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Aquatic ecosystems in Canada’s north face increasing pressures from both expanding development and climate change. Stream salmonids are an important component of northern aquatic ecosystems and a valued species for fisheries. Monitoring and assessment of stream salmonids is a priority management need identified by northern resource management agencies in order to assess the vulnerability of fish species and habitats to environmental variability and to establish thresholds for development activities. Arctic grayling (Thymallus arcticus) are a freshwater salmonid, which are sensitive to disturbance and require habitat connectivity over large home ranges, making them a good species for monitoring ecosystem health at a watershed-scale (Steward et al. 2007). There is a need to develop more effective approaches to monitor northern stream salmonids, as well as advance our understanding of Arctic grayling ecology in order to use it as a monitoring species for detecting changes in aquatic ecosystems over time.
Monitoring approaches that focus on species distributions and temporal patterns of occurrence in suitable habitats are being broadly adopted (Mackenzie et al. 2006). Vast and remote areas require monitoring that can be applied rapidly and inexpensively, yet still provide accurate trend detection, statistical rigor and scientifically defensible answers (Isaak et al. 2009). Distributional monitoring approaches have the potential to address these monitoring challenges. More recently, techniques have been developed to accurately detect the distribution of juvenile salmonids in the northwest United States (Isaak et al. 2009); however, it has not been tested on northern fishes. Figure 1 below from Isaak et al. 2009 shows hypothetical results between 2 distributional monitoring assessments. The top two panels show how monitoring results can track spatial and temporal patterns of fish species distribution within a stream (habitat patch) and how those patterns can change between assessments. The bottom two panels show how monitoring results can tell if fish species distribution within the broader watershed has changed between assessments.
Monitoring approaches that focus on species distributions and temporal patterns of occurrence in suitable habitats are being broadly adopted (Mackenzie et al. 2006). Vast and remote areas require monitoring that can be applied rapidly and inexpensively, yet still provide accurate trend detection, statistical rigor and scientifically defensible answers (Isaak et al. 2009). Distributional monitoring approaches have the potential to address these monitoring challenges. More recently, techniques have been developed to accurately detect the distribution of juvenile salmonids in the northwest United States (Isaak et al. 2009); however, it has not been tested on northern fishes. Figure 1 below from Isaak et al. 2009 shows hypothetical results between 2 distributional monitoring assessments. The top two panels show how monitoring results can track spatial and temporal patterns of fish species distribution within a stream (habitat patch) and how those patterns can change between assessments. The bottom two panels show how monitoring results can tell if fish species distribution within the broader watershed has changed between assessments.
Figure 1. An example from Isaak et al. 2009 of maps showing hypothetical patterns of change in bull trout site and patch occupancy, within a stream and a watershed respectively, between two distributional monitoring assessments. These maps show how fish species trends at different scales can be assessed and distribution mapped to identify important habitats using results from a distributional monitoring approach.
A foundation of the distributional monitoring approach relies on our ability to delineate suitable habitat patches based on objective, repeatable and defensible biophysical criteria related to species occurrence (Mackenzie et al. 2006 and Isaak et al. 2009). Limited information is available on the distribution of Arctic grayling habitats in the Northwest Territories (Sawatzky et al. 2007), in addition to a limited understanding of species-habitat relationships in arctic regions (Jones and Tonn 2004). Improving our understanding of the range of habitat used by Arctic grayling will improve our ability to identify preferred or critical habitat for the species.
Project Objectives
The objectives of the 2014 research on Arctic grayling in the Little Nahanni River watershed were to:
- Test a distributional monitoring approach to accurately assess Arctic Grayling in a northern watershed using a standardized protocol;
- Identify abiotic and biotic attributes (ecological thresholds) that influence Arctic Grayling distribution, in order to improve our understanding and to refine criteria for accurately predicting and identifying suitable habitats.
- Collect direct observations in a northern watershed for development of models to predict Arctic Grayling occupancy and distribution in unsurveyed areas of the north (occupancy-based models).