Research Article: The decline in the size of ribbonfish, Trichiurus lepturus (Linnaeus ۱۷۵۸), 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 ۲۰۰۸-۲۰۱۷. 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 ۲۰۰۸ (p<۰.۰۵). The length-weight relationship (WT=۰.۰۰۰۰۴LT۳.۴۴) was found to be significant at ۱% level of significance and indicated positive allometric growth.  The Von Bertalanffy growth parameters of all fish were =۱۱۹.۳۵ cm, K=۰.۳ year-۱, and t۰ = -۰.۳۸ year. Total, natural, and fishing mortality were estimated as ۱.۱۶ year-۱, ۰.۵۳ year-۱, and ۰.۶۳ year-۱. The annual instantaneous rate of fishing mortality was higher than the target (Fopt= ۰.۲۶ year−۱) and limit (Flim=۰.۳۵ year−۱) reference points, indicating that the ribbonfish stock is at the risk of unsustainable exploitation.

Keywords:

Trichiurus lepturus , Size decline , Population dynamics , Persian Gulf