The Mollusk Assemblage Associated with Fronds of Giant Kelp (Macrocystis pyrifera) off Santa Catalina Island, California

Abstract

The mollusk assemblage associated with giant kelp (Macrocystis pyrifera) fronds off Santa Catalina Island, California was examined monthly from June 1975 through December 1976. Mollusks comprised 1.0, 1.6, and 2.9% (by number) of all invertebrates associated with kelp fronds in the canopy, middle, and bottom zones of the kelp forest, respectively. Forty one species (36 gastropods, 5 bivalves) were collected, ranging from 14-28 for any given month. The mean number of species present was greater in the bottom (16.9) and middle zones (15.6) than in the canopy (9.3). Most species (29) were rare in occurrence (<1/kg kelp) and small (Polycera tricolor was more abundant in the canopy than in the lower zones. As a group, mollusks were most abundant on Macrocystis fronds during summer-fall.