Springer Verlag, Coral Reefs, 1(31), p. 247-251
DOI: 10.1007/s00338-011-0840-5
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Density-dependent processes are critical for regulating species’ populations, and piscivory of coral-reef fishes is frequently density dependent. However, the mechanism driving this density-dependent mortality is poorly understood, but may be caused by changes in a predator’s feeding rate at different prey densities (its functional response). An aquarium experiment replicated in winter and summer examined the functional response after 22 and 47 h of Cephalopholis cruentata feeding on Halichoeres pictus. With the exception of summer data after 47 h (density-independent mortality), mortality was inversely density dependent across all prey densities and increased with higher summer temperatures. The absence of an asymptotic pattern of inverse density-dependent mortality was caused by type II (summer) or dome-shaped type IV (winter) functional responses, with the benefits of schooling likely to cause the low mortality rates at higher prey densities. Predators’ functional responses may underlie the inverse density-dependent mortality reported in field studies of aggregating fishes.