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<br />002838 <br /> <br />3) Reproductive tradeoffs cannot be assumed equal or insignificant between established <br />patterns in Grand Valley sites and new sites upriver with respect to spawning <br />behavior, spawning success, hatching success, and larval and young-of-the-year <br />survival. <br /> <br />Given that the adult Colorado squawfish population is about 4 fish/mile in the Grand <br />Valley reach and 3-3.4 fish/mile in the Utah reach below Westwater, and recruitment of strong <br />year classes is currently infrequent, depletion of the donor population from either source appears <br />possible. If one considers the lower end of the interval estimates provided in Osmundson and <br />Burnham (160-190 fish) rather than the midpoint, which is within the 95 % confidence limits for <br />estimated population size, than depletion of the donor population seems likely. Given a survival <br />rate of 0,86 and the translocation of 10 fish/year, it would require the translocation of 100 adults <br />over a 10 year period to create a new population of 55 fish. Reliance upon occurrence of <br />another strong year class during the period of translocation effects seems risky for a population <br />considered vulnerable to extinction from stochastic demographic changes. <br /> <br />This should not be construed as opposition to translocation as part of the strategy for <br />establishing Colorado squawfish populations in the unoccupied reaches of the upper Colorado <br />and Gunnison rivers. In addition to fish that use the Redlands passageway, it would also appear <br />desirable to translocate fish captured immediately below the barrier within the plunge pool <br />downstream of the dam, This can be viewed as assisting the passage of fish that cannot or will <br />not use the constructed passageway and facilitating natural mechanisms of migration, dispersal <br />and recruitment, Osmundson et al, (1997) demonstrated significantly greater nonspawning <br />movements upstream for juvenile/early adult Colorado squawfish than for larger, older adults. <br />Though not stated explicitly by Osmundson et al, (1997), this attribute may be evidence of a <br />population dispersal mechanism by which young fish recruit into and thus maintain the upstream <br />adult populations, The use of the Redlands passage structure in 1996 by a single, small <br />Colorado squawfish may be viewed as preliminary support of this dispersal/recruitment <br />hypothesis, Without benefit of passage at the Colorado River barriers above Palisade, similar <br />translocation of Colorado squawfish captured below the barriers should still be considered, <br /> <br />DRAFT - June 4, 1997 <br /> <br />14 <br />