Spawning pattern, length at maturity, and fecundity of the southern blue whiting (Micromesistius australis) in the south-west Atlantic Ocean

Southern blue whiting (Micromesistius australis Norman. 1937) inhabits the waters of the Southern Hemisphere, and in the south-west Atlantic Ocean is distributed over an area next to the Malvinas Islands. At present, this spe cies is suffering over-exploitation and its biomass has decreased drastical ly. The histological analysis of ovaries and the oocyte size frequency dist ribution of gravid females indicate that southern blue whiting is a batch s pawner with determinate annual fecundity. The spawning season of M. austral is in the south-west Atlantic Ocean extends from August to October, with a main peak during September. Spawning females were recorded mainly in the wa ters south and south-west of the Malvinas Islands, close to the 200 m isoba th. Total fecundity of seven M. australis females ranged from 148300 to 713 900 yolked oocytes (46-55 cm total length (TL)). The mean total fecundity w as 477700 (206783 SD) oocytes for one 51 cm TL female. Mean relative fecund ity was 706 (258 SD) oocytes per g female weight. ranging from 277 to 967. The percentage of sexually mature females for each total length class indic ated 50% female maturity was reached at 37.8 cm. This value was similar to those reported for this species between 1980 and 1990.