...there are very few "old, large" bluefin left. It's most likely at least some, if not all, the bluefin sushi was from smaller fish. The population is in severe decline and most fish are caught before they get the chance to be old and large. The WWF has a good summary of the growing bluefin crisis.

Oceana: Protecting the world's oceans.

Do you have a link that shows the bio-accumulation of methylmercury in fatty tissues is slow and not all fish have it?

Here's a link that says that many variables determine mercury levels, in any fish:

http://www.ec.gc.ca/MERCURY/EH/EN/eh-ec.cfm

"In general, levels of mercury increase with fish size and age, although not always. Levels also vary by species and location. Bioaccumulation in fish is influenced by the amount of methylmercury present, which is in turn affected by local biogeochemical processes and by mercury inputs from atmospheric pollution."

The seafood selector is at http://EnvironmentalDefense.org/seafood

Lauren Guite
Environmental Defense

finding the ways that work

60 Minutes did a pretty decent story on the world wide trade of Bluefin tuna, and how a once traditional fishing method has become industrialized. The full segment can be seen online.

grist.org

Larger fish species, like the bluefin, tend to accumulate more methylmercury because they 1) are a longer lived species comparatively and 2) eat other fish (which have themselves accumulated the CH3Hg).

"Comparatively" is the operable word. It's true that bluefin species are in pretty dire straits the world over. They're overfished, and they're getting smaller and smaller (see the oft-cited "90% fished out" study published in Nature May 2003 for starters). However, they're still the largest tuna species by size, and they  still feed at the top of the food chain. Thus, any bluefin will likely have more methylmercury than, for instance, sardines (which are much lower on the food chain) or a species whose diet consists solely of plants.

And if that isn't complicated enough, some fish stand still while others widely roam. Mercury concentrations, like some other pollutants (e.g., PCBs) can vary by geography as another comment noted. Bluefin are highly migratory, transversing wide areas of the ocean; for this reason, I would think it to be a pretty good indicator of the prevalence of methylmercury in our global oceans. It might be interesting to note whether the Southern Bluefin (in the Pacific Ocean) has more/less mercury on average than the Northern Bluefin (in the Atlantic and Mediterranean), but now we're splitting hairs.

Bottom line, bluefin is overfished and so, for those seafood lovers who care about their choices (shouldn't we all?), you probably want to avoid it regardless of the mercury issue!

Several groups have gotten savvy and developed seafood guides geared specifically to sushi lovers - see for example the NRDC guide, and the Monterey Bay Aquarium is apparently getting ready to launch its own version this year. The Environmental Defense seafood selector posted already does a good job of providing the eco- and health-conscious impacts. Consumer guides and cards are also becoming more prevalent in other countries - there are cards in the UK, Netherlands, Switzerland, Germany South Africa, Australia and now one in Hong Kong.

For the 411 on all of these cards by geography, visit http://www.seafoodchoices.org (and click on "Resources" to see the links)

Joey Brookhart
Seafood Choices Alliance - an international non-profit bridging the conservation and seafood communities

I'd also like to add that many pseudo and self-styled "consumer advocacy" groups take issue with the Times story because, they claim, mercury in the ocean comes from natural sources. Let's review some facts, as established by government and scientific sources:

It's true that there are both natural (e.g, volcanoes) and man-made sources for mercury in the environment. Man-made sources include mining operations, coal-burning (as in, from power plants) and incineration of medical waste among others.

We've been burning fossil fuels for 150 years now, since the industrial revolution (and burning coal far longer).

Furthermore, our own US government acknowledges that "atmospheric deposition is the dominant source of mercury over most of the landscape." This covers both natural and man-made sources.

Something is... well something is just downright fishy with the claim that volcanoes are to blame for mercury in the ocean. It stands to reason that man-made sources would be contributing greatly to the accumulation of mercury currently in the environment.

And consumers, take note! Any organization that truly puts consumers' interests first would not raise this smoke screen or play such a 'blame game' - regardless of where the  mercury comes from, the fact is that whether we like it or not mercury IS present in our seafood and environment. Just because it occurs naturally doesn't mean it's safe. Arsenic occurs naturally, too, but I wouldn't recommend chowing down.

At the same time, there are many wonderful seafood options to choose from that aren't contaminated with mercury - so neither should we stop eating seafood altogether.

A good overview of the natural (and unnatural) mercury cycle can be found at the USGS website - with a graphic for those so visually inclined.

USGS Mercury Fact Sheet
National Academy of Science, Institute of Medicine
US government websites, including FDA and EPA

Joey Brookhart
Seafood Choices Alliance

There's an easy way to estimate your mercury in-take from consuming seafood with a free on-line seafood mercury calculator.

Just go to http://www.GotMercury.com and list the fish you eat and your put in your weight.