More to come, please check back.
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*Lab members: Marie Veillard and Mark Poesch. Check out opportunities in the lab!
More to come, please check back.
Also Read:
*Lab members: Marie Veillard and Mark Poesch. Check out opportunities in the lab!
Abstract
The invasion of non-native fish species poses a major threat to native salmonids in freshwater ecosystems. We investigated the potential displacement of threatened Bull Trout (Salvelinus confluentus) by non-native Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta) in 44 headwater streams across Alberta, Canada. Using electrofishing surveys and a combination of single- and multi-species N-mixture models, we examined how fish abundance responds to instream habitat characteristics, landscape features, and species interactions, while accounting for imperfect detection. Results revealed that reduced Bull Trout abundance was correlated with the abundance of Brook Trout in cold streams (mean August temperature <11°C) that lack habitat complexity, particularly where large woody debris and heterogeneous channel features are limited. Conversely, Brown Trout were associated with reduced Bull Trout abundance in larger, lower-elevation systems, likely due to competitive dominance in deeper and slower habitats. These findings highlight that temperature alone likely does not dictate displacement risk; and that habitat structure and species-specific traits also play critical roles. Management strategies should prioritize the protection of cold, structurally complex streams and consider targeted removals or exclusion strategies to limit further invasion. Habitat restoration and assisted colonization to suitable, non-invaded refugia may further enhance Bull Trout conservation under ongoing climate and land-use change.
Citation: Pallard J. and M. S. Poesch. (In Press) Factors affecting Bull Trout (Salvelinus confluentus) abundance and potential displacement by non-native Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta) in headwater streams. Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.70227.
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*Lab members: Jacquie Pallard and Mark Poesch. Check out opportunities in the lab!
Abstract
The expansion of invasive species significantly threatens ecosystem biodiversity and stability, often leading to alterations in food web dynamics and trophic interactions. This study examines the impacts of two invasive species, the Chinese Mystery Snail (Cipangopaludina chinensis) and Northern Crayfish (Faxonius virilis), in Alberta’s reservoir ecosystems. These species, originally from Asia and Canada’s eastern regions respectively, have established populations in Alberta, raising concerns about their effects on local aquatic food webs. Using stable isotope analysis across five reservoirs with varying invasive species presence, we assessed shifts in trophic structure, resource use, and isotopic niche overlap among native and invasive species. Findings reveal that reservoirs with invasive species showed significant changes in food web length, trophic diversity, and isotopic niche overlap, especially in systems where both species coexisted. Notably, both invasive species reduced macrophyte availability, or availability of isotopically similar resources, leading to shifts in fish diets toward higher trophic levels and affecting their trophic positions. Additionally, niche overlap between the two invasives suggests potential competition for resources, with Northern Crayfish possibly predating on Chinese Mystery Snail in resource-scarce environments. These results indicate that invasive species presence can significantly impact trophic structures, leading to competitive exclusion, changes in fish feeding strategies, and broader ecosystem productivity alterations. Future management should prioritize containment and monitor these invasives’ long-term impacts, particularly given their potential to disrupt biodiversity and ecosystem function.
Citation: Edgar M.*, Kimmel, N. and M. S. Poesch. (2025) Community trophic structure within reservoirs change in the presence of invasive Chinese Mystery Snail (Cipangopaludina chinensis) and Northern Crayfish (Faxonius virilis). Aquatic Sciences 87: 99. DOI: 10.1007/s00027-025-01220-z.
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*Lab members: Megan Edgar and Mark Poesch. Check out opportunities in the lab!
