Population biology and assessment of the orange-spotted grouper, Epinephelus coioides (Hamilton, 1822), in the southern Arabian Gulf

The demography and status of Epinephelus coioides in the southern Arabian Gulf were established using a combination of size frequency, biological and size-at-age data. Transverse sections of sagittal otoliths were characterised by alternating translucent and opaque bands. Edge analysis revealed an annual periodicity of formation with the opaque zone being deposited during the summer months in association with increasing seawater temperature. Parameter values of the von Bertalanffy growth function fit to size-at-age data (males and females combined) were: k = 0.14, L-infinity = 97.9 cm (L-T) and t(o) = - 1.5 years. There was a well defined peak in reproductive activity with spawning occurring during May and a significant female bias in the male:female sex ratio (1:48). The mean size at first capture (28.9 cm L-T) was considerably smaller than both the mean size at sexual maturity for females (43.5 cm L-T) and the size at which yield per recruit would be maximised (59.1 cm L-T). The fishing mortality rate (F=0.78 year(-1)) was by far in excess of the precautionary target (F-opt = 0.10 year(-1)) and limit (F-limit = 0.13 year(-1)) biological reference points. In addition to growth overfishing, the stock was considered to be recruitment overfished as the biomass per recruit was less than 10% of that at the theoretical unexploited level. The results suggest that an increase in the mesh size of traps in combination with a substantial reduction in fishing effort will be required if resource conservation and stock rebuilding objectives are to be achieved for E. coioides in the southern Arabian Gulf. (C) 2005 Elsevier B.V. All rights reserved.