Predator-prey relationships in surfperches

Abstract

Five species of relatively large surfperches (Embiotocidae) exploit the small prey in benthic `turf' on a kelp-forested reef off southern California. Turf contained inorganic debris and `items of doubtful food value' (plants, colonial animals, etc.) which fish mostly rejected, and `items of food value' (amphipods, etc.) which they selected. In mode of food handling, two species selected their food by taking careful bites and swallowing all items, either by picking out small amphipods etc. from algae or plucking larger prey and crushing it between strong pharyngeal teeth. The three others selected food by winnowing bites of turf in their mouth and spitting out the cast. For each species, distribution of foraging effort among microhabitats differed significantly from random, for one species more noticeably so than for the others. All species generally preferred microhabitats with highest densities of valued food items. All but one foraged during the day only. Functional morphological specializations may constrain their foraging modes and diets. The presumed most generalized mode is `browser-picker'; `crunching' and `oral-winnowing' are more specialized. The surfperches' elaborate pharyngognathy is a likely basis of these specializations for greater foraging efficiency.