ASTORIA - Tuna or not tuna? That is the question. With albacore season in full swing off the West Coast, and school lunch season fast approaching, many people are asking: How safe is our tuna? It's a question that focuses on very different levels of mercury found in albacore tuna harvested in different parts of the world.
According to Michael Morrissey, director of Oregon State University's Seafood Lab in Astoria, Ore., the answer has to do with how big the tuna is and where it was caught.
OSU researchers at the Seafood Lab have found that small, troll-caught albacore tuna from the West Coast of the U.S. contain less than half the level of mercury found by a recent government study of brand-name canned albacore.
In addition to lower mercury levels, the OSU researchers found that West Coast albacore have higher levels of omega-3 oils than most canned tuna. Omega-3 oils help protect humans against heart disease, cancer and other diseases.
In the OSU study, sponsored by the Oregon Albacore Commission and the Western Fishboat Owners Association, Morrissey and colleagues tested 91 albacore tuna caught in waters from southern California to British Columbia. The average mercury concentration was 0.14 parts per million, well below the limit of 1.00 part per million set by the Food and Drug Administration.
Morrissey said he hopes the results of the study will ease consumers' concerns and help them understand the difference between locally-caught albacore and the fish in the can.
Throughout most of the U.S., there are just two choices of tuna, and they're both canned. Typically, "light" is skipjack, a small tuna caught in oceans throughout the world, and "white" is albacore, usually caught in the southern Pacific Ocean in more tropical waters.
For locals on the West Coast, there's a third choice. Smaller white albacore tuna are caught during late summer and early fall when their annual migration brings them within range of local fishing boats.
"It's impossible to look at a can of tuna and decide how big the fish was," Morrissey said. "But with locally caught albacore, you get reduced levels of mercury and high levels of omega-3 fatty acids. That's good news for consumers."
A recent study by the FDA and the Environmental Protection Agency warned pregnant and nursing women and young children against eating more than six ounces once a week of canned "white" albacore tuna because of mercury levels in the fish.
However, most studies of mercury levels in canned tuna have been done on the major brands using albacore caught in the southern Pacific, according to Morrissey. These are larger fish, up to 60 pounds, and their mercury level averages 0.36 parts per million.
Morrissey and his fellow researchers, Tomoko Okada and Rosalee Rasmussen, found that albacore typically found off northern California, Oregon and Washington are smaller -10 to 24 pounds - and averaged less than half the level of mercury reported for canned albacore in the EPA study.
Morrissey speculated that because larger fish tend to be older and eat more fish, they tend to bioaccumulate more mercury, which would account for the higher levels found in the larger southern Pacific albacore tuna. The EPA study found that the smaller "light" skipjack tuna was within the safe range, with average mercury levels of 0.12 parts per million.
The West Coast tuna fishery is made up of small boats and local crews using surface hook-and-line gear. The albacore are sold fresh off the boat in many coastal ports or from local fish markets and specialty canneries for about $3.50 to $4 a can. In 2001, the Oregon albacore fishery was valued at $7.5 million, according to the Oregon Department of Agriculture.
Mercury is a neurotoxin that is most dangerous to unborn babies, infants and young children. Although mercury occurs naturally in trace amounts throughout the world, pollution from the burning of fossil fuels concentrates mercury in lakes, rivers and oceans, where it accumulates over time in the flesh of long-lived predatory fish.