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12 <br />sub-adults produced in the backwater (assuming a 1:1, but <br />undetermined, sex ratio for recovered young). However, this level <br />of production is inadequate to replace the existing adult <br />population of about 60,000 individuals. If 5-10 years is a <br />reasonable time frame for complete replacement of the Lake Mohave <br />stock (also the span within which the adult population is expected <br />to decline to non-sustainable level), then NFWG must find Trays to <br />annually produce 6,000 to 12,000 sub-adults for augmentation (20 to <br />40 times the production achieved in 1992). <br />Several constraining factors seem especially important, and these <br />must be dealt with effectively if production is to be substantially <br />increased: (1) Space available in the Yuma Cove backwater does not <br />appear sufficient to produce target numbers of juvenile fish, <br />unless harvest and removal to other locales can be effected at <br />smaller sizes before mortality reduces numbers. Additional <br />habitats should thus be identified and incorporated into the NFWG <br />program. (2) Mortality between hatching and attainment of juvenile <br />size probably results in the greatest absolute and proportionate <br />losses of young fish; mechanisms should be identified and <br />implemented to reduce such losses. Further, juvenile mortality <br />associated with periods of poor water quality apparently reduced <br />total numbers by about a third. Capture and handling stresses <br />likely contributed to this mortality, and sampling should be <br />reduced or curtailed when similar conditions occur. If potentially