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annual larval production derives from a great number of adults and thus includes far more <br />variability than could be assured under either the most favorable hatchery or bay-culture <br />conditions. <br />Variability will be most reliably conserved if possible seasonaUannual periodicity in <br />spawning and/or geographic localization of different genetic groups (which have not been <br />specifically assessed for Lake Mohave razorback suckers) are accounted for by sampling <br />several time periods (early, mid-, and late in the spawning period) and across widespread <br />geographic locations over a number of years. While potential problems exist (e.g., inability to <br />insure equalization of parental contributions, selection for phototactic response), larvae <br />obtained in this manner would nonetheless represent far more parents and thus better conserve <br />existing diversity than could be achieved under either of the other two alternatives. An <br />immediate and substantial effort, if successful, would at least minimize the loss of genetic <br />variability that is sure to occur as wild adults die. <br />While the above discussion focuses on maintenance of existing genetic diversity, it also <br />essential that monetary costs of species' maintenance -and recovery be considered. A "quick <br />fix" of hatchery culture to achieve a numerical recovery goal is likely the most expensive and <br />least desirable from the perspective of maximizing genetic variability. Use of cutoff bays is <br />next in levels of cost and maintenance of genetic variability; however, they may be even <br />more costly in today's currency than use of existing hatcheries if heavy equipment is used to <br />constrict isolated habitats. The Last option clearly seems most cost-effective and biologically <br />desirable. Diverse "grow-out" habitats for rearing larvae captured directly from the reservoir <br />can vary from expensive-to-operate hatchery ponds or raceways to cutoff ba,-s, or other <br />waters such as livestock ponds and urban lakes; all have already proven successful (Marsh, <br />1990; Hinckley et al., 1991; Burke et al., in press). <br />27 <br />