TAC Assessment of Multiple Species and Single Fishing Gear^⍏: case study on mackerel and jack mackerel caught by the large purse seine fleet

This paper provides a total allowable catch assessment model for single fishing gear and multiple species fishery in South Korea. To estimate appropriate allowable biological catch of mackerel and jack mackerel caught by the large purse seine fleet within the territorial waters of South Korea, this paper uses an extended Beverton-Holt yield per recruit model and a biomass-based cohort analysis. The extended Beverton-Holt yield per recruit model adds two terms, a relative bycatch index (w_i) and a relative instantaneous fishing mortality index (a_i), to the original Beverton-Holt model. The reason for adding new terms is because the bycatch of those species caught by the large purse seine fleet is able to affect the instantaneous fishing mortality as well as the recruitment of each species. In conclusion, this paper suggests that the current allowable biological catch level of mackerel needs to be lowered to prevent overfishing of jack mackerel with the small stock due to bycatch.