2010-11-22_REVISION - M2009023 (7)

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However, the Four Corners Power Plant (Arizona Public Service) Diversion at RM 163.3 can act as a fish barrier when the control gate for the structure is closed (Masslich and Holden 1996). Above the PNM weir, the Fruitland Irrigation Canal Diversion (RM 178.5) may block pikeminnow access during flows less than 2,000 cfs (typical for July-September). Fish may pass through a sluiceway during higher flows and during the winter at low flows when the sluice gates are left open (Masslich and Holden 1996). Between 1991 and 1995 nineteen (17 adult and 2 juvenile) wild Colorado pikeminnow were collected in the San Juan River by electrofishing (Ryden 2000a). Wild adult Colorado pikeminnow were most abundant between RM 142 (the former Cudei Diversion) and the Four Corners at RM 119 (Ryden and Ahlm 1996) and they primarily use the San Juan River between these points (Ryden and Pfeifer 1993, 1994, 1995a, 1996). The multi-threaded channel, habitat complexity, and mixture of substrate types in this area of the river appear to provide a diversity of habitats favorable to Colorado pikeminnow on a year-round basis (Holden and Masslich 1997). However, recently stocked fish inhabit the river up to the confluence with the Animas. River and several miles into the Animas River (Dale Ryden, USFWS, pers. comm., 2004). Based on.Adio telemetry studies and visual observations, two potential spawning areas have been located at RM 132.0 and 131.15 (Miller 1994, Ryden and Pfeifer 1995a). Both of these sites are located in an area of the river known as the "Mixer" (RM 133.4 to RM 129.8). Ryden and Ahlm (1996) report that a Colorado pikeminnow captured at RM 74.8 (between Bluff and Mexican Hat) made a 50-60 mile migration to the Mixer during the suspected spawning season in 1994. The fish then returned to within 0.4 river miles of its original capture location. Successful reproduction was documented in the San Juan River in 1987, 1988, 1992, 1993, 1994, 1995, and 1996 by the collection of larval and/or young-of-year Colorado pikeminnow. The majority of the young-of-year pikeminnow were collected in the San Juan River inflow to Lake Powell (Archer et al. 1995, Buntjer et al. 1994, Lashmett 1994, Platania 1990). Some young-of- year pikerninnow have been collected from the vicinity of the Mancos River confluence in New Mexico and in the vicinity of the Montezuma Creek confluence near Bluff, Utah, and at a drift station near Mexican Hat, Utah (Buntjer et al. 1994, Snyder and Platania 1995). The collection of such young fish (only a few days old) at Mexican Hat during 2 years suggests that perhaps another spawning area for Colorado pikeminnow exists somewhere below the Mixer (Platania 1996). Capture of a larval Colorado pikeminnow at RM 128 during August 1996 was the first larvae collected immediately below the suspected spawning site in the Mixer (Holden and Masslich 1997). Platania (1990) noted that, during 3 years of studies on the San Juan River (1987-1989), spring flows and Colorado pikeminnow reproduction were highest in 1987. He further noted catch rates for channel catfish were lowest in 1987. Subsequent studies (Brooks et al. 1994) found declines in channel catfish in 1993; declines that have been attributed to a successive series of higher than normal spring runoffs beginning in spring 1991 through 1993. Recent studies also found catch rates for young-of-year Colorado pikeminnow to be highest in high water years, such as 1993 (Buntjer et al. 1994, Lashmett 1994). Experimental stocking of 100,000 young-of-year Colorado pikeminnow was conducted in November 1996 to test habitat suitability and quality for young life stages of this species 10