9553 - Laserfiche WebLink

Home Browse Search

ECOLOGY AND CONSERVATION OF NATNE F1SHES IN THE UPPER COLORADO RiVER BASIN 189 · a genetic refuge is maintained in the lower basin. Use of hatchery fish is vital to recovery of bonytail. A broodstock has been developed from a small number of wild fish that is believed to repre- sent the wild genome for establishment of new popu- lations (Minckley et al. 1989), and fish are being successfully cultured in hatcheries (Hamman 1985). Initial releases oflarge fish into the wild were un- successful (Chart and Cranney 1991), but smaller fish released more recently are being recaptured af- ter 1-2 years in the river, indicating good growth and survival in the wild. Specific life history aspects ofbonytail are unknown, such as habitat require- ments. It is hypothesized that bonytail use inundated floodplains as nursery areas and that restoration of these habitats will benefit most native species. Razorback Sucker According to the 2002 recovery goals (U.S. Fish and Wildlife Service 2002d), recommended criteria for recovery and long-term conservation of razorback sucker are: 1. Finalization and implementation of site- specific management tasks to minimize or remove threats to attain necessary levels of protection. 2. Establishment and maintenance of four ge- netically and demographically viable, self- sustaining populations, two in the lower Colorado River basin and two in the upper basin; one each in the Green River subbasin and upper Colorado River subbasin, as well as the San Juan River subbasin, if target numbers are not met in the upper Colorado River subbasin. Each population is main tained such that: · trends in annual adult (age 4+) point esti- mates do not decline significantly, · mean estimated recruitment of age-3 natu- rally produced fish equals or exceeds aver- age annual adult mortaliry, · annual point estimates for each of the four populations exceed 5,800 adults, and · a genetic refuge is maintained in Lake Mohave. The population of the middle Green River in 1999 was fewer than 100 wild adults, and numbers of wild fish throughout the upper basin are few and scattered. Large numbers of hatchery fish have been released in the upper basin since 1995 to augment wild populations and some of these fish have been recaptured as ripe adults on an established spawn- ing bar in the middle Green River. Increased col- lection oflarvae in the Green River and first collec- tions oflarvae in the Gunnison River indicate suc- cessful reproduction by the stocked fish. The principal reason for decline of razorback sucker in the upper basin is believed to be reduced availability of floodplains that are used by all life stages and serve as nurseries for larvae emerging from mid-channel cobble bars during spring runoff. Levees have been breached to allow the river to con- nect and inundate these floodplains during critical larval stages and some recruitment is evident. flood- plain management plans for the Green River subbasin (Valdez and Nelson 2004) and the upper Colorado River subbasin (Valdez and Nelson 2005) provide guidance and strategies for maximizing available floodplain habitat. Implementation of flow recommendations is necessary to floodplain restora- tion so that releases from Flaming Gorge Dam can coincide with Yampa River flows to maximize flood- ing over breached levees. The current strategy al- lows floodplains to become inundated seasonally for 2-3 flood cycles to allow for entrainment oflarvae and 1-2 years of growth that minimizes the threat of predation by large main-stem predators. Tests with hatchery-reared fish stocked in floodplains show good growth and moderate survival (Birchell and Christopherson 2004). The alternative strategy of repatriation by isolating floodplains and removing or poisoning nonnative fish before release of hatch- ery razorback sucker (Minckley et al. 2003) is not currently being used in the upper basin. Kendall Warm Springs Dace The only population of Kendall Warm Springs dace is extremely localized and prospects for recovery and long- term conservation of this species have been greatly im- proved with establishment of the Kendall Warm Springs Biological Management Unit. The unit is sur- rounded with fencing that protects the springs, stream,