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Home / Science / Dungeness crab season is approaching in California, but toxins are a known threat

Dungeness crab season is approaching in California, but toxins are a known threat



The days are getting shorter, pumpkin spice lattes are here and once again it's time for this other Bay Area rite of the fall: worry about the levels of toxins in local Dungeness crabs.

With the state's recreational Dungeness Crab season scheduled for November 3 and the commercial season on November 15, the California Department of Public Health has preliminary test results on Dungeness Crab for Domoic Acid, the neurotoxin that delays in two of the last three Crabs caused seasons in the Bay Area.

To date, elevated concentrations of domoic acid have been found in five Dungeness crabs collected from Bodega Bay and Trinidad (Humboldt County) in late September and early October. These are the latest available data. The San Francisco, Half Moon Bay, Monterey and Morro Bay regions were clean in this test phase. The tests will continue in the coming days and weeks.

"The California Department of Public Health oversees the level of domoic acid to ensure safe food for consumers," said Corey Egel of the department's Office of Public Affairs. "At this point, it's still too early to determine if the reported values ​​could affect the recreational or commercial Dungeness crab season."

In Oregon, crab fishing was closed on Oct. 1

5 due to Domoic's acid after state officials found high levels during testing. It remains closed from the California border north to Cape Blanco.

Domoic acid is a by-product of algal blooms that form when sea temperatures are warmer, causing diseases and even the deaths of marine animals and humans. Although they are common in the summer and early fall, the flowers usually disappear when the Dungeness crab season starts in November. In recent years, however, climate change and El Niño conditions have resulted in warmer ocean surface temperatures lasting into the winter and with them also domoic acid. The California Department of Public Health defines increased concentrations of domoic acid as more than the federal action level of 30 parts per million.

"Yes, tests have shown warm anomalies along the north coast, and we've seen domoic acid spike Up in Humboldt Bay – but not in Monterey Bay – is definitely where some local hotspots are going," says Raphael Kudela , Algae blooms specialist and Lynn Professor of Ocean Health at UC Santa Cruz via email. "However, we do not expect any major warm anomalies this year." Nonetheless, oceanographers are observing conditions that could cause warmer ocean temperatures to recur this winter, such as the development of a blob-like feature off the coast of Alaska.

The high-pressure concentration of warm water is similar to the California coast from 2013 to 2015, which many believed to be a factor behind the California drought.

In addition, the National Oceanic and Atmospheric Administration has just announced a 70 percent chance that an El Niño will form this winter. The warmer water temperatures during the El Niño system, which began in 2014, led to delays in the Dungeness crab season 2015-2016 and to the collapse of the sardine population.

Other parts of the California coast have shown signs of unusually warm conditions in recent months. In August, the warmest sea temperatures of all time were reported in San Diego. Last week, biologists reported a growing outbreak of a bacterial infection in California sea lions, due in part to rising sea surface temperatures.

The State Department of Health tests the vapor acid level in the Dungeness crab from California ports every one to two weeks. The tests must be clean for two weeks before making sure that the crabs from this area are safe. In calendar year 2017, $ 47 million was landed on Dungeness crabs in California.

Tara Duggan is an associate of the San Francisco Chronicle. Email: tduggan@sfchronicle.com Twitter: @taraduggan


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