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<br />002831 <br /> <br />excess of those needed for production of the brood stock have already been designated as suitable <br />for stocking in the Colorado and Gunnison rivers (Czapla 1997), Burdick et al. (1995) have <br />already conducted a risk assessment associated with stocking and the stocking plan has already <br />been approved for implementation by the Recovery Program Biology Committee, <br /> <br />The modifications proposed by this plan with respect to Burdick et al, (1995) are the <br />stocking numbers proposed and stocking in an additional reach of the Colorado River (Palisade <br />to Stateline). A target biomass objective for rawrback sucker of 5 % of the total fish community <br />biomass in each of the river reaches designated was arbitrarily selected, The numbers of <br />razorback sucker required to equal this biomass was estimated to be 475 fish/mile using average <br />weight and length data for adult fish at maturity (Age 5), Stocking of razorback sucker will <br />intelject an additional species into the existing fish community, and has the potential to induce <br />changes in the relative abundance and biomass of these species' populations in each of the <br />targeted reaches. The stocking numbers proposed are influenced by the following assumptions: <br /> <br />1) the upper Colorado River reach (Rifle to Debeque) from which biomass estimates in <br />Anderson (1997) were made was at carrying capacity, <br />2) the Upper Colorado River reach and the Gunnison River reach are similar with respect <br />to lhis carrying capacity based on similar geohydrology and predominating native fish <br />communities based on observed native/nonnative species relative abundance as described <br />in Burdick (1995) and Anderson (1997), This similarity is also assumed to extend to the <br />Palisade-Stateline reach of the Colorado River. <br />3) Adult riverine habitat is not limiting in the upper Colorado River reach for razorback <br />sucker, and likely not limiting in the other two reaches, <br />4) Successful reproduction and self-sustaining status will necessitate the presence of <br />adequate distribution and amounts of nursery habitat in flooded bottomlands or <br />backwaters maintained by a natural flow regime and favorably enhanced by nonnative <br />fish control activities, <br /> <br />DRAFT - June 4, 1997 <br /> <br />7 <br />