Today is the opening day of California’s sport fishery for Dungeness crab. The 2013-2014 season runs from November through June. We don’t get much happy environmental news these days and so it’s nice to write about an abundant local animal whose population is healthy and fishery sustainable. Dungeness crab (Metacarcinus magister, formerly Cancer magister) is a favorite of mine, not so much for the eating (which is good), but for observing. This summer thousands (my rough estimate) dotted our beaches. They were a constant companion that fascinated me during long beach walks.
Most of the “dungies” that I encountered on sandy beaches were small — the carapace about an inch (2.5 cm) across. That’s nowhere near the 5.75-inch (14.6 cm) minimum size for the fishery or the full-grown 9-inch (23-cm) adults. These little dungies were juveniles somewhere around 1 to 2 years after hatching. Littering the beaches I found mostly live hard-shells and soft-shells, and later in the summer, discarded molts (it’s sometimes hard to tell the difference without handling them – carefully). Little crabs on their backs kicking wildly appeared very much out of their element.
What were all these lively crabs doing on the beach at my feet?
Dungeness crabs hatch from eggs — a mature, berried-up female may carry as many as 2.5 million. Upon hatching, they drift as oceanic plankton for the first year or so, and develop into forms that appear nothing like an adult crab. During the first two years they may molt (discard the old and grow a new shell) as much as six times a year. Upon reaching maturity, at about three years, the molts tend to decline to once a year. They can live six to ten years.
Juveniles live in protected, shallow waters of estuaries and sandy beaches with pier pilings and eelgrass beds. They find shelter by burying themselves in the sand. (I discovered that if I scooped out a little trench behind a live crab on a wet beach, it would quickly back into it and disappear. This proved easier, and safer, for me than tossing pinching crabs into the water.)
I think what happens along our beaches is that during the molt season the little crabs in the shallows get picked up by waves and tossed onto the beach or an ebbing tide leaves them high and dry. On the sand they’re vulnerable to hungry crows and gulls, the drying sun and playful children (although the claws even at that size are a great deterrent, speaking from a painful experience). How a population can handle this kind of carnage, I don’t know. I can understand if the beach were littered with molts and a few live crabs were among them. The process must be grueling. It was obvious that there were a lot of molting juvenile crabs just off the beach, and synchronizing their molting surely helps individuals among so many to avoid predation. But I saw more struggling crabs on the beach than I did molts (until late summer). Maybe it’s an adolescent test, but it seems like a wasteful strategy. I’m looking forward to next summer (even with the fog). I want to see if this was the usual or an unusual year.
All summer the dungies kept me curious and entertained. I watched them, watched people interacting with them, photographed them, tossed them into the surf and dug many little trenches for them. On each walk I learned something new (like how to tell a Dungeness crab from a graceful crab – but that’s another post). Even though November is the start of Dungeness crab season for many here, as you can see, my favorite crab season is a summer watching dungies.