THE EFFECT OF WAVE EXPOSURE ON CRAB PREDATION OF LITTORINIDS ON SAN SALVADOR ISLAND, BAHAMAS

Biotic and abiotic factors combine to govern the interactions between species. Previous studies, primarily from high latitudes, suggest that exposure to waves in intertidal habitats frequently results in a reduction of predation by crabs, while at sites protected from waves the frequency of predation increases. A total of 5940 gastropods were collected from five localities on San Salvador Island to test the hypothesis that exposure to high wave intensity affects crab predation on gastropods. Specimens were collected exhaustively across four intertidal zones along three two-meter wide transects at each locality. Shell height, shell width, aperture lip thickness and instances of repair scars were recorded for each specimen. Repair scars were compared at four levels within species, locality, sample, specimen and two-millimeter size bins. The percentage of scarred individuals for the two most abundant species, Echinolittorina dilatata and Cenchritis muricatus, was significantly lower at exposed versus protected sites in comparisons at sample, specimen and size bin levels (α=0.05). These results are consistent with the expectations based on previous studies from higher latitudes and suggest that, when biotic and abiotic factors are similar between localities, comparison of repair scar frequencies may yield an accurate depiction of relative predation intensities.