George Poitras, of the Mikisew Cree First Nation in Fort Chipewyan, Alta., says he's glad a fish found in Lake Athabasca last summer did not have two mouths, as originally believed. (Courtesy of Ling Wang)

Residents of Fort Chipewyan, Alta., remain convinced that pollution from the oilsands is harming their environment, an aboriginal official says, even after a biologist found that what appeared to be a mutated fish was not deformed.

Residents in the remote northern Alberta community said the goldeye had two mouths when it was caught from the shore of Lake Athabasca in August, raising fears it may have been contaminated by oilsands development upstream.

But University of Alberta biologist Joe Nelson, who examined the fish, said its tongue — which has teeth on it — fell through the soft tissue under its chin, forming what looked like a second mouth.

The scientist's finding that the fish was not mutated was a relief to members of the Mikisew Cree First Nation in Fort Chipewyan, First Nation official George Poitras told CBC News on Tuesday.

But Nelson's findings do not mean the water in the community is safe, Poitras said.

"What we do clearly observe in Fort Chipewyan and we've heard anecdotally in the past that there have been mutated fish," Poitras said in an interview.

"We've also observed fish with lesions on them, with cancerous tumours on the outside, with diseased insides … fish that don't taste normal, and many other types of deformities."

Poitras said people in Fort Chipewyan have yet to receive any acceptable explanation for high rates of cancer in the community.

Last month, a report from Alberta Health Services found that the number of cancer cases in Fort Chipewyan is higher than expected, with 51 cancers found in 47 people there between 1995 and 2006.