Evaluation of the Japanese eel fishery in the lower reaches of the Kao-Ping River, southwestern Taiwan using a per-recruit analysis

Yield-per-recruit (YPR) and spawning stock biomass-per-recruit (SPR) models were used to investigate the impact of fisheries on the yellow and silver eels of the local stock of Japanese eel (Anguilla japonica) in the Kao-Ping River (southwestern Taiwan). The current fishery status and uncertainty of biological reference points (e.g., Fmax, F0.1, F40%, and F50%) were assessed using Monte Carlo simulation. Probabilities of the current fishing mortality rate for yellow and silver eels (Fcur) being higher than Fmax ranged 15-20%, and being higher than F0.1 ranged 58-66%. The probabilities of Fcur being higher than F40% and F50% ranged 26-93% and 73-99%, respectively. The Japanese eel in the lower reaches of the Kao-Ping River appeared to be fully exploited in terms of YPR. This local stock is also subject to a high risk of recruitment overfishing because the contribution of the SPR of the local stock to the entire Japanese eel stock is possibly below a minimal acceptable level (40%). Estimates of F0.1 and Fmax, and to a lesser extent those of F40% and F50%, were relatively robust, but estimates of the maximal YPR and SPR at Fcur were highly sensitive to the uncertainty of the input parameters.