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63 <br />Discussion and conclusions <br />Addition of nutrients to an aquatic system tends to effect <br />increases in densities of invertebrates (Geiger 1983; Geiger et al. <br />1985; Pace 1986), which could, in turn, enhance food-related survival <br />and growth of fishes. Based on chlorophyll a and zooplankton samples, <br />these projected results were evident in my experimental ponds. <br />Populations of primary producers and invertebrate consumers increased <br />rapidly after filling of both unfertilized and fertilized ponds at <br />Dexter NFH (Figs. 1-2). Patterns of biological development were <br />similar in all ponds, although variability was high. Fertilized ponds <br />developed greater numbers and bimiass of invertebrates than did <br />untreated ponds. Numbers were positively correlated with. <br />fertilization rates, but biomass in untreated ponds and those <br />fertilized at an intermediate level were similar and far lower than in <br />high-fertilization treatments (Fig. 2). Invertebrates were dominated <br />by small-sized taxa, especially early in the experiment. There was <br />greater size diversity of invertebrates when ponds were fertilized <br />than when they were not (Fig. 4). <br />There were, however, no significant differences in survival of <br />larval razorback suckers in the various treatments (Fig. 5). <br />Presence or absence of tiger salamander larvae, which are both <br />potential competitors and demonstrated predators on razorback sucker <br />larvae (Collins and Holamizki 1984; Papoulias unpubl. data), had no <br />discernible effect on sucker survival or growth.