Site-specific differences in the feeding ecology of the California sheephead, Semicossyphus pulcher (Labridae)

Synopsis

The feeding ecology of four populations of Semicossyphus pulcher was examined with respect to such factors as site-specific prey availability, density of the sheephead population, and size of the sheephead. The diets of the sheephead were typically broad, though only a few prey categories dominated. There was considerable between-site differences in the dominant prey. The availability of potential prey (in terms of abundance) also differed between sites both in total abundance and abundance of specific prey types. The diets of the sheephead generally reflected the availability of prey where prey were abundant (i.e. San Nicolas Island) but not where prey were scarce (e.g. Cabo Thurloe). Where prey were scarce and the sheephead population biomass was large (e.g. Cabo Thurloe and Isla Guadalupe), the sheephead apparently switched to alternative, and presumably, lower priority prey (i.e., bryozoan encrusted algae). Some abundant, potential prey were avoided in areas where sheephead were typically small, suggesting an inability of the small fish to handle large prey. The interaction of the kind and abundance of prey, and the size and abundance of the sheephead is discussed in relation to the influence of sheephead predation on their prey populations and community structure.