The most common crabs on Icelandic shores are the Arctic lyre crab (Hyas coarctatus) and the great spider crab (Hyas araneus). They are very similar in appearance but the great spider crab grows much larger. Both species are found all around Iceland and are common in the northern fjords.
The Arctic lyre crab is found from just below the seashore all the way down to a few hundred meters depth, whereas the great spider crab is only found in shallow waters near shore.
The northern stone crab (Lithodes maja) has also been found in the fjords. This wonderful crab is covered in large spines. It generally keeps to deep water, but occasionally ventures into shallower water.
Many other crab species are found in Icelandic waters, but mostly in the warm waters to the south and west. One of them, the green crab (Carcinus maenas), has also been found in the north but is very rare.
However, animals and plants often find ways to colonize new regions and sometimes they disappear from others. In recent years, three new crab species have established stable and expanding populations in Icelandic waters. The edible crab (Cancer pagurus) and toothed rock crab (Cancer bellianus) from Europe, and the Atlantic rock crab (Cancer irroratus) from Canada. These populations most likely arrived in Icelandic waters as larvae in the ballast water of ships from the two continents. The Atlantic rock crab has now been found in northern Icelandic waters.
Many crab species are found in the cold oceans of the world where water temperatures are similar to those on Iceland‘s north coast. It is thought that the reason crabs do not disperse easily between larger oceanic regions is that the larvae are not planktonic for long enough to be carried great distances.
Off the coast of Greenland and in the Barent Sea the snow crab (Chinonoecetes opilio) is an economically important crab. Along the coast of Norway the red king crab (Paralithodes camtschaticus) is invading from the north. This species has recently become famous due to its starring role in the television series “Deadliest Catch.” These crabs have not yet been found in Icelandic waters (save for one king crab found dead), but they may well come at some point. People are encouraged to report any unusual crabs they find in Icelandic waters.
Also found in Eyjafjörður is a smaller cousin of the aforementioned crabs, known as the hermit crab (Pagurus pubescens). This crab has a soft body except for its face, walking legs, and pincers. They live with their body inside of an empty snail shell to keep it safe. It was long thought that they just find empty shells to inhabit, but on several occasions they have been observed apparently attacking snails that are still alive in the shell.
The squat lobster (Munida rugosa) is not in fact a lobster but is related to the hermit crab and is found in much of the fjord. Though it is closely related to the hermit crab, the squat lobster has a hard exoskeleton covering its whole body and does not need to live in a snail shell.
Crabs are opportunist feeders and a large part of their diet is carrion.