Evaluating Potential Sources of Mortality for Larval Bloater (Coregonus hoyi): Starvation and Vulnerability to Predation

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Abstract
We evaluated the relative importance of starvation and predation as potential sources of mortality for larval bloater (Coregonus hoyi) in the laboratory. Fifty percent of starved bloater larvae survived 25 d after hatching; some individuals survived 35–40 d. Bloater larvae did not exhibit a point of no return, but length and weight after 30 d were inversely related to the delay in first feeding. Bloaters were swimming about half of the time within 1 h after hatching and almost continuously after 6 h. Twenty-one days after hatching, starved larvae were still swimming continuously at 0.9 cm∙s−1; fed larvae swam more than four times faster. Bloater larvae up to 30 d old were captured with about 80% success by 95- and 135-mm bloaters and 100-mm alewives (Alosa pseudoharengus). Susceptibility to predators generally decreased with increasing size, and starved larvae were more susceptible than similar sized fed larvae. Because of their swimming ability and resistance to starvation, it seems unlikely that bloater larvae starve to death in nature. However, starvation can contribute to mortality, as reduced growth and swimming capabilities may result in increased or prolonged susceptibility to predation.