Littoral Fish Response to Experimental Logging around Small Boreal Shield Lakes

Littoral minnow trap catch in three small (26−39‐ha), dimictic, oligotrophic headwater lakes in northwestern Ontario, Canada, was monitored for 5 years before and after moderate to extensive watershed and shoreline clear‐cutting. An abundant and diverse littoral fish community, dominated by Cyprinidae, persisted in the study lakes 5 years after logging, suggesting that logging impacts were small, compensatory, or delayed. The species richness of the catch among lakes ranged from 6 to 10 species and was constant within lakes. Although catch and average fish size varied significantly over the 10‐year study, changes were not clearly linked with logging impacts. In the postlogging period, total catch was 17% less in the moderately disturbed lake (45% of watershed logged, with shoreline buffer strips) and 2−27% less in the two intensively disturbed lakes (75% of watershed and 60% of shoreline logged) than in the prelogging period. However, total catch began to decline 1−2 years before the experimental logging treatments in all cases. A similar pattern of reduced catch was evident for most of the abundant littoral fish species individually, although each lake had at least one relatively uncommon species that increased in abundance during the postlogging period. Average fish size in the moderately disturbed lake was 1−7% smaller in the postlogging period. In the extensively disturbed lakes, average size of the most abundant species increased by 1%; other species showed various responses, ranging from an 11% increase to an 11% decrease. Removal of approximately 23,000 fish from two of the lakes in the last year of the study did not produce an immediate reduction in total catch.