Dead fish rising to surface after rotenone spray will be disposed of, group says

·3 min read
Smallmouth bass are considered an invasive species in southern and western New Brunswick.  (Nathan Wilbur, ASF - image credit)
Smallmouth bass are considered an invasive species in southern and western New Brunswick. (Nathan Wilbur, ASF - image credit)

Dead smallmouth bass and other fish that float to the surface of Miramichi Lake after they're poisoned will be scooped up and disposed of, according to a federal document.

Disposal will happen in a provincially approved manner, says the Department of Fisheries and Oceans document prepared in September 2021 and provided to cottager John Hildebrand after a right to information request.

But most of the fish that are killed by the rotenone spraying planned for this summer will stay below the surface, said Neville Crabbe, spokesperson for the Working Group on Smallmouth Bass Eradication in the Miramichi.

Any fish that do float up will be collected by hand and with a dip net, he said.

"We can't go to the bottom and pick up fish," said Crabbe. "There's no expectation of that."

Pierre Richard/Radio-Canada
Pierre Richard/Radio-Canada

He said cottage owners near Miramichi Lake had requested his group add a fish collection component to the spray project.

The spray group hopes getting rid of smallmouth bass will allow for the return of salmon.

The group has permission for two sprayings separated by a minimum of two weeks, but no date has been announced for when that will happen. Cottagers were informed earlier that they'd get only 24 hours' notice. 

Smallmouth bass numbers not known

There is no estimate of the size of the smallmouth bass population in the lake, but Crabbe said the number is "irrelevant" because it takes just a handful of the invasive fish to start a population.

"The threat remains the same whether you have six or 6,000," Crabbe said. "A population estimate is insignificant."

A 2018 report by DFO said the population in Miramichi Lake is likely small, since catch rates from methords such as electrofishing and gill nets were low.

Shane Fowler
Shane Fowler

The odour

While there is an odour associated with the rotenone product, Crabbe said it would be short-lived.

"There is an odour associated with the product, like any product dish, so bleach, you know, things do have a smell that's detectable by humans," he said.

Crabbe said he does not anticipate any "significant odour concerns" except for at the disposal site about one kilometres from the lake.

He said the working group has had a hole dug where the dead fish from the surface of the lake will be buried and covered with lime to mitigate the smell.

The spray will kill smallmouth bass and other fish and insects.

According to the DFO document provided to Hildebrand, Noxfish Fish Toxicant II, the rotenone product, will modify the food web, the fish habitat, and ecological structure of the lake as result for the decomposition of what's been killed.

Treatments to be made

Shane Fowler/CBC
Shane Fowler/CBC

The first spraying of rotenone will cover Miramichi Lake, Lake Brook, and the Southwest Miramichi River.

The second treatment will only cover Lake Brook and the river.

"It's a far less uniform environment than the lake," said Crabbe.

Beaver dams will be removed to ensure proper chemical dispersal when necessary, and nearby trails and roads will be cleared, the document states.

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