Will post when finalized.
Citation: Tayebi A. T., Schmid J., Simmons S., Poesch M. S., Ramazi P. and M. Lewis. (In Press) 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. (In Press) 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!
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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:
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.
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*Lab members: Sebastian Theis, Jonathan Ruppert (former member) and Mark Poesch. Check out opportunities in the lab!
Abstract:
This study was conducted to meet regulatory requirements under the Fisheries Act in Canada, specifically for a hydroelectric facility on the Yellowknife River in the Northwest Territories. The research focused on annual snorkel surveys of adfluvial fish and their spawning habitat below the facility. Initial observations of egg mortality, potentially due to overcrowding, prompted the investigation of natural and enhanced habitat for spawning Lake trout (Salvelinus namaycush), lake whitefish (Coregonus clupeaformis) and cisco (Coregonus artedi) from 2016 to 2019. The design and composition of the installed habitat were based on fish utilization of the natural channel below the hydro facility and design principles from previous habitat rehabilitation projects for anadromous fishes. Pre- and post-enhancement data on egg density and survival were collected using 1 m2 plots on both natural and artificially enhanced substrates. Three years of post-enhancement monitoring indicated higher egg densities and a greater proportion of live eggs in the artificially enhanced habitat compared to the natural habitat, with more pronounced trends observed for coregonids (lake whitefish and cisco) compared to lake trout. These findings suggest that habitat enhancement has the potential to enhance juvenile recruitment for adfluvial fish. A critical factor in the design was the substrate composition, providing adequate interstitial spaces for egg development and protection. This study represents the first documented attempt at habitat improvement in a regulated sub-Arctic river in Canada. The findings offer valuable guidance for stakeholders involved in new or existing development projects that require conservation actions to maintain fisheries productivity.
Citation: Miller, M., Stevens, C. and M. S. Poesch. (2025). Effectiveness of spawning substrate enhancement for adfluvial fish in a regulated sub-Arctic river. River Research and Applications 41(2): 412-425.
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*Lab members: Mark Poesch. Check out opportunities in the lab!
Abstract:
Urbanization can homogenize species composition across aquatic ecosystems by introducing disturbance that can destroy the habitat of unique endemic or native species and/or create an alternative habitat for the few species able to adapt to these conditions. Here, we use a long-term decadal dataset (1971 to 2010) on the fish species presence in 16 subwatersheds within three watersheds in the Greater Toronto Area, Canada; and assessed whether fish communities have changed over time for three categories of species assemblages: (1) native species community only, (2) nonnative species community only, and (3) a combination of all species (all species). We considered three significant variables for which data exist: catchment area, distance to a species pool source, and percentage of urban cover (i.e., percent of the impervious area within a catchment) to determine whether these variables alter species richness. We used the nestedness metric to evaluate the degree of interdependence among site assemblages and site compositional degradation over time to contrast trends in native and non-native sets of species. Overall, nestedness temperatures (NTs, which is ‘heat of disorder’) for native fish is lower [T=11.01] than nonnative fish assemblages [24.47], indicating that native fish are more nested than non-native fish species assemblages. Among the four decadal scales, the native species community showed high nestedness during the 1970s, which declined later (the 2010s), and an opposite trend occurred for the non-native species community. Although total species richness increased over time, native richness decreased with urbanization, with non-native species richness increasing and overcompensating native losses. The study further suggests that the non-native fish communities become patchier (less predictable and less nested). This implies that further changes in fish communities are likely, and the patchiness may isolate communities making them more prone to perturbations.
Citation: Pandit, S., Poesch, M. S., Kolasa, J., Pandit, L. K., Ruppert, J. L. W., and E. Enders (2024). Long-term evaluation of the impact of urbanization on native and non-native fish assemblages. Aquatic Invasions: 19(3): 345-360.
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*Lab members: Shubha Pandit and Mark Poesch. Check out opportunities in the lab!
