Fishes are vertebrates with gills that live in water. Three major groups of fishes are recognized: the cartilaginous fishes (e.g., sharks and skates), the jawless fishes (e.g., lampreys), and all the others - the bony fishes (e.g., chars, whitefishes, herring).

Fishes are excellent indicators of water quality and ecosystem health. The presence or absence of certain species can provide immediate clues about the conditions within a given area. Fish are one of the most important food and economic resources in the NWT. We are known for our trophy-sized fishes, for healthy populations, and for delicacies.

A total of 104 species of fish can be found regularly in our rivers and lakes, and in the NWT’s section of the Western Arctic Ocean. An additional 5 species are vagrant and may be seen in the NWT irregularly and an additional 14 species of marine fishes are expected to be present. Two species were introduced (alien) in the NWT.

Research on Great Slave Lake

Great Slave Lake is the 11th largest lake in the world and the deepest lake in North America. Since 2018, Fisheries and Oceans Canada (DFO) implemented a project on lake trout stock assessment, genetic discrimination, and sustainable yield estimation in Great Slave Lake. This project is done in collaboration with the NWT Cumulative Impact Program (NWT-CIMP), local communities, and commercial fishermen. It aims to answer questions regarding the cumulative impact of activities on lake trout population dynamics in Great Slave Lake. The results will promote the proper management of Great Slave Lake trout stocks to ensure their conservation and sustainability by establishing defensible, biologically-based management reference points and providing scientific advice for its future management to reduce the cumulative impact of activities.

Lake whitefish is one of the dominant benthivorous salmonids in Great Slave Lake, sustaining the largest commercial freshwater fishery in the NWT since the 1950s. Despite the recent downturn in commercial market value, lake whitefish is still one of the staple subsistence fish resources for the communities around the lake. Since the inception of the commercial fishery, lake whitefish has been a focus of research and monitoring activities. Long-term data collection includes fish biology, fishing capture efficiency, tag-recapture data, trophic ecology, and fisheries stock assessment. The recent focus of research has been to establish a community-based eco-monitoring framework through a multidisciplinary research design and depth-stratified sampling approach. The overarching objectives are to better incorporate community-specific traditional knowledge into the fisheries management system and to enhance the capacities of research and management of Arctic freshwater fisheries.

Inconnu is a top predator that serves as an indicator species of ecosystem health. This species is harvested in subsistence and commercial fisheries in Great Slave Lake. Inconnu are highly vulnerable to human activities. As a result of overharvest in the 1970s, stocks declined significantly in Great Slave Lake, particularly the Buffalo River stock. Inconnu are vulnerable because they are highly migratory. This leads to a concentration of fish both spatially and temporally, which in turn makes these populations especially susceptible to exploitation. During the last few years there has been an increase in the commercial harvest of inconnu and local water levels have decreased. A second phase of a comprehensive study on inconnu genetic stocks discrimination is ongoing in collaboration with local communities. This phase is focused on identifying spawning sites and other critical habitats in lotic systems using eDNA snapshots and mixed stock analysis. Other research on inconnu includes collecting long-term abundance index and biological data for Buffalo River and short term for Slave River inconnu.

Details on lake whitefish, lake trout, and inconnu spawning locations and rearing, feeding, overwintering areas and other critical areas in Great Slave Lake watershed remain largely unknown. This information is necessary for the sustainable management of these species. Habitat use patterns may change over time due to changes in the ecosystem resulting from development or climate change. Inconnu also exhibit a high degree of population variation.

An acoustic tagging study is being conducted in Great Slave Lake watershed to assess the overall health of these species in relation to human impacts. The initial focus of this study is on the Buffalo River system. Acoustic transmitters will be surgically implanted in the inconnu and receivers will be installed in Great Slave Lake and tributary rivers to track fish movement. This will be coupled with genetic sampling and assessments of parasites as natural tags for stock discrimination. As a result, new information on inconnu seasonal movements, spawning, and stock discrimination will be gathered, which will aid in the study of the cumulative impacts of human activities and natural processes on these stocks and their habitat. Additionally, ongoing research on inconnu includes the collection of long-term abundance index data (since the late 1960s), biological characteristics and harvest data (since 1947), and tag-recapture data (since 1995). These long-term datasets have contributed greatly to the management of this species.

