Study of Natural and Fishing Mortality and Exploitation Rate of Largehead hairtail, Trichiurus lepturus (Linnaeus, 1758) from the Northern Persian Gulf, Iranian waters

Monthly data of length composition for Trichiurus lepturus, were recorded from the Northern Persian Gulf (Bushehr province), from January 2010 to December 2010. Length frequency data analyzed with ELEFAN software. The maximum measured pre-anal length was 29.75±4.62 cm. The parameter values of the von Bertalanffy growth function were: L?= 124 cm; k = 0.91 year-1 and t0= 0.011 year-1. The estimated value of the instantaneous rate of total mortality (Z) based on length converted catch curve was 3.76 yr-1. The instantaneous rate of natural mortality (M) based on the growth parameters and mean environmental temperature was 1.09 year-1. The annual instantaneous fishing mortality rate (F) was estimated to be 2.67 yr-1. The exploitation rate (E) was 0.71 year-1. It indicate that resource of T. lepturus is heavily exploted,heavily over-exploited, and some measures of management should be implemented to protect the T. lepturus population in the Northern Persian Gulf.