Reproductive ecology of the female pink cusk-eel (Genypterus blacodes) - Evaluating differences between fishery management zones in the Chilean austral zone

Abstract

The pink cusk-eel (Genypterus blacodes), a benthic-demersal fish confined to the southern hemisphere, supports an important commercial fishery in Chile where it is exploited over an extensive geographic area. Although the fishery was originally divided into a northern (41º28′–47º00′S) and southern (47º00′–57º00′S) zone for the purposes of fisheries management, recent studies have reported significant differences in life history parameters between these zones. Individuals from the southern zone reached larger asymptotic sizes and possessed higher survival rates compared to the northern zone. We estimate and compare the gonadosomatic index (GSI), shape of the maturity ogive, and length at 50 % maturity (L_50%) of female G. blacodes between management zones and across time using biological data collected from the industrial fleet between 1985 and 2009. Females in the northern zone had higher monthly mean GSI than females in the southern zone. Our analyses also revealed L_50% to be significantly higher in the southern zone than in the northern zone from 1985 to 2009. The significant differences in life-history traits between fishery management zones agree with the trade-offs predicted by Charnov’s life history theory. Together these results provide additional support for the hypothesis that two separate stocks exist and suggest that females from the northern zone have developed a life-history strategy, which favours early maturation and a proportionally greater investment in reproduction than females from the southern zone.