Population dynamics of the Spanish mackerel (Scomberomorus commerson) in coastal waters of Oman Sea

Length composition data of narrow-barred Spanish mackerel, Scomberomorus commerson (Lacepede 1800), landed between April 2002 to March 2004, were monthly used to estimate the growth, mortality and exploitation parameters of the stock. Maximum fork length and weight were 170 cm and 38 kg, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L¥=178 cm (FL); K=0.28 and to= -0.36 years. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z=0.95 year-I. Natural mortality based on growth parameters and mean environmental temperature (T=26.5°C) is M=0.36 year-1. Furthermore, the annual instantaneous fishing mortality rate of 0.59 year-I was by far in excess of the precautionary target (Fopt=0.18 year-1) and limit (Flimit=0.24 year-1) biological reference points, indicating that the resource is heavily over-exploited and the management of this species should be implanted rapidly if they are to remain sustainable.