Potential Determinants of Stable Catch in the Brook Trout (Salvelinus fontinalis) Sport Fishery in Quebec

Evaluation of four existing empirical models of fish yield showed their applicability to be limited for the brook trout (Salvelinus fontinalis) sport fishery in the Laurentian shield because these models explained < 60% of the variation in catch. In at least 80% of the lakes, observed catch exceeded that predicted by two of the models. The other models overestimate catch by 100% or more in at least 25% of the lakes. As a first step to improve these models, we identify correlates of "stable catch," defined by the absence of a significant temporal trend in fishing success in lakes for which at least five consecutive years of data were available. Data available or calculable from government sources and maps were used to construct models that identified fish size, lake trophy, altitude, and pH as promising correlates. A second series of models based on our own field determinations confirmed these findings. After fishing effort had been taken into account, these variables reduced the unexplained variation by up to 50%. Although our estimates of trophy and acidity were crude, this study suggests that these indicators should be included in future models to describe and predict the yield of sport fisheries.