Stock assessment and reproductive biology of bluespotted seabream Pagrus caeruleostictus (family: Sparidae)

Abstract

Bluespotted seabream Pagrus caeruleostictus, a member of the family Sparidae, is one of the high-priced seabream species in Ghana. Although the fish has been exploited in the Gulf of Guinea for over hundreds of years, there is scanty information on the state of the fish stock. Hence, we sought to investigate the exploitation status and aspects of the reproductive biology of the species by collecting monthly length and weight data for 18 months (February 2016 to July 2017). These data were fitted to growth and mortality models. The sexual maturity, fecundity and spawning seasons were also determined within the same period. The growth model of the fish revealed that the asymptotic length (L_∞) and growth coefficient (K) values determined were 52.7 cm (total length) and 0.52 year⁻¹, respectively. The mortality models also showed that the fishing mortality (F) of the fish was 2.20 year⁻¹, whereas its natural mortality (M) was 0.83 year⁻¹, with F/M > 0.5 indicating that the fish is over-exploited. The lengths at first sexual maturity (L_m) of the males and females were 36.2 and 28.0 cm, respectively. Pagrus caeruleostictus, which was found to be highly fecund, had two spawning periods in a year, occurring in September and March, both with unimodal ova diameter frequency distributions. Based on these findings, we recommend that catch limits and other appropriate management measures (e.g. temporal and spatial closures) should be prescribed for the seabream fishery in the Gulf of Guinea to ensure the sustainability of the fishery.