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

The struggle towards invasive smallmouth bass has moved to a lake in japanese Nova Scotia the place a chemical aimed 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, stated 1,500 litres of an answer containing the pesticide rotenone was pumped into Dobsons Lake close to Canso, N.S.

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

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

“It’s a really small quantity as soon as it’s combined with water that’s required to be poisonous to fish,” he stated. “It’s early, however thus far there aren’t any indications that there are stay fish in Dobsons Lake.”

Rotenone, which has been in use because the Fifties, targets fish gills and inhibits their respiratory whereas leaving birds and mammals unaffected. Nonetheless, it does kill all fish within the space the place it’s used and also can have an effect on amphibious invertebrates resembling 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 studies that the species had been illegally transferred there.

Earlier than resorting to rotenone, LeBlanc stated the lake’s outflow was blocked off and unsuccessful makes an attempt had 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 won’t end in full eradication,” he stated. “You possibly can definitely management populations that method, however you’ll by no means do away with all of them. One of the best ways to strategy full eradication is utilizing a fish toxicant.”

LeBlanc stated 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 stated. “There have been no fish detected in followup surveys within the spring and thru 2021.”

LeBlanc additionally stated aquatic organisms resembling zooplankton had been discovered to have rebounded shortly at Piper Lake, and frogs and salamanders had been detected within the space as effectively.

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 stated that whereas use of rotenone is “not excellent,” it’s higher than letting an invasive species ceaselessly change a specific watershed.

Nonetheless, the pesticide has sparked controversy in neighbouring New Brunswick, the place a gaggle of cottagers on Miramichi Lake obtained an injunction final month towards 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 Court docket 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 most important part of the undertaking, on Miramichi Lake and the encircling watershed, would start. Protesters had been capable of efficiently stymie the usage of rotenone within the space final 12 months.

“Our intention is to finish our approved undertaking this 12 months,” Crabbe stated.

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

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