Phenotypic variation within populations is common in many salmonids, especially when inhabiting northern postglacial systems. We compared life-history traits among four lake trout morphs co-existing in the shallow-waters of Great Bear Lake (Northwest Territories, Canada). Adult growth rate, age- and size-at-maturity, and survival differed among morphs, consistent with their degree of foraging specialization and predictions from foraging theory, e.g., reduced somatic growth and higher reproductive investment in the generalist morph, high growth throughout life in the piscivorous morph, and intermediate life-histories in the more benthic- and pelagic-oriented morphs. Fecundity and egg size also varied among morphs. However unexpected findings also arose, such as comparable immature growth rates among morphs. Other traits, such as a high proportion of resting individuals among all morphs, suggest life-history adaptations to northern latitudes. Longer resting periods are likely needed to obtain enough energy for reproduction, and may also allow greater investment in post-maturation growth. Overall, lake trout from Great Bear Lake demonstrated remarkable longevity and exceptional asymptotic sizes, even for a northern freshwater ecosystem. Our study provides new insights into life-history evolution among lake trout morphs that use different food sources and habitats. In addition, it contributes to our understanding of this complex aquatic ecosystem, which exhibits one of the highest known levels of intraspecific diversity among freshwater fish.
Bibliographical noteFunding Information:
We thank Déline Renewable Resources Council, Déline Lands and Finance Corporation, the community of Déline, DFO in Hay River, and the Department of Environment and Natural Resources in Déline, which provided valuable help with field planning and logistics. We especially thank J. Chavarie, S. Buckley, L. Harris, G. Lafferty, M. Lindsey, M. Low, Z. Martin, S. Wiley, and Chris Yukon who helped lead sampling teams and coordinate logistics along with the following individuals who helped conduct field sampling in various years: 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 Charity, Cameron, and Cyre Yukon. We thank Laura Heuring, Lenore Vandenbyllaardt, and Rick Wastle for preparation and reading of age structures, and Tracie EisBrenner, Sheri Freisen, and Lenore Vandenbyllaardt for conducting egg counts and measures. Finally we will like to thank Nigel Lester, Ontario MNR, for location information for the McDermid populations. Financial support was provided by Fisheries and Oceans Canada (DFO) , Natural Sciences and Engineering Research Council of Canada , Sahtu Renewable Resource Board , Association of Canadian Universities for Northern Studies , Canadian Circumpolar Institute's Circumpolar/Boreal Alberta Research and Northern Scientific Training Program ( 360150 , N011000001 , N011000529 ), D. Alan Birdsall Memorial Scholarship Fund , and Aboriginal Affairs and Northern Development Canada Northwest Territories Cumulative Impacts Monitoring Program grants ( YELLOWKN#547571 ). Logistical support was provided by the Polar Continental Shelf Program.
© 2015 International Association for Great Lakes Research.
- Biphasic model
- Lake trout