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Abstract: Effects of maternal age–size and condition on oocyte dry weight were analysed for Merluccius hubbsi. Samples of mature females were collected in the Patagonian spawning area during 10 research surveys carried out between 2000 and 2005. Dry weight of 50 hydrated oocytes ranged from 0.80 to 1.90mg. Relationships of this variable with total length and age were best described by a logarithmic model during the spawning peak. At the beginning and at the end of the reproductive season no significant relationship between these variables was observed, but a decrease in egg dry weight was detected during the spawning period. In general, young spawners (≤5-year-old) showed more variability in egg dry weight, which was associated with a reproductive season shorter than that of old females. Relative condition factor did not shows a significant relationship with oocyte dry weight, and mean values of this index were similar for different months of the spawning seasons analysed. [Copyright &y& Elsevier]

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]

Presents a study which hypothesized that a change in spawning site for the Patagonian stock of Argentine hake, or Merluccius hubbsi, can affect species recruitment. Background on Argentine hake; Relationship between egg production and recruitment; Abundance of hake and location of spawning females; Spatial pattern of M. hubbsi spawning aggregation inshore and offshore of the north Patagonian area in Argentina and Chile between 1988 and 2001.

The reproductive biology of the Argentine hake, Merluccius hubbsi, inhabiting the Patagonian waters at south of 41°S was studied by using histological analysis of the ovaries. The samples were collected during the reproductive season from December 2000 to March 2001. Argentine hake is a batch spawner with indeterminate annual fecundity that spawns from the end of spring to summer with a main reproductive peak in January. Old females (>5 years) had a spawning season longer than young individuals. Spawning frequency, determined from the proportion of females with day 1 postovulatory follicles (POF), ranged between 0.10 and 0.15, being higher during the spawning peak. At these frequencies, a female hake would spawn on average 14 times between December and March. Batch fecundity (BF) was positively correlated with total length, total weight (without ovary) and age, ranging between 100,000 (32 cm TL) and 2,300,000 (87 cm TL) hydrated oocytes. Monthly egg production showed considerable variation during the spawning season with the main pulse of production in January (57% of the eggs spawned during the period). In spite of its low frequency, larger females showed the same level of contribution to the reproductive potential of the stock than young females. From December to February the number of eggs produced by unit-weight of hake did not change. In March the relative egg production decreased significantly coinciding with an increase of atresia. [Copyright &y& Elsevier]