Kejimkujik National Park in Nova Scotia has decided to halt its annual brook trout census due to the severe 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 to aid Parks Canada in species monitoring, has been paused this year.
Parks Canada disclosed to CBC News that the census suspension is a result of the prevalence of chain pickerel, which constituted nine out of ten fish caught in the national park in western Nova Scotia in 2025. The agency stated that the invasive chain pickerel’s presence has significantly diminished the number of brook trout recorded in the census, rendering the data insufficient for statistical analysis.
Chain pickerel, illicitly introduced to Nova Scotian waters in 1945, infiltrated the province and made their debut at the park in 2018. Once established, they swiftly dominate the ecosystem by preying on various species, including fish, reptiles, frogs, dragonflies, and even ducklings.
The angler diary program data from the park indicates a substantial increase in chain pickerel catch rates, escalating from 18% in 2020 to 66% in 2021 and exceeding 80% the following year. Ken Donnelly, the executive director of Invasives Canada, emphasized the difficulty of eradicating chain pickerel once they establish themselves, expressing understanding for Parks Canada’s decision to pause the census.
Parks Canada highlighted the challenge of safeguarding the entire Kejimkujik or Mersey River system from chain pickerel due to their widespread presence. Despite unsuccessful attempts to implement fish barriers due to flooding, the agency remains committed to mitigation efforts, with over 5,300 chain pickerel already removed by Parks Canada staff with the assistance of volunteers.
At Kejimkujik, chain pickerel must be retained, and anglers are prohibited from releasing them back into the water. Native fish species, including trout, are to be released if caught. The monitoring of brook trout will continue through alternative methods such as the angler diaries program and the annual deployment of fyke nets in various water bodies to track native fish populations.
Conservationists are advised by Donnelly to shift their focus to areas where chain pickerel have not been introduced, emphasizing the importance of early intervention in invasive species management. Trevor Avery, a biology and mathematics professor at Acadia University, has been researching chain pickerel at Kejimkujik since their introduction, studying their feeding habits and advocating for population management strategies.
Nova Scotia’s reputation for hosting exceptional brook trout fisheries is well-known, with Andrew Lowles, resource manager at the Nova Scotia Department of Fisheries and Aquaculture, highlighting the historical significance of the region in fishing literature. Despite the challenges posed by chain pickerel, which are popular among anglers for their strong fighting abilities, opportunities exist for recreational fishing in the area.
