Giant red king crabs from Russia which can grow up to 6ft across and weigh 28lbs have been found in UK waters.
Fishermen have been finding the alien species in waters off Yorkshire, and have been catching them for the local restaurant market.
But there are fears they could wipe out local fish species - including scallops and native crabs.
One fisherman told the Sun Online : “I’m really excited, but worried about our native seafood.”
Giant red king crabs are native to North America, though scientists introduced them to Russia in the 1960s and they thrived in the Arctic Ocean.
The huge crabs then travelled to Norway, where they sparked another fishing boom.
Fish supplier Shaun Henderson, who sells to more than 80 restaurants, said one of his fishermen pulled up 40st of king crabs off Bridlington, East Yorks this week.
It was the first time anyone in his family had caught a king crab, he said, despite them having fished in the area for two generations.
