C150094 Addendum to Biological Assesment for Long Hollow

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Addendum to Biological Assessment for the Proposed Long Hollow Reservoir 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, U.S. Fish and Wildlife Service). Some survival is indicated by these fish, and recent discoveries of young fish in the system may be attributed to reproduction by the hatchery fish. Also, approximately 250,000 young-of-the-year (YOY) Colorado pikeminnow were stocked above the Hogback diversion in November 2002. 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 prevents upstream movement of this species at all flows. Three other diversions also 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), Fruitland Diversion (RM 177.2). All five 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 sub basin are separated from the Upper Colorado River and Green River sub basins 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, 1999), a midpoint between the San Juan River and upper Colorado River, but movement of Colorado pikeminnow between these sub basins has not been documented. Colorado pikeminnow are currently found outside of the project area, in the San Juan River, however, they presently do not occur in the La Plata River or Long Hollow. The La Plata River enters the San Juan River in Farmington,NM approximately 45 river miles downstream from the proposed Long Hollow Reservoir. The confluence of the La Plata River is located at 991-077.080 Wright Water Engineers, Inc. Page 4 November 2003