Lake charr Salvelinus namaycush spawning behaviour: new field observations and a review of current knowledge

In this paper, we (1) describe field observations of lake charr (trout) reproductive behaviour, focusing on two morphs from Great Bear Lake, N.T; (2) review and synthesize observations from the literature; and (3) summarize uncertainties and pose hypotheses regarding lake trout spawning behaviour. Our description is set within the context of an existing conceptual model that included three sequential stages to spawning behaviour—traveling, sinking, and gamete release. Spawning morphs did not overlap in time and space. Strong onshore winds seemed to trigger lake trout movement toward shoals in mid- to late-August where males outnumbered and seemed to precede female arrival at the shoals. A new behaviour termed finning was observed and interpreted as display courtship. Finning was observed at all spawning sites in Great Bear Lake and involved two or more fish that were either stationary or moving slowly just beneath the water surface with a partially erect dorsal fin, adipose fin, and only occasionally the dorsal lobe of the caudal fin breaking the water surface. On the basis of our observations and review of the literature, we propose to modify the Esteve et al. model to add (1) pre-courtship and spawning behaviour and (2) display courtship behaviour as occurring prior to traveling, sinking, and gamete release. Potential future research questions are described to address uncertainties regarding how spawning lake trout relate to their physical habitat, environmental cues to spawning, factors driving assortative mating among morphs, and the role of olfactory cues in spawning.