Genetic & Phenotypic Diversity in Lake Trout At Isle Royale National Park, Lake Superior

The lake trout is an iconic species at Isle Royale National Park, supporting a thriving commercial fishery prior to the establishment of the park, and a popular recreational fishery. Historic reports suggest lake trout diversity around Isle Royale not currently observed elsewhere in the Great Lakes basin. Determining the level of genetic and phenotypic diversity potentially preserved (or lost) around Isle Royale could influence future management goals for lake trout within the park. Previous sampling of non-spawning congretations of lake trout found weakly differentiated morphotypes and high variation within those groupings. The objective of this study is to determine if sampling during the fall spawning period will allow for clearer discrimination of lake trout morphotypes in Isle Royale National Park. We sampled historic spawning areas during October in 2010 and 2011, as part of a four year study. Geometric morphometric analysis and biological characteristics from lake trout collected from only three spawning sites in 2010-11, suggested general grouping of lean and siscowet, two morphotypes commonly found throughout Lake Superior. High variation within the groups suggested either the presence of other morphs (not discriminated due to low sample size) or introgression of morphotypes influenced by the dramatic long term changes to the Great Lakes ecosystem. Future sampling for this study will increase our spatial coverage and sample size, which in addition to the genetic analyses, may improve our discrimination of lake trout diversity.