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Topic: Snow crab

Snow crab are found in the North Atlantic and North Pacific oceans. In the North Atlantic, they are found from Greenland in the northeast Atlantic and from southern Labrador of the Gulf of Maine in the northwest Atlantic. 

In the northern Pacific Ocean, they are naturally distributed from the Sea of Japan, east of the Korean Peninsula, further north to the Sea of Okhotsk, the Beaufort Sea and the Bering Sea. Now the snow crab is also found in the Barents Sea and the Kara Sea.

About the snow crab

The snow crabs prefer deep and cold-water conditions and lives in water temperatures between -1°C up to 6°C. The juvenile (the smallest crabs) prefers the coldest water, while the adults prefer it warmer within this temperature range. Throughout the life cycle, the snow crab will use various depths and types of substrate, ranging from shallower areas with coarser structures that can act as hiding places, to soft-bottom areas such as clay and sand, which can also serve as a hiding place for larger crabs. 

It is known from the other snow crab populations that they mate in late winter or early spring. It has not been shown exactly when the snow crab is mating in the Barents Sea, but there are indications that mating starts in late May and June. The female crabs carries the eggs until hatching just before the next mating. After the larvae release the female mate again. The larvae will live in the free water masses for two to three months and graze on small phytoplankton. The larval stage consists of three stages called zoea1, zoea 2 and megalopea. Depending on temperature the planktonic larval development can last three to five months before settling on the sea bottom. 

The crab grows slowly and gradually by shedding their shells (moult) each year, usually in late winter or early spring. It can take around eight to nine years for a male snow crab to reach legal size for the fishery. After a moult, the crab can use up to nine months to harden the shell and increase the meat yield. The male snow crab grows larger than a female, and to protect the species and its reproduction, commercial harvester can only catch male snow crabs. Catching or landing females crabs are not allowed. 

In both male and female crabs, growth stops after the last moult, as they also become sexually mature. In male crabs, the last moult can occur at a carapace width between 58 and 165 millimeters. The equivalent for females is between 37 and 100 millimeters. The life expectancy of a male is approximately 5 to 6 years after the last moult. 

Old crabs are usually inactive and are included to a small extent in the catches. It is believed that the male crabs are available for commercial fishing three to four years after the moult. The snow crabs feed by preying or scavenging on polychaetes (marine worms), crustaceans (shrimps and smaller crustaceans such as amphipods), bivalves and gastropods (small mollusks), fish, brittle stars, sea urchins, hydrozoans and large zooplankton.