Snow crab | Oceana Canada

Cephalopods, Crustaceans & Other Shellfish

Snow crab

Chionoecetes opilio

Also known as

Queen crab, spider crab, kani (sushi)

Distribution

North Pacific and Northwest Atlantic oceans

Ecosystem/Habitat

Soft, muddy bottoms

Feeding Habits

Foraging omnivore

Conservation Status

Not listed

Taxonomy

Order Decapoda (crayfish, crabs, lobsters and shrimp); Family Oregoniidae (crabs)

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Snow crabs are a large, coldwater species of crab that can be found on soft mud bottoms throughout the North Pacific and Northwest Atlantic oceans. Like other crustaceans, their “shell” is actually their skeleton which is found on the outside of their body and is called an exoskeleton. In order to grow, they must shed this exoskeleton and reveal the new one growing underneath through a process called molting. When a snow crab is ready to molt, it will absorb a lot of water and swell up until its shell pops open. They will then wriggle out of this shell and absorb even more water to increase their size before the new, growing shell hardens. On average, a snow crab will molt 10 to 14 times before they stop growing after their last “terminal molt”.

Snow crabs have a flat, round shell, known as a carapace, and long, slender legs. They have four pairs of legs that they use for walking and one pair of claws. They are a brownish-red colour with a lighter coloured underbelly but the older the crab, the duller their colouration. Over time, they eventually become a dull olive colour with a yellowish underbelly. Male snow crabs can grow to a carapace width of about 15 centimetres and leg spans of up to 90 centimetres, with males growing almost twice as large as females. Male and female snow crabs can be distinguished by the shape of the abdominal flaps on the underside of their bodies; on males their abdominal flap is triangular and on females it is rounded.

Female snow crabs produce anywhere from 16,000 to 160,000, depending on her size, with larger crabs producing more eggs. The female will carry these eggs for up to two years. The larvae hatch in the spring when there is lots of food in the water column, and they feed on plankton for three to five months. In this larval stage they look like tiny shrimp and will undergo a couple of molts before settling on the ocean floor as megalops. In the megalop stage, they look like small crabs with long tails. They will undergo a couple more molts before metamorphosing into the first crab stage. From the time they settle on the ocean floor, snow crabs will molt on average 10 to 14 times before they stop growing after their last, or terminal, molt.

Right after a molt, snow crabs are very soft which leaves them vulnerable to predators until their new shell hardens. After their terminal molt, snow crabs can live for up to six more years under optimal conditions, with scientists estimating that snow crabs live for up to 20 years in total. Snow crabs will feed on practically anything they can get their claws on, including fish, shrimp, starfish, worms, clams, snails and sea urchins. They are also known to scavenge on anything dead they can find. In turn, snow crabs are predated on by seals, sea otters, octopus, other carbs and several species of fish will feed on snow crabs, especially during their soft-bodied stage.

Snow crabs are harvested commercially in trap fisheries in Atlantic Canada, with Canada being the world’s largest producer of snow crab, supplying about two thirds of the global supply. The snow crab fishery began in 1960 with accidental catches of snow crab in the groundfish fishery near Gaspe, Quebec, but didn’t really expand into its own, targeted fishery until the late 1970’s. In most areas, snow crabs are fished in the spring and summer months, but in some fishing areas the season operates until November. Only male crabs are targeted by the fishery, due to their larger size, helping protect the reproductive potential of populations.

Snow crabs have not been assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) nor listed under the Species at Risk Act (SARA). Under the Precautionary Approach Framework set out by Fisheries and Oceans Canada, which is used to assess the health of wild fish stocks, or populations, some stocks are listed as Healthy, while others fall into the Cautious and Critical zones, and even more fall into the Uncertain category. While snow crab may be one of the largest and most lucrative fisheries today in Canada, overfishing still poses a  threat to some stocks and uncertain impacts from climate change are also a concern, especially for stocks at the southern limit of their range. There is still much we need to learn about the populations of snow crab in Canadian waters to ensure their fisheries are managed sustainably.

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