Observations on the Biology and Distribution of the Thorny Stingray, Dasyatis Centroura (Pisces: Dasyatidae)

Observations on the biology and distribution of the thorny stingray, Dasyatis centroura, off the southeastern United States are presented and discussed. Adults of D. centroura are among the world's largest stingrays, attaining disk widths of 180-200 cm and weights of 250-300 kg. The females seem to attain a greater mean size than males, and are sexually mature when about 155-160 cm wide, whereas males are mature when about 145-150 cm wide. An average brood-size of five, with parturition occurring in fall and early winter is indicated. In the northwestern Atlantic the principal population of this species inhabits the shelf areas between Cape Cod, Massachusetts, and southeastern Florida, apparently spending the warm seasons off the Middle Atlantic and New England states and wintering off the southeastern states. It occurs most commonly in waters ranging from 15°-22° C, and temperature seems to be the most important single factor governing its distribution. The wintering population off the southeastern coast exhibits statistically significant depth and north-south distributions relative to size; the smallest individuals occur in the deeper waters (20-40 fm) of the outer shelf off the Carolinas; juveniles and subadults in intermediate depths (15-35 fm) off South Carolina, Georgia, and northern Plorida; while adults dominate in still shoaler depths (10-25 fm) off central and southeastern Florida. The species occurs in a variety of benthic habitats, but local abundance is probably determined by temperature and local richness of the benthos. It is not a specialized carnivore, but the dominant macrocrustaceans in an area make up most of its diet. In the northwestern Atlantic, the species is also represented by an accessory population in the Gulf of Mexico which maintains at least partial contact with the primary population through individuals inhabiting deeper waters off southern Florida. The relationship of these northwestern Atlantic populations to those of other large, “thorny-tailed” species of Dasyatis in the eastern and southwestern Atlantic is speculative at present.