DFO has captured and destroyed tens of thousands of green crabs in P.E.I. in the last two years. (CBC)

The population of green crabs, an invasive species from Europe that eats mussels and scallops, is growing and spreading across P.E.I., say government officials.

A monitoring program from the Department of Fisheries and Oceans has been catching thousands a year along the eastern shore of the province.

Cody McKenna, who works on the DFO program, said the crabs are showing up in large numbers in Montague, north to the Gulf of St. Lawrence.

"They're extremely aggressive, outcompete other crabs, because they're so quick and aggressive and stronger," said McKenna.

Last year DFO began a program to trap and destroy the crabs, but early numbers are not encouraging. Twelve thousand were trapped last year, and close to 10,000 have been trapped already in 2010.

The worst area is Basin Head, where the crabs are not only feasting on shellfish and tearing through the local red crab population, they are also disturbing a rare form of Irish moss found in the area.

The province has also been monitoring green crabs. Provincial aquaculture director Neal MacNair has been watching them spread along the Northumberland Strait. Summerside never used to see any, and now there are hundreds.

"We're concerned with that because there's quite an oyster resource in there," MacNair said.

While concerned, the province does not have a plan to stop the little green invaders.

"Other places in the world that have tried to eradicate them, that hasn't been successful anywhere. They're pretty much here to stay," he said.