Lake trout (Salvelinus namaycush) spawning habitat in a northern lake: The role of wind and physical characteristics on habitat quality

Lake trout (Salvelinus namaycush) have a broad distribution across Canada's North, yet most studies that describe reproductive habitat are from the southern extent of their range. We assessed whether lake trout spawning habitat, typically characterized as wave-swept shoals with clean cobble that face predominant wind directions, is similar for a northern lake. Specifically, we examined a dozen sites around Alexie Lake, Northwest Territories, to test if physical habitat and wind exposure were important determinants of spawning site use and embryonic survival. Spawning occurred in ~ 2 m water depth, on 3-15 cm diameter clean substrate found on the leading edge of shoals that ended in a rock crib rising abruptly in nearshore regions around the lake. Wind direction was predominantly from the west, although it was highly variable within and among spawning seasons. We found evidence of lake trout spawning at each site examined, but not limited to shoals facing a predominate wind direction. High variation in embryonic survival (2-83%) from incubation trays was observed among spawning sites, suggesting a large gradient in habitat quality exists within a given lake. Modelled wind exposure did not predict embryonic survival, nor did physical characteristics that may influence interstitial water flow on spawning shoals. Our findings challenge the conventional role of wind as a predominant predictor of lake trout spawning site quality. We propose that the unpredictable nature of wind and abundance of suitable habitat may favour lake-wide spawning by lake trout as a bet-hedging strategy in northern lakes with limited fetch.