LOUISE CHAVARIE

The recent attention on lake charr over the past decade has demonstrated how polymorphism in lake charr has been underestimated and the processes contributing to this diversification remain poorly understood. Great Bear Lake (GBL) is the most northerly lake of its size and provided unique opportunities within functional ecology for the study of lake charr diversification. My research demonstrated four coexisting shallow-water forms of lake charr which challenged the idea that lake charr forms are segregated primarily by depth; furthermore, we identified an additional layer of diversity within forms, demonstrating a new spatial scale at which sympatric polymorphism can occur. Our data indicated that morphotypes of lake charr from GBL are genetically differentiated from one another. The integrated results of molecular biomarkers suggested that polymorphism in the lake charr of Great Bear Lake was maintained not only by diet differences, but also by shallow-water habitat partitioning. However, the overlap and seasonality found among diets of different morphs bring into question the degrees to which diet and habitat partitioning are involved as drivers of divergent selection. Finally, my collaborators and I provided new insights into life-history evolution among lake charr morphs by developing a new back-calculated growth methodology and applying this bi-phasic model to our data. Despite growing interest in sympatric polymorphism, several knowledge gaps remain to be investigated, including the extent of intra-specific diversification that is possible in large northern lakes. Intraspecific variability contributes significantly to biodiversity in northern freshwater fish faunas, where the few species living there profit from the depauperate postglacial systems by colonizing open niches. Thus, morphotypes of a specie represent unique components of Canadian biodiversity and their conservation should be a management goal in the face of substantive and pervasive threats (e.g., climate change, overfishing, industry expansion), to avoid extinction, similar to what likely occurred in other large lakes of Canada, such as the Laurentian Great Lakes.

Supervisors: William Tonn and Kimberly Howland

The field work associated with this study was done in collaboration with Department of Fisheries and Oceans (DFO) and Sahtu Renewable Resource Board.

We especially thank sampling teams: J. Baptiste, D. Betsidea, D. Baton, L. Dueck, R. Eshenroder, G. Menacho, N. Modeste, I. Neyelle, L. Neyelle, M. Smirle, A. Swietzer, C. Takazo, A. Vital, F. Vital, B.Yukon, M. Yukon, T. Yukon and Chris, Charity, Cameron, and Cyre Yukon.

Field Pictures

McVicar 2008

McTavish 2009

Dease 2010

Smith 2011

Russel Bay (Keith) 2012

Dease 2010

Smith 2011

Russel Bay (Keith) 2012

McVicar 2013

Arctic Fisheries Research