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<br />' cohorts that arrived in Au st were still small enou h for laz a red shiners to eat at the end of the <br />t~ g g <br />' season. <br />' Date of arrival iri backwaters by Colorado squawfish may influence survival beyond the <br />first summer. Our simulations suggest that larvae with early colonization dates consistently <br /> <br /> <br /> <br /> <br /> <br />attain larger size. Over-winter survival of age-0 Colorado squawfish has been hypothesized to be <br />influenced by size. Other studies have demonstrated that larger size confers an energetic <br />advantage (Cazgnelli and Gross 1997). Thus, the effects of date of colonization may continue to <br />act on a fish for months or even years and may be a significant factor affecting cohort strength. <br />Effect of Predator Density <br />The density of red shiners used in previous simulations (3/mz) is conservative compared <br /> <br />1 <br />1 <br /> <br />1 <br />to densities observed in the field which may exceed twice this level (Haines and Tyus 1990). To <br />examine the effect of predator density we ran a series of simulations using 1 to 6 shiners/mZ. <br />Predator density had a strong effect on number of larvae attacked and captured; survival declined <br />from >50% at 1 red shiner/m2 to 3-7% at 6 shiners/mZ (Figure 10). This nonlineaz effect is due to <br />the exponential change in the number of attacks and capture rates of larvae as predator density <br />increases. These results suggest that any management action that decreases the abundance of <br />predators will result in a proportionately lazger increase in the number of larvae that escape <br />predation. <br />1 <br />20 <br />