Ruler crab is also known as stone crab or rock crab, that is, crustaceans of stone crab family. They are not real crabs, but mainly distributed in cold sea areas. Named for its huge size, it is known as the “king of crabs”. King crab belongs to deep-sea crab, with a survival depth of 850 meters and a survival water temperature of 2-5 ℃. The lowest water temperature that king crab can survive is 1 . 4 degrees Celsius.
It is not a kind of crab with emperor crab (giant shore crab). Please don’t confuse it. Because of their huge size and delicious meat, many species are widely caught as food, the most common of which is the Kamchatka stone crab. In September, 2011, scientists found more than one million giant king crabs in a mud bed basin located 850 meters below the continental shelf off Antarctica. Scientists say the appearance of this large exotic predator may be the first sign of an ecological catastrophe in the Antarctic waters
The breeding rate of king crab is amazing, and each female crab can produce nearly 10000 surviving crabs every year. Emperor crabs usually spawn in the shallows about 350 meters away from each year from April to June. This kind of organism mostly lives in the muddy sand of the shoal and inhabits the waters along the Barents Sea and its southern region. 
During the breeding season, female king crab and male king crab hatch after mating. Generally speaking, the fertile period of a king crab is four years in its 30-year life span.
The hatching ratio of eggs is about 16000 / 80000.
Fishing method: trap box.
Average annual output of the United States: 10000 tons.
Fishing season: Bering Sea: red and Blue King Crab: September to October.
Southeast Alaska: November (red king crab) and February (Golden King crab).
Like other crabs, the yield of king crab varies significantly from year to year. In 1980, the output of king crab reached a record high of 60000 tons. And after two years, it plummeted to 6000 tons. The average annual output ranges from 7000 to 12000 tons. Alaskan biologists set annual quotas with regard to red and blue king crabs. Except for a small amount of fishing in the waters of southeast Alaska, golden emperor crab can be caught in the very deep waters of the Aleutian Islands all year round without quota restrictions.