Size-Selective Predation Mortality and Growth Rates of 0-group Bivalves Macoma balthica Modeled from Size Distributions

Abstract

We simulated growth and size-selective predation mortality of juvenile Wadden Sea bivalves, predicted size distributions of prey Macoma balthica shaped by their predators Crangon crangon (Brown shrimp), and compared these predictions with observations in the field. Under the assumption that all mortality is caused by shrimp, size-selective predation could explain bivalve size structure in several cases with quite realistic and consistent prey choice functions. In about half of the 14 studied time periods, bivalve size structures could not be reproduced by selective shrimp predation, but unselective mortality never led to a reliable fit of the field data. We conclude that size-dependent abundance changes are the rule in the early life of these bivalves. Various size-dependent processes such as migrations could affect local abundances. The results strongly support that a major determinant of young M. balthica abundance and size distribution of the survivors is predation by shrimp.