Life history and ecological characteristics of humper and lean ecotypes of lake trout stocked in Lake Erie

Through combined effects of over-exploitation and predation by invasive non-native sea lamprey Petromyzon marinus (Linneaus 1958), the lake trout Salvelinus namaycush (Walbaum 1972) population in Lake Erie collapsed and was considered extirpated by 1950; annual stocking occurred in 1969 to bolster and maintain this population as natural recruitment ceased. While various hatchery strains of lean ecotype lake trout remain the focus of Lake Erie’s stocking, between 2004 and 2011 a humper-like ecotype was stocked to aid re-establishment efforts. We assessed ecotype performance via adult fish collected during the summer-stratified period (2004–2017) and evaluated if life history and ecological characteristics varied between stocked ecotypes. Ecotype-specific differences in survival, length-at-age, accumulation of weight with length, and diet were observed. Lean lake trout grew faster (length-at-age) and matured at larger sizes than the humper ecotype. Humper lake trout exhibited higher sea lamprey wounding and lower survival rates than lean lake trout. Humpers also consumed more benthic prey fish than lean lake trout, suggesting this ecotype may exhibit a more benthic orientation than leans. Our study represents the first evaluation of how a non-lean ecotype lake trout performs outside their native ecosystem and provides fishery managers with valuable information relevant to re-establishing lake trout populations in the Great Lakes.