San Juan River Recovery Implementation Program Summary Report 1991-97

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' No young wild razorback sucker were collected in the San Juan River during the 1987 -1995 period, so habitat use by small razorback sucker is not known. It is likely that smaller razorback sucker would also use habitat types similar to the ones that have been collected from in the Green River and ' other Upper Basin rivers. The preferred habitat appears to be flooded bottomlands, which do not occur along the present San Juan River. ' Other Native Fishes Habitat requirements for other native fishes are poorly understood. Relatively little information is available from other portions of the Colorado River Basin on habitat use of other native species. Three other native fish, flannelmouth sucker, bluehead sucker, and speckled dace are relatively abundant in the San Juan River study area, and one other, the roundtail chub, is quite rare (Platania 1990; Propst and Hobbes 1993, 1994, 1995; Ryden and Pfeifer 1993, 1994, 1995a). Although habitat requirements for these species have not been specifically studied, the study area appears to meet the requirements of these species since they are found in large numbers and reproduce successfully during most years. During the integration effort in 1997, the Biology Committee investigated several avenues for development of habitat requirements for other native fish. These included looking at habitat preference data collected by Miller et al. (1993, 1995) for the fishes from San Juan River tributaries and investigating the relationship between species abundance in the San Juan River from electrofishing data (Ryden and Pfeifer 1993, 1994, 1995a, 1996a) with habitat availability by geomorphic reach. Other analyses that were conducted included comparing year class strength and condition factors among years with differing flow and habitat patterns. Although it provides interesting information on the other native fishes, especially the flannelmouth sucker and bluehead sucker, the available information does not provide clear analyses of habitat use or requirements. Summary Studies conducted under the Program indicated that Colorado squawfish habitat use in the San Juan River is generally similar to habitat use in other Upper Basin river systems. Adult fish used low velocity habitats such as eddies, pools, and slackwaters as staging areas prior to spawning. During spawning periods the fish tended to move to specific locales that provided habitats necessary for spawning, such as runs over clean cobble bars for egg deposition and low velocity habitats such as eddies and slackwater for resting. Following spawning the fish dispersed and used different habitats during the remainder of the year. Use of run habitats appeared to be slightly higher in the San Juan River and may be related to prevalence of this habitat type in the system. YOY Colorado squawfish primarily used low velocity habitats, particularly backwaters, which provided seasonally warmer temperatures and other early life history requirements. During low flow periods these types of habitats are more abundant in secondary channels than mainchannels. Yearlings found in 1997 used a greater variety of habitats with some velocity associated with them and were primarily found in mainchannels. Information on habitat requirements of razorback sucker has primarily been collected from radio - telemetry studies of stocked razorback sucker adults. These studies have shown that razorback sucker use a variety of habitats including pools, eddies, and runs. Less is known about habitat ' San Juan River Recovery Implementation Program December 199/ Summary Report 22 PR -602 -1