Description of Echinoderm Populations on Georges Bank and the Potential Modifying Role of Marine Protected Areas on These Populations

Echinoderms represent the majority of biomass on the benthos of Georges Bank. This study examines the population structure and spatio-temporal variation of the distribution of echinoderms in this ecosystem from 2005-2012. Using video survey techniques we estimated density and mean body size of four groups of echinoderms (brittle stars, sand dollars, sea stars, and sea urchins), in areas open and closed to fishing. While sea stars had higher densities inside closed areas, brittle stars, sand dollars, and sea urchin densities were similar among closed and open areas. Echinoderm body sizes were larger in the areas with the lowest densities. Sand dollars and brittle stars exhibited a patchy distribution both in closed and open areas. Sea stars were more aggregated inside the area with the highest density, and sea urchins were randomly distributed in all areas. Our results indicate that density-dependence is a pivotal mechanism for regulation of echinoderm populations, directly influencing body sizes and distribution patterns. Differences in sea stars density between marine protected and open areas may be attributed to reduced fishing disturbance. This study enhances current biological information towards the implementation of Ecosystem Based Fisheries Management since echinoderms are the preferred prey for some commercially targeted groundfish species.