Use of a Structured Approach to the Analysis of Management Options and Value of Information for a Recreationally Exploited Fish Population: A Case Study of Walleyes in Saginaw Bay

摘要

Saginaw Bay Walleyes Sander vitreus contribute to fisheries throughout Lake Huron including a recreational fishery and by-kill stemming from the state-licensed commercial fishery in the bay. Two critical uncertain states of nature exist concerning the true magnitude (catchability) of the by-kill and the future of Alewives Alosa pseudoharengus in Lake Huron, the latter being a strong determinant of Walleye recruitment. After consulting with fishery managers, a stochastic simulation model was developed and used to evaluate management options for the recreational fishery in the form of a decision analysis and the value of information for improved estimates of by-kill magnitude. Decision analysis sought to identify the maximum sustainable recreational harvest. Sustainable harvest was defined as the average across 250 stochastic simulations for each management option considered while penalizing any simulation year with a value of zero if sustainability criteria were exceeded. Decision analysis indicated that sustainable harvest would be maximized if recreational fishing mortality were increased 50% from recent levels. Realizing this potential, however, would require more intensive management to ensure that desired levels of fishing mortality occurred. Choices by managers for allocating surplus harvest are a matter of policy, but concerns over maintaining predation pressure on Alewives to suppress their resurgence may be reasons to manage conservatively by electing instead to maintain a higher predator abundance. The value of information analysis revealed that the improvement in the recreational fishery warrants investment in further research on the uncertainty over by-kill catchability.