Abstract:
The ability to accurately detect harmful aquatic invasive species in a species-specific manner is crucial to monitoring and management efforts. The Canadian province of Alberta currently harbors North America’s only invasive Prussian Carp populations, in addition to invasive Goldfish populations. The ability to quickly and accurately distinguish between these phenotypically similar fish, while also determining their presence in various waterbodies, is important in tracking invasions. In this work, we develop a cytochrome B–based assay, as well as an ND2-based assay to distinguish between these two fish. The 84-bp-long CytB assay featured a limit of detection of 5.8 and 4.8 copies/sample for Prussian Carp and Goldfish, respectively, while the 95-bp-long ND2 assay featured LODs of 6.3 and 1.6 copies/sample, respectively. We demonstrate that each of these assays fails to amplify these markers in closely related fish species common to Alberta. They also fail to amplify key invasive carp species, apart from the Goldfish ND2 assay, which cross-reacts with Common Carp. We then implement these assays and find 13 Goldfish and 47 Prussian Carp environmental DNA detection events throughout the Canadian province of Alberta. Finally, we show that assays broadly agree with visual observation data gathered from various reporting mechanisms, highlighting their validity in a monitoring program.
Citation: Hambrook J., Kimmel N., Robinson R., Foster D., Poesch M.S. and P. Hanington. (2025) Development, validation and implementation of eDNA-focused qPCR assays to detect and distinguish between Goldfish (Carassius auratus) and Prussian Carp (Carassius gibelio). Environmental DNA 7(2): e70092.
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*Lab members: Mark Poesch. Check out opportunities in the lab!
Abstract:
Reliable angler activity data inform fisheries management. Traditionally, such data are gathered through surveys, but an innovative cost-effective approach involves utilizing online platforms and smartphone applications. These citizen-sourced data were reported to correlate with conventional survey information. However, the nature of this correlation—whether direct or mediated by intermediate variables—remains unclear. We applied Bayesian networks to data from conventional surveys, the Angler’s Atlas website, the MyCatch smartphone application, and environmental data across Alberta and Ontario, Canada, to detect probabilistic dependencies. Using Bayesian model averaging, we quantified the strength of connections between variables. Waterbody webpage views were directly related to daily- and weekly-aggregated boat counts in Ontario (51% and 100% probability) and to weekly-aggregated creel survey-reported fishing duration in Alberta (100%). This highlights the value of citizen-sourced data in providing unique insights beyond meteorological factors, with online interest serving as a potentially reliable proxy for angler pressure and effort.
Citation: Tayebi A. T., Schmid J., Simmons S., Poesch M. S., Ramazi P. and M. Lewis. (2025) Website views as a proxy for angler pressure and effort: Insight from Bayesian networks. Canadian Journal of Fisheries and Aquatic Sciences.
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*Lab members: Julia Schmid and Mark Poesch. Check out opportunities in the lab!
Abstract:
Citation: Schmid J., Simmons S., Poesch M. S., Ramazi P. and M. Lewis. (2025) Analyzing fisher effort – Gender differences and the impact of Covid-19. Canadian Journal of Fisheries and Aquatic Sciences.
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*Lab members: Julia Schmid and Mark Poesch. Check out opportunities in the lab!
Abstract:
Citation: Theis S., Shirton J., Barbeau M., Ruppert J. W. L. and M.S. Poesch (2025) Growth and diet of Northern Pike (Esox lucius) in Boreal lakes: Implications for Ecosystem Management. Hydrobiologia 4(1): 1.
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*Lab members: Sebastian Theis, Jonathan Ruppert (former member) and Mark Poesch. Check out opportunities in the lab!
Abstract:
Environmental DNA (eDNA) assays represent a non-invasive approach for biomonitoring. To assess Arctic grayling (Thymallus arcticus) populations in the Little Nahanni watershed of Northwest Territories (NWT), Canada, an eDNA assay that has been previously validated for use in fish of the Beringia lineage was used in conjunction with traditional survey methods (i.e., electrofishing). Forty-six 100-metre reaches of streams were assessed in August 2015. The assay successfully detected Arctic grayling of the Nahanni lineage, with an eDNA signal recorded at each of the 17 sites in which Arctic grayling were observed by traditional fish surveys, but also at 3 of the 29 sites where Arctic grayling were not observed. The presence of eDNA was related to habitat metrics via Random Forest and correlation analyses. Riffles and water temperature were identified as being predictive of Arctic grayling eDNA abundance; however, no significant relationship between eDNA abundance and biomass proxies (fish abundance and fork length metrics) could be established. The high congruence between traditional approaches and eDNA surveys suggests adoption of the latter method will enhance the temporal and spatial acuity of biomonitoring, thereby improving field assessment of Arctic grayling populations and contributing towards more effective conservation management of this species.
