The Response of Lake Trout to Manual Tracking

The use of telemetry is widespread in fisheries research, and manual tracking of fish is considered acceptable for data collection. However, it has never been shown whether the use of boats with powered engines, which is common in manual tracking, influences the distribution and behavior of fish. We examined whether general boat traffic or focused manual tracking activity altered movement patterns of adult lake trout Salvelinus namaycush in a small boreal lake at the Experimental Lakes Area of northwestern Ontario, Canada. In the summer and fall of 2002, we used automated fish positioning systems to compare the behavior of lake trout during 1‐h disturbance periods (boat traffic or manual tracking) with behavior in the preceding 1‐h baseline periods (no disturbance). In addition, we compared behavioral differences of lake trout during disturbance and baseline periods (experimental trials) with a similar period of time when no boats were on the lake (control trials). This comparison allowed us to determine whether the observed changes in behavior during normal boat traffic or manual tracking were within the natural range of variation. Overall, we observed no effect of boat traffic or manual tracking on the depth, speed, and path predictability of lake trout. Similarly, the changes in lake trout behavior between the disturbance and baseline periods of the experimental trials were all within the natural range determined by control trials. The response of lake trout to manual tracking was not related to their proximity to the motorboat, both when lake trout were in deep water (6 m; summer) and when they were in shallow water (2 m; fall spawning season). The lack of significance of the relationship between patterns of fish behavior and manual tracking activity provides support for the continued use of this method in fisheries research.