Ecological genomics of anadromous migrations in a changing Arctic

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Salmonids are dominant aquatic species in Canada's North and they underpin local economic development and food security. Predicting possible adaptive responses to a rapidly changing Arctic is a priority. Anadromy (i.e. migrations between fresh- and saltwater) is a key trait underlying the ecological success and the economic importance of northern salmonids because anadromous individuals are larger and higher-quality. But a changing climate increases the productivity of fresh- compared to saltwater, thus favoring non-anadromous individuals. This could have devastating impacts on subsistence and emerging commercial fisheries. Our work will use cutting-edge genomic tools to document extent genetic diversity likely to fuel adaptation to a changing Arctic, and will describe the genetic basis of anadromous migrations in two Northern salmonids of economic importance: Objective I: Predicting adaptation to a changing Arctic in Arctic Char Arctic Char are the freshwater fish with the northernmost distribution in the world and they are the most harvested fish in Nunavut and Nunavik. Work in this objective will leverage the recently sequenced Arctic Char genome to use a whole-genome resequencing approach to address two questions crucial to predicting the species response to a changing Arctic. First, we will document the impacts of post-glacial recolonization of the Canadian Arctic on extent genomic diversity. We will model historical demography and map the distribution of both putatively advantageous and deleterious alleles. Second, we will identify the genomic underpinnings of anadromous migrations with samples from Arctic Char populations where both anadromous and non-anadromous individuals co-exist in sympatry, thus significantly contributing to our ability to predict response of this trait to climate change. Objective II: Anadromous migrations in Lake Trout Lake Trout are generally regarded as a freshwater specialist species. In two Arctic locations, however, anadromous individuals have been observed. These populations offer an exceptional opportunity to understand how the genetic underpinnings of a complex trait like anadromy have been maintained. First, we will track the marine movements of Lake Trout using acoustic telemetry. We will then compare anadromous and non-anadromous individuals captured in the wild using RNAseq to characterize genetic and functional differences associated with anadromy. Finally, we will experimentally expose Lake Trout derived from freshwater-restricted populations to saltwater in an aquaculture setting and perform RNAseq to understand how the capacity to tolerate saltwater is maintained. Our work will contribute significantly to our ability to predict the response of key northern aquatic resources to a rapidly changing Arctic and will train 4 graduate and at least 3 undergraduate students who will acquire diverse marketable skills in Arctic field ecology, bioinformatics, and genomics.