Profit and equity trade-offs in the management of small pelagic fisheries: the case of the Japanese sardine fishery

The management of small pelagic fisheries is notoriously difficult due to environmental regime changes that generate multi-decadal cyclic fluctuations in stock abundance. Lagged management responses to environmental factors can amplify the effects of fishing and may even result in stock collapse. In this paper, we develop an age-structured bioeconomic model to explore the effectiveness of alternative management approaches for cyclically fluctuating small pelagic fish stocks. The fishery outcomes are evaluated against the overall profit of the fishery and the intertemporal distribution of fishing profits. The model is parameterised for the Japanese sardine fishery, once the largest fishery in Japan, which has experienced a prolonged period of stock collapse over the last 100 years. The results show that the duration of fishery collapse is mostly determined by the extent of cyclic fluctuations in the recruitment of immature sardines, but that the effects of the fluctuations on the fishery are heightened by the cumulative impact of fishing. We further show that restricting fishing reduces the fishery's overall profits, but smooths the intertemporal distribution of profits, resulting in greater intergenerational equity. This income smoothing effect is particularly pronounced when the stock exhibits high levels of cyclic fluctuations.