9334 (2) - Laserfiche WebLink

Home Browse Search

BACKGROUND ~ Propagation is one of the five primary components to achieving recovery of the endangered fish species of the upper Colorado River basin. To this end, stocking plans have been developed and implemented in the upper basin (Burdick et aL 1995, Lentsch et aL 1996, Wydoski 1996). Propagation efforts in Colorado and Utah are currently being implemented under the guidance of the most recent stocking plans for the respective states: the Five-Year Stocking Plan for ~ Endangered Colorado River Fish Species in Colorado (Kesler 1998) and the State of Utah Stocking Plan for Endangered Fish Species of the Upper Colorado River Basin (Hudson et aL 1999). Hudson et al. identified the need for stocking razorback sucker in three reaches (middle Green River, lower Green River, and Colorado River in Utah) and bonytail in two reaches (lower Green River and Colorado River in Utah) with the ultimate goal of establishing populations of ~ these endangered fish within each of these river reaches in Utah. Razorback sucker was Federally Listed as endangered in 1991 under authority of the Endangered Species Act (USFWS 1991). The adult population size of razorback sucker in the middle Green River is currently unknown. It was estimated to be 524 individuals (95% confidence interval, 351- ~ 69b) based on capture-recapture data collected from 1980-1992 (Modde et aL 1996). An earlier study using data from 1980-1988 estimated the population at 948 individuals (95% confidence interval, 758-1,138) (Lanigan and Tyus 1989). However, with limited recruitment occurring into the population, the adult population size of the middle Green River nosy be considerably less than the last estimated population size. Augmentation efforts in recent years through the floodplain ~ restoration program may be contributing to an increase in the adult population size of the middle Green River. The adult population sizes of razorback sucker in the lower Green River and the Colorado River in Utah are currently unknown. However, collections of juvenile and larval razorback suckers ~ (Gutermuth et aL 1994, Muth and Wick 1997, Chart et al. 1998, Muth et al. 1998) suggests the presence of an adult spawning aggregation in the lower Green River. In 1980, the bonytail (Gila elegans) was Federally listed as endangered under the Endangered Species Act by the U.S. Fish and Wildlife Service due to the serious threat of extirpation (USFWS ~ 1980). Since that time, very few wild bonytail have been captured and positively identified as such in the upper Colorado River basin. Bonytail that have been stocked in Utah under the respective stocking plans have resulted in the recapture of increasing numbers of bonytail by UDWR through monitoring efforts covered under RIP project #25 (Bonytail Reintroduction). However, the majority of these recaptures have been within a year of the stocking date. The Genetics Management Plan (Czapla.1999) identifies razorback sucker and bonytail as Priority 1 and Priority 2 species, respectively, for recovery. Brood stock development has been under way for razorback sucker since 1989. There are 23 family lots comprising the developed brood stock which are currently being held at Ouray National Fish Hatchery. These family lots ~ represent adult razorback sucker that were collected from the Jensen spawning bar in the middle Green River. The Genetics Management Plan identifies the need for 25 family lots. The remaining two family lots needed will be developed from upper basin razorback sucker currently being held at the Grand Valley Endangered Fish Facility. ~ 2