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I I I I I I I I I I I I I I I I I I I Propagation and Genetics Management Burke, T. Bureau of Reclamation, Boulder City, NV Lake Mohave Razorback Sucker Program Update. During the late 1980's, over 90% of the wild, adult razorback sucker population left in the world, roughly 63,000 fish, resided in Lake Mohave. Despinte annual spawning along the lake's shoreline, natural recruitment of new fish into the population was almost nonexistent due to predation from nonnative fishes. Razorback suckers live about 40-45 years, and Lake Mohave was formed in the early 1950's. Without help, this population was expected to die offaround the turn of the century. The Native Fish Work Group has been working since 1991 to replace this stock. The NFWG is a team of fishery biologists representing Arizona Game and Fish, Nevada Division of Wildlife, National Park Service, Geological Survey, Fish and Wildlife Service and Bureau of Reclamation. The team collects young fry from the early spring spawning and transfers them to a local hatchery where they are raised to approximately 4 inches. The young fish are then moved to lakeside ponds for further rearing. When the fish reach 10-12 inches in length, they are tagged and released into the main body ofthe reservoir. The Native Fish Work Group's goal is to build up the spawning population to 50,000 adult fish. To date, over 52,000 juvenile fish have been repatriated to the lake, and an additional 117,000 are at some stage of rearing to target release size. An overview of the program is presented, along with results to date. Mueller, G. us. Geological Survey Are the razorback suckers we're stocking, couch potatoes? Post stocking drift and low survival of razorback sucker continues to plague reintroduction efforts. The author discusses environmental, behavioral, and physiological factors that influences fish performance and survival. Stocking dispersal (30 d) of 8 test groups (15 fish each) of razorback sucker was examined using telemetric equipment. Fish were released in three different locations: (1) a reservoir (Lake Powell), (2) a small seasonal backwater (Green River) and (3) a large backwater (> 10 ha) on the lower Colorado River, near Laughlin, Nevada. Subgroups were also released (1) immediately, (2) site acclimated 3 to 7 days prior to release, and (3) large backwater subgroups included fish physically conditioned to flow. Post-stocking dispersal was rapid and declined with time for all tests. Most movement was detected 3 weeks following release. Dispersal in the Green River was pronounced (5<=69.5 k/month) and significantly (Kruskal-Wallis P<O.OI) greater than either the reservoir (5<=3.73 k/month) or large backwater (x=7.72 k/month) groups. Fish were found in slack water habitats that provided adequate cover. Site-acclimation tests were inconclusive but downstream dispersal was significantly (Wilcoxon P<0.05) less for flow-conditioned fish (x=1.89 k/month) compared to unconditioned fish (x=7.73 k/month). Data suggests razorback sucker dispersal can be significantly reduced if fish are preconditioned to flow and stocked in moderately large (> 1 0 ha) backwater habitats. 17