A multi-species catch reduces risk and enhances stability in the fishery? Implications from a portfolio analysis of the Hokkaido setnet fishery

The large-scale setnet fishery is a traditional multispecies fishery in Japan. This fishery is vital to the seafood industry to maintain stable annual landing volume and create employment in coastal areas. The 2018 fisheries policy reforms decided to expand the total allowable catch (TAC) managed species and introduce single-species-based fishing quotas. Such quantitative management may lead to landing regulation on specific species, potentially destabilizing revenue of the large-scale setnet fishery as the multispecies fishery. This study has quantified the impact of landing regulation on specific species due to the management measures of single-species-based fishing quotas on revenue of the large-scale setnet fishery in Hakodate, Hokkaido, by applying the fishery portfolio analysis. The results show that, when landing regulation on Japanese flying squid Todarodes pacificus, not only is average revenue reduced by about 52%, but the revenue risk increased by about 120%, and the portfolio effect decreased from 8.1 to 3.5 compared with the case without landing regulation. These results indicate that landing regulation on specific species due to the management measures of single-species-based fishing quotas not only reduces average revenue but also destabilizes revenue from the large-scale setnet fishery.