McPherson, M. (2020) Habitat use by fluvial Arctic Grayling (Thymallus arcticus) across life stages in northern mountain streams.

Thesis Title: Habitat use by fluvial Arctic Grayling (Thymallus arcticus) across life stages in northern mountain streams.

Author: Morag McPherson 


Northern aquatic ecosystems face increasing pressures from climate change and natural resource development, raising conservation concerns for species in these understudied regions.  The Arctic Grayling (Thymallus arcticus) is a widely distributed, but sensitive, northern freshwater fish that is a good indicator of general aquatic health. In the Northwest Territories (NWT), there has been little focus on studying riverine Arctic Grayling populations or their use of stream habitats within mountain river watersheds. The purpose of my research is to characterize fluvial Arctic Grayling distribution among mountain streams in the NWT, and to determine habitat characteristics and ecological factors that influence Arctic Grayling habitat use across life stages. Sampling sites (n=183) were selected in four sub-basins within the Little Nahanni River watershed in the southwest NWT. In the summer of 2015, each site (100 meters in length) was electrofished and stream habitat parameters were measured. Arctic Grayling were collected for biological analyses of age, size, weight, and reproductive development. Results showed shifts in Arctic Grayling development by size and age class that corresponded with shifts in distribution observed across the study streams. From these findings, four distinct post-emergence life stages for Arctic Grayling were identified: young-of-year (YOY), juvenile, sub-adult and adult. Step-wise logistic regression was used to explore the relationship between the occurrence of Arctic Grayling life stages and stream habitat characteristics. Multivariate regression tree (MRT) analysis was used to identify environmental thresholds and habitat-based life stage segregation, and redundancy analysis (RDA) was used to determine potential life stage-specific habitat correlations. Differences emerged in how Arctic Grayling life stages use habitat across a range of available stream conditions. YOY Arctic Grayling were found exclusively in low elevation, low gradient habitat dominated by silty-sand substrate with average water temperatures >10oC. Similarly, juvenile Arctic Grayling occupied low elevation, warm water stream habitat, but associated strongly with run habitats, as well as showing movement towards cooler water temperatures and more riffle dominated habitats. Sub-adult Arctic Grayling used the widest range of habitats across the study area, being found at a range of elevations and water temperatures, demonstrating the ability of this life stage to use a diversity of available habitats. Sub-adults showed a relationship to in-stream riffle, pool, and cascade-boulder habitats. Adults had a strong correlation to elevation and water temperature, using habitats with high elevation (>1200 m) and low temperature (7oC), and increased proportions of pool and boulder habitat. The four sub-watersheds studied provided distinct stream habitats and Arctic Grayling life stages separated across the habitat types, advancing our understanding of the life cycle habitat requirements for fluvial populations in mountain systems. It provides insight on the important and potential limiting factors, such as availability of warm water habitats, to population success in cold regions. The dynamic nature of Arctic Grayling habitat use in mountain streams highlights the need to consider habitat complexes at the watershed scale when defining species life stage requirements, managing habitats, monitoring populations, and assessing potential impacts into the future. Improved understanding of the distribution, habitat requirements and ecology of different life history types and life stages of Arctic Grayling is crucial for the effective management and monitoring of this species in northern environments

Research in the lab was highlighted in “This self cloning crayfish is scuttling into rivers and streams throughout Alberta (News: CBC)”

It’s not unusual to spot a trout species in a Calgary river but you might not expect to find a lobster-like crustacean. In the last 10 to 20 years however, the marbled crayfish — a crustacean not native to the Bow River — has begun spreading to rivers and lakes throughout Alberta. It’s a problem that Nicole Kimmel, aquatic invasive species specialist for Alberta Environment and Parks, is trying to tackle. Historically, the crustaceans are normally found in between Wainwright and Ryley in the Beaver River watershed south of Edmonton, Kimmel told The Calgary Eyeopener. But now they’ve been showing up in water bodies anywhere from the Edmonton area, down to Calgary and Medicine Hat, as well as in the Milk River region. It’s not likely that the critters are crawling between rivers and lakes, though they can move on land for short periods, Kimmel said. Instead, the province suspects the movements of the crayfish might be aided by humans either for bait use or they are potentially being brought back home and discarded in local waters.

