Getting To The Bottom Of Things: The Dungeness Crab
They met last spring. Perhaps it was the heady perfume of pheromones wafting through the salt-tanged water. He sensed she would be receptive; vulnerable, but in a positive way. No longer imprisoned in her hard, ill-fitting carapace, and teeming with eggs - between 500,000 and 2 million of them - she accepted his courtship. They'd spend the next several days together, during which he would carry her in a protective, pre-mating embrace. When she was fully molted and ready, he’d transfer his sperm into her special organ, the spermatheca. Their union would not bear fruit until late fall or winter. Then, she would extrude her bright golden fertilized eggs and carry them under her abdominal flap until they hatched as larvae, sometime between November and February. The larvae would experience five distinct phases of metamorphosis and growth, until as adults they could continue their cycle of life as a Dungeness crab, Metacarcinus magister.
NATURAL HISTORY: The Dungeness crab is a marine crustacean that lives only in the shallow waters off Western North America. Dungeness crabs have a broad, hard shell, or carapace which is periodically molted as they grow, and five pairs of legs. Their colors may range from reddish brown to mauve-purple, with white markings. Their formidable, white-tipped claws are used both for defense and to tear apart prey. While clams are the preferred diet of M. magister, other crustaceans and small fish are on the menu, too. "Dungies" also scavenge, contributing to the ocean's nutrient recycling system.
VIEW FROM THE BOTTOM: The broad expanse of shallow Continental Shelf waters protected as Greater Farallones National Marine Sanctuary is ideal habitat for Dungeness. Its mostly sandy substrate provides a vantage for ambush and concealment from predators, plus nutrient-laden waters that support a proliferation of marine life throughout the food web. These bottom-dwellers have it all here. For more general information on Dungeness crabs, see NOAA Fisheries article at https://go.usa.gov/xECgj
DELECTABLE! This species is prized for its sweet meat (best savored, in this author's opinion, with a quick dip in clarified sweet butter and fresh sourdough bread). In Northern California and the Pacific Northwest, Dungeness are a traditional Thanksgiving specialty, and enjoyed throughout the ensuing season as well.
THE HARVEST: Dungeness have been landed commercially since Gold Rush days. The fishery is regulated based on crab size, sex, and season. Each fall you can see the early-harvest fleet dotting the waters off Duxbury Reef and other soft-bottom sites. This is the most commercially important crab in the region. The 2016-17 harvest in California alone netted record landings of $83 million. However, in 2015-16 the fishery was almost entirely shut down in many areas due to contamination by a biotoxin known as domoic acid, produced by a proliferation of tiny sea plants. When the crab season finally opened, though, the crabs were safe and succulent, with up to 27% meat content. Although domoic acid levels this season have trended upwards, especially in Northern California, it is hoped that a repeat of the 2015-16 season will not occur.
CONSERVATION: Scientists are concerned that changing sea conditions such as temperature and ocean acidification caused by use of carbon fuels will have serious impacts on this species, a key component of the Northwest marine ecosystem, and this fishery, with repercussions throughout. Recently, West Coast crabbers sued the fossil fuel industry over climate change damage. Noah Oppenheim of the Pacific Coast Federation of Fishermen’s Associations said the “new normal” of dealing with domoic acid and delayed seasons is one of the main reasons his organization filed the suit. "These companies buried the truth about the impacts climate change will have about oceans, society and commercial crab fisheries.” For more on how ocean acidification is affecting Dungeness crabs: https://go.usa.gov/xEC4N
WHALE IMPACTS: Unfortunately, the Dungeness crab and other fisheries pose a serious threat to whales that become entangled in crab pot lines, buoys, and other gear. NOAA, other agencies, scientists, and the fishing community are working together to find solutions, such as modifying fishing gear, to minimize these sometimes fatal incidents. The California Department of Fish and Wildlife is planning to submit a conservation plan to minimize whale entanglements in this fishery.
LEARN MORE: Whether as a part of our ecosystem, our economy, or gracing our tables, the Dungeness crab is a superb representative of the bounty that the ocean can bring us. Discover more about Greater Farallones National Marine Sanctuary and its other marine life at http://farallones.noaa.gov.
