As global common-pool resources, many highly migratory fish stocks are overexploited and so fishers must work harder and harder to catch fewer and fewer fish. One result of this international tragedy of the commons is the sudden collapse of once-abundant stocks, such as the Pacific anchovetta and the North Atlantic cod, along with the fisheries they supported. On the other hand, for some overfished stocks such as northern Atlantic swordfish and eastern Pacific bigeye tuna, countries have cooperated and invested to reduce harvests, giving the stocks a chance to rebuild and the fisheries time to recover. Our project will identify the major sources of stability and instability that lead to such wide variation across otherwise similar systems. We will do this by creating, validating, and exploring 'Fishscape', a fully integrated, geo-spatial model of the international fishery targeting tropical tunas in the eastern Pacific Ocean (EPO). Coupling the human and natural elements in this complex system - the oceans, the fish, the fishers, the markets, and even the political policies - is the only way to fully understand the observed dynamics of resilience and collapse. By connecting realistic models of oceanographic conditions, fish population dynamics, and fisher behavior, Fishscape will shed light on still-unanswered key ecological questions, such as the relationships among nutrient availability, ocean currents, and reproductive success in a pelagic environment. Realistic assumptions about fishers' biases and shortcuts will also be integrated into Fishscape, yielding measures of the effects of factors like skipper skill, technological change, and market forces on relative gains among national fishing fleets. Once the model is cross-validated, the project will use robust decision making methods to explore through simulation over a wide range of social and ecological factors to discover what makes the system resilient and what leads to instability. Specifically, we will test three meta-scenarios: (1) climate change, (2) increasing price of oil, and (3) technological improvements, in order to identify sources of stability and instability within the system.
Top predators like tuna are critical to marine ecosystems, global food supplies, and international industries. Identifying sources of resilience or collapse in these systems could prevent much of the suffering that has been seen in other fisheries. Fishscape provides a tool that explores relative and absolute gains. It will break down barriers to cooperation by moving focus away from conflict over who gets what - and the related inability to prevent the decline of stocks - to agreement on management that can improve conditions for everyone, even the fish. Participation in the Fishscape education program should lead people to think about environmental trade-offs differently: as a complex but comprehensible part of daily life, rather than as a desperate search for a single sub-optimal solution.
