Biological aspects of rays Dasyatis guttata and Dasyatis americana (Myliobatiformes: Dasyatidae) caught by the artisanal fishery in Margarita Island, Venezuela

摘要

Dasyatis guttata and D. americana are target species of some artisanal fisheries in Venezuela. Because there are directed fisheries for their catches and there have been few studies on its biology, both species are listed in the IUCN as Data Deficient. Therefore, the objectives of this research were to analyze the catches of the artisanal fishery in Margarita Island in order to provide reproductive data to contribute to the management of both species. For this reason, 3 fishing communities and 2 markets selling fish were sampled once a week, from January 2006 to December 2007. Disc width, sex and maturity were determined for each specimen captured. A total of 355 specimens of D. guttata showed that females (32-173 cm) were larger than males (28.6-113 cm), 35 of the catches were immature individuals, and although exists differences in the sex ratio there were no difference in the size at maturity (L 50 to both sexes: 56 cm); nonetheless, all individuals were mature above 78 cm. A gravid female was observed in June 2007 with 5 embryos. For D. americana a total of 224 specimens were analyzed; 40 of these had not reached sexual maturity; females showed higher sizes (21.2-164 cm) than males (35-147 cm) and also a higher size at maturity (L-50 : females: 64 cm, males: 56 cm), but all specimens were mature above 70 cm. Differences in the sex ratio and gravid females were observed only for August 2006 and March 2007, with a highest fecundity of 5 embryos. We recommend setting minimum catch lengths and periods of closure of the fishery.