Monitoring the depth distribution of lake trout in two lakes with different food webs

Acoustic telemetry has become a useful tool for studying spatial behaviour of aquatic organisms. This technique allows continuous monitoring of fish through the use of implanted acoustic tags that send information to receivers which are deployed in the water bodies. Recent technological advances incorporate sensors inside the tags that measure the acceleration of the fish in two or three axis and report a root mean square of that acceleration. This method offers an additional advantage in studying fish behaviour, as it is possible to correlate the acceleration information with the depth distribution. This study reports the results of the recent use of these tags in studying lake trout behaviour in two lakes in the Experimental Lakes Area, Northwestern Ontario, Lake 373 and Lake 626. Lake trout rely on different prey items in each lake: in 373 Mysis is abundant and is a primary diet item; in 626, Mysis is absent and lake trout feed on yellow perch. This study was conducted during the summer, when stratification of the lakes imposes a reduced habitat on lake trout: surface waters are warmer than their preferred temperature and the deeper waters have the lowest oxygen concentrations of the year.