Reproductive biology and growth of the yellowbelly rockcod Epinepheluse marginatus (Serranidae) from South-East Africa

Abstract

Investigation of the reproductive biology and growth of the yellowbelly rockcod Epinephelus marginatus from South-East Africa confirms that the species is a monandric protogynous hermaphrodite, i.e. males are derived from females, probably as a result of environmental or social cues. Spawning occurred during summer, female size-at-50% maturity was 622mm TL and the smallest male recorded was 800mm TL. Sex ratios of mature fish were female biased (1:0.18). Tetracycline marking revealed that deposition of growth bands is annual, and the von Bertalanffy growth parameters determined by means of otoliths were L∞ = 1 249mm TL, k = 0.09 year^–1 and t₀ = –1.43 years. The species is therefore long-lived, slowgrowing and matures late. Other studies indicate that E. marginatus aggregate for spawning, and tagging work has shown that they exhibit high site fidelity. The life history of the species indicates that it is vulnerable to overexploitation.

Keywords: grouper, growth, hermaphroditism, protogyny, Serranidae

African Journal of Marine Science 2006, 28(1): 1–11