Ecological and economic sustainability in fishery management: A multi-agent model for understanding competition and cooperation

Recent studies have shown that many marine ecosystems are experiencing an accelerating loss of population and biodiversity. It is apparent that there is a growing disparity between the available supply of fish and the desire of the growing world population to catch them. Although studies have begun to question the ecological sustainability of managed fishery systems, they often omit the corresponding effects on the economic sustainability of fishery industries. This is particularly important in rural coastal areas where the fishing industry is often a dominant employer. In this article, we analyze the interactions between economic and ecological dynamic systems using a multi-agent dynamic model of fishery management. Multiple agents (fishers) harvest multiple fish species and adapt the amount and allocation of their effort to their value functions, which are given as net profits of the fish harvest sold for a market price. This is largely unique in fishery models, since many econometric studies view fishers as represented by homogenous 'average' agents. We introduce and compare two different decision rules governing the behavior of fishers engaged in a competitive market. We demonstrate a situation where both behaviors lead to a decline of all fish stocks, as well as profits for most fishers. As an alternative, we introduce a cooperative approach in which fisheries jointly set sustainable limits for total harvest and effort that are then distributed to the fishers according to distribution rules. The simulation reveals that fish stocks and profits can stabilize at significantly higher levels in the cooperative case, leading to a continuous accumulation of capital for all fishers. This model demonstrates key aspects of overfishing conflicts that can be overcome through planned fishing quotas and cooperative market mechanisms. It also demonstrates a novel approach for simulating the dynamic behavior of heterogeneous fishers.