KODIAK — Perhaps you have gone out in a boat and set some crab pots, and perhaps you were lucky and when you pulled them up, they were filled with Dungeness crabs. If the crabs were males and measured more than 6.5 inches across the widest part of the carapace (spines not included), you took them home and cooked them either simply in boiling water, or prepared as your favorite crab recipe. “Dungies” are quite a delicacy!
Dungeness crabs are named after the city of Dungeness in Clallam County, Wash., which in turn was originally named New Dungeness in 1792 by George Vancouver after Dungeness in Great Britain, at the tip of Rommey Marsh Peninsula in Kent at the English Channel. The term stands for “headland” and the spit in Dungeness, Wash., reminded the explorer of the headland in his home country. While the English Channel does not have Dungeness crab, Dungeness in Washington was the first place to commercially harvest and market the species, which is how the crab got its common name. The scientific name has actually been changed recently from Cancer magister to Metacarcinus magister. As with all things in biology, the only constant is change.
In 2001, Kodiak researcher Brad Stevens prepared an Alaska crab species checklist, which can be found online. The list features all crab species documented in waters within 200 nautical miles of Alaska coastlines. There are 80 species on the list: 28 hermit crabs, 18 stone crabs (those include the king crabs), 14 spider crabs (those include the snow and tanner crabs), and a few others, which include Dungeness.
Crabs have their skeletons on the outside and those skeletons are also their armor and defense. The shell does not grow, but periodically gets shed when the crab grows. When I explain this process to kids I remind them of coats they used to wear and have outgrown. The process is called molting and it is a very critical and stressful time in a crab’s life. When we watch lab crabs molting, it can take hours for them to shed the old armor, and then it can take several days before the new shell hardens. During this time, the crab is vulnerable, and in fact needs to be separated to protect it from other crabs (which are cannibalistic!).
All that hard armor on the outside also presents challenges to the crab’s sex life. Mating can only occur when the female crab molts. Female Dungeness molt between May and August. When she is getting ready to molt, pheromones in her urine attract the male, and the male crab clasps the female under its own belly until she is ready. When she molts, he deposits his sperm. She then extrudes an egg mass but keeps it attached to her underside, protected from predators and well ventilated. Gravid Dungeness females have been observed to form groups and bury in the sand of shallow bays. As a graduate student, I was once privy to a shallow dive in the submarine Delta, when we came across such a group of brooding females with their bodies buried in the sand and only the crabby faces and claws sticking out.
After about five months, the larvae hatch and begin life as miniature plankton. It takes several more months and many molts before the offspring resembles its parents and settles to the bottom. Of course, as in almost all marine animals, development time depends on the water temperature and food supply. Survival also depends on how well the little crabs can avoid the many predators, including cod, crabs, octopus and seabirds. If all goes well, they will grow up to find your crab pot.
As a closing word of caution: In Kodiak, you are advised to only consume the crabmeat, not the viscera (called crab butter). This is because the algae generate toxin that can cause paralytic shellfish poisoning can concentrate in the Dungeness crab viscera (liver).