DFO is leading a study in the Great Bear Lake to assess trends in water quality and primary productivity, demographic traits, and current status of harvested species, with a focus on evaluating sustainable harvest levels of lake trout, a cold-adapted species with a relatively narrow thermal niche. Analyses will be conducted using information collected over the past two decades through previous DFO-led studies with comparisons to historical studies from the 1960s and 1980s. Project results will provide updated information on the population trends and status of key harvested fish stocks and climate-related changes in water quality and productivity together with further extending baseline datasets to provide information on trends in water quality, invertebrate and fish assemblages, and biological traits of harvested fish species. These data contribute to better our understanding of cumulative impacts due to climate change and harvest on the functioning of large northern lakes ecosystems, in particular, on fish production. The study will provide a benchmark for monitoring further change. Results will assist decision makers, including DFO Fisheries and Aquaculture Management (FAM), the Sahtú Renewable Resources Board, Délı̨nę Renewable Resources Council, and the Tsa Tue Biosphere Reserve Stewardship Council, in developing effective strategies for maintaining community-led aquatic monitoring and managing natural resources, particularly fish. The project will maintain a strong level of community involvement, including youth through the Guardian Program, to facilitate capacity building and community-leadership in long-term monitoring of Great Bear Lake fisheries and the aquatic ecosystem.

Salmon program

The Arctic Salmon program operates at the community level and monitors the relative abundances and geographic distributions of salmon species in the NWT and, more broadly, throughout the entire Canadian Arctic. This is accomplished by outreach, training, and awareness delivered by DFO staff to community members and the voluntary reporting and provision of samples from subsistence harvests from community fishers.

In recent years the number of salmon reported to the program has increased exponentially from over 760 salmon in 2017 to over 2,400 in 2019. There is also high inter-annual variability. All five species of Pacific salmon have been harvested in the NWT. Chum salmon are the most numerous in any given year. Since 2016, the number of sockeye salmon harvested has increased, especially from coastal Beaufort Sea communities such as Sachs Harbour and Ulukhaktok, NWT.

Salmon are not invasive, meaning they are not introduced by humans outside known distributions; rather, salmon can be characterized as natural colonizers possibly expanding their ranges as a result of the ecosystem effects of climate change. Thus, their presence potentially represents new harvest opportunities, as well as possible risks and benefits to native species. The following questions are a priority for the program. Where might salmon possibly spawn? Is spawning successful and if so, where do juveniles rear? Do salmon compete with native fishes, and to what extent do salmon expand in range each year? The answers will have implications for salmon management and subsistence fishes in future years. Potential salmon colonization represents a tangible example of recent aquatic biodiversity shifts likely associated with changing environmental conditions in northern freshwater and marine ecosystems.

Arctic Coast is a community-based monitoring framework that assesses coastal and near shore shelf ecosystems across trophic levels in a standardized and transferrable way. Once established through consultation with relevant communities, followed by outreach, training, and guidance delivered by DFO staff, the program transitions to a locally-led, year-round initiative delivered by community members in the Canadian Arctic. Information and samples across multiple trophic levels of the coastal ecosystems are utilized in follow-on analyses derived from the “Arctic Coast” framework for key coastal areas as identified by local and scientific knowledge, which provide the context and document change in important local ecosystems. The field protocols of this program were developed and tested in Darnley Bay, NWT, in the Anguniaqvia niqiqyuam Marine Protected Area (ANMPA) since 2014, and have been applied to other communities in the western Arctic (Kugluktuk, NU in 2017 and Sachs Harbour, NWT in 2018) as well as in Hudson Bay in 2020 (Igloolik, NU, Kinngait, NU, and Whapmagoostui, QC).

The field program in the ANMPA has been community led since 2018 and has now expanded to include both summer and winter sampling. Fishes and habitat association information has been gathered for all these programs to gather key baseline information regarding local biodiversity of fishes and benthos, habitat characteristics, natural variability, trophic structure, and ecological linkages. These baselines provide the initial context from which ongoing monitoring can be established and change documented. Recent projects have documented new occurrence information for coastal fishes in the Beaufort Sea (Bering wolffish Anarhichas orientalis and banded gunnel Pholis fasciata) as well as novel information on co-occurring invertebrates and their biodiversity. By coordinating, sharing, and building upon local, traditional, and scientific knowledge in a rapidly changing environment, we can better predict the ecosystem impacts in a future Arctic and thus foster better adaptation to changes.

Research on marine fishes

Research to understand diversity and distributions of marine fishes in Arctic Canada has been ongoing for many decades; however, the first complete overview from museum specimens with additional data from the 2011-2015 Beaufort Offshore Marine Fishes Project was published in 2018. Species of marine fish were added to the list based on these studies, but the number of fish species present in NWT waters are still likely underestimated because sampling of some habitats such as deep offshore waters under ice, distant areas, and unique habitats like kelp forests has been limited to date, and occurrences of larger, pelagic species are rare. For example, a Pacific salmon shark (Lamna ditropis), originating from North Pacific waters, was documented in Kitikmeot waters, NU in 2019 (however, it must have passed through NWT waters to get to that area so is included in our list). Ongoing environmental shifts associated with climate variability and change in the Arctic will likely result in additional re-distributions of fish species from the western Arctic and perhaps also eastern Arctic, thus ongoing regular monitoring is highly relevant.