Multi-species approach for stock management of kilka fish (genus: Clupeonella) in Iranian waters of the Caspian Sea

There have been recent changes in the Caspian Sea ecosystem, such as those due to changes in sea level or those caused by the invasive ctenophore, Mnemiopsis leidyi. It is believed that these changes had significant impacts on the absolute and relative abundance of the commercially important anchovy kilka (Clupeonella engrauliformis) and common kilka (C. cultriventris caspia) leading to decline in the former and increase in the latter species in the Iranian waters. Consequently, more rigorous management is required. The mixed-species yield-per-recruit was applied to the Iranian conical lift-net. This study showed that the pooled fishing mortality at F40% was 0.70 yr-1 which is higher than fishing mortality of main species of anchovy kilka, but lower than the pooled fishing mortality at F0.1 (0.75 yr-1). The ABC under the best information available, at pooled species reference points for two species of anchovy and common kilkas, was estimated to be 8260mt. An analogous goal in a multispecies situation would be fishing at a fishing level, denoted Fws, such that the fishing rate for the weakest stock (in this case; anchovy kilka) does not exceed its F40% rate. Under this harvest strategy at F40% for anchovy kilka, it is suggested that the ABC of pooled species of anchovy and common kilkas was estimated 7920mt to be selected in kilka fishery in Iranian waters.