The Role of Fish Predators in Structuring the Crustacean Community Associated with the Giant Kelp, Macrocystis Pyrifera
The presence and absence of a predator, juvenile kelp bass (Paralabrax clathratus), was experimentally manipulated to test predator effects on structuring the crustacean assemblage associated with giant kelp, Macrocystis pyrifera. Cages containing and excluding this predator were interspersed throughout the upper portions (approx. 1m below the surface) of the kelp beds located at Santa Catalina Island, bass gut California. A comparison of caged and uncaged kelp contents showed that the fish ingested primarily gammarid amphipods and harpacticoid copepods. The relative abundance of both these species was not significantly influenced by the presence of the kelp bass. Both uncaged and caged kelp bass affected the availability of gammarids by selectively preying upon the largest sizes. This selectivity did not, however, occur with harpacticoids. The cage (the means of exclusion) is suspected of having a strong effect on structuring the crustacean community as a result of excluding other predators.