“Prior to the treatment, we were actively moving the trout and some crucian carp and holding them in another location until the lake starts to recover, and then we’ll move those native fish back,” said Jason LeBlanc, inland manager. fisheries department.
The department said invasive smallmouth bass were illegally introduced into the 52-hectare lake and pose a threat to native fish in a 5,400-hectare watershed that is home to one of the best remaining wild trout populations in Nova Scotia. Bass eat some native species and compete with others for food.
“It’s an important fishery there. Local residents really enjoy trout fishing in the area. By eliminating bass in Lake Dobsons they will protect those lakes and further down in the watershed,” LeBlanc said.
Smallmouth bass were discovered in Dobsons Lake near Canso in May 2020 and were quickly quarantined to prevent the spread.
Efforts to remove smallmouth — including targeted fishing and electrofishing — have failed.
After the bass were discovered, dams were installed to prevent the spread in a 5,400-hectare watershed that contained one of the best remaining wild trout populations in Nova Scotia. (Nova Scotia Fisheries and Aquaculture)
Over the weekend, 1,500 liters of pesticide containing 5 per cent rotenone will be pumped into the lake. Rotenone is taken up by the gills of fish and works by blocking the absorption of oxygen into the cells of insects and fish.
The province says it’s not a threat to people or animals, but public access to the lake will be restricted while the department is on site this weekend.
In October 2020, the department used 53 liters of the same pesticide to kill introduced bass in Lake Piper – a shallow five-hectare lake also on the eastern mainland.
LeBlanc said it worked. The bass were eliminated, frogs and invertebrates began to repopulate Lake Piper the following spring. Native fish are recolonizing the lake as well.
LeBlanc expects the same to happen at Dobsons Lake, but he can’t say when native trout will return to the area.
“That’s going to put them in a bit of a bind. It’s a free-flowing system. Once we remove the barriers that we currently have in place for containment — which we would do once we’ve confirmed that we’ve eradicated the bass — then the native fish species can go back into Dobsons Lake on their own LeBlanc said.
