Description of a Morphologically and Genetically Distinct Form of Lake Trout from Elk Lake, Michigan

Efforts to reestablish Lake Trout populations in Lake Michigan depend on identifying strains that can successfully reproduce (Burnham-Curtis et al. 1995).  Elk Lake is a small inland lake that was hydrologically separated from Lake Michigan during the mid 19^th century and contains a self-sustaining population of Lake Trout (Salvelinus namaycush).  The substrate composition of Elk Lake is clay marl.  Rocky substrate or reefs that are typically used by spawning Lake Trout have not been identified.  Lake Trout from Elk Lake are genetically different from forms currently stocked into Lake Michigan and lean forms from Lake Superior.  Both truss and geometric analysis differentiated Lake Trout from Elk Lake, Lake Michigan, and Lake Superior.  Elk Lake Lake Trout had a more elongated and narrow head region and an upturned head when compared with fish from Lake Michigan and Lake Superior, whose head shape were more similar.  Elk Lake fish have a more fusiform body form.  The caudal area was relatively narrower and the adipose fin set back further aligning with the anal fin posterior insertion.  Netting studies indicate that Elk Lake fish reside in deep-water for most of the year and Cisco and deepwater sculpin have been observed in their diets.