Kejimkujik National Park, located in Nova Scotia, has decided to halt its annual brook trout census due to the detrimental impact of an invasive species on the local ecosystem. The census, which commenced in the 1990s with volunteer fly fishers participating in counting, weighing, and measuring brook trout, aimed to assist Parks Canada in species monitoring.
Parks Canada recently informed CBC News that the current census is on hold because of the overwhelming presence of chain pickerel, which accounted for 90% of the fish caught in the national park in western Nova Scotia in 2025. The agency spokesperson stated that the invasive chain pickerel’s invasion has significantly reduced the brook trout numbers reported in the census, affecting the statistical power required for the monitoring project.
Originally introduced illegally to Nova Scotian waters in 1945, chain pickerel gradually spread across the province, making their first appearance in the park in 2018. Once established in a water system, chain pickerel quickly dominate by consuming various species, including fish, reptiles, frogs, dragonflies, and even ducklings.
Despite efforts by Kejimkujik staff to implement fish barriers to control the spread of chain pickerel, challenges such as flooding rendered these measures ineffective. Nevertheless, Parks Canada remains committed to mitigation efforts, with over 5,300 chain pickerel already removed by staff and volunteers.
In light of the situation, Parks Canada will continue monitoring brook trout populations through alternative methods, such as the angler diaries program and deploying fyke nets annually in different water bodies within Kejimkujik. Conservationists are advised to shift focus to areas not yet invaded by chain pickerel, as early intervention is crucial in managing invasive species.
Trevor Avery, a biology and mathematics professor at Acadia University, has been tracking chain pickerel in Kejimkujik since their introduction. His research involves analyzing the contents of chain pickerel stomachs to understand their predatory behavior. Chain pickerel, being ambush predators, consume prey that fits into their mouth, posing a challenge to ecosystem balance.
Recreational fishing enthusiasts in Nova Scotia have historically enjoyed world-class brook trout fisheries. Andrew Lowles, resource manager at the Nova Scotia Department of Fisheries and Aquaculture, highlighted the allure of chain pickerel for anglers due to their fighting abilities, offering a different fishing experience during summer vacations and cottage stays.
Kejimkujik National Park’s diverse waterways, comprising 46 lakes, over 30 streams and rivers, interconnected within the Mersey River watershed, present a complex challenge in protecting the ecosystem from the invasive chain pickerel. Despite the difficulties, Parks Canada remains dedicated to conservation efforts to safeguard native fish populations and maintain the ecological balance within the park.