‘Freak accident’ leads to quick reproduction

“Once they’re introduced to a breeding pair, they can breed pretty fast,” Kimmel said — the creatures can produce 200 to 400 eggs in a reproduction cycle.  Kimmel calls the marbled crayfish a kind of “freak accident” of two crayfish species that may have been imported from Florida into Germany in the ’90s and  were able to mate. Through that mating, the crayfish kept an additional set of chromosomes that allowed them to reproduce asexually, meaning all the females could lay unfertilized eggs which develop into genetically identical offspring. In essence, a self-cloning crayfish was born. To attempt to control their spread, Alberta has banned the crayfish province-wide unless it’s kept as a pet. Most pet stores have stopped carrying the specimens, but it’s still possible to find them sold online by individuals. Ducks have been munching on them, along with some humans, but Kimmel says its important to make sure the ones used for consumption are coming from clean water sources. Kimmel says the province has partnered with Mark Poesch, Associate Professor in Agricultural Life and Environmental Sciences at the University of Alberta, to understand what the effects are on the habitats the creatures are invading. “We highly suspect that they’re probably impacting food webs where they’re being moved around,” she said.

Other crayfish creeping into Canadian waters

The marbled crayfish aren’t the only species of their kind causing concerns — there’s an extensive list of crayfish-type creatures being found in Canadian waters, Kimmel explained. For example, B.C. is worried about red swamp crayfish and in Manitoba there are concerns about crusty crayfish. Meanwhile Saskatchewan, along with Alberta, has ramped up its legislation around marbled crayfish. If you spot a crayfish, Kimmel says to report it to the province along with the location it was found. “We’re very much interested in knowing the location that you’re finding them as well as if you can snap a picture of what they look like,” Kimmel said. “We don’t want any of those other invasive ones that other jurisdictions are worried about.” The province isn’t actively getting rid of the crayfish right now until there’s a better understanding of where the crayfish are located and what can be done for eradication.

Link to CBC article.

Theis, S.*, Ruppert, J.W.R*, Roberts, K.*, Koops, M., Minns, K. and M.S. Poesch. (2020) Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters. Conservation Biology 34(1) 41-53.


Land‐use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland, creek), offsetting measure (e.g., enhancement, restoration, creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.

Highlighted by CBC Radio: (link).

Citation: Theis, S.*, Ruppert, J.W.R*, Roberts, K.*, Koops, M., Minns, K. and M.S. Poesch. (2020) Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters. Conservation Biology 34(1) 41-53.

Also Read:

Theis, S.*  Koops, M. and M.S. Poesch. (2022) A meta-analysis on the effectiveness of offsetting strategies for harm to freshwater fishes. Environmental Management 70(5): 793-807.

*Lab members:  Sebastian Theis, Jonathan Ruppert, Karling Roberts and  Mark Poesch. Check out opportunities in the lab!

Donadt, C. (2019) Trace element concentrations in riverine fish: relationships with body size, food web dynamics and trace element concentrations in surface water.

Thesis Title: Trace element concentrations in riverine fish: relationships with body size, food web dynamics and trace element concentrations in surface water.

Author: Caitlyn R. Donadt


Freshwater fish are an important resource and form an essential component of freshwater ecosystems. However, stressors such as water pollution are negatively impacting freshwater biodiversity. Trace elements can be environmental pollutants and have the potential to negatively impact the health of fish, humans and wildlife.  My research builds upon results from a previous study in the Red Deer River watershed, which found trace elements in surface water at concentrations which pose a risk to humans and wildlife.  I examine trace element concentrations in fish from the Red Deer River watershed to determine: 1) the concentrations of trace elements in fish tissue and potential risk of these concentrations to humans and wildlife, 2) whether patterns in fish trace element concentrations reflect those in the surface water and 3) if biological characteristics influence trace element concentrations in fish.

To reach these objectives, I examined trace element concentrations in fish muscle tissue from streams and the river mainstem within the Red Deer River watershed. I compared patterns of trace element concentrations in fish to those in the surface water, which vary across four tributary streams, or upstream to downstream in the river mainstem. In both lotic environments, I included physical characteristics (age, body size) as well as food web tracers (stable isotope signatures d15N and d13C) together with trace element analysis. My results show most trace elements were at low concentrations in fish muscle tissue or not detected. However, mercury in many fish exceeded concentration criteria for human consumers, piscivorous wildlife and fish health. Patterns in fish trace elements did not reflect spatial patterns in surface water trace element concentrations and were often species-specific. Correlations between trace element concentrations and fish biological factors varied depending on the fish species and element considered, but the strongest relationships were with mercury. Mercury was often associated with trophic position and body size, but this relationship was stronger in the mainstem community compared to stream fish. This research indicates that trace element accumulation in fish, particularly mercury, is not limited to areas of high environmental concentrations within this watershed.

Fish DNA in lake sediment can help determine native species, study shows (Magazine: Folio)

New research by members of the lab could aid fish conservation efforts in provincial parks in Alberta and British Columbia. 

Also Read:

Nelson-Chorney, H.*, Carli, C.M., Davis, C.S., Vinebrooke, R.D., Poesch, M.S., and M.K. Taylor (2019) Environmental DNA in lake sediment reveals biogeography of native genetic diversity. Frontiers in Ecology and Evolution 17: 313-318.