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New Crab Found in Swedish Waters

News: May 19, 2008

A new kind of crab has been found on the Swedish West Coast. The crab, which has its normal northern boundary outside Scotland, was found by students who dissected a cod caught outside the estuary of Gullmar Fjord.

The Goneplax rhomboides crab has its normal northern boundary outside Scotland and the Shetland Islands. Two spectacular discoveries of the species on the Bohus Coast suggest that it has now moved into Swedish waters. The first discovery was made by some students on our course in Fish Ecology, who dissected trawled cod outside Gullmar Fjord. They found a strange crab in the stomach of a smaller cod.

"They gave the crab to their tutor, who in turn gave it to me”, says Matz Berggren, Researcher at the Department of Marine Ecology at the University of Gothenburg and who also works at the Sven Lovén Centre for Marine Sciences at Kristineberg. The crab turned out to be a specimen of Goneplax rhomboides, a species that has not been caught North of the Shetlands, and never in Skagerrak.
The specimen the students found was more or less intact, which means that the cod must have caught and eaten the crab just before it was trawled. This in turn means that the crab must have been the cod’s prey on the seabed somewhere outside the estuary of Gullmar Fjordjorden.

Just a few weeks later, during sample-taking as part of the programme for environmental control of seabed fauna on the West Coast, yet another discovery of this crab was made at the same place.
”The interpretation of the first find was that it was not an isolated incident, and that the crab could have established itself in the soft seabeds of the West Coast, says Matz Berggren, who is also responsible for Crustaceans for Nationalnyckeln (The Swedish National Key).

Goneplax rhomboides is a relatively small crab, but clearly distinguishes itself from our domestic crabs with its rectangular carapace, long eyestalks and claws, and slightly yellow-white or reddish colour over the body. The caught specimen has been handed over to the Gothenburg Natural History Museum.

Matz Berggren, Department of Marine Ecology, University of Gothenburg:
+46 523 185 32


Facts about Goneplax rhomboides

Name: There is no Swedish name for the species, but in Germany it is called the Quadratkrabbe and in England the Angular crab
Size: Can be up to 37 mm at the carapace
Colour and pattern: The carapace is yellowish to pale red/pink, sometimes fringed with violet and is often divided into a light area and a darker area. Claws and legs yellowish to pale orange.
Lives: Found in its normal distribution area from the beach zone (uncommon) and down to nearly 600 metres deep. Normally lives in the mud and sandy mud in which it digs shallow burrows in the sediment.

Geographic distribution: From the British Isles (but is uncommon in the North Sea) and as far south as South Africa. Also found in the whole of the Mediterranean.

(46) 31-786 49 12

Note of clarification

In case of doubt or confusion, the Swedish version of this press release takes precedence.

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