9437 - Laserfiche WebLink

Home Browse Search

24 WESTERN NORTH AMERICAN NATURALIST [Volume 60 transmitters (Trammell et al. 1993) were incon- clusive: 3died within 36 d, and the survivor, found in the impoundment on 12 June, moved downstream of the reservoir and was located 12 km below the dam on 9 August 1990. To date, no hatchery-reared fish have displayed the type of spawning migration documented for the White River, nor have they utilized unoccupied habitats upstream of Kenney Reservoir. However, behavior of wild fish was similar to our results. One of 3 wild adults implanted with transmitters died within 8 d, but the remaining 2 behaved similarly to the fish we studied: 1 moved upstream of the re- servoir to occupy riverine habitats and the other moved downstream over the reservoir spillway. Contact was lost with the latter fish from 12 June to 11 September; thus, it could have migrated to a spawning area during this time. Apparently, there is a net upstream move- ment of subadult fishes into preferred habi- tats, but post-spawning Colorado pikeminnow often exhibit home-range fidelity by returning to the area (i.e., home range) they occupied before migration (Tyus 1986, 1990). Because of these behaviors, efforts to restore access (i.e., fish ladders, etc.) of adult fish to historic habi- tats may not be productive. Instead, younger fish would slowly colonize as they mature, thus increasing the time necessary to occupy re- stored habitats. However, our study demon- strates that adult fish will use habitats if access is provided them. - = - Migration and habitat use of White River fish indicate that powerful selection mecha- nisms have developed over perhaps thousands of years of evolution. This is evident in migra- tion patterns and habitat use. When provided access, wild adult Colorado pikeminnow uti- lized historic; unoccupied habitats rather than returning to sites below the dam where they had been restricted following closure of Taylor Draw Dam. This assumes that these study fish and other wild fish present before the dam was built have been attempting to ascend the White River since dam completion in 1985. On the other hand, hatchery-reared fish exhib- ited a different behavior. They did not show the same tendency to occupy riverine habitats upstream of Kenney Reservoir nor undertake such migrations. If restoration efforts connect occupied Habitats with historic reaches via fish passages, wild adult fishes may access historic habitats, establish new home ranges, and con- tinue successful reproduction by using high- quality habitats. However, hatchery-reared fishes may not. This study suggests that wild adult Colorado pikeminnow might use a fish passage facility if it were in place at Taylor Draw Dam. Research conducted by Burdick and Pfeifer (1999) shows that Colorado pikeminnow will use the fish passage structure at Redlands Diversion Dam on the Gunnison River near Grand Junction, Colorado, to access riverine habitats upstream of this 12-ft dam. Since 1996, when the fish passage facility was opened, 47 subadult/adult (TL 383-763 mm) Colorado pikeminnow have passed upstream through this structure. Six fish that used the structure in July and August 1997 and 1998 successfully passed downstream over the dam after that date and then used the passage structure again irr either 1998 or 1999. One fish has been found upstream as far as 49 km. This information can help guide present recovery efforts in areas where historic habi- tats have been blocked. Further, translocation of wild fish offers another feasible alternative to stocking hatchery-reared fish whose behav- ior may be problematic, such as not being imprinted to a successful spawning area nor being able to congregate with juvenile fish reared in high-quality nursery habitats. Finally; recovery efforts can be more successful if life- history needs of Colorado pikeminnow are better understood in areas where fish are most abundant and least disturbed. ACKNOWLEDGMENTS This study was initially proposed by the Colorado Division of Wildlife. We thank T. Nesler and B. Elmblad for their assistance in developing the study. A..Brady, Rio Blanco Water Conservation District, and M. Caddy, Colorado Division of Wildlife, provided local assistance in data collection and landowner permission. Assistance in field data collection was provided by H. Husband, B. Hilbert, D. Beers, J: Baker, Q. Bradwich, B. Sheffer, R. Arment, and H: Hines. We are especially grate- ful for thorough and thoughtful reviews by H. Tyus, K. Bestgen, M. Trammell, and K. Irving. Finally, we wish to thank Dinosaur National Monument of the U.S. National Park Service, Ouray National Wildlife Refuge of the U.S. ~~ ~ ~ k ~' yt'f;%;~"',,i~ . t}.'t,._rx~.~..~ .~