WSPC138 - Laserfiche WebLink

Home Browse Search

00D524 The onset of a viable population of opossum shrimp (Mysis relicta) in Ruedi Reservoir in the mid- 1980's-- which subsequently began flushing through the outlet tubes--has enhanced both the biomass and numbers of both brown and rainbow trout, especially for the rrrst few miles just below the dam (Colorado Division of Wildlife, 2000; Nehring, 1991). The larger fish that result from this diet are probably particularly predatory on the young of other trout species, especially when flows decrease and less opossum shrimp are available (Nehring, 2000). Releases of opossum shrimp have clearly altered the diet of brown and rainbow trout in the reach immediately below the dam (Nehring, 1991). Both brown and rainbow trout use similar redds (gravel beds) for spawning, but, beyond this, have significantly different reproductive cycles as shown in Table 3.4. Table 3.4. Approximate Time and Duration of Spawning, and the Critical Early Development Life Stages for Brown and Rainbow Trout in the Fryingpan River Below Ruedi Dam. ADULT EGG EGG FRY SPECIES SPAWNING INCUBATION HATCHING EMERGENCE Brown trout October 15- October 15-May1 April I-June 1 May 15-June 15 . November 15 Rainbow trout April I-May 1 April I-June 15 June I-July 1 June 15-July 15 (Nehring and Anderson, 1993) Threatened and Endangered Fish. The Colorado River basin upstream of Lake Powell is home to 14 native fish species, four of which are .now endangered. These four fish - the Colorado pikeminnow, razorback sucker, bony tail and humpback chub - evolved in the Colorado River basin and exist nowhere else on earth. Critical habitat for two of the four endangered fish, the Colorado pikeminnow and razorback sucker, occurs within the 15 Mile Reach and upstream to Rifle, Colorado, an area affected by the Proposed Action. The fish use backwaters and side channels along this stretch to reproduce, feed, and grow. In recent times, multiple factors have contributed to the loss of habitat and decline of these native species. One factor, loss of stream flows in the 15 Mile Reach, caused by depletions in the watershed upstream of 15 Mile Reach directly impacts sustainability of the two species. Insufficient flows limit both the quantity and quality of the habitat for the Colorado pikeminnow and razorback sucker, and directly affect key reproductive life stages. The existing depletions in the Upper Colorado River basin above the Gunnison River are estimated at approximately 1 million AF/year (USDI, 1999) There are currently two contracts that make water from Ruedi Reservoir available for the 15 Mile Reach to benefit endangered fish. The first, executed in 1990, is a forty-year contract with the CWCB (Colorado Water Conservation Board) for 10,000 AF for the 15 Mile Reach. The contract stipulates that 5,000 AF be made available annually, with an additional 5,000 AF to be made available at least 4 out of 5 years throughre-regulation. The second contract is a short-term (one-year) agreement with CWCB and the Service to make 10,825 AF available for the 15 Mile Reach. This short-term agreement will be replaced by the 2012 agreement currently being negotiated with the CWCB and Service. (The 2012 agreement is not part of the Proposed Action.) Several other contracts and agreements are associated with other reservoirs that directly and indirectly enhance endangered fish habitat in the 15 Mile Reach: the Municipal Recreation Agreement between Reclamation and the municipalities of Grand Junction, Palisade, and Fruita; and the West and East Slope 14