7715 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I (5,076 to 29,935/lb of body weight) with a mean of 7,838 (17,283/lb of body weight); egg viability averaged 67.5 percent. Eggs were hatched in Heath incubators at 21.10C (700F). Bony tail chub have been placed into ponds at Arizona State University Research Park as well as earthen tanks at the Buenos Aires National Wildlife Refuge, Arizona; these stockings were made for research purposes and to produce grow- out populations for stockings elsewhere (Buddy L. Jensen, U.S. Fish and Wildlife Service and Dean Hendrickson, Arizona Department of Game and Fish, pers. comm.) (Marsh 1988). In 1983, 10,000 fry were shipped to the California Department of Fish and Game, and approximately 2,000 of these fish were placed into a small golf course pond. The young survived and grew despite an expanding population of nonnative mosquitofish (Gambusia affinis) and African cichlids (Tilaoia spp.) (Linda Ulmer, California Department of Fish and Game, pers. comm.). Moreover, bony tail chub annually produce substantial yea,r ~lasses throuQh natural soawning under pond conditions at Dexter (B. Jensen, pers. comm.). These data may indicate that bony tail chub can be maintained and propagated sufficiently in semi natural habitats (artificial backwaters, grow-out ponds, etc.) along the Colorado River (Minckley 1985). These populations are no longer viable or useable for captive propagation. Augmentation stockings of bony tail chub into Lake Mohave have been conducted by the Service and the Arizona Game and Fish Department using individuals from the Dexter and Willow Beach hatcheries. In the fall of 1981, about 41,000 tetracycline-marked fingerlings from Dexter were placed into Lake Mohave (Jensen 1981); a fish captured in 1982 at 142 mm (5.6 in.) TL was probably a survivor of this stocking (T. Lyles, pers. comm.). In July 1982, 13,320 more bony tail thub were stocked into lake Mohave from Willow Beach (l. Miller, pers. comm.). Approximately 28,000 swim-up fry from Dexter were stocked in 1983 into an isolated embayment adjacent to lake Mohave (Dean Hendrickson, pers. comm.). later surveys failed to recover any of these fish and the embayment was found to have been invaded by abundant numbers of nonnative fishes. In 1985, 12,618 fingerlings (102 mm [4 in.] TL) derived from natural spawning in a hatchery pond were stocked into lake Mohave (Hamman 1985). During November 1987, 13,971 naturally spawned fingerling bony tail chub from Dexter, consisting of 12,264 individuals that averaged 76 mm (3 in.) in Tl and 1,707 that averaged 165 mm (6.5 in.), were stocked. Another 20,000 fingerlings were stocked in October 1988 (B. Jensen, pers. comm.). It is not yet known whether any of the above augmentation attempts have been successful on a long-term basis. Five of eleven bony tail chub collected from lake Mohave in 1988 subsequently died in hatcheries and their otoliths were used by Dr. W, l. Minckley (pers. comm.) to estimate ages. Four were estimated to have been born in 1981 and thus presumably represent fish produced at Dexter and stocked in the lake. The remaining individual was estimated to be at least 10 years old. If these age estimates are correct, the latter specimen must be the product 'of reproduction in the wild and recruitment since the first stocking of this species in lake Mohave was of the 1981 year class produced at Dexter. In 1988, the Service, Bureau of Reclamation, and Utah Division of Wildlife Resources entered into a 2-year cooperative agreement to evaluate the success of introducing bony tail chub into the Green River. Objectives of the 8