During the summer of 2013 I got to know Dungeness crabs very well. (Also see my 2013 post.) For three months, small crabs (about an inch or two across) and crab molts (old shells discarded so the crab can grow) littered the beach I walk regularly. Some days there were a few and some days they were everywhere.
I started tossing them back into the water, but given the numbers, gave up. I found that when I rolled them off their backs and dug a little trench behind them, they would back into a hiding spot in the sand.
I haven’t seen young Dungeness crabs along this stretch of beach since that summer. Populations of crab larvae naturally fluctuate with sea surface temperature, correlated to the Pacific Decadal Oscillation. Dungeness crabs prefer cooler waters and the lack of beached crabs recently could be related to a warm-water El Niño and the blob off our coast. Another explanation for the excess crabs on this particular beach that year could have been beach nourishment. [During the winter of 2012 – 2013, approximately 7,500 m³ of Monterey Harbor dredge material was used to nourish this critical south Monterey Bay erosion area, according to a Currents 2013 poster by A. Snyder et al.] Who knows for sure?
Why talk about 2013 now? Dungeness crab seasons open this month, and it takes the crabs about 3 years to grow enough to be part of the fishery. The crabs I saw in 2013 are now being harvested.
Last week (November 5), the recreational Dungeness crab season opened along the California coast. It was accompanied by a health warning to fishers catching crabs north of Point Reyes (Marin County) to not eat the viscera (guts) due to elevated levels of domoic acid (a natural toxin produced by single-celled algae). Domoic acid is a powerful neurotoxin and poisoning effects range from nausea to death in birds and mammals, including humans and possibly dogs eating sand crabs at the beach.
This week (November 15), the commercial season will open from Point Reyes (Marin County) south. However, according to California Department of Fish & Wildlife (CDFW), the CDFW Director is moving on state health agencies’ advice to close the commercial fishery between Point Reyes and the Sonoma/Mendocino county line (see CDFW website for related rock crab info). This is also due to domoic acid. (Most of last season was closed for the same reason.)
Update (as of Nov. 24) on open and closed areas from CDFW: https://wordpress.com/read/feeds/357812/posts/1234769465
The good news is that the Dungeness crab fishery is considered sustainable according to CDFW’s 2011 status report. So as coastal waters cool this year during a La Niña, I hope little “dungies” will return this summer to my beach.
During low-tide walks this week sand dollars (Dendraster excentricus) have been the dominant life form. Everywhere dotting the exposed sand were white tests (as in dead shells), soft deep-purple disks (the healthy live ones), and shapely sand traces (from under-sand burrowing). The feeding must be good and the living easy on this beach. (I just learned that more than 500 individuals can crowd into a square yard!)
Sand dollars are often collected as souvenirs and used in art projects. The white tests are beautiful (although several people collecting the purplish shells didn’t realize these were living animals).
To counter the notion of sand dollars as art, I thought I’d post the art created by sand dollars. Don’t you think their living works are lovelier than those adorning our bureaus and walls?
References & Resources
If you want to learn more about our Pacific coast sand dollar, visit this nicely done San Francisco State biogeography class post from 2005.
This week sanderlings showed up on my local beach en masse — nearly a thousand little pinball birds, along with marbled godwits, whimbrels, and a variety of gulls. All were feeding on sand crabs in the wash of very big surf (which we’re expecting all week).
I love watching sanderlings moving in unison as waves recede, then turning and running quickly in unison chased by waves washing up the beach. Between ebb and flow they mill around in disarray, or are shooed away by the other birds. Their energetic behaviors are comical and their tenacity remarkable. All this activity for a bite of sand crab.
The most amazing thing about these little birds is that they’re here from the Arctic and are heading to the south end of South America. That’s an incredible migratory trip for any species, but I find it astounding for an 8 inch, 3 ounce (20 cm, 100 g) bird. Whenever they visit here, I’m enthralled.
The elegant terns are back. For the past couple of weeks I’ve spotted them resting in the Monterey Harbor and feeding in the waters off Fisherman’s Wharf #2 and Del Monte Beach. They’re migrants, visiting us after nesting in Southern California and Mexico. According to the Cornell Lab of Ornithology, approximately 90-97% of all elegant terns nest in one colony on Isla Rasa in the Gulf of California — a seabird sanctuary since 1964. (Heermann’s gulls breed there, too, and are also back in the Monterey area.)
Elegant terns (Thalasseus elegans) are fairly easy to find. Just zero in on the midair squeeky-gate-hinge sound. It’s a medium-sized tern with a yellow-orange bill, short forked tail, and a full black cap (during breeding season). Right now, the forehead is more whitish and the cap looks like a slipping black toupee.