Influence of Trophic Relations on Form and Behavior Among Fishes and Benthic Invertebrates in Some California Marine Communities

Study of interactions among fishes and benthic invertebrates off southern California's Santa Catalina Island showed the great extent to which taxa are defined by trophic relations. The dominant fishes there are acanthopterygian teleosts, with the serranine serranid Paralabrax clathratus morphologically nearest the evolutionary mainstream. Because mainstream species have morphologies similar to their progenitors, marine communities have a long history of adaptations to threats from generalized predators like P. clathratus. Species examined at Santa Catalina indicate this experience has produced four basic defenses: smallness, which presents difficulties for predators with large and simply constructed feeding mechanisms; dissemblance, as through camouflage, which makes detection by visual hunters difficult; inedibility, which is attained by incorporating materials that an unspecialized digestive system cannot accommodate; and nocturnality, which results in avoiding diurnal predators altogether. Examination of trophic relations among the major fishes in Santa Catalina communities shows each with specialized ways to counter these defenses. Prey smallness has been met by reducing size of mouth relative to size of prey, either by evolving as smaller fishes or through structural changes in head and jaws. Prey dissemblance has been accommodated through enhanced visual acuity and varied means to remain an unrecognized threat while waiting for prey to move. Inedibility has been countered by developing specialized features of the alimentary tract, including dentition, while adjustments to nocturnality have included enhanced sensory capabilities that detect prey in low light. These adaptations to prey defenses define varied lines of divergence from the teleost mainstream as represented atbreak Santa Catalina.