Protecting Native Species of Fish in Nova Scotia

The government is taking steps to protect Nova Scotia’s native species of fish, including Atlantic salmon and brook trout.

This weekend, staff from the Department of Fisheries and Aquaculture will use a fish pesticide called rotenone in Dobsons Lake, Guysborough County, to kill invasive smallmouth bass and prevent their spread to other waterways.

“We’ve seen the harm this invasive species has had on native fish communities in hundreds of lakes and waterways throughout Nova Scotia, where once strong populations of brook trout and other fish have been dramatically reduced or entirely eliminated by smallmouth bass,” said Steve Craig, Minister of Fisheries and Aquaculture. “Rotenone is a measure of last resort, but it’s one we know from experience works to protect our native fish species and the ecosystems that support them.”

Local anglers first reported smallmouth bass in Dobsons Lake in the spring of 2020. Efforts to contain and control the population – including temporary barriers, targeted angling, and electrofishing – have been helpful in the short term but are not sustainable or effective long-term solutions.

Rotenone is a biological pesticide derived from plants. It works by preventing the absorption of oxygen in the cells of insects and fish and has been used for hundreds of years to manage invasive fish species. Rotenone-treated water poses no ongoing risk to humans or animals.

Rotenone was successfully used to eradicate smallmouth bass from Piper Lake in Pictou County in October 2020. The lake is now recovering, with frogs and other amphibians already back, along with invertebrates like zooplankton that support the recovery of fish populations. Monitoring has confirmed some local fish species have started to come back, too.

Public access is restricted at Dobsons Lake while Department staff and project team volunteers are onsite. Dobsons Lake will be monitored daily for several weeks after the rotenone treatment and periodically over the next several months. It will remain closed to recreational angling until it can support a sport fishery.