7281 (2) - Laserfiche WebLink

Home Browse Search

I CHAPTER III AFFECTED ENVIRONMENT D. Nonnative Fishes (With Emphasis on Sport Fishes) Forty-one species from eleven families have been introduced, either intentionally through stocking or accidentally by release of live bait fish, and have become established in the Upper Basin (Table III-D-1) (see Tyus et al. [1982:12-70] for maps showing the distribution of introduced fish in the Upper Basin). Rather than cover all nonnative fish species, this assessment focuses on those nonnative species of greatest interest to the public, i.e., coldwater sport fish found in reservoirs and associated tailwaters, and warmwater sport fish found in the major Upper Basin rivers. ' Coldwater Fishes Three Federal storage projects and their tailwaters could be affected by efforts to manage and protect the endangered fish: Ruedi and Flaming Gorge Reservoirs and the reservoirs that make up the Aspinall Unit. These reservoirs and their tailwaters support rainbow, brown, lake, cutthroat, and brook trout and kokanee salmon. These salmonids occupy coldwater habitats and do not normally coexist with the rare native warmwater fishes. [Note: There may be small "transition zones" with some overlap.] Flaming Gorge Reservoir provides 42,000 surface acres of habitat for rainbow, brown, lake, cutthroat, and brook trout and kokanee salmon. The Utah "blue- ribbon" tailwater fishery in the 30 miles below Flaming Gorge Dam has rainbow, brown, brook, and cutthroat trout. Ruedi Reservoir (1,000 surface acres) and the Aspinall Unit (10,304 surface acres) both support populations of rainbow, brown, and lake trout and kokanee salmon. The tailwaters of these two reservoirs occur in the Fryingpan River and Gunnison River, respectively, and support good populations of rainbow, brown, and to a lesser degree, brook and cutthroat trout. The Fryingpan River is designated as Resource Category 1 by the Service, being of high value, unique, and irreplaceable on a National basis or in its ecoregion section. The Gunnison River is designated a "Wild Trout Water" by the Colorado Division of Wildlife and supports a naturally reproducing and self-sustaining trout population. The assumed releases from these reservoirs (see Table IV-A-2) do not go below the minimum streamflows recommended for trout: a flow of 300 cfs in the Gunnison River below Crystal Dam, and 800 cfs in the Green River below Flaming Gorge Dam. Minimum flows vary from 31 cfs from November 1 through April 30 to 110 cfs between May 1 and October 31 in the Fryingpan River. r Warmwater Fishes Many warmwater sport fish and other nonnative fishes have been introduced into the Upper Basin. Introduced sport fish include channel catfish, bullheads, sunfishes, smallmouth bass, largemouth bass, crappie, striped bass, walleye, yellow perch, and northern pike. Nonnative species (other than sport fishes) established in the Upper Basin include threadfin shad, numerous minnows, suckers, killifishes, darters, and mosquitofish. Many of the nonnative III-13