Spawning and reproductive potential of the Northern stock of Argentine hake (Merluccius hubbsi)

The reproductive activity of the Argentine hake Merluccius hubbsi Northern stock takes place mainly during autumn and winter in the Argentine Uruguayan Common Fishing Zone (AUCFZ) (34°30′–39°30′ S and 52–59° W). At the present scarce information about spawning pattern and reproductive potential of M. hubbsi of this area is available. Therefore, the purpose of this work is to analyze variation of the spawning area, estimate batch fecundity, spawning frequency, oocyte dry weight and size at maturity of Northern stock of Argentine hake.The results showed that the main reproductive activity of this hake stock during April 2003 occurred between 37° and 38°30′ S while in May 2009 spawning groups moved north to the 37° S. In both cases reproduction took place near the 50 m isobath, in a temperature range between 9 and 15 °C, in coincidence with a bottom thermal front. Size at maturity for hake males (25.7 cm TL in April 2003 and 26.8 cm TL in May 2009) was significantly less than that estimated for females (29.3 cm TL in April 2003 and 32.6 cm TL in May 2009), and also showed significant differences for individuals of the same sex in different years. Spawning frequency, estimated in one spawning every 13 days during May 2009, was about haft to that reported for the Southern hake stock, which distributed between 41° and 55° S. Batch and relative fecundity values estimated for the Northern stock in April 2003 showed no significant differences with data obtained in May 2009, and were similar with those obtained for the Southern stock during its reproductive peak. The oocyte dry weight for spawning females of the Northern stock was lower than that estimated for the Southern stock, which might be associated with the size composition of each reproductive group.