Reproductive biology and abundance of the white dotted skate, Bathyraja albomaculata, in the Southwest Atlantic

RUOCCO, N. L.; LUCIFORA, L.; DÍAZ DE ASTARLOA, J.M.; WÖHLER, O. C.

ICES JOURNAL OF MARINE SCIENCE

OXFORD UNIV PRESS

Año: 2006 vol. 63 p. 105 - 116

1054-3139

The size at maturity, sexual dimorphism, gonad development, and abundance of the white-dotted skate, Bathyraja albomaculata, are analyzed along its geographic range in the southwest Atlantic, from off Uruguay to Tierra del Fuego (Argentina). A total of 291 specimens from 8 research cruises conducted between 1998 and 2003 were examined. Length-mass relationships were sexually dimorphic, with adult females significantly heavier than males. The largest female observed was 762.00 mm total length (LT), and 50% maturity (LT50) was attained at 653.68 mm LT. The largest male was 732.00 mm LT, and male LT50 was 628.81 mm LT. Female and male LT50 were not significantly different and correspond to ~86% of maximum size, which is similar to other Bathyraja species. This suggests a high vulnerability to exploitation. The lack of sexual dimorphism in size at maturity and the slight difference in maximum size support the hypothesis of relaxation of selection for large female size in oviparous elasmobranchs. Liver size was not sexually dimorphic. Mature females had symmetric gonads in terms of mass, ovarian follicle number, and ovarian follicle size. Females carrying egg cases were found in April, September and October, which is consistent with previous observations around Malvinas Islands suggesting a year-round egg laying season. Bathyraja albomaculata was most abundant on the outer continental shelf and slope between 36º30’ and 45ºS (northern area). In contrast, the species, formerly reported to be abundant between 48º and 52ºS (southern area), was mostly absent there. These differences are coincident with the development of a fishery targeting skates in the southern area, while in the north B. albomaculata is mostly discarded alive.