Developing a bioeconomic model for WCPO tuna fisheries to assess potential economic outcomes under alternative management options

1 Developing a bioeconomic model for WCPO tuna fisheries to assess potential economic outcomes under alternative management BLOCKINoptions Executive BLOCKINSummary Globally, the value of including economic information in the management of fisheries is being increasingly recognized. For most fisheries, the long‐term maximum economic yield (MEY) that can be achieved occurs at higher biomass levels than the long‐term maximum sustainable yield (MSY), therefore providing a buffer against scientific uncertainties to help ensure ecological sustainability of the resource as well as providing higher economic returns. The purpose of this paper is to present a preliminary bioeconomic model for WCPO tuna fisheries. The model will allow both an examination of management limits that maximize a specified economic outcome (e.g., fleet profitability), and a comparative analysis of economic outcomes by gear for any set of management options. Also, the model allows for the analysis of biological consequences of fishery conditions that achieve various economic outcomes. The 2014 MULTIFAN‐CL stock assessments for bigeye, skipjack and yellowfin tunas and the 2012 assessment for south Pacific albacore are used as the basis of the biological and fishery dynamics. For the economic component, the net present value (NPV) of profits is calculated over a 20‐year time horizon in order to provide a measure of the relative economic outcomes of different management options. In the projections, effort for four defined fisheries – tropical longline, southern longline, and associated (fish aggregation device and floating log sets) and unassociated (free‐school sets) purse seine – was varied individually between +25% and ‐50% of 2012 levels. Future recruitment was assumed to follow the long‐ term spawner‐recruitment relationship. Some examples of the types of patterns found in these preliminary results include:  Catch revenue can be expected to fall under 2012 effort levels, with southern and tropical longline fleets becoming unprofitable. Profits are predicted to exist only in the purse seine fishery;  There is scope for increasing profits through reductions in effort. Increased stock sizes are expected to increase profits through increased catch per unit effort, but this conclusion is based on standard catch / abundance relationships and developing alternative models of the relationship between abundance and fishing success will be crucial to determining robustness of results; and  Positively, the abundance of all four species is predicted to increase under scenarios that maximize NPV of profits. As the bioeconomic model is further developed, there are many applications and extensions that could be …