Site Fidelity and Spawning Behavior: The Role of Acoustic Telemetry in the Suppression of Lake Trout in Yellowstone Lake

Yellowstone Lake once supported the largest assemblage of genetically unaltered cutthroat trout in North America.  However, during the past two decades predation by an invasive species, lake trout, has substantially reduced the abundance of Yellowstone cutthroat trout in the lake.  The National Park Service has suppressed lake trout for almost 20 years, but as lake trout numbers decline, actions need to be more focused and less expensive.  Acoustic telemetry was used to investigate habitat use, movement corridors, potential spawning/aggregation sites, and document exploitable behaviors. In 2012, we recorded two-dimensional locations of lake trout and used a state-space model to characterize movement patterns of individuals at a verified spawning site.  Twenty-six fish were positioned >100 times, and 32 spawning segments were defined by the state-space model.  Evaluations of minimum convex polygons data consistently showed lake trout with larger summer distributions than during the winter.  Despite detections of lake trout being wide spread, many individuals showed a disproportionately large percent (>60%) of their detections at a single location regardless of the season. Continued monitoring efforts will aid in the identification of additional spawning sites, narrow the area of focus at spawning sites, and document population movement patterns as lake trout numbers decline.