On July 2, 2011, Seattle area divers Laurel LaFever, of Bellevue, Greg Oliver, of Kirkland and Steve Martino, of Bothell made a dive at the Mile Marker 4, between Sekiu and Neah Bay, on the Olympic Coast of Washington. This dive was one of five that a group of Bubbles Below staff completed as part of a three day weekend to this spectacular area. Curley’s Resort, a well known Sekiu diver-friendly facility provided air and accommodation.

Mile Marker 4 is a shallow shore dive and on this day, the threesome took advantage of about 40ft (12m) visibility and enjoyed a 70 minute dive to a maximum depth of 21ft (7m). While exploring a zone of red and brown algae near a large bed of eelgrass, they found a single swarm of small crabs that numbered at least a couple of hundred. Laurel obtained the accompanying photograph and forwarded it with questions about an identity for the subjects and what this gathering might represent.

What Laurel and her buddies had encountered was an impressive cluster of juvenile Dungeness crabs (about an inch across) Cancer magister huddling upon some brown algae.
Like a majority of other Arthropods (crabs, shrimps and their relatives), after hatching, a Dungeness crab spends the first few months of its life as a pelagic (floating) larva. The last version of several stages, bearing no resemblance to an adult, is called a megalops. Barely visible to a diver, this form recruits to the typical adult bottom habitat and then metamorphoses into a recognizable young crab.

The tiny crabs Laurel and her buddies encountered were survivors of this process, possibly released by the same female. For those of us who enjoy watching and eating Dungeness crab, this encounter bodes well for a good population of Cancer magister along the Olympic Coast several years hence. ■