Citation: Veilleux, H., McPherson, M., Cott, P., Poesch, M., S., Glover, C., and G. Goss. (2025) Environmental DNA as a tool to detect Arctic grayling and their habitat preferences in the Northwest Territories, Canada. Arctic Science 11: 1-12.
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*Lab members: Morag McPherson and Mark Poesch. Check out opportunities in the lab!
Abstract:
To enhance management of aquatic systems, long-term monitoring programs are crucial. However, managers often lack sufficient guidance in decision-making. In this study, we analyzed nearshore electrofishing data from Lake Ontario spanning 18 years and over 100,000 caught fish to assess sampling designs for various coastal habitats. Using simulation, we evaluated precision of Catch Per Unit Effort (CPUE) for all species, piscivores, and specialist species, at different levels of electrofishing sampling effort. For overall CPUE in any habitat type, increased precision declined with additional electrofishing runs, particularly after reaching 30–40 runs. Adjustments in sampling effort, such as adding 10 runs per year for open-coast sites, increased precision of overall CPUE by 10%. Adding 8 runs per year for wetlands increased precision of specialist-species CPUE by 10%. However, additional runs in embayments did not increase precision for all species, piscivores, or specialist species. Our findings underscore the importance of considering community composition and abundance when evaluating CPUE precision, and illustrates a flexible approach to optimize sampling effort in aquatic monitoring programs.
Citation: Theis, S., Cartwright, L., Chreston, A., Coey, B., Graham, B., Little, D., Poesch, M. S., Portiss, R., Scott, R., Wallace, A., and J. L. W. Ruppert. (2025) Balancing sampling effort against costs for nearshore fish communities in Toronto waterfront, Lake Ontario. Fisheries Management and Ecology: 31(1): e12733.
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*Lab members: Sebastian Theis, Jonathan Ruppert (former member) and Mark Poesch. Check out opportunities in the lab!
Abstract:
Understanding the spatial structure and diversity of fish communities in urban environments is crucial for effective conservation and management. Our study investigates the complexity and spatial structuring of fish communities across urbanized watersheds and waterfronts in the Toronto region, identifying distinct groups based on sampling locations using modularity analysis and partial least square path modeling (PLS-PM). We evaluated the influence of environmental factors, including habitat, human impact, and species traits, on fish community composition. Our results reveal three distinct fish community groups. The first group, primarily located in major watersheds such as Humber and Rouge, is characterized by lower human impact and larger tracts of less developed land, where habitat variables like water quality play a significant role. These areas support species with intermediate tolerance levels. The second group includes diverse waterfront and nearshore habitats, where high species richness and variability are influenced by varied environmental conditions and riparian zones, with limited urban impact. The third group, encompassing some of the more urbanized areas, faces the constraints of urbanization and a high density of instream barriers, resulting in lower species diversity and a dominance of disturbance-tolerant species. Our findings highlight how different urban environments shape fish communities based on available habitat in interatom with species traits. This underscores the importance of tailored urban watershed management strategies based on urbanization levels and habitat constraints.
Citation: Theis S., Chin, A. T.M., Wallace, A., Cartwright L., Fortin M.J., Poesch, M.S. and Ruppert, J.L.W. (2025) Complexity and spatial structuring of fish communities across urbanized watersheds and waterfronts. Urban Ecosystems 28: 1–18.
Also Read:
*Lab members: Sebastian Theis, Jonathan Ruppert (former member) and Mark Poesch. Check out opportunities in the lab!