Fisheries research represents one of the most interesting and intensely studied interactions between economic and ecological systems. While many of such interactions involve the consumption of primary producers at the base of highly managed and simplified agricultural or silvicultural ecosystems, the industrial-scale hunting of fishes exploits fish much higher on food chains and more directly dependent on the dynamics of more complex and much less managed ecosystems. In stark contrast to such complexity, fisheries science and economics are largely based on models that explicitly consider only the target species despite many long-standing calls for ecosystem approaches to managing fisheries. Here, we respond to such calls by developing an ecosystem approach that explicitly considers the complex web of interdependent species that determine the abundance of fishes and their response to fishing pressure. Our initial development explores a three-trophic-level Allometric Trophic Network model informed by consumer-resource body-size ratios and nonlinearities in feeding behavior. We then compare our findings with those from simpler yet classic models.
Results/Conclusions
Our results illustrate significant differences between expectations based on the simplistic logistically growing populations and the more realistic Allometric Trophic Network models. Under virtually all conditions, fishery exploitation at the optimum rate predicted by the logistic model results in the extirpation of similarly parameterized species in the Allometric Trophic Network models. Given the widespread collapse of fisheries whose management is largely based on logistic population models, our results provide a noteworthy explanation of widespread fisheries failure. Regarding fish body size, larger bodied species can lead to larger amounts biomass yields and profit using less harvest effort. This suggests there is an especially large return on financial investment when exploiting larger bodied fishes. However, maximizing profit when exploiting smaller bodied fishes requires comparatively greater effort, which implies greater employment that decreases profit, return on investment, and yield of fish biomass. We summarize model behavior by visualizing how bioeconomic regimes makes sustaining coupled natural-human systems more difficult as the body size of targeted fishes decrease. We conclude by showing how our findings form essential steps towards the next research phase that has preliminarily incorporated much more species diversity and ecological complexity.