The FAO has warned that fishing rates from natural marine reserves have reached alarming levels such that nearly 90 percent of global fish stocks are either fully-fished or over-fished. Furthermore, global per-capita fish consumption and general demand continues to rise. Considering both these ecological and economic realities is essential to developing long-term sustainable fishing strategies. By incorporating mechanisms to optimize profit and employment, studies have begun to facilitate potential strategies to manage the economic drivers causing unwillingness or inability to handle short-term costs of reduced fishing. However, the advances made in studying the economic components of these socio-ecological systems have not been matched by the traditional methods used to measure ecological costs of extraction. The maximum sustainable yield (MSY) for a particular stock is often based on single-species models which neglect the influence of the complex dynamical effects from the surrounding communities. By incorporating the dynamics of fishing effort into complex, realistic network models of fishery ecosystems, our research can more concretely ask: How does food web structure drive the effect of fisheries on food webs and how do different economic models affect the sustainability of fisheries?
Results/Conclusions
Building upon previous efforts, we took steps toward synthesizing food web ecology with natural resources economics. We did this by modelling food-web dynamics using the allometric trophic network (ATN) framework to which we added either fixed or variable fishing effort that depends on harvest and yield price. While we find that the initial direct effects on the biomass of the extracted species correlates with the level of fishing effort, the longer term effects on overall food-web structure and community biomass depend upon the identity and connectivity of the species harvested. Intuitively, the structural properties of the food-web itself feed back into the effects of different extraction rates in complex ways. The additional complexity of variable fishing effort through different economic strategies makes clear the need to consider how to measure economic sustainability in such oscillating systems when many traditional economic models look for dynamic equilibrium. Similarly, the optimal ecologically sustainable strategy can vary depending whether sustainability is measured through total biomass of the fished species, biomass of the overall community, the number of species, or diversity indices. We will explore the needs to develop clear metrics and goals in the search for sustainable bioeconomic endeavors.