CRAB-SNAIL SIZE-STRUCTURED INTERACTIONS AND SALT-MARSH PREDATION GRADIENTS

Authored by BM Johnson, DE SCHINDLER, NA MACKAY, N BOUWES, JF KITCHELL

Date Published: 1994

DOI: 10.1007/bf00317908

Sponsors: University of Wisconsin Sea Grant Program

Platforms: No platforms listed

Model Documentation: Other Narrative Flow charts

Model Code URLs: Model code not found

Abstract

We studied size-structured predator-prey interactions between blue crabs (Callinectes sapidus) and marsh periwinkles (Littoraria irrorata) with a combination of field studies, laboratory experiments and individual-based modeling. Size distributions of Littoraria differed among years at the same sites in a salt marsh and could largely be explained by dominance of strong cohorts in the population. At a given site, abundance increased with elevation above tidal datum. Size-selective predation by blue crabs does not appear to be an important regulator of snail size distributions but may have a major effect on local abundance. Laboratory studies indicated that predator-prey interactions between Callinectes and Littoraria are strongly size-dependent. Crabs were generally effective at feeding on periwinkles at size ratios greater than approximately 6 (crab width: snail length). At lower size ratios crabs were far less effective at manipulating the snails, which often survived but with damaged shells. An individual-based model which incorporated information about incidence of snail shell scarring (resulting from non-lethal interactions) and snail density, predicted reduced predation rates and smaller average crab size with distance from the low tide refugium for crabs.

Tags

Community patterns Prey Marine-invertebrates Littorina-irrorata Blue crabs Gastropod