may be remnant native populations derived from fluvial Arctic grayling from the Big Hole River and isolated by recent habitat fragmentation, but widespread stocking of these and other locations with hatchery-reared Arctic grayling during the 1930s-1950s (e.g., Everett 1986, p. 4, 16; Kaya 1990, pp. 31, 75-80) also makes it possible that these fish are introduced populations or that the existing populations are a mixture of native and introduced Arctic grayling.

Ecology

Northcote (1995) and Kaya (1990) reviewed the ecology of Arctic grayling and fluvial Arctic grayling of the upper Missouri River, respectively. Much of the information on fluvial Arctic grayling in the upper Missouri River system comes from the Big Hole River, Montana (see Figure 1 above), which contains a fluvial population. Arctic grayling exhibit life history and migratory forms present in other species of inland trout and charr, including fluvial and adfluvial. Fluvial populations are characterized by a cycle of migratory behavior over their lifespan between spawning, feeding, and overwintering habitats within rivers or streams (Northcote 1995, pp. 156-160). Fluvial Arctic grayling typically migrate upstream to spawn in tributary or mainstem river locations and downstream to overwintering habitats. Such movement patterns have been observed in fluvial Arctic grayling in Big Hole River, Montana (Shepard and Oswald 1989, pp. 18, 27-28). Migrations to feeding habitats may occur if these locations differ from spawning or overwintering habitats (Kaya 1990, pp. 9-11). Overall, movements by fluvial populations within and among tributaries and mainstem rivers may cover hundreds of kilometers (Armstrong 1986, p. 7). Fluvial Arctic grayling in the Big Hole River system have been shown to migrate in excess of 80 km (50 mi) between spawning, feeding and wintering areas (Shepard and Oswald 1989, pp. 18, 21; Lamothe and Magee 2003, pp. 7, 11, 17). Adfluvial Arctic grayling feed and overwinter in lakes, but migrate to inlet or outlet streams to spawn (Northcote 1995, p. 148- 149; Northcote 1997, pp. 1030-1034).

Age at maturity and longevity in Arctic grayling varies among systems and is probably related to growth rate, with populations in colder, less productive habitats maturing at later ages and having a greater lifespan (Northcote 1995, pp. 155-157). Fluvial Arctic grayling in the Big Hole River system typically mature at 2 years of age (males) or 3 years of age (females), and individuals older than 6 years of age are rare (Liknes 1981, pp. 16-18; Kaya 1990, pp. 18-20; Magee and Lamothe 2003, p. 22). Arctic grayling are spring spawners. In Montana, Arctic grayling typically spawn from late April to mid-May by depositing adhesive eggs over gravel substrate without excavating a nest or redd (Shepard and Oswald 1989, pp. 24-25, 29; Kaya 1990, pp. 15-16). In general, the reproductive ecology of Arctic grayling is somewhat different from other salmonid species (trout and salmon) in that Arctic grayling eggs tend to be comparatively small (Behnke 2002, p. 328), and males establish and defend spawning territories rather than defending access to females (Northcote 1995, p. 150). The time required for development of eggs from embryo until they emerge from stream gravel and become swim-up fry varies with water temperature, but averages about 3 weeks for Arctic grayling in the upper Missouri River basin (Kaya 1990, pp. 16-17). Small, weakly swimming fry of fluvial Arctic grayling prefer low velocity stream habitats (Kaya 1990, pp. 23- 24; Northcote 1995, pp. 152-153).

Arctic grayling of all ages feed primarily on aquatic and terrestrial invertebrates captured on or near the water surface (Northcote 1995, pp. 153-154; Behnke 2002, p. 328). They also will feed opportunistically on fish and fish eggs (Northcote 1995, p. 154; Behnke 2002, p. 328). Feeding locations for individual fish are typically established and maintained through size-mediated dominance hierarchies (e.g., Hughes 1992, pp. 1994-1995).

Although fluvial Arctic grayling may have specific habitat requirements depending on their life stage (e.g., fry) and ecological activity (e.g., spawning), individuals inhabiting streams and rivers often exhibit a preference for pool habitats (Liknes 1981, pp. 22, 28; Kaya 1990, pp. 20-21; Lamothe and Magee 2003, pp. 13-14, 17; Lamothe and Magee 2004, p. 24). Vincent (1962, pp. 39, 42) concluded that fluvial Arctic grayling in Montana typically reside in

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streams with low-to-moderate gradient (