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### SUMMARY OF ARGUMENTS PRESENTED BY THE PETITIONERS

This section summarizes arguments made by the petitioners (ONRC et al. 1993) to support a designation of the Umpqua River sea-run cutthroat trout as a threatened or endangered species under the ESA. Organization of this section, and references to the criteria of Reproductive Isolation, Ecological and Genetic Diversity, and Population Trends, follows that of the petition. The information relevant to these criteria is discussed in the following sections of this status review. Finally, in the Discussion and Conclusions sections, we will evaluate this information as it pertains to the identification and population trends of one or more ESUs for cutthroat trout in the Umpqua River Basin. 

### Reproductive Isolation

Philopatry 

The petitioners (ONRC et al. 1993, p. 2) argue that "homing ensures that sea- run cutthroat, which reproduce in the North and South Umpqua River, maintain their genetic integrity distinct from sea-run cutthroat that home to other rivers (e.g., Smith River, Siltcoos River, etc.)." In support of the above argument, the petitioners cite a report by Pearcy et al. (1990) and a personal communication from W. Pearcy to R. Nawa which states: "A sea-run cutthroat tagged at sea was later captured near Elkton...in the Umpqua River, 290 km south of the tagging location" (ONRC et al. 1993, p . 2, footnote 9) 

State Agency Designation 

The petitioners also argue (ONRC et al. 1993, p. 2) that because "Nehlsen et al. [1991] state that individual fish stocks defined by Ricker (1972) could qualify for protection under the ESA" and that the petitioned stocks are recognized and managed as distinct population segments by ODFW (Chilcote et al. 1992), "therefore North Umpqua and South Umpqua sea-run cutthroat must qualify as a "species" under the Endangered Species Act."

Geographic Isolation 

The petitioners (ONRC et al. 1993) argue that upper Umpqua River Basin sea-run O. clarki are isolated because in both the North and South Umpqua Rivers, they spawn over 265 km from their nearest sea-run cutthroat trout neighbor (in the Smith River) and 240 km from the ocean. The petitioners document these locations (Steamboat Creek and Canton Creek drainages) where sea-run cutthroat trout spawn in the North Umpqua River from historic accounts and local sources. In the South Umpqua River, the presence of cutthroat trout spawning locations is based "on observations by Forest Service biologist Jeff Dose, [that] some sea-run cutthroat in the South Umpqua River probably spawn in tributaries above South Umpqua Falls" (ONRC et al. 1993, p. 3).

Genetic Isolation 

Ecological and Genetic Diversity 

The petitioners argue that sea-run O. c. clarki in the upper Umpqua River Basin represent substantial ecological and genetic importance to the species (O. clarki) as a whole because 1) upper Umpqua River Basin cutthroat trout migrate farther inland (240 to 280 km) than any other cutthroat trout; 2) they display a unique timing of adult migration due to high summer temperatures which block upstream passage at certain times of the year; 3) they have unique physiological adaptations to withstand the high summer temperatures in the river; 4) they are anadromous and can "re-colonize streams where local extinctions may have occurred," 5) they "have a competitive advantage through large body size and increased fecundity"; 6) they inhabit "a unique geographic location" in relation to the biological species distribution; and 7) they are part of a subspecies which is declining across its range (Gerstung 1981, Trotter 1989).

In relation to the last two points, the petitioners argue that ecological and genetic diversity has a "contextual aspect." They contend that although an imperiled fish stock from an otherwise healthy population may not represent a substantial portion of that species' ecological and genetic diversity, the same stock in a population that is broadly declining across its range may be representative. Since sea-run O. clarki are considered to be at some risk of extinction across their range, the petitioners argue that sea-run cutthroat trout in the Umpqua River Basin meet this last criterion to be considered a species under the ESA.

### Population Trends 

North Umpqua River 

The petitioners contend that sea-run cutthroat trout in the Umpqua River suffered a severe decline in numbers in the early 1950s and that the population has been unable to recover due to habitat degradation (ONRC et al. 1993). The petitioners cite counts of cutthroat trout passing Winchester Dam near Roseburg, Oregon as evidence for the decline in numbers of fish. The data, collected from 1946 to 1992, show that hundreds of cutthroat trout passed the dam each year from 1946 to 1956, but dropped to only 87 fish in 1957 and remained low until hatchery supplementation began in 1961. Following the end of hatchery supplementation, the number of cutthroat trout in the river dropped to pre-supplementation levels and has continued at this level ever since. In 1991-1992, only 10 cutthroat trout were counted at the dam and none were counted in 1992-1993 (ONRC et al. 1993). 

The petitioners argue that although approximately 20,000 hatchery smolts of Alsea River origin were stocked into the North Umpqua River each year from 1961 to 1976, these fish were not adapted to the Umpqua River and did not contribute to the "wild population" (ONRC et al. 1993, p. 5). The petitioners believe "the prompt decline in the run when stocking ceased is evidence that Alsea hatchery stock failed to interbreed successfully, and the low but persistent return since then represents the original adapted native stock" (ONRC et al. 1993, p. 6).

South Umpqua River 

The petitioners state that there are no counts of sea-run cutthroat trout in the South Umpqua River, but believe "one can reasonably infer that South Umpqua sea- run cutthroat have experienced declines similar to those recorded in the North Umpqua River and are presently at a very low level" (ONRC et al. 1993, p . 6). In support of this statement, they quote a U.S. Forest Service (USFS) report that "a very small, wild, sea-run cutthroat trout population probably exists in the South Umpqua system" and that this run was once "widespread" and "dramatically larger than at present" (USDA 1992, p. 25). The petitioners also footnote a personal communication that "Jeff Dose (Umpqua National Forest fish biologist) has observed sea-run cutthroat trout in the South Umpqua River above South Umpqua Falls" (ONRC et al. 1993, p. 6 footnote 34).

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