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t <br />exists for humpback chubs at two sites in the upper basin. The humpback chubs <br />in Black Rocks Canyon could be in jeopardy from a catastrophe such as a <br />chemical spill because a railroad track passes through the canyon. The <br />Westwater Canyon stock of humpback chubs are also at catastrophic risk since <br />Westwater is very close to Black Rocks. Thirty wild adult humpback chubs will <br />be collected from Black Rocks Canyon in 1995 to be held in a refuge at the <br />Horsethief State Wildlife Area CO to safeguard the wild stock from <br />catastrophic risk and for use in developing future broodstocks if needed for <br />recovery. <br />Colorado squawfish were considered to be stable in the Upper Colorado River ' <br />Basin with the exception of the upper Colorado River stock upstream from <br />Westwater Canyon. Seventeen family lots of this stock have been developed and <br />are being held in a refuge for use as future broodstock. Three males and <br />three females are needed to develop eight additional family lots to complete a <br />5 X 5 di-allele breeding strategy. This broodstock would be available for <br />production of fish for experimental stocking (including augmentation and <br />restoration stocking) if warranted at a later date. This stock could be used <br />for restoration stocking in the Colorado River between Palisades and Rifle CO <br />and in the Gunnison River above the Redlands Irrigation Diversion Dam if wild <br />fish do not occupy these reaches after fishways are constructed at these <br />sites. <br />Assignment of priorities to stocks within species was more difficult because <br />all stocks may be important in the recovery process. However, stock <br />priorities were made by considering identified or suspected spawning sites, <br />recruitment, the possibility of catastrophic risk, and the probability of the <br />stock being extirpated from the wild (Table 3). <br />Breeding Strategies <br />The recommended target breeding strategy to be used in propagation of the <br />endangered Colorado River fishes is to mate 25 females with 25 males to <br />produce 25 pedigreed family lots if sufficient adults are available and <br />removal from the wild will not jeopardize the genetic characteristics of the <br />founder stock. An inbreeding rate of 1% was estimated for an effective <br />population size of 50 fish that is acceptable for maintaining the genetic <br />diversity of wild fish stocks used as founders. When stocks are low, a <br />minimum breeding strategy using a 5 X 5 di-allele cross will be used to <br />develop broodstocks. A 5 X 5 breeding strategy has an effective population <br />size of 10 fish and an estimated inbreeding rate of 5%. In the event that 5 <br />males and 5 females are not available, a factorial mating will be used to <br />capture the genetic contribution from all fish of the least numerous sex. <br />However, additional wild adults will be used to supplement the broodstock that <br />are developed from a 5 X 5 or factorial cross when they are available to <br />increase the effective population size that will reduce the estimated <br />inbreeding rate to an acceptable level. Adaptive management approaches will <br />be used in the captive propagation of endangered fish stocks because of low <br />numbers of fish, logistical problems in obtaining fish, and uncertain culture <br />problems. <br /> <br />Propagation Facilities <br />Small ponds (0.1-acre and 0.2-acre) are considered optimal for rearing <br />endangered fishes in family lots to maintain genetic diversity and to reduce <br />