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Sport Fish Contain Toxin Produced During Algal "Blooms"
Sea Grant to Study Anglers' Exposure
SANTA CRUZ - Sport fish caught from the Santa Cruz Wharf can become contaminated with a potent neurotoxin, two UC Santa Cruz scientists have found.
Professor Mary Silver of the Ocean Sciences Department at UC Santa Cruz says that the algal toxin, domoic acid, has been detected in the viscera (guts) of two popular sport fish - white croaker and staghorn sculpin. The toxin has not been detected in muscle tissue of either fish.
Sea lion poisoned by domoic acid, a toxin produced by marine algae. (Credit: Frances Gulland, The Marine Mammal Center)
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A person could dramatically reduce the risk of poisoning by removing a fish's head, tail and viscera before cooking and eating it. Silver, however, is cautious about drawing too many conclusions or raising any red flags about the public's risk from exposure to the toxin because only a limited number of fish have been collected and tested. Additionally, the toxin has been detected in fish only during the relatively infrequent times when it is also present in seawater.
The preliminary findings, however, do present compelling evidence of the need for further study, as domoic acid was found in white croaker specimens four of the 13 times the fish were caught off the wharf. The toxin was found in staghorn sculpin on only one of the 10 sampling dates. It was not detected in any samples of surfperch or bocaccio, the only other sport fish sampled in numbers sufficient for scientific analysis.
Silver and her graduate student Spencer Fire, also at UC Santa Cruz, recently published their findings in a report for the California Department of Fish and Game.
Professor Mary Silver of the Ocean Sciences Department at UC Santa Cruz
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To expand the study and more fully document public health risks, California Sea Grant has awarded a research grant to Silver, Sea Grant marine advisor Carrie Pomeroy, a social scientist with an expertise in fisheries and Raquel Prado, a statistician at UC Santa Cruz. Besides analyzing many more fish, the investigators will begin to quantify toxin exposure rates for different sub-groups of anglers at the wharf. Motivating the study is the concern that consumption patterns and cooking methods vary significantly along socioeconomic and cultural lines. As a result, some people may be ingesting toxins in amounts exceeding federal safety limits.
"Domoic acid has been studied in the natural environment but there is no systematic understanding of people's risk from consuming contaminated fish," said Pomeroy, who will be leading a pilot survey of anglers' seafood consumption patterns.
"We want to look at what people are catching and what they are eating," she said. "There may be people who are at risk because of the way they prepare and consume what they catch."
Pseudo-nitzschia
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Domoic acid is an algal toxin produced by diatoms of the genus Pseudo-nitzschia that has caused die offs of marine mammals and sea birds in California and elsewhere. The toxin is ingested by fish and is poisonous to people. Cooking does not denature the toxin.
Although commercially sold fish and shellfish are tested for domoic acid, similar safeguards for protecting public health are not in place for recreationally caught fish. In fact, very little is known about how much domoic acid recreational fishers consume.
Culinary practices, however, are thought to play a large role in exposure rates, Silver said. In some cultures, anchovies and other fish are eaten whole. Crab "butter" (the liver) is also prized in some cultures and could be a source of toxins. Even cooking techniques influence toxicity, she said. While boiling can help remove domoic acid, assuming the broth is not consumed, frying does not. Stir-frying in a wok can thus seal in toxins.
(Credit: Frances Gulland, The Marine Mammal Center)
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"Once we figure out the cultural and economic dimensions of the situation, we can work with health officials and community groups to target public education efforts," Pomeroy said.
NOAA's California Sea Grant College Program is a statewide, multi-university program of marine research, extension services, and education activities administered by the University of California. It is headquartered at Scripps Institution of Oceanography at UC San Diego. The National Sea Grant College Program is part of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.
Investigators
Mary Silver, Ocean Sciences Department, UC Santa Cruz, T. 831-459-2908
Caroline Pomeroy, California Sea Grant Extension Program, UC Cooperative Extension, Santa Cruz County, T. 831-763-8002
Raquel Prado, Department of Applied Mathematics and Statistics, UC Santa Cruz, T. 831-459-1488
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