Tests show we may have healthy crab season
The fate of the Dungeness crab season will hang on the test results coming out of an East Bay lab.
With the beginning of the season approaching in November, the California Department of Public Health has begun safety tests on Dungeness crab a few weeks earlier than usual. Dungeness crab samples collected from Crescent City (Del Norte County) all the way down to Monterey are filing in to the Food and Drug Laboratory Branch in Richmond, where they are tested for domoic acid, the naturally occurring but potentially devastating neurotoxin that wreaked havoc on last year’s season.
So far, results are normal for this time of year, said Patrick Kennelly, chief of food safety at the state health department — even though crabs from four of six regions are testing positive for domoic acid.
“To have a couple samples with some level of domoic is not uncommon at this time,” Kennelly said. Blooms of pseudo-nitzschia, the algae that produces domoic acid under certain conditions, are common in California waters in spring and fall, and then normally dissipate by crab season, he said. “We’re at the tail end of the time we would normally expect to see pseudo-nitzschia and domoic acid present in certain species. It’s not alarming.”
But you can be sure that crabbers, as well as officials from the departments of public health and fish and wildlife, are watching the results closely,
with Dungeness crab season due to start Nov. 5 for recreational fishers and Nov. 15 for commercial crabbers.
Last year, record-high ocean temperatures and a persistent algal bloom that stretched from Southern California to Alaska kept the California fishery closed all the way to March, meaning that local Dungeness crab was kept off Bay Area tables.
While there are still pockets of pseudo-nitzschia on the coast this year, ocean temperatures aren’t as high. Kennelly said his department will have a better idea whether there is a chance of delay by the end of October, after more tests come in.
Around this time last year, crabs collected up and down the coast had unusually high levels of domoic acid. Craig Shuman, marine region manager of the California Department of Fish and Wildlife, also said it is too early to make any predictions. “Levels this year are lower than what we saw last year at this time, and we remain cautiously optimistic that the season will open on time,” Shuman said.
The Department of Public Health will continue conducting tests around once a week, taking samples of six crabs from at least two depth levels in each fishing region. After the samples come into the lab, they are separated to avoid potential cross-contamination, and steamed for 15 minutes — mirroring how most cooks prepare crabs — and then cracked.
The viscera, or internal organs, are where toxins concentrate, so they are separated from the meat and blended. Domoic acid is then extracted and analyzed for concentration levels. Crabs that test with levels above 30 parts per million of domoic acid in the viscera are considered at risk, in case someone eats the guts. (The lab doesn’t test the meat until the viscera shows much higher levels of contamination, around 100 ppm.)
Right now, tests show no substantial levels of domoic acid in Dungeness crabs from the Half Moon Bay/San Francisco region or the Bodega Bay/Point Reyes area. However, crabs from Monterey Bay, Bodega Bay/Russian River, Fort Bragg and Crescent City are currently testing at levels above the action level of 30 ppm.
Half of the crabs collected in Monterey Bay have tested above 30 ppm. One out of 6 crabs collected from Fort Bragg, Bodega Bay/Russian River and Crescent City is testing above action levels. For comparison, at this time last year, 4 out of the 6 crabs in Crescent City and all of the crabs in Eureka tested above 30 ppm.
Typically, all crab samples from all regions have to test below action levels to open the fishery. However, it’s possible that the Department of Fish and Wildlife could open certain parts of the fishery and keep others closed if problem areas arise.
In the Monterey Bay, where there is currently an advisory against eating bivalve shellfish and rock crabs because of domoic acid, the water temperatures are in a relatively normal range, unlike last year. However, algae growth has gone up because there have been more upwellings than usual and lower levels of nutrients in the water, said Raphael Kudela, an algal bloom specialist and Lynn Professor of Ocean Health at UC Santa Cruz.
“Those conditions also favor toxic algae because they like some upwelling, but produce more toxin when nutrients run out,” said Kudela in an email. “So I’m not surprised the toxicity has started going up.”
However, Kennelly expects levels there to normalize, noting a decrease in domoic acid in tests of rock crabs, a species that’s studied separately, in Monterey Bay since August.
“We’re optimistic we’ll continue to see improvements,” he said.