Ecology of the American eel (Anguilla rostrata) in a large hydropower regulated river
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Date
2025-09
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University of New Brunswick
Abstract
The endangered, facultatively catadromous American eel (Anguilla rostrata) has experienced severe population declines, largely driven by habitat fragmentation and migration barriers caused by dams. In the Wolastoq | Saint John River in Canada, the Mactaquac Dam acts as a major barrier to upstream migration, restricting access to historical habitats. An upcoming dam refurbishment could include an upstream eel passage, but determining whether such a passage should be installed depends on a solid understanding of eel ecology in the river. This dissertation provides a comprehensive assessment of the movement patterns, habitat use, and life-history traits of American eels in the lower Wolastoq, establishing essential baseline data for future conservation and management efforts.
This thesis comprises four complementary studies that together advance understanding of eel ecology in the Wolastoq | Saint John River. First, I sampled the upstream-migrating juvenile eel population along the 150 km stretch between the river mouth and the Mactaquac Dam over two migration seasons. Age structure analyses indicated that upstream eel migration can take multiple years and involves phases of juvenile residency. I then conducted a mark-recapture study at the Mactaquac Dam over three consecutive migration seasons, which produced annual estimates of 150,000 to 950,000 juvenile eels arriving at the dam. To support this effort, a laboratory study confirmed that the visible implant elastomer tags used in the mark-recapture study did not significantly affect eel survival. Lastly, I carried out an acoustic telemetry study examining the movement ecology of yellow-phase eels in the lower Wolastoq, which revealed limited longitudinal movement (mean linear range ± SD: 6.4 ± 10.9 km) and high site fidelity over time.
By establishing novel baseline data on movement patterns, habitat use, and population structure of American eels prior to any potential upstream passage implementations, this dissertation offers a critical reference point for assessing the outcomes of future management efforts in the Wolastoq | Saint John River and informs decision-making surrounding eel passage at the Mactaquac Dam. Beyond its regional relevance, this dissertation advances understanding of how migratory fishes interact with large, fragmented river systems, contributing new perspectives to movement ecology and freshwater conservation science.
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FORESTRY, AGRICULTURAL SCIENCES and LANDSCAPE PLANNING::Animal production::Fishery