Using Multiple Techniques to Identify Lake Trout Spawning Distribution in Yellowstone Lake

Lake Trout (Salvelinus namaycush) were discovered in Yellowstone Lake in 1994 and have been the focus of an intensive gill-net suppression program ever since.  To supplement gill-netting and trap-netting, managers also want to target early life stages on spawning reefs to aid control efforts.  To evaluate the efficacy of early life stage control, the location of spawning sites must first be determined.  Low species diversity and absence of interstitial egg predators in Yellowstone Lake may impose different constraints on choice of spawning substrate than in the Great Lakes.  We used bathymetry data, visual observations of substrate, wave energy models, gill-net catches, and acoustic telemetry data to identify potential locations of additional spawning sites.  These locations were sampled with traditional egg and fry collection gear, a remotely operated vehicle, and a benthic sled to determine the presence of spawning.  Spawning was confirmed at three sites, one of which was previously unknown.  Information on substrate type, depth, and presence of predators and prey where Lake Trout successfully spawn may help identify reasons for the rapid population growth of Lake Trout in Yellowstone Lake and provide a useful perspective for Great Lakes Lake Trout restoration.