USE OF AN ACOUSTIC BEAM ACTOGRAPH TO ASSESS THE EFFECTS OF EXTERNAL TAGGING PROCEDURE ON LAKE WHITEFISH SWIMMING ACTIVITY

We conducted laboratory tests on the effects of externally applied aco ustic tags on the swimming activity of lake whitefish Coregonus clupea formis. Using an acoustic beam actograph, we evaluated the swimming ac tivity patterns of 15 fsh over a 40-d period and tagged 12 of the fish at mid-experiment, after 20 d. Fish activity was continuously recorde d by counting the number of beam interruptions per hour. Before fish w ere tagged, the activity pattern of 8 of the 15 fish showed more activ ity during the day than at night; 5 fish were equally active during da y and night, and 2 fish were predominantly active at night. After they were tagged, one control (33%) and seven tagged fish (58%) kept the s ame activity pattern. A consistency in day and night swimming activity levels was observed between the two periods for two control fish and two tagged fish. Day activity levels before or after the tagging date were not statistically different between the three groups tested (cont rol. small and large fish), whereas night activity levels increased fo r the large fish. This study showed that handling, attachment surgery, and tag presence did not seem to critically affect swimming activity levels or patterns in lake whitefish. Growth rates over the 40-d perio d of observation were also not significantly different between control and ragged fish.