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<br />002839 <br /> <br />Natural recolonization of the upper Colorado River reach is also possible with the <br />placement of passageways around existing barriers similar to Redlands on the Gunnison, but the <br />success of these devices in terms of use by Colorado squawfish has yet to be established, both <br />in terms of numbers of fish and the contribution of observed rates of passage (e,g, number of <br />fish per season) to population goals for the Gunnison River or recovery goals for the species, <br />Similar to the translocation approach, though perhaps even more variable in terms of progress, <br />natural recolonization would likely require a long time period to establish an adult population <br />of even 4 fish/mile (200 fish total) similar to the Grand Valley reach now, or the 20 fish/mile <br />target proposed here from the Anderson (1997) biomass results. With regard to acceptable time <br />frames within the Recovery Program to achieve progress toward recovery goals and the <br />uncertainties associated with reliance upon the existing adult stock and natural movement <br />mechanisms, and use of artificial passage,. stocking of genetically compatible fish is <br />recommended over translocation or natural recolonization as the preferred approach to 'extending <br />the species range and establishing adult populations within the unoccupied reaches of the upper <br />Colorado and Gunnison rivers in a timely manner. It is further recommended that translocation <br />of Colorado squawfish also occur as a supplementary approach, using fish captured in the plunge <br />pools below the instream barriers at Redlands on the Gunnison River and Price-Stubb and <br />HigWine on the Colorado River. <br /> <br />The stocking numbers proposed below are based on biomass estimates of fishes in the <br />Colorado River in Anderson (1997) and survivorship curve estimates in Table 4, The goal <br />would be for reintroduction stocking to result in a multi-year class population at a desired <br />density of 20 fish/mile, Assumptions made that influence stocking numbers and target reaches <br />include: <br /> <br />1) Populations of Colorado squawfish extended naturally upstream prior to placement of the <br />instream barriers within the Colorado and Gunnison rivers, and were comprised largely <br />of adults, similar to the size and age composition of Colorado squawfish populations in <br />other Colorado tributary streams. Burdick (1995) documented the existence of a remnant <br />population of adult Colorado squawfish in the Gunnison River upstream of Redlands <br /> <br />DRAFT - June 4, 1997 <br /> <br />15 <br />