Quantitative Decision Analysis for Sport Fisheries Management

Abstract

Fisheries managers often are faced with difficult decisions on how to satisfy needs of the public while maintaining or restoring important sport fisheries. Such decisions are fraught with complexity and uncertainty associated with both ecological systems and multiple management objectives and alternatives under consideration. Quantitative decision analysis provides a means to formalize these complexities into a framework consisting of probabilistic relationships among management actions, sources of uncertainty, and management outcomes. We present an example of quantitative decision analysis for managing largemouth bass (Micropterus salmoides) in West Point Reservoir, Georgia. We developed the decision model to choose among four length limit alternatives: no minimum, 305-mm, 356-mm, and 406-mm minimum total length limits. The model consisted of population dynamics components from published studies, estimates of future reservoir trophic status, and a composite angler satisfaction score. The model indicated that a 305-mm length limit would result in the greatest angler satisfaction, but the model was very sensitive to estimates of angling mortality. To minimize the potential risks of error in the angling mortality estimates, we suggested a 356-mm length limit that was adopted by the Georgia Department of Natural Resources. The model transparency also helped biologists illustrate the decision-making process to the public, garnering support for the length limit change. We believe that decision analysis is a useful tool for fisheries management and encourage its use by fisheries biologists.