Chionoecetes is a genus of crabs that live in the northern Pacific and Atlantic Oceans.

Common names for crabs in this genus include "queen crab" (in Canada) and "spider crab". The generic name Chionoecetes means snow (, ') inhabitant (, '); ' means shepherd, and C. opilio is the primary species referred to as snow crab. Marketing strategies, however, employ snow crab for any species in the genus Chionoecetes. The name "snow crab" refers to their being commonly found in cold northern oceans.

General

Snow crabs are caught as far north as the Arctic Ocean, from Newfoundland to Greenland and north of Norway in the Atlantic Ocean, and across the Pacific Ocean, including the Sea of Japan, the Bering Sea, the Gulf of Alaska, Norton Sound, and even as far south as California for Chionoecetes bairdi.

In 2019, the Norwegian Supreme Court ruled that the species is considered a sedentary species living on the seabed, and thus governed by the United Nations Law of the Sea.

Species

thumb|left|Bagged frozen snow crab legs for sale in a supermarket

Seven extant species are currently recognised in the genus:

Food web position and importance

Snow crabs are an important part of the ecosystem throughout the Pacific and Atlantic Oceans. They eat other invertebrates on the benthic shelf like crustaceans, bivalves, brittle stars, polychaetes, phytobenthos, foraminiferans, annelid worms, and mollusks. They are also fed on by halibut, cod, larger snow crabs, seals, squid, and Alaskan king crabs. Snow crabs are also highly sought after for the commercial fishing industry.

Life history stages and vulnerabilities

Juvenile snow crabs mature in cold-water pools on the ocean floor that are sustained by melting sea ice. If waters warm above the 2 °C maximum necessary for juvenile development, their normal nursery habitat will be reduced significantly. Adults are similarly unlikely to tolerate conditions of more than 5 °C. With a gestation period of up to two years and an average spawn size of up to 100,000 eggs, their fecundity (i.e., fertility) is high, but recent trends have shown that these characteristics do not make them impervious to threats like a warming climate.

Population decline in the Bering Sea

2018 was one of the warmest years coinciding with periods of the lowest sea ice extent on record in the Bering Sea. The driver of this trend was the northeast Pacific marine heatwave, which contributed to significant die-offs in a number of species. 2019 was yet another year of record-breaking temperatures, attributed to a weakened North Pacific High, which reduced evaporative cooling in the Northeast Pacific

In 2021, crabs of all ages declined, and their habitat range shrank substantially. Increased water temperatures also increase snow crabs’ metabolism, so one theory is that their increased metabolic rate – combined with fewer resources due to a shrinking habitat – left them to either starve or consume each other. Predator range expansion is another possibility; as waters warm, predators that normally inhabit warmer southern waters (such as the Pacific cod) can travel further north in search of prey. A third theory is that a reduction in habitat area could increase the spread of diseases like bitter crab syndrome. The Bering Sea shelf break (a zone where the shallower continental shelf drops off into the North Aleutians Basin) is the dominant driver of primary productivity in the Bering Sea – upwelling brings nutrients from the cold waters of the Aleutian basin to mix in shallow waters. This area is called home to many ecologically important species, including the snow crab.

To assess trends and impacts of the warming climate in the Bering Sea, a recent study created a regional model of both physical and biological elements of the Bering Sea using three global climate simulations from the Intergovernmental Panel on Climate Change Fourth Assessment. This model detected overall trends of warmer temperatures and a retreat of sea ice in the southeastern Bering Sea. Primary drivers of these higher water column temperatures include increasing air temperature and northward wind stress.

  • Alaska Department of Fish and Game: Tanner Crab
  • Pacific Seafood Group - Snow Crab