The male Coregonus googelii, or 'googly-eyed cisco,' was captured by Paul Vecsei's team in October 2008. (Submitted by Paul Vecsei)

A fish biologist in the Northwest Territories says he may have found an entirely new species of cisco in Great Slave Lake.

Paul Vecsei of Golder Associates said he and some federal government researchers were at the Sub Islands near Yellowknife in October, pulling up nets, when they hauled up the unusual-looking cisco with large fins, enormous eyes high up on its head and an upturned mouth.

The male fish, 27.8 centimetres in length, has been named Coregonus googelii, or the "googly-eyed cisco."

"It had enormous eyes for the size of the individual. It had eyes that were unlike other cisco or fish in general," Vecsei, whose company is based in Yellowknife, told CBC News in an interview that aired Monday.

"The eyes are positioned very high, so when you look at it from a dorsal view, the eyes are almost joining at the top and you have just a narrow separation."

Vecsei said researchers are trying to determine if the fish is a relic of a very old species, a newly-evolved species, or just a variation of cisco that's specific to the Sub Islands.

"At the time, I frankly didn't even consider that maybe we discovered something," he said of the find.

"Rather, I thought it's just some of the lesser-known species that exist elsewhere, and we thought it just may look a little different here."

New and different species?

Already common in Great Slave Lake, ciscos can range from tiny fish that live in fast-flowing rivers, to fish as large as whitefish that live in deep lakes.

After checking with other fish experts across Canada, Vecsei realized what he had found was new and different.

But whether it's a separate species is up for debate, said Jim Reist, head of Arctic fish ecology with the federal Department of Fisheries and Oceans in Winnipeg.

"What one individual may conclude and defend and say, 'This is the way the world is,' another individual working in the same area and on the same material may come up with a differing opinion," he said.

Reist said the definition of what constitutes a new species can change on a case-by-case basis.

He added that the line between cisco species is blurry and especially difficult to establish in Canada's North, where plants and animals have only been around since the last Ice Age and continue to evolve today.

The decision on whether Coregonus googelii should be a new species will come down to a professional judgment call, Reist said. Even after that call is made, he said the matter could remain up for debate.