Variations in growth, longevity and natural mortality for the protogynous hermaphroditic eightbar grouper Hyporthodus octofasciatus between the Indian and Pacific Oceans

Abstract

Increased fishing pressure on deep-water demersal fishes in relatively recent times highlights the need for a better understanding of their biology, demography and relative abundance. The eightbar grouper Hyporthodus octofasciatus is one of the largest species of Epinephelidae and is highly valued in relatively deep-water fisheries throughout the Indo-West Pacific region. Currently, information on the life history of H. octofasciatus is limited to the south-eastern Indian Ocean. We compared estimated life history parameters for H. octofasciatus from this region with the western central Pacific Ocean. Histological examination of gonads of H. octofasciatus from a wide length and age range (295-1740mm TL and 6-65 years) suggested that this species is a protogynous hermaphrodite in the Pacific Ocean, which is consistent with data for this species in the south-eastern Indian Ocean and its congeners. However, the maximum length (1740mm TL), asymptotic length (L<inf>8</inf>, 1912mm TL) and longevity (65 years) were much greater in the Pacific compared to the Indian Ocean (1509mm TL, 1166mm TL and 47-56 years), resulting in substantially different growth trajectories and a lower instantaneous rate of natural mortality in the Pacific Ocean (i.e., 0.06 vs 0.09 year<sup>-1</sup>). Such regional variations in life history traits across the Indo-Pacific need to be considered in assessments and management of H. octofasciatus stocks within and across jurisdictions.