Metacarcinus magister, known as the Dungeness crab, inhabits the Pacific Ocean from Alaska to California. It thrives in sandy, muddy bottoms of bays and estuaries. Notable for its large, fan-shaped carapace, it is a sought-after seafood, playing a key role in marine food webs.

Metacarcinus magister, commonly known as the Dungeness crab, is native to the west coast of North America. Its geographical distribution ranges from the Aleutian Islands in Alaska, through British Columbia, Washington, Oregon, and California, down to Santa Barbara, California. It is primarily found in the Pacific Ocean along these coastal regions.

The Dungeness crab typically inhabits sandy and muddy substrates in coastal bays, estuaries, and the continental shelf. It can be found at depths ranging from the intertidal zone to about 230 meters (750 feet). The species thrives in water temperatures between 8 to 13 degrees Celsius (46 to 55 degrees Fahrenheit) and is often associated with areas that have strong tidal currents and ample food supply.

Metacarcinus magister plays a significant role in its ecosystem as both a predator and prey. It feeds on a variety of organisms including fish, shrimp, clams, and other crustaceans, and is known for its scavenging behavior. As a prey species, it supports populations of marine predators such as sea otters, octopuses, and several fish species. The Dungeness crab's ecological niche is closely linked to its ability to adapt to different substrates and its role as an important contributor to the benthic food web.