Dynamic angling effort influences the value of minimum-length limits to prevent recruitment overfishing

Recruitment overfishing occurs when stocks are fished to a level where recruitment declines proportionally with adult abundance. Although typically considered a commercial fishery problem, recruitment overfishing can also occur in freshwater recreational fisheries. This study developed an age-structured model to determine if minimum lengthlimits can prevent recruitment overfishing in black crappie, Pomoxis nigromaculatus (LeSueur), and walleye, Sander vitreus (Mitchill) fisheries considering angling effort response to changes in fish abundance. Simulations showed that minimum-length limits prevented recruitment overfishing of black crappie and walleye, but larger minimum-length limits were required if angler effort showed only weak responses to changes in fish abundance. Low angler-effort responsiveness caused fishing mortality rates to remain high when stock abundance declined. By contrast, at high effort responsiveness, anglers left the fishery in response to stock declines and allowed stocks to recover. Angler effort for black crappie and walleye fisheries suggested that angler effort could be highly responsive for some fisheries and relatively stable for others, there by increasing the risk of recruitment overfishing in real fisheries. Recruitment overfishing should be considered seriously in freshwater recreational fisheries, and more studies are needed to evaluate the responsiveness of angler effort to changes in fish abundance.