Shellfish - Resources and Invaders of the North


Shellfish are the diamonds of the sea

​​​​​The mollusks and crustaceans that make up the shellfish group are a high-valued, high-quality food source and support substantial fisheries in boreal, subarctic and arctic areas. There is already a strong interest in both the North Pacific and the North Atlantic for shellfish resources, their population dynamics and their management, especially under changing environmental conditions. Global warming is now stressing indigenous cold-water species at the southern limit of their distribution range and promoting their shift northward, possibly into the High Arctic where receding ice will make exploitation of these and perhaps new species commercially feasible.

Large fisheries for northern shrimp have been established across the North Atlantic since the mid-1990s. Several crab fisheries developed toward the end of the last century, in particular those for snow crab and king crab off Canada, Greenland, Russia and Norway. American lobster and Norway lobster have been fished intensively in the North Atlantic for decades. The sea scallop fishery in the western North Atlantic has recently made a remarkable recovery, while fisheries for the Iceland scallop in the North Atlantic and weathervane scallop in the northeast Pacific never sustained a high level of exploitation.

Population dynamics of most important shellfish resources have, however, been changing considerably in recent years. These changes are believed to be related to climate, but the resulting stock dynamics differ geographically and across species. For example, in the northwestern Atlantic, many shrimp and some snow crab stocks are declining rapidly while in the northeast Atlantic and adjoining Arctic the shrimp stock remains high. In addition, the non-native snow crab has invaded this latter area and is predicted to become the world's largest snow crab resource.

​The edible crab, which supports fisheries from Spain through the North Sea to coastal mid-Norway, is spreading northwards and is now “meeting" the red king crab which is on the move westward in the coastal waters off northern Norway. The implications of this meeting are uncertain. 

The blue mussel has reappeared in Svalbard after a 1000-year absence. As the coastal waters are warming, the European lobster, the Norway lobster and the Great scallop are expanding their distribution northwards. Further south, the invasive Pacific oyster is “moving" northwards, with unknown interactions and success. In the North Pacific, the snow crab has expanded its distribution from the eastern Bering Sea into the Chukchi and Beaufort Seas. Although snow crabs are more abundant in the Chukchi than Beaufort Sea, only snow crab in the Beaufort Sea currently achieve marketable sizes. The decline of ice cover in the Arctic may also spark commercial interest for hitherto unexploited species which are of potential interest, for example sculptured shrimp. Ecosystem-scale clashes resulting from northward-extending or invading shellfish and indigenous Arctic shellfish are to be expected.

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​Photo: Erlend Astad Lorentzen, IMR

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