Public health officials in California have advised people not to eat any rock crabs and shellfish from the central coast because of a possible toxic contamination.
The state's Health Department announced on Friday, Aug. 19, that it has found dangerously high levels of the toxin known as domoic acid in several rock crabs and bivalve shellfish, such as scallops, oysters, mussels and clams, from Monterey Bay and Half Moon Bay.
This prompted the agency to declare a warning against capturing these particular crabs and shellfish in both bays.
Rock crabs captured in Half Moon Bay contained toxin levels that were more than 10 times the 30-parts-per-million level necessary to declare a warning. Officials also detected high amounts of domoic acid in several shellfish found in the area.
So far, there have been no reports of any illnesses associated with the domoic acid warning.
The California Public Health Department said that oysters, mussels, clams and scallops commercially sold from approved sources are not subject to the warning since certified harvesters and dealers follow frequent mandatory testing in order to monitor toxin levels in their products.
According to the National Oceanic and Atmospheric Administration (NOAA), domoic acid is produced by marine microorganisms known as diatoms from the Pseudo-nitzschia genus.
While the toxin is not particularly harmful to fish and shellfish, it is considered to be highly dangerous to humans and marine mammals as it can infiltrate the brain and interfere with the normal transmission of nerve signals.
Low doses of domoic acid can cause people to suffer severe brain damage manifested by a permanent loss of short-term memory, while high doses of the toxin can lead to coma or even death.
People who consume fish or shellfish contaminated with the toxin can experience dizziness, headache, vomiting, diarrhea and abdominal cramps.
The presence of domoic acid in the West Coast has been linked to the poisoning of more than 200 sea lions and Guadalupe fur seals in 2015.
Researchers from the Marine Mammal Center in Sausalito, California treated the animals for seizures, which they believe have been caused by high levels of the toxin in the water.
Domoic acid contamination also forced this year's Dungeness crab fishing season to be delayed until May. This caused local fishermen to lose an estimated $48 million.
Some portions of Half Moon Bay, especially those located north of Pigeon Point, are still affected by a fishery closure.
Photo: Paul Asman and Jill Lenoble | Flickr
