Study of the natural and fishing mortality and exploitation rates of bigeye kilka (Clupeonella grimmi) in the southeast part of the Caspian Sea (Babolsar)

摘要

The natural, fishing and total mortality survival and exploitation rates of bigeye kilka were studied. The survival rate and natural mortality were calculated using catch curve and Pauly methods, respectively. Natural and fishing mortality have been estimated up to 0.881 and 0.309 yr-1, respectively. According to the catch curve method, the annual survival rate of bigeye kilka has been estimated to be 0.304 yr-1. Owning to this survival rate, the instantaneous coefficient of the total mortality of bigeye kilka has been estimated up to 1.19 yr-1, while the exploitation rate of bigeye kilka has been estimated up to 0.260. The catch amounts of bigeye kilka decreased gradually mainly due to overfishing, predators and ecological disturbances which occurred in the Caspian Sea. Using the conclusion of this study and the previous studies of other researchers, it is suggested that the population of bigeye kilka were overexploited in the past years and were vulnerable to their natural predators.