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parents in the illustration of a di-allele cross (Figure 4) will maintain the genetic contributions of all parents. Note the genetic diversity in offspring from full-sib (Al X Al) or half-sib (Al X A2) crosses. The resulting offspring of the full-sib cross is illustrated in the lower left diagram and the half-sib cross is illustrated in the lower center diagram. A rather detailed explanation of the di-allele cross in Figure 3 on page 28 explains its use in maintaining genetic diversity.. If space is limiting for propagation of all family lots from a 5 X 5 di- allele cross, maintaining separate groups of the family lots represented in the diagonal cells as illustrated in Figure 3 would be preferred to maintaining the 20 other matings because these 5 family lots contain the entire genetic contribution from the 10 parents. If adult fish are extremely rare and five fish of each sex cannot be obtained, factorial matings (Kapuscinski et al. 1993) will be used to increase the genetic contribution from the least numerous sex (See Item 4 in Box 10). After a broodstock has been developed from a 5 X 5 cross or a factorial mating, additional wild endangered fish should be used to supplement the genetic contribution of the parent stock until a minimum effective populations size of 50 is achieved, providing that no adverse affect will occur to the wild stock (See Item 5 in Box 10). Additional lots from mating one male with one female should replace the half-sib lots in the di-allele cross to maximize the genetic contribution from the wild parents. In some situations, it may be feasible to spawn wild fish at the site of capture and return them to the habitat from where they were collected. However, in most situations, fish will be captured, transported to holding facilities at refuges or hatcheries, and held until they can be spawned. The stress of capture and transporting may prevent potential broodstock from spawning during the year of capture. Even if fish spawn in the year of capture or a subsequent year, the wild adults may be retained at the refuge or hatchery for an additional year to ensure that F, progeny survive from the initial spawning. IX. IMMEDIATE, SHORT-TERM, AND LONG-TERM NEEDS FOR CAPTIVE-REARED ENDANGERED FISH Only some immediate (1 year) and short-term fish needs (2-5 years) from propagation could be identified by the Biology Committee at this time. Beyond 3 years, it became increasingly difficult to define captive-reared endangered fish needs. Long-term (> 5 years) endangered fish needs for Program propagation efforts cannot be made with certainty. ic to an b D fi i i t t ti t k i f d d y as s n ng s ve s oc e a presump s us, tren s, an prior ties o recovery program. The summaries of status, trends, and priorities (Tables 1, 2, and 3) of presumptive endangered fish stocks in the Upper Colorado River Basin provided the baseline for identifying propagation needs for endangered fish. This plan summarizes fish needs by species and presumptive stocks within each species. i ¦ 36