Analyses of yield and spawning stock biomass per recruit for the South Atlantic albacore (Thunnus alalunga)

Yield per recruit and spawning stock biomass per recruit models were developed to study the interaction between the Taiwanese longline and South African baitboat fisheries for South Atlantic albacore. The Taiwanese longline fleet was found to have a logistically-distributed selectivity pattern with many age classes contributing significantly to the catch. The South African baitboat fleet, on the other hand, had a normally-distributed selectivity pattern with relatively few ages contributing to the catch. This fact profoundly influenced the response of yield and spawning stock biomass per recruit to different levels of fishing mortality exerted by each fleet. The results indicated that, in order to maximize total equilibrium yield per recruit to about 2.2 kg, the South African fishing mortality rate should probably be increased substantially whereas the Taiwanese fishing mortality rate is near optimal. In order to keep the spawning potential ratio above the 20% minimum suggested by Goodyear [Coll. Vol. Sci. Pap. 32 (2) (1989) 487], the Taiwanese apical fishing mortality rate should not exceed 0.55 yr−1, regardless of the South African apical fishing mortality rate. [Copyright &y& Elsevier]