Pesticide utilized in try to eradicate invasive fish species in Nova Scotia lake – Halifax

The battle in opposition to invasive smallmouth bass has moved to a lake in jap Nova Scotia the place a chemical geared toward killing the species was used this previous weekend.

Jason LeBlanc, director of the inland fisheries division within the provincial Division of Fisheries and Aquaculture, mentioned 1,500 litres of an answer containing the pesticide rotenone was pumped into Dobsons Lake close to Canso, N.S.

LeBlanc mentioned the eradication undertaking is geared toward preserving native brook trout within the Cole Harbour watershed, into which Dobsons Lake feeds. It follows an identical fish kill at Piper Lake in Nova Scotia’s Pictou County that was carried out in October 2020.

In an interview Monday, Leblanc mentioned what was used within the 52-hectare lake was a combination containing 5 per cent of the pesticide’s energetic ingredient.

“It’s a really small quantity as soon as it’s blended with water that’s required to be poisonous to fish,” he mentioned. “It’s early, however up to now there are not any indications that there are stay fish in Dobsons Lake.”

Rotenone, which has been in use because the Nineteen Fifties, targets fish gills and inhibits their respiratory whereas leaving birds and mammals unaffected. Nevertheless, it does kill all fish within the space the place it’s used and can even have an effect on amphibious invertebrates corresponding to frogs and salamanders early of their life cycle, when they’re nonetheless respiratory by means of gills.

The issue with smallmouth bass in Dobsons Lake was first recognized within the spring of 2020 when the division obtained stories that the species had been illegally transferred there.

Earlier than resorting to rotenone, LeBlanc mentioned the lake’s outflow was blocked off and unsuccessful makes an attempt have been made to take away the invasive species by means of focused angling and electrofishing, which entails fatally stunning fish utilizing a rod or specialised boat.

“Mechanical removals alone is not going to end in full eradication,” he mentioned. “You’ll be able to definitely management populations that means, however you’ll by no means do away with all of them. The easiest way to strategy full eradication is utilizing a fish toxicant.”

LeBlanc mentioned the division additionally eliminated native brook trout and minnows from the lake and plans to reintroduce them as soon as lake circumstances enhance, probably within the spring.

At Piper Lake, which at 5 hectares is way smaller than Dobsons, it’s believed use of the pesticide in 2020 resulted in full eradication of smallmouth bass, he mentioned. “There have been no fish detected in followup surveys within the spring and thru 2021.”

LeBlanc additionally mentioned aquatic organisms corresponding to zooplankton have been discovered to have rebounded rapidly at Piper Lake, and frogs and salamanders have been detected within the space as nicely.

The usage of the chemical within the Nova Scotia lakes has been largely supported by sport-fishing organizations such because the Atlantic Salmon Federation. In an interview final month, Raymond Plourde, senior wilderness co-ordinator for the Halifax-based Ecology Motion Centre, additionally mentioned that whereas use of rotenone is “not splendid,” it’s higher than letting an invasive species ceaselessly change a selected watershed.

Nevertheless, the pesticide has sparked controversy in neighbouring New Brunswick, the place a gaggle of cottagers on Miramichi Lake obtained an injunction final month in opposition to a smallmouth bass eradication undertaking there and within the surrounding Miramichi watershed.

That court docket motion was quickly deserted and a gaggle of Indigenous “water protectors” then sought a judicial evaluate of the undertaking earlier than the Federal Courtroom of Canada, which is but to make a ruling.

The group advocating the chemical’s use, the Working Group on Smallmouth Bass Eradication, has since introduced that it accomplished the primary part of its remedy undertaking final Thursday in Lake Brook and in about 15 kilometres of the Southwest Miramichi River.

Spokesman Neville Crabbe wouldn’t reveal Tuesday when the biggest part of the undertaking, on Miramichi Lake and the encompassing watershed, would start. Protesters have been in a position to efficiently stymie using rotenone within the space final 12 months.

“Our intention is to finish our licensed undertaking this 12 months,” Crabbe mentioned.

The group’s undertaking obtained federal approval in June 2021 after smallmouth bass have been first detected within the Miramichi watershed in 2008.

This report by The Canadian Press was first printed Sept. 13, 2022.