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 (WT=0.00004LT3.44) was found to be significant at 1% level of significance and indicated positive allometric growth.  The Von Bertalanffy growth parameters of all fish were =119.35 cm, K=0.3 year-1, and t0 = -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 (Fopt= 0.26 year−1) and limit (Flim=0.35 year−1) reference points, indicating that the ribbonfish stock is at the risk of unsustainable exploitation.