A mechanistic understanding of hyperstability in catch per unit effort and density-dependent catchability in a multistock recreational fishery

Mechanisms resulting in hyperstability (where catch per unit effort (CPUE) remains high as fish density declines) in recreational fisheries are poorly understood owing to a lack of experimental data. We collected data on angler CPUE and fish density to determine whether hyperstability exists in the rainbow trout (Onchorhynchus mykiss) lake fishery of British Columbia. We contrasted the relationship between CPUE and fish density in an open-access recreational fishery with an experimental fishery (a set of lakes that had restricted access, standardized fishing methods, and no heterogeneity in angler experience) to assess the mechanistic cause of hyperstability. We detected no evidence of hyperstability in the experimental fishery, but significant hyperstability in the open-access fishery. In the open-access fishery, the composition of the angler population varied among lakes: anglers who fished at low-density lakes were more experienced than anglers fishing at high-density lakes. This segregation of angler experience across lakes appeared to explain the observed hyperstability in this fishery. Our results provide a mechanistic understanding of hyperstability in an open-access recreational fishery and suggest that CPUE data be used in conjunction with data on angler experience when assessing the status of a fishery.