© 2005 International Council for the Exploration of the Sea
Reproductive biology and abundance of the white-dotted skate, Bathyraja albomaculata, in the Southwest Atlantic
a Universidad Nacional de Mar del Plata, Departamento de Ciencias Marinas Funes 3350, B7602AYL Mar del Plata, Argentina
b Dalhousie University, Department of Biology 1355 Oxford Street, Halifax, NS B3H 4J1, Canada
c Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), and Universidad Nacional de Mar del Plata, Departamento de Ciencias Marinas Mar del Plata, Argentina
d Instituto Nacional de Investigación y Desarrollo Pesquero Paseo Victoria Ocampo s/n, B7602HSA Mar del Plata, Argentina
*Correspondence to L. O. Lucifora: tel: +1 902 4942146; fax: +1 902 4943736. e-mail: luis.lucifora{at}dal.ca.
Size at maturity, sexual dimorphism, gonad development, and abundance of white-dotted skate, Bathyraja albomaculata, were assessed along its geographic range in the Southwest Atlantic, from Uruguay to Tierra del Fuego (Argentina). In all, 291 specimens from eight research cruises conducted between 1998 and 2003 were examined. Length–mass relationships were sexually dimorphic, adult females being significantly heavier than males of the same length. The largest female observed was 762 mm total length (LT), and 50% maturity (LT50) was attained at 653 mm LT. The largest male was 732 mm LT, and male LT50 was 628 mm LT. Female and male LT50 were not significantly different and were about 86% of observed maximum size, similar to other Bathyraja species. The lack of sexual dimorphism in size at maturity and the slight difference in maximum size between sexes support the hypothesis of relaxation of selection for large female size in oviparous elasmobranchs. Liver size was not sexually dimorphic. Mature female gonads were symmetrical in terms of mass, and similar in ovarian follicle number and size. Females carried egg cases in April, September, and October, consistent with previous observations around the Islas Malvinas and suggesting year-round egg laying. Bathyraja albomaculata was most abundant on the outer continental shelf and slope between 36°30'S and 45°S (northern area). In contrast, it was generally absent between 48°S and 52°S (southern area), a region where it was formerly reported as abundant. These differences are coincident with the development of a fishery targeting skates in the southern area, whereas in the north B. albomaculata taken as bycatch are mostly discarded alive.
Keywords: Argentina, elasmobranch, life history, oviparity
Received 30 May 2005; accepted 23 August 2005.
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