Selection of spawning site microhabitat for lake trout and coregonids

Native Great Lakes fishes such as lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) use reefs for spawning in the Great Lakes.  However, the specific areas, habitat characteristics, and timing of spawning by each species are not well understood.  Potential spawning reef habitats were evaluated prior to the fall spawning period in 2008 and 2009.  Reef slope, interstitial depth, substrate size, substrate roundness and dreissenid mussel coverage were determined during gear deployment while physical disturbance and predator densities were determined during and post spawning.  During the spawning period, egg deposition was measured and related to reef habitat characteristics.  Lake trout spawning site selection is influenced by physical disturbance and slope of the spawning reef, while coregonid egg deposition is influenced by physical disturbance.  Other habitat characteristics such as interstitial depth and substrate roundness are correlated with reef slope and could be contributing to spawning site selection.  Evaluation of spawning habitat use will assist fisheries managers in making more informed decisions for management actions such as and habitat protection and rehabilitation.