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. . Area Manager DRAFT 39 summer 2002 were recaptured upstream of the structure in summer and fall, 2002 (Jason Davis, Service, pers.comm., 2002). Channel catfish is one of the weaker-swimming fish species found in the San Juan River. Therefore, it is highly likely that pikeminnow, razorback sucker, and other native fishes can negotiate the ladder. We believe the removal ofCudei Diversion and installation of the fish ladder at Hogback Diversion improved access for native fishes over a 24.5 mile reach of river. Until 2003, the PNM weir (RM 166) was also a barrier to fish passage. With the completion of the PNM selective fish ladder in 2003, passage is now possible past that structure. Between June and December 2003, 17,394 native fish used the passage including 9 pikeminnow and 4 razorback suckers (Albert LaPabie, Najavo Fish and Wildlife, unpublished report 2003). 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). Transformation of riverine into lake habitat Lake Powell inundated the lower 87 km (54 mi) of the San Juan River and Navajo Reservoir inundated another 43 km (27 mil. The two reservoirs reduced the potential range and habitat for the two endangered fishes from about 523 km (325 mi) to 362 km (225 mi) and inundated potential pikeminnow spawning areas in the upper San Juan River (Holden 2000). Although the loss of habitat is substantial, several other problems for native fishes resulted from the creation of lakes. The larvae of razorback sucker and pikeminnow drift downstream until they find suitable nursery habitat (backwaters or other low velocity areas) (Holden 2000). Because the river has been truncated 87 km (54 mi) on the lower end, there are many fewer stream miles available for nursery habitat. Some pikeminnow in the Green and Colorado River systems drift up to 322 km (200 mi) from spawning areas before finding nursery habitat, even though some used nursery areas are only a few rniles below the spawning areas (Tranunel and Chart 1999). The majority of YOY pikeminnow that have been collected in the San Juan River have been at the inflow to Lake Powell (Buntjer et al. 1994, Lashmett 1994, Archer et al. 1995, Platania 1995). Because of the many predators present, it is unlikely that larvae survive in Lake Powell. In 1961, prior to the filling of Navajo Dam, New Mexico Department of Game and Fish used rotenone "to eliminate trash fish species" from the Pine River (24 km [15 miD, the Navajo River (9.6 km [6 miD, and the San Juan River (120 km [75 miJ) (Olson 1962). Fourteen species offish were eliminated (Olson 1962). There were three drip stations on the San Juan that effectively killed all fish from the state line, near Rosa, New Mexico, down to Fruitland, approximately 64 km (40 mi) below Navajo Dam (Olson 1962). Included in the list offish eliminated was pikeminnow (Olson 1962). The number offish killed was not recorded because of the large scale of the project (Olson 1962). The intent of the project was to reduce (eliminate) competition and predation between native fish and the non-native trout fishery that was to be established.