Abstract:
The twin crises of climate change and biodiversity loss requires Notably, as one of the largest projects of its kind in the Great Lakes region (~500 hectares), extensive aquatic enhancement and restoration has been completed to support terrestrial and aquatic ecosystems with the intent of improving overall ecosystem health and biodiversity. Using twenty years of fish community data, we examined ecosystem responses in a spatio-temporal context across wetland and embayment ecotypes. Fish communities were assessed through a multi-metric index based on species life-history traits and habitat association. Generally, fish communities along the waterfront have transitioned from cool and coldwater pelagic species. Further, there are higher proportions of generalists and a higher proportion of native warmwater species, many of them piscivores, associated with cover and vegetation, that tend to meet community targets. Notably, these changes are more pronounced at Tommy Thompson Park compared to the rest of the waterfront, where communities approach natural reference levels. This result indicates the benefits and effectiveness of the decade long restoration efforts and subsequent monitoring of responses. This study provides important implications for large scale restoration and enhancement activities globally.
Citation: Theis S., Cartwright L., Chreston A., Coey B., Graham B., Little D., Poesch M.S., Portiss R., Wallace A. and J. L. W. Ruppert (2024). A multi-metric index for assessing two decades of community responses to broad scale shoreline enhancement and restoration along the Toronto waterfront. Aquatic Conservation: Marine and Freshwater Ecosystems 34: e24141.
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*Lab members: Sebastian Theis, Mark Poesch. Check out opportunities in the lab!
Abstract:
Aquatic habitat in the Greater Toronto Area has been subject to anthropogenic stressors. The subsequent aquatic habitat degradation that followed led to the Toronto and Region waterfront being listed as an Area of Concern in 1987. Thus, extensive shoreline and riparian habitat restoration have been implemented as part of the Toronto and Region Remedial Action Plan in conjunction with local stakeholders, ministries, and NGOs in an overall effort to increase fish, bird, and wildlife habitat. A key aspect of current fish habitat restoration efforts, monitored by Toronto and Region Conservation Authority, is to account for long-term community changes within the target ecosystem to better understand overall changes at a larger spatial scale. Here we use electrofishing data from the past 20 years with over 100,000 records and across 72km of coastline to show how declines and fluctuations in fish biomass and catch along the waterfront are driven by a few individual species across three main ecotypes, such as coastal wetlands, embayments, and open coast sites, with the remaining species showing a high level of stability. Using community traits and composition for resident species we demonstrate native warmwater species have become more dominant along the waterfront in recent years, suggesting that restoration efforts are functioning as intended. Additionally, piscivore and specialist species have increased in their relative biomass contribution, approaching existing restoration targets. Altogether this waterfront-wide evaluation allows us to detect overall changes along the waterfront and can be beneficial to understand community changes at an ecosystem level when implementing and monitoring restoration projects.
Citation: Theis S., Cartwright L., Chreston A., Wallace A., Graham B., Coey B., Little D., Poesch M.S., Portiss R., and J. Ruppert (2024). Nearshore fish community changes along the Toronto Waterfront in accordance with management and restoration goals: Insights from two decades of monitoring. PLos One: 19(2): e0298333.
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*Lab members: Sebastian Theis, Mark Poesch. Check out opportunities in the lab!
Abstract:
Mitigation banking is part of the ever-expanding global environmental market framework that aims to balance negative approved anthropogenic impacts versus third-party provided ecosystem benefits, sold in the form of credits. Given the need to conserve freshwater biodiversity and habitat, banking has received great traction in freshwater systems. While extensive reviews and studies have been conducted on evaluating if equivalency between impacts and offset can be achieved, there is almost no research being done on the way credits are being generated. Synthesizing banking data through cluster analyses from 26 banks in the United States generating credits for freshwater species and systems, we show two dominant approaches: removing barriers and targeting whole communities. Both address crucial freshwater conservation needs but come with their risks and caveats. Using common characteristics and management practices within these two groups, we showcase and conclude that credit generation via barrier removal can be at risk of granting credit generation for too large of an area, leading to over-crediting. Banks targeting whole freshwater communities and accounting for landscape-level interactions and influences can potentially be detrimental for species on an individual level and large-scale credit availability as well as transfer can incentivize non-compliance with the mitigation hierarchy.
Citation: Theis S. and M. S. Poesch. (2024). What makes a bank a bank? Differences and commonalities in credit calculation, application, and risks in mitigation banks targeting freshwater fish species and associated ecosystems. Environmental Management: 73(1): 199-212.
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*Lab members: Sebastian Theis, Mark Poesch. Check out opportunities in the lab!
