Conflicting objectives in trophy trout recreational fisheries: evaluating trade-offs using an individual-based model

Abstract

Standard fisheries models, based on average populations metrics are inadequate for analyzing recreational fisheries where fishing is size-selective and management objectives are related to preserving population size structure. Using data from the steelhead (Oncorhynchus mykiss) fishery in the Santa Cruz River (Patagonia, Argentina) we developed an individual-based harvest model to characterize the relationship between growth, mortality and size structure under different size-based harvest strategies. We evaluated fishery performance with indicators associated to catch-related components of anglers? satisfaction: yield (kg), population size, and availability of trophy-size fish. Large declines in trophy-size fish are to be expected at fishing mortalities much too light to cause a sizeable decline in recruitment from virgin values. When somatic growth is density independent, fish harvest occurs at the expense of other indicators associated to the quality of fishing experienced by individual anglers. Our results clearly expose such trade-offs, providing the kind of quantitative information managers need to decide where to operate. Size limits provide some tools to better accommodate harvest without compromising fishing quality. When preserving population size is favored over preserving trophy-size fish, minimum size limits constitute the best policies overall, whereas maximum size limits are best when the emphasis is on preserving trophy-size fish.