Life‐history strategies of the rock hind grouper Epinephelus adscensionis at Ascension Island

Abstract

Epinephelus adscensionis sampled from Ascension Island, South Atlantic Ocean, exhibits distinct life-history traits, including larger maximum size and size at sexual maturity than previous studies have demonstrated for this species in other locations. Otolith analysis yielded a maximum estimated age of 25 years, with calculated von Bertalanffy growth parameters of: L = 55·14, K = 0·19, t = -0·88. Monthly gonad staging and analysis of gonad-somatic index (I ) provide evidence for spawning from July to November with an I peak in August (austral winter), during which time somatic growth is also suppressed. Observed patterns of sexual development were supportive of protogyny, although further work is needed to confirm this. Mean size at sexual maturity for females was 28·9 cm total length (L ; 95% C.I. 27·1-30·7 cm) and no females were found >12 years and 48·0 cm L , whereas all confirmed males sampled were mature, >35·1 cm L with an age range from 3 to 18 years. The modelled size at which 50% of individuals were male was 41·8 cm (95% C.I. 40·4-43·2 cm). As far as is known, this study represents the first comprehensive investigation into the growth and reproduction of E. adscensionis at its type locality of Ascension Island and suggests that the population may be affected less by fisheries than elsewhere in its range. Nevertheless, improved regulation of the recreational fishery and sustained monitoring of abundance, length frequencies and life-history parameters are needed to inform long-term management measures, which could include the creation of marine reserves, size or temporal catch limits and stricter export controls.