THE ROLE OF THE PREDATORY CRAB, LIOCARCINUS DEPURATOR, IN A MARINE

SUMMARY (2) Cages covering 1 m2 maintained crab densities from zero to eight crabs m-2 (0-32 times natural densities) for a period of 24 days. The total number of prey individuals, the number of species in samples and abundance of selected species were compared between treatments using ANOVA. Overall differences in assemblages were explored using multidimensional scaling. Effects on population size structure for four common species were also examined. (3) Contrary to expectation, there was little evidence that predation by Liocarcinus had any significant effect on the abundance of benthic species. The number of species in samples and the total number of individuals in samples were not significantly different between treatments and there were no effects on individual species which could be interpreted in terms of predation. The multivariate analysis, however, suggested some effects of caging, possibly due to the exclusion of other predators in addition to crabs in the case of infauna.