These articles from the Poulsbo Marine Science Center will appear monthly, showcasing the fascinating saltwater world surrounding us.
As appetizers or entrees, they’re pretty appealing. Great on a plate! But Dungeness crabs, a favorite dish in our region, are interesting in themselves, while they’re still alive crawling about, making a living, doing what comes naturally.
On a late winter shoreline stroll, I came upon a startling sight: dozens of Dungeness crabs washed up on the beach as if some huge, horrible die-off had occurred in adjacent waters. Closer inspection revealed that these were actually the molts, or the shed outer skeletons, of male crabs that were still alive and well somewhere out there in the briny, patiently growing new armor.
The “exoskeleton” (skeleton on the outside) of a crab is a hallmark of its biological group, the crustaceans, which include the shrimps and lobsters. All have hard external shells that are shed periodically so the animals can grow. While the new shell forms, the creature is particularly vulnerable to predators, and so it generally hides until the new outer layer hardens.
The crab molts I’d encountered on that winter walk were all males because there’s a seasonal plan to the process. The females shed their shells a bit later in the year, at various times through spring and summer. As usual, nature has orchestrated all this for a reason. Once they’ve molted in synchrony, the males turn to thoughts of love, going in search of a temporary mates (permanent bonds are not a part of the crab repertoire).
As a female starts to molt, she advertises her situation using a special scent. A male joins her until her new shell has hardened somewhat and her eggs can be successfully fertilized. Over the winter she carries the eggs attached to her abdomen; by spring the tiny embryos have hatched to become drifters among the plankton. After several molts, they’ve grown to about a quarter inch in size, large enough to sink. On the bottom, they take up their lives as scavengers, non-unionized members of the ocean’s army of sanitary engineers.
If you walk along the shore during summer, you might spy a juvenile Dungeness in a tide pool, or even on a float. At three years of age, the crabs are sexually mature; they move away from the shore to take up residence on sandy bottoms. Males reach market size at about four years.
The status of this important fishery is intimately connected to the health of the environment in which the crabs live, mate, and grow. That means that estuaries, where crabs spend their juvenile stages, need to remain unpolluted, free of invasive plant species, allowed to maintain a natural water flow. It also means that eel grass beds, another important habitat where the Dungeness crab finds food and shelter, need to be kept alive and well off our shores; this is possible only in the absence of polluted water.
Viva la Dungeness! May it thrive, not only for its culinary appeal, but also for its own sake, as an integral player in the Northwest’s near shore communities.
Nancy Sefton is a Trustee of the Marine Science Society of the Pacific Northwest, operators of the Poulsbo Marine Science Center. New members and volunteers are welcome; phone (360) 779-5549. Visit the web site at www.poulsbomsc.org.
