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<br />002772 <br /> <br />3.2.2 Broodstock Breeding Strategies <br /> <br />An acceptable breeding and rearing strategy will be used to develop broodstocks and progeny with <br />genetic diversity similar to that of the presumptive stocks (Williamson et al. 1994). According to the <br />Genetics Management Guidelines, if sufficient adult endangered fish are available and removal from <br />the wild will not jeopardize the genetic characteristics of the founder stock, a minimum target of 50 <br />adults (25 males and 25 females) should be used to develop broodstocks to minimize the likelihood <br />of inbreeding. Broodstocks will be developed through paired matings that would produce 25 <br />pedigreed family lots. An inbreeding rate of 1 percent is estimated for an effective population size <br />of 50 fish, and is considered to be acceptable for maintaining the genetic diversity of wild fish stocks <br />(Williamson et al. 1994). <br /> <br />When wild fish stocks are low, a minimum breeding strategy using a 5 x 5 di-allele cross will be used <br />to develop broodstocks of25 family lots. A 5 x 5 breeding strategy has an effective population size <br />of 10 fish and an estimated inbreeding rate of 5 percent In the event that 5 males and 5 females are <br />not available, a factorial mating will be used to capture the genetic contribution from all fish of the <br />least numerous sex. However, additional wild adults will be used to supplement the brood stock that <br />are developed from a 5 x 5 or factorial cross when they are available to increase the effective <br />population size that will, in turn, reduce the estimated inbreeding rate (Williamson et al. 1994). <br /> <br />The lack of sufficient adult fish has resulted in the application of different spawning matrices. The <br />status of broodstock development for each of the four endangered fishes is discussed in the following <br />sections. <br /> <br />3.2.2.1 Colorado Squawfish <br /> <br />Initial development of Colorado squawfish broodstock took place at Dexter National Fish Hatchery <br />(NFH). From a total of 10 adult squawfish taken from the Upper Colorado River upstream of <br />Westwater Canyon, a total of 18 family lots were spawned at Dexter in 1991 using a di-allele 5 x 5 <br />breeding matrix; these 18 lots were reared at the Bellvue Fish Research Unit near Fort Collins, <br />Colorado (US. Fish and Wildlife Service 199Ib). <br /> <br />Currently, 17 ofthe 18 lots reared at Bellvue remain at Horsethief State Wildlife Area (Baker 1996). <br />The 10 adult squawfish are also being held at Horsethief The development of a broodstock using <br />a breeding matrix of25 paired matings is "on hold" because available propagation facilities are in use <br />developing the two razorback sucker brood stocks that are considered by the Biology Committee to <br />be a higher priority (Czapla 1997). No brood stock have been developed for the other presumptive <br />populations (Yampa, Desolation-Gray Canyon, Gunnison). <br /> <br />As of November 1, 1996, Dexter NFH held the following quantities of adult Colorado squawfish: <br />113 - 1974 year-class first generation (F,) from Yampa/Green Rivers; 188 - 1981 year-class F, <br />fromYampa/ Green/Colorado Rivers; and 726 - 1991 year-class from Grand Valley (Czapla 1996b). <br /> <br />12 <br />