Reproductive pattern of the Patagonian stock of Argentine hake (Merluccius hubbsi)

Abstract: This study is the first analysis of the spatial distribution pattern of Patagonian hake during the spawning period, from December to March. In December, spawning females were concentrated in a small area located between 43° and 44°S. During January and February, reproductive activity expanded to the southern area, three main spawning aggregations being observed. In the late March, isolated spawning schools could be observed offshore. Most of the hydrated or ripe females were detected in waters with bottom temperatures higher than 9°C. As the reproductive season progressed, an increase in proportion of postovulatory follicles (POF) and atresia was noted. In general, males were more abundant than females except in January, when large numbers of larger females arrived on the spawning ground. In late March, the oldest females left the area while a large number of immature fish arrived from the nursery ground located south of the study area. The Patagonian hake showed a main reproductive peak in January–February, when about 10% of females had hydrated oocytes and new POFs. Males exhibited an increase of length at maturity (L 50%) during the spawning season, ranging from 27 to 30cm TL (p <0.001). In the case of females, L 50% was similar from December to February (about 32cm TL), but increased significantly in March (34cm TL; p <0.001). This increment in the L 50% was a consequence of the incorporation of immature females in the spawning area. We conclude that a correct management of Patagonian hake population must take account of the spatial and temporal variations of the reproductive pattern of this species before assessing the spawning stock size or deciding the closure of the spawning area. [Copyright &y& Elsevier]