We found that an introduced population of lake trout (Salvelinus namaycush) in Flathead Lake, Montana, USA, exhibited divergent life history, diet, and morphology after the invasion of Mysis diluviana. A correspondence between stable isotopes (δ13C and δ15N) in lake trout muscle and their prey suggests that individual lake trout exhibited depth preferences. Lake trout 451-600mmtotal length showed morphological distinctness between shallow (0-25 m) and deep (60-100 m) collections wherein the latter had deeper bodies and larger eyes. Furthermore, these deep lake trout fed more heavily on Mysis, grew slower, and matured at a smaller size. Lack of genetic divergence between depth groups and the rapid divergence of life histories after Mysis invasion suggest a strong role for environment in producing the observed ecotypic variation. Our research supports resource partitioning by depth and diet as a drivers of phenotypic diversity in lake trout, providing insights into the origins of morphotypes and guidance for conservation of native populations.
|Number of pages
|Canadian Journal of Fisheries and Aquatic Sciences
|Published - 2014