By Jeff Embleton
If you look closely into the depths of the estuaries around the Bay, you may spot a Dungeness Crab resting near the sea floor. Dungeness Crabs make temporary homes in our watershed. They use the blend of salt and fresh water to grow into the large and grumpy-looking water dwellers that many people know and love (to eat). Dungeness Crabs generate tens of millions of dollars for their value as food for humans, but they also play an important role in the marine food chain. The Latin name Cancer magister means “chief crab.”
These crabs’ claws make them easily identifiable. Dungeness Crabs have five pairs of legs; including two large claws used to defend against predators and to tear apart larger prey. The crabs are typically beige to light brown with blue trim, and often tinted with light orange. The crabs have short eye stalks with small orbits, and a wide shell that they periodically molt.
Dungeness crab can be found in coastal waters from Southern California to the islands of Alaska. There is debate as to precisely how far they naturally range, but it is generally agreed that they can be found in and around all estuaries on the western coast.
Dungeness crabs have a hefty appetite. They feed on shrimp, mollusks, crustaceans, eelgrass and other aquatic vegetation.
Dungeness crabs spawn in offshore waters, such as the Gulf of the Farallones. The larvae hatch during the winter months and drift toward coastal waters, tidal flats and estuaries to mature. The crabs use tidal currents and jellyfish to hitch a ride from the deeper and cooler ocean waters to coastal locations. Juvenile crabs can spend over a year in estuaries before returning to the ocean in fall.
The Dungeness crab is not currently considered an endangered species. The Seafood Watch has named it a “Best Choice” of seafood to eat. During the juvenile stage of development, the Dungeness crab utilizes the estuaries as habitat during its maturation period. Any change to the estuary, such as dredging, may impact the crab’s continued success. Population numbers have dwindled in recent years from over-fishing and changes in water temperature.