Use of Acoustic Telemetry to Inform Suppression of a Non-Native Piscivore: Movement and Behavior of Lake Trout within a Fine-Scale Telemetry Array in Yellowstone Lake, WY, USA

Lake Trout were introduced to Yellowstone Lake in 1994, and the non-native predator has caused substantial declines in abundance of native Yellowstone Cutthroat Trout.  Suppression efforts through gillnetting have limited Lake Trout population growth, but abundance remains high.  Increasing the mortality of Lake Trout at the developing embryo and fry stages, coupled with ongoing gillnetting could enhance the probability of success.  Therefore, it is critical to identify Lake Trout spawning areas to expedite suppression with a variety of techniques.  We used a fine-scale acoustic telemetry positioning system to identify spatial and temporal use of a known spawning area by 48 acoustically tagged Lake Trout.  Preliminary results suggest depth distribution was not significantly different between day and night, and between males and females.  However, males made excursions to deeper water during the day.  Residency time differed between females and males.  Average time between first and last detection within the array during the 33-d study period was 9.8 d for females and 22.7 d for males.  These data, in conjunction with egg baskets, fry traps, and underwater video, are being used to accurately locate Lake Trout spawning sites and movement patterns into, and out of these areas.