Effects of Fisheries Exploitation on Salmonid Communities in Oligotrophic Lakes

Abstract

In many oligotrophic lakes intense fisheries exploitation preceded severe cultural eutrophication by several decades at least, except perhaps in stream and inshore areas near shore. Attempts to infer the effects of exploitation from historical fisheries data must allow for the high rates of capture associated with the "fishing-up" process that follows initiation of a new fishery, introduction of a new gear, change in capture or vessel technology, etc. The nature of the fishing-up process is examined in some detail. Interactions of new species introduction and of eutrophication with exploitation are outlined.Within the salmonids, different taxa appear to respond somewhat differently to exploitation stress. Some taxa appear to have greater capabilities to compensate for this stress than others. Responses of the taxa are examined in the context of well-known properties of their niches and population variables.Some inferences concerning responses at the community level are proposed. Compensatory capabilities seem directly related to the degree of eutrophy of the lake. Events such as the virtual disappearance of taxa, or eruptions of new taxa, and the relative variability in year-class abundance of dominant taxa, are examined in this context.