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

Abstract

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 species is suffering over‐exploitation and its biomass has decreased drastically. The histological analysis of ovaries and the oocyte size frequency distribution of gravid females indicate that southern blue whiting is a batch spawner with determinate annual fecundity. The spawning season of M. australis in the south‐west Atlantic Ocean extends from August to October, with a main peak during September. Spawning females were recorded mainly in the waters south and south‐west of the Malvinas Islands, close to the 200 m isobath. Total fecundity of seven M. australis females ranged from 148 300 to 713 900 yolked oocytes (46–55 cm total length (TL)). The mean total fecundity was 477 700 (206 783 SD) oocytes for one 51 cm TL female. Mean relative fecundity 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 indicated 50% female maturity was reached at 37.8 cm. This value was similar to those reported for this species between 1980 and 1990.