Physical habitat associations of fish species in the Kivalliq region of Nunavut, Canada

Abstract

The Canadian arctic and subarctic (areas north of 60° latitude) support distinct aquatic environments governed by the unique geomorphology and climate of the region. Historically, fish and fish habitat impacted by development activities in this region have been assessed using literature derived from southern populations. Using these assumptions from southern populations on environmental impact assessments for northern regions may not accurately capture differences in physical fish habitat associations. To better characterize northern habitat associations for use in northern environmental assessments, this study sought to achieve three objectives. First, to determine patterns in the depth of occupancy of a model species, Lake Trout, using two databases in Canada, comparing northern and southern regions. Second, to provide an assessment of freshwater fish habitat associations in 11 species specific to the Kivalliq region of Nunavut. Finally, where feasible, to develop Habitat Suitability Indices (HSI) with northern-specific data based on these associations. To achieve these goals, a novel method of estimating depth-of-occurrence was developed and applied to an analysis of standardized fish capture data from both arctic and Ontario (southern) lakes. Habitat association data sourced from populations north of 60° was then used to develop evidence-based arctic-specific HSI values for comparison to the existing Habitat Ecosystem Assessment Toolkit (HEAT) model. Depth-of-occurrence analysis indicated significant differences in the abundance of Lake Trout between northern and southern regions, but not significant differences in habitat associations with depth. However, the results of HSI analysis integrating information from several peer-reviewed studies indicated significant differences in depth patterns across latitude for both Lake Trout and Burbot; both species had stronger associations with depth in Ontario (southern) lakes across three life stages (adult/juvenile, young-of-the-year and egg/spawning) relative to the arctic, suggesting that depth may indeed more strongly shape habitat associations in southern vs. northern populations. No other species had sufficient data to facilitate quantitative analysis, however, qualitative descriptions of northern habitat associations were summarized where feasible. Conclusions from this study demonstrate potential differences in fish habitat associations between northern and southern regions but a larger sample size of lakes will be required north of 60° latitude to make a determination. Region-specific habitat association models are recommended, along with increased observations and study of fish-habitat associations in the north, as this study highlights many data gaps that exist for several species in establishing HSI models specific to arctic freshwater fishes in the arctic.