Reproductive parameters of females of butterfly ray Gymnura micrura (Elasmobranchii) in the southern Gulf of Mexico

Abstract

The butterfly ray Gymnura micrura is a relatively abundant batoid species in southern Gulf of Mexico, where is incidentally caught and commercialized for human consumption. In this region, however, there are no estimations of reproductive parameters needed to assess population dynamics and vulnerability to fishing pressure by means of ecological risk assessments. From the analysis of 142 females with a disc width (DW) range of 23-87 cm, it was estimated a DW at maturity (DW50%) of 56.8 cm. The female reproductive cycle is annual, and the ovulation and parturition occur from February to July. Gestation last 10-11 months, and is concurrent with the vitellogenesis. Fecundity resulted of 1-11 embryos (average = 4.3), and is directly proportional to maternal DW. The sex ratio of embryos was female biased (1.2 females per each male), however, the mean number of females and males were not statistically different. There are apparent differences in the DW at maturity and the reproductive cycle of females between the southern Gulf of Mexico and the coast of Brazil populations.