BATHYMETRIC DISTRIBUTION AND POPULATION-SIZE STRUCTURE OF PAXILLOSID SEASTARS (ECHINODERMATA) IN THE CABO-FRIO UPWELLING ECOSYSTEM OF BRAZIL

Sampling of paxillosid seastars by 20-min trawls was made monthly at d epths of 30, 45 and 60 m, from January, 1986 to December 1988. Bottom water and sediments were analyzed. Four thousand one hundred twenty-on e individuals comprising five species were collected: Astropecten cing ulatus (54.6%); A. brasiliensis (26.4%); Luidia ludwigi scotti (18.9%) ; L. alternata (<1%) and Tethyaster vestitus (<1%). Astropecten brasil iensis occurred primarily at 30 m (from very well to well-sorted mediu m sand) and 45 m (from well to moderately-well sorted medium sand), wh ile A. cingulatus and L. ludwigi scotti were most common at 45 m and 6 0 m (from well to moderately-well sorted fine sand). Differences in si ze-frequency distributions of A. brasiliensis were recorded at 30 and 45 m depths. Population densities were higher and body size smaller (R = 4-5 cm) at the shallower depth (30 m). At deeper depth (45 m), indi viduals were larger (R = 7-10 cm) and coexisted with other species of seastars. Astropecten cingulatus showed similar size-frequency distrib utions at both 45 and 60 m depths (R = 4 cm). No species showed a patt ern of seasonal variation in density. Highest densities occurred when sea water temperatures were lower than 18 degrees C, suggesting some r elation with periods of upwelling. Differences in population size stru ctures of seastars suggest that the recruitment rate is independent of local densities.