the decline in the size of ribbonfish, trichiurus lepturus (linnaeus 1758), over the past decade in the persian gulf

Size-dependent variation in growth, mortality, and recruitment over time are potentially controlled by changes in length -frequency distribution that is dependent to capture probability. the changes in the length-frequency distribution of ribbonfish, trichiurus lepturus were studied along northern coasts of the persian gulf during the period 2008-2017. the length- frequency distribution of ribbonfish indicated the exploitation of larger sizes over the past decade. the mean total length was significantly smaller than the mean length recorded a decade earlier in 2008 (p<0.05). the length-weight relationship (w_t=0.00004l_t^3.44) was found to be significant at 1% level of significance and indicated positive allometric growth. the von bertalanffy growth parameters of all fish were l∞=119.35 cm, k=0.3 year^-1, and t_0 = -0.38 year. total, natural, and fishing mortality were estimated as 1.16 year^-1, 0.53 year^-1, and 0.63 year^-1. the annual instantaneous rate of fishing mortality was higher than the target (f_opt= 0.26 year^−1) and limit (f_lim=0.35 year^−1) reference points, indicating that the ribbonfish stock is at the risk of unsustainable exploitation.