The European green crab, an invasive species has been destroying shellfish stocks in the Maritimes since at least 2002 and in B.C. since 1999, has been found in Placentia Bay, N.L., the federal Department of Fisheries and Oceans confirmed.

It's not clear how the crab — known in the fishing industry as the "cockroach of the sea" — ended up in waters off Newfoundland, DFO research scientist Cynthia MacKenzie said Friday, but local speculation is that the crabs migrated with ballast water from oil tankers.

"We can't confirm it came in a specific way," MacKenzie told CBC News. "But where it was found in the Maritimes, we can safely say that it was vessel traffic," she said, adding that the crab most likely got to Placentia Bay the same way.

The department is organizing a green crab population survey and will begin collecting samples to get a sense of the sex and ratios of the crab in the area, MacKenzie said.

The green crab,which has no natural enemies,preys on shellfish, may compete with lobster for food stocks and can also feed on juvenile lobster.

The crabs were introduced to North America in the 1950s. By last year, they had expanded their range around Cape Breton, north to Prince Edward Island and the Magdalen Islands of Quebec. On the West Coast, the green crab has invaded waterways from San Francisco to Vancouver Island.

Recently, fishermen in Placentia Bay noticed a mass of strange looking crab feeding on fish offal.

Earle Johnson, a fisherman in North Harbour, found some of the crab and said he was worried immediately when he saw the species, because of the havoc it wreaks on local shellfish stocks.

"They're very destructive to the mussels and scallops, clams," Johnson said. "They're certainly quite capable of tearing up the small lobsters."

A study in 2006 said the crab's northern success could be thanks to from multiple invasions introducing new genetic lines to the population.

According to DFO, the European green crab can be identified by five spines on the top front edge of each side of the shell and its somewhat flattened rear legs. It cannot easily be distinguished by its colour, as some native species are also green.