Reproductive biology of species of Bathyraja (Chondrichthyes, Rajidae) on the Argentinean continental shelf.

SCENNA, LORENA B.; BARBINI, SANTIAGO A.; DIAZ DE ASTARLOA, JUAN. M.; FIGUEROA, DANIEL E.; COUSSEAU, MARÍA B.

New Orleans, E.E.U.U.

Congreso; Joint Meeting of Ichthyologists & Herpetologists; 2006

American Society of Ichthyologists and Herpetologists - American Elasmobranch Society

Skates have become the sixth most economically important fish resource (over a total of 46 commercial fish species) landed by commercial bottom-trawlers in Argentina. Biological data of skates (especially on reproduction) are needed to improve management of their fisheries. Despite the abundance and diversity of Bathyraja genus in Argentinean waters (eight species), very little is known about its basic biology and ecology. Specimens of Bathyraja brachyurops (n=383), B. macloviana (n=360), B. albomaculata (n=229), B. magellanica (n=120), B. griseocauda (n=88), B. multispinis (n=29), B. cousseauae (n=26) and B. scaphiops (n=16) were collected from research cruises carried out by the Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP, Argentina) since 2003. Study area extended along Argentinean continental shelf between 36°S and 55°S. Size at maturity of the four most abundant species was assessed from the allometric growth pattern of uteri, oviducal glands and clasper with respect to total length (LT). The length at which 50% of the skates were sexually mature (LT50) was estimated from a logistic ogive fitted to the data using maximum-likelihood approach. Females of B. brachyurops and B. macloviana matured at a larger size than males, while both sexes of the other two species appeared to attain sexual maturity at about the same LT. LT50 in both sexes of the four species was achieved at >75% of the maximum LT observed. Females carrying egg cases in their uteri (in different egg case formation stage) were found, and the date and geographic position of these females were recorded to identify egg-laying seasons and areas. Furthermore, egg cases were removed and preserved in order to describe them. Other reproductive characteristics of these species are being analysed. These preliminary results are part of an ongoing study about biology, ecology and biodiversity of species of Bathyraja on the rgentinean continental shelf.