2011-05-12_PERMIT FILE - M2011028 (2)

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Lake Powell inflow (Jordan 1891; Koster 1960; Olson 1962; Holden 1999; Propst 1999). Natural reproduction of Colorado pikeminnow is currently known from the Green, Yampa, upper Colorado, Gunnison, and San Juan Rivers. The number of wild Colorado pikeminnow in the San Juan River subbasin is considerably lower than in the Upper Colorado River or Green River subbasins; only 17 wild adults and 2 juveniles were captured in the entire San Juan River between 1991 and 1995. Fifteen sampling trips were conducted between June 1991 and October 1995 (three trips per calendar year) from river mile (RM) 136.6 (Stump Camp) to RM 119.2 (Four Corner's Bridge). The 17.4-mile reach was the only common section of the San Juan River sampled during all 15 trips, and only 15 adult Colorado pikeminnow were captured in this reach. Radiotelemetry confirmed that these 15 fish were year-round residents of this river section. Of the 15 fish captured, 9 were recaptured (3 were recaptured twice). A population estimate for fish captured and recaptured between 1991 and 1995 derived a total of 19 adult fish (95 percent confidence intervals = 10-42). It is estimated that there were probably fewer than 40 wild adult Colorado pikeminnow in the entire San Juan River as of October 1995 (Personal Communication, Dale Ryden, FWS). Only three wild Colorado pikeminnow were captured in the San Juan River between 1995 and 2001; 2 juveniles (363 and 432 millimeters (mm) TL) near Lake Powell in 1996; 1 adult originally captured in April 1993, recaptured in 1998, 1999, and 2000 (all from RM 136.6 to RM 119.2). Radio-telemetry studies indicate that the fish were able to ascend the Cudei Diversion, but present upstream extension of wild fish in the San Juan River is the Hogback Diversion at RM 158.6 (Ryden and Pfeifer 1998; Ryden 2000a). The Hogback Diversion has now been rebuilt, however, and includes a fish ladder, so this may change in the future. Fifty adult Colorado pikeminnow were stocked in the San Juan River in October 1997. Fifteen of these fish were implanted with radio-transmitters and monitored for habitat use through 1998; the fish showed little movement from areas of release. Drift studies showed that young Colorado pikeminnow are found only in the lower river reaches and the high water zone of Lake Powell. Over 300,000 hatchery-produced Colorado pikeminnow have been released in the San Juan River since 1996 (Ryden and Ahlm 1996; Holden 1999; personal communication, F.Pfeifer, FWS). Some of these fish survived, and recent discoveries of young fish in the system may be attributed to reproduction by the hatchery fish. Historical information on the population of Colorado pikeminnow in the San Juan River is lacking, but anecdotal accounts suggest that the species was found in the San Juan River to present-day Navajo Dam and the lower Animas River (Koster 1960; Platania 1990). Present distribution of the species is from the San Juan arm of Lake Powell, near Piute Farms Marina (RM 0) upstream to the Hogback Diversion (RM 158.6). The Hogback Diversion formerly prevented upstream movement of this species at all flows, but has recently been rebuilt and now includes a fish ladder. The Cudei Diversion (RM 142.0) is located downstream of the Hogback Diversion, and is passable by fish during high flows and using the fish ladder. Three other diversions act as barriers to upstream fish movement; i.e., Four Corners Generating Station Diversion (RM 163.3), San Juan Generating Station Diversion (RM 166.1), and Fruitland Diversion (RM 177.2). Other than Hogback, these four diversions would have to be modified to allow Colorado pikeminnow access to upstream reaches and the Animas River (Masslich and Holden 1996). Colorado pikeminnow in the San Juan River subbasin are separated from the Upper Colorado River and Green River subbasins by about 320 km across Lake Powell, habitat not normally inhabited by Colorado pikeminnow, but through which passage is possible. Several adults have been captured in this reservoir (Valdez 1990); most recently near Bullfrog, Utah (personal communication, W. Gustaveson, Utah Division of Wildlife Resources), a midpoint between the San Juan River and upper Colorado River, but movement of Colorado pikeminnow between these subbasins has not been documented. B-6 Weerninuche Construction Authon-11? P.O. Box AA - Towacc, CO 813 `I AN(MA,S :r LAe 1UZ 6ZevaL, LQY441 OtT N - P,461? N • 58 ___.._ a- _?a: ._?e...?.a:.. ?s.n?v- ...,c.;._??_-. ._..u_.._?_ .`_ ...5,,. -;.o.. 1sr'g,,.; ?.•?.. _? .<_:. :?.r? - ?:_-..?._ei.. ... ..?. ?_. ,.ssri?.m-..?:ar