Developing a new ecosystem-based management approach: using ecosystem models to calculate a better estimate of population scale for single-species models

E/PD-13

The single-species models used to manage quotas for individual fishery stocks rely heavily on estimates of population “scale” (abundance). For apex predators such as tunas, sharks and swordfish, estimates of virgin stock biomass are difficult to generate because their population scale is heavily dependent on the state of the ecosystem, including prey availability, primary production and environmental factors. Apex predators are also more susceptible to overfishing. The Fellow will compare the results of two population models for common thresher sharks (Alopias vulpinus), a migratory apex predator with considerable uncertainty in their stock status. The first model will be a traditional fisheries single-species dynamic model. The Fellow will then develop a second model that includes non-traditional data and ecological processes. Comparing the two models will identify the key drivers of population dynamics, strengths and shortcomings for each approach. The Fellow will also identify methods to utilize ecosystem-level data to generate more robust estimates of population scale for use in single species stock assessment.