Abstract

An object oriented, agent-based model is developed and used to help explain the dynamics of the interaction between individual fishing units and individual fish in a small scale fishery, and how these interactions influence the estimation of catch per unit of effort (CPUE) as an abundance index. The model allows animals to have individual characteristics and interact spatially with one another. A fleet exerts fishing effort on the available fish stocks. Each vessel has individual characteristics including a varying propensity toward risk taking, and based on this factor, will alter targeting behavior (selectivity) to maximize revenue. Various scenarios are explored and suggest that while standardizing CPUE may be practical and lead to unbiased estimator of abundance for large-scale fisheries targeting a single species, the same estimators are unlikely to perform as well on data derived from small-scale commercial fisheries. Fleets from these fisheries frequently redistribute fishing effort across multiple species and gears causing changes in catchability that are difficult to incorporate in traditional CPUE standardization procedures. A disaggregated, individual vessel-based analysis can be implemented in order to evaluate the robustness of such estimators

PDF Preview