Seasonal egg production pattern of the Patagonian stock of Argentine hake ( Merluccius hubbsi)

Abstract

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.