The Toothed Rock Crab was caught in a trawl by local whitefish boat Venture north of Muckle Flugga last week.
Fisherman Ivor Moffat brought it to the NAFC Marine centre in Scalloway where scientists identified it as Cancer bellianus, normally found off the west coast of Africa and southern Europe.
The large male crab measured 157mm across its widest point and was caught at a depth of 110 metres.
Shellfish research assistant Kathryn Allan said it was closely related to the more common brown crab.
“It has similar features with a broad oval shaped back and black tipped claws. It differs by having rows of small serrated teeth around the edge of the shell which is pale brown and spotted with red,” she said.
“We were quite surprised to see this species in Shetland as it is more abundant in the southern part of its range, such as the Canary Islands and the Azores, and it is much less common further north.”
The last published records of it in Shetland waters were back in the 1960s when a male was caught in a creel off Foula in December 1963 and a second male in a creel at Ronas Voe in August 1964.