Nature or nurture: a genetic basis for the behavioral selection of depth in siscowet and lean lake char (Salvelinus namaycush) ecomorphs

Leans and siscowets are lake char ecomorphs in Lake Superior that exhibit distinct depth selection behavior in the wild with leans occupying shallow (<50 m) depths and undergoing small vertical movements. In contrast, siscowets exhibit several types of depth selection behavior but generally remain at great depths (>80 m) and undergo extreme vertical movements. The present study used movement and temperature data from popup satellite archival tags (PSATs) to test the hypothesis that the difference in depth selection behavior of leans and siscowets is a genetic trait. Laboratory leans and siscowets produced from wild gametes taken from Lake Superior and reared in a common garden study for nine years were tagged with PSATs and released in southern Lake Superior. Tagged siscowets remained deep after release and exhibited extensive vertical movements. Most tagged leans remained <50 m after deployment and exhibited smaller vertical movements. Overall, the depths and temperatures occupied by the laboratory ecomorphs were significantly different throughout the deployment and the results support the hypothesis that depth selection in lake char ecomorphs is heritable.