<P> The red king crab is native to the Bering Sea, North Pacific Ocean, around the Kamchatka Peninsula and neighboring Alaskan waters . It was introduced artificially by the Soviet Union into the Murmansk Fjord, Barents Sea, during the 1960s to provide a new, and valuable catch . Red king crabs have been seen in water temperatures that range from − 1.8 to 12.8 ° C (28.8--55.0 ° F), with average being 3.2 to 5.5 ° C (37.8--41.9 ° F). Immatures prefer temperatures below 6 ° C (43 ° F). The depth at which it can live has much to do with what stage of its lifecycle it is in; newly hatched crab (larvae) stay in the more shallow waters where food and protection are plentiful . Usually after the age of two, the crabs move down to depths of 20--50 metres (66--164 ft) and take part in what is known as podding; hundreds of crabs come together in tight, highly concentrated groups . Adult crabs are found usually more than 200 m down on the sand and muddy areas in the substrate . They migrate in the winter / early spring to shallower depths for mating, but most of their lives are spent in the deep waters where they feed . </P> <P> It is the most coveted of the commercially sold king crab species, and is the most expensive per unit weight . It is most commonly caught in the Bering Sea and Norton Sound, Alaska, and is particularly difficult to catch, but is nonetheless one of the most preferred crabs for consumption . </P> <P> Red king crabs are experiencing a steady decline in numbers in their native far east coastal waters for unclear reasons though several theories for the precipitous drop in the crab population have been proposed, including overfishing, warmer waters, and increased fish predation . Fishing controls set by the United States in the 1980s and 2000s have failed to stem the decline . </P> <P> In the Barents Sea, however, it is an invasive species and its population is increasing tremendously . This is causing great concern to local environmentalists and local fishermen, as the crab eats everything it comes across and is spreading very rapidly . Since its introduction, it has spread westwards along the Norwegian coast and also northwards, having reached the island group of Svalbard . The species keeps on advancing southwards along the coast of Norway and some scientists think they are advancing around 50 km (31 mi) a year . </P>

How long does it take for a king crab to grow to full size