Seasonal Distribution and Movement Patterns of Invasive Lake Trout in Yellowstone Lake

In an attempt to protect Yellowstone cutthroat trout in Yellowstone Lake, the National Park Service has been actively suppressing lake trout since 1995.  An acoustic telemetry study was initiated in 2011 to increase the efficiency of the current suppression program by identifying movement patterns and seasonal behavior adult lake trout.  Fifty-two receivers were deployed around the lake, and 279 fish were implanted with acoustic transmitters.  Lake trout were frequently observed moving within and between the western and southern regions of the Lake.  During the winter, movement was limited, but movement was frequent and extended during other seasons.  Except for punctuated foraging forays into shallow water, there was a strong relationship between depth of occurrence and water temperature.  Lake trout were most commonly found at depths coinciding with the 8-10 ºC thermopleth.  Lake trout occurred at shallower depths in the spring and early summer period, but moved deeper as the lake became thermally stratified.  As water temperatures declined during the fall spawning period, lake trout were detected at the shallowest depths observed during the study. These findings are being integrated into future suppression efforts in Yellowstone Lake and are potentially applicable to other western lakes.