Mercury rising in pacific tuna

Transcript

A new study led by the University of Michigan suggests that the Pacific's premium yellow fin tuna may be inedible in 50 years time.

The report which used findings from reports published in 1971, 1998 and 2008 concludes that mercury concentrations in the highly migratory yellow fin tuna species caught near Hawaii were increasing by nearly four percent a year.

Co author of the report Associate Professor Carl Lamborg from the University of California at Santa Cruz spoke to Koroi Hawkins about what is wrong with the fish.

CARL LAMBORG: Well there's nothing really wrong with it it's got a little, it's got some mercury in it. Yellow fin tuna isn't crazy high in mercury concentrations the way some other, top, top predator fish in the ocean do. But what we found in the study was that by stitching together a few other previously published studies, we think we found some pretty compelling evidence for documentation of the increase of the concentration of mercury in yellow fin tuna over time, since the nineteen seventies or so. And it wasn't surprising, but it was essentially what we would have predicted we would find, based on other work that people have done, where they made predictions or they made measurements of the amount of mercury going into the environment as a whole. And its interesting, you know, there have been a lot of research on mercury in the environment and fish and over several decades. But the sort of holy grail that we've never really been able to show, was that if you put more mercury in the environment you get more mecury in fish. It's sort of it seems like it should be obvious, but it wasn't something that we really ever had any definitive evidence for. I think until now, until this study that Paul Drevnick was the lead author on, I think really shows that fairly well.

KOROI HAWKINS: So how much of an increase since the first original study that you were quoting in, 1970 did you say?

CL: What we found is that since the 1970s or so, the concentration of mercury in these particular kind of fish from near Hawaii, has been increasing at about 3 or 4 percent per year or so. Or something that's consistent with that kind of rate of increase, which is about what we would have predicted from atmospheric measurement.

KH: So are the fish dangerous to eat now or will they be very dangerous to eat in the future? What is the sort of what are you taking out from your findings?

CL: I am not a public health person whose, make those kinds of measurements. But what I know is that in the United States for example, Federal and state governments will issue consumption advisories. And they will advise the public against eating fish of a certain concentration of mercury. And some times supply information regarding which species tend to be above that kind of concentration, or which species tend to be below that kind of concentration. And that allows the public to make their own decisions, based on what they want to do and you know the kinds of risks that they would like to take. Different state, federal, international organisations issue different guidelines on this number. So some people say 0.1 part per million mercury in the fish, some say 0.5 part per million in the fish. So depending on which numbers you use these yellow fin tuna are all already over that number or getting close to that number. Depending on which number you use.

KH: And in terms of your findings, what does that mean for the environment and what can be done about it?

CL: So now that we have evidence that the fish are responding to loadings to the ocean, we can then turn to work that other people have done in terms of the future. And the rate at which people are putting mercury into the environment appears to be accelerating to some extent. So there are some models for example that predict that in the next 50 years we'll put as much mercury in the environment as we have put into the environment in the last 150 years. Which has gotten us to this point that we are at now with the mercury concentrations in tuna that we have today. So moving forward into the future, I think even if the yellow fin tuna are relatively  low now. I think we ought to be worried about where they are headed, really is maybe more the important take home of this story.

KH: And what are the biggest culprits in terms of putting mercury into the ocean?

CL: Well there are natural sources to be sure and vulcanism and weathering of soils is sort of the primary natural source of mercury. And that's pretty substantial that's maybe, 25 to 30 percent of the total amount of mercury going into the environment each year these days. The rest is pollution sources and there are numerous, the sort of two biggest ones that people tend to talk about is the burning of coal and the mining of gold, using kind of low tech methods that use mercury. That's collectively known as small scale and artisanal gold mining or ASGM.