Experimental studies of selective predation on ampibpods: Consequences for amphipod distribution and abundance

Abstract

Aspects of the relationship between the amphipods found associated with eelgrass ( Zostera marina L.) and the common predators of this habitat have been examined by laboratory experiments and field sampling. Laboratory experiments showed that of the most abundant potential predators on eelgrass amphipods, the pinfish Lagodon rhomboides (L.) and the grass shrimp Palaemonetes vulgaris (Say) were amongst the most effective predators. Selective feeding by these two species with respect to prey species, size, and sex was demonstrated. Habitat complexity was shown to play a major rôle in the predatory effectiveness of the pinfish and grass shrimp. An examination of the field data in the light of the laboratory selection experiments suggests that the presence of pinfish may 1. 1) determine the relative abundances in the community of different types of amphipod species, 2. 2) determine seasonal changes in species diversity by selectively removing certain species, and 3. 3) to some degree, through an interaction with habitat complexity, determine the spatial distribution of amphipod abundance and diversity within eelgrass beds.