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Eradicating smallmouth bass from the Miramichi watershed


Invasive species are a high-level threat to biodiversity worldwide. In the Miramichi, Fisheries and Oceans Canada has determined that, "a measurable decrease in abundance of native populations is likely to occur" if smallmouth become established. This will have negative repercussions for fisheries and human cultures tied to the Miramichi ecosystem as well. 

The International Union for the Conservation of Nature has determined that prevention I paramount, but once an invasive species has arrived, "early detection, monitoring and eradication can stop the species spreading."

The actions of the Working Group in the Miramichi watershed constitute a conservation activity to prevent future harm, permanent alteration of the ecosystem, and a loss of biodiversity. 

The Plan

Full details

The full details of our proposed eradication project, including mitigation and monitoring plans can be found in the registration document submitted to New Brunswick's Department of Environment and Local Government in October 2020. The full document can be viewed on the government's public registry or below:


Containment and control efforts may slow the spread of alien invasive species, but are never effective for eradication. DFO's experience at Miramichi Lake beginning in 2009 supports this conclusion: despite thousands of individuals being removed from the site of the illegal introduction, in each year smallmouth bass of every age class were discovered.

In 2017 the Working Group contracted Fish Control Solutions and the Canadian Rivers Institute to create an expert report on smallmouth bass eradication in Miramichi Lake. The auth that conducted an analysis of options to eradicate. They included:

  • Dewatering the lake

  • Explosives

  • Genetic manipulation

  • Predator introduction

  • Barrier construction

  • Rotenone use

All except the use of rotenone were considered to be impractical, have a low likelihood of success, or carry significant risks on their own. The authors of the expert report concluded, "Treatment of Miramichi Lake with rotenone is most likely to eradicate smallmouth bass and eliminate a source of future smallmouth bass invasion to the Miramichi River system." 

Based on that conclusion, and drawing from the extensive body of knowledge and experience with rotenone in fisheries management, the Working Group began formulating a plan to use a Health Canada approved rotenone product in Miramichi Lake. Following the discovery of smallmouth bass in the Southwest Miramichi River in 2019, the plan was expanded to include an approximately 15-kilometre stretch of the river. 

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