**The title, authors, and abstract for this completion report are provided below.  For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**

Morphological and Life History Variation with Depth in an Introduced Lake Trout Population

Craig P. Stafford¹, Megan V. McPhee², Lisa A. Eby¹, Fred W. Allendorf³

¹ College of Forestry and Conservation, University of Montana, 32 Campus Drive, Missoula, MT 59812

² Flathead Lake Biological Station, University of Montana, 32125 Bio Station Lane, Polson, MT 59860

³ Division of Biological Sciences, University of Montana, 32 Campus Drive, Missoula, Montana 59812

June 2009

ABSTRACT:

We compared stable isotopes, diets, life history patterns, morphologies, lipids, and microsatellite genotypes between shallow and deep captured lake trout in an introduced population. Isotopic signatures demonstrated that the depth fish were captured (shallow and deep) indicate a longer term depth bias in distribution. Deep caught lake trout matured earlier, grew more slowly, relied more heavily on Mysis relicta, and differed in their morphology relative to shallow caught fish. We found no differences in lipid content or microsatellite allele frequencies between depth groups. Many aspects of the diet and life history of the deep Flathead fish resemble the humpers of Lake Superior. Morphologically, the deep Flathead fish show a general correspondence to the patterns exhibited by native deep water forms in Lake Superior and elsewhere.