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.