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<br />002823 <br /> <br />Colorado squawfish, the two sizes represent the first and subsequent sizes at which the fish may <br />be PIT tagged prior to stocking, Based on monitoring results after replication of each <br />combination in each river, production may be modified in the third year to focus on the apparent <br />optimal fish size and season to stock in each river, This approach is consistent with draft <br />recommendations made by Burdick and Bonar (1997) for stocking razorback sucker, <br /> <br />The target objective of stocking for each of the three species is to meet the <br />abundance/biomass based criterion with the presence of three adult age groups surviving in each <br />river reach, For razorback sucker, these age groups are 5-7; for bonytail, age groups 4-6; and <br />for Colorado squawfish, age groups 6-8, The cumulative survival/abundance/biomass of these <br />age groups is desired to achieve the population objective in the river. Using monitoring to <br />evaluate survival and abundance post-stocking, subsequent numbers of fish stocked may have <br />to be increased or decreased to compensate for actual survival in the river. The presence of an <br />adult, multi-year-class population in the target river reaches is desired to further determine <br />spawning and reproductive success, and the effects of limiting environmental factors that may <br />be influential, The persistence of a potentially long-lived, stocked adult population would thus <br />contribute to recovery of subsequent self-sustaining wild populations of these species in these <br />river reaches, <br /> <br />Stocking of humpback chub in Colorado is not anticipated at this time, This position is <br />based on (1) the characteristic association of this species with canyon-bound river habitat, which <br />dictates where stocking would occur, and (2) the relative stability or lack of significant threat <br />of extirpation to the existing populations in these habitats in Colorado within Yampa Canyon on <br />the Yampa River and Black Rocks on the Colorado River. Also, with respect to the recovery <br />goals described for this species (USFWS 199Gb), five natural populations currently exist in the <br />Upper Basin, and appear to have persisted in these locations in relatively stable numbers since <br />their initial discovery and identification. <br /> <br />DRAFT - June 4, 1997 <br /> <br />5 <br />