Importance of considering reproductive characteristics for management of marine fisheries

Abstract

Status of fish stocks in relation to fishing may differ from one area to another, but there is a general consensus that several fish stocks need effective management measures by taking into consideration different indicators of stock status. Through a review of literature, this paper shows the importance of integrating the reproductive characteristics into the plan for management and conservation of marine fisheries as well as ecosystems. Overexploited fishes display symptoms of (i) advancements in age and/or size at sexual maturity and (ii) reduction in fecundity in gonochoristic (bisexual) fishes. Protogynic hermaphroditic fishes show symptoms of advancement in sex/age at sex change and decrease in Reproductive Life Span (RLS). Consequent to these changes in reproductive characteristics, the Spawning Stock Biomass (SSB) will decrease leading to depletion and collapse of a stock or species of fishes. In response to advancement in Age at Sexual Maturity (ASM) and/or Size at Sexual Maturity (SSM), the depleted stock/species may display one of the following symptoms: (a) decrease in fecundity, as in European hake Meruluccius meruluccius, or (b) decrease in egg size, as in Gadus morhua or (c) both decrease in fecundity and egg size, as in roughy Hoplostethus atlanticus. The protogynics economize male and sperm availability by behavioral acts like spawning aggregation; however, the longer residency of such spawning aggregation in a particular site increases the vulnerability of reproductively active parents. Analyses of limited publications show that (i) overexploitation reduces not only male biomass but also female biomass and (ii) reduction in RLS to 50% in Available online at: www.mbai.org.in doi: 10.6024/jmbai.2014.56.1.01750s-08 female e.g. Epinephelus niveatus and 33% in male e.g. Pagrus pagrus through precocious sexual maturity and sex change.