FOR IMMEDIATE RELEASE March 3, 2026
Early-stage zebra mussel colonization confirmed in the Wolastoq | Saint John River
collaborative CRI–NB Power monitoring identifies limited but infrastructure-focused presence
The Canadian Rivers Institute (CRI) based at the University of New Brunswick and NB Power have released preliminary findings from a 2025 collaborative bio-monitoring program assessing zebra mussel colonization in the Wolastoq.
Although zebra mussels are already well established in Lac Témiscouata, Québec (which connects to the Wolastoq via the Madawaska River), our 2025 surveys indicate that their presence in the Wolastoq (Saint John River) remains low. Only a small number of individuals were detected and they were found in scattered locations rather than continuously throughout the river. Detections extended as far south as the confluence of Belleisle Bay and the Wolastoq.
During the 2025 field season, researchers surveyed 81 locations and documented 22 adult zebra mussels at just three sites. Of those, 21 individuals were associated with hydroelectric infrastructure, with the highest concentration observed at Mactaquac Generating Station (19 mussels) and two individuals detected at Beechwood Generating Station.
“The current low-level colonization provides an important opportunity to take informed, proactive steps to better mitigate negative impacts to infrastructure and reduce the risk of spread to other waters in New Brunswick,” said Dr. Meghann Bruce of the CRI.
What Was Done
In 2025, the CRI partnered with NB Power to carry out biomonitoring research to assess the state of zebra mussel colonization in the Wolastoq River. Field investigations were conducted at four hydroelectric facilities between June and October 2025. Work included visual infrastructure inspections, sub-surface observations, environmental monitoring and laboratory analysis.
Key Findings
Zebra mussels were detected at 3 of 81 survey locations in the Wolastoq.
No zebra mussels were detected at Tobique Narrows Generation Station or Grand Falls Generation Station.
The majority of detections occurred at Mactaquac Generating Station (19 mussels); two individuals were detected at Beechwood Generating Station.
One zebra mussel was detected near the confluence of Belleisle Bay and the Wolastoq, marking the furthest downstream confirmed discovery to date.
Colonization patterns appear to reflect local hydraulic and structural conditions rather than simple proximity to upstream sources (Lake Témiscouata).
Why This Is of Public Interest
Zebra mussels are an invasive species capable of rapid population growth and infrastructure fouling. In regions where they have become established, populations can expand quickly. Once densities increase, management becomes significantly more difficult, more costly and less effective.
What remains uncertain is how growth conditions in this region compare to other invaded systems and what level of colonization may ultimately occur in New Brunswick waters. Some areas may experience more extensive establishment than others. Ongoing monitoring is aimed at understanding what colonization could look like for New Brunswick’s freshwater systems.
The 2025 results indicate that the Wolastoq is not yet experiencing widespread colonization, but localized low-level establishment on infrastructure is occurring. Researchers also note that prolonged low-flow conditions during late summer 2025 may have enhanced settlement opportunities, reinforcing the importance of continued seasonal monitoring.
Looking Ahead
Continued collaboration between CRI and NB Power will focus on refining monitoring strategies and assessing colonization rates to proactively plan mitigation of negative impacts, but this work will also be extended through collaboration with the New Brunswick Invasive Species council to understand the potential broader impacts to NB freshwaters, strengthening early-detections efforts and aim to prevent spread to other New Brunswick Freshwaters.
Media Contact
Dr. Meghann Bruce
Canadian Rivers Institute
University of New Brunswick
meghann.bruce at unb.ca
506-230-1652