Seasonality matters: A multi-season, multi-state dynamic optimization in fisheries
本文构建了一个多季节、多状态的生物经济模型，运用动态规划求解最优捕捞策略，发现季节性禁渔或海洋保护区能形成永久均衡周期，而年度模型会忽略这种最优关闭。
Many biological and economic processes in fisheries occur seasonally though most of the extant literature tends to neglect periodicity. This work is an attempt to treat seasonality in a systematic way. We present a multi-season multi-state bioeconomic model and apply a periodic Bellman approach using dynamic programming to obtain the optimal feedback policy of each season. Our approach has rich potentials. It could deal with seasonal patterns of arbitrary uneven lengths: some may span years and some may occur within a year. Our numerical illustration demonstrates that a seasonal dynamic optimization model allows for naturally occurring seasonal moratorium or potentially a Marine Protected Area (MPA). It shows that there exists optimal dynamic paths that develop into a permanent equilibrium cycle, which consists of one harvesting season followed by a moratorium period. This indicates an optimal closure of the fishery that a yearly model would overlook. Fishing pressure on the mature stock elicits even heavier harvesting in the next season on the same group. A protective moratorium of the immature hinders the value of the whole stock.