Ted Danson, BBC Green Room 15 Sep 08;
The Atlantic bluefin tuna is a magnificent creature in a desperate plight, says Ted Danson. It may be possible to save it - but what about the wider issue of our overfished oceans?
I'm an actor, but ocean issues have been important to me for a big part of my life.
I became involved in the mid-1980s when I took my daughters to the beach, only to find it had been closed for swimming as a result of pollution.
Since then, I've spent the last 20-plus years as an ocean advocate, working with Oceana (and its predecessor organisation) to help in its efforts to restore the oceans to vitality and health.
I am on Oceana's board of directors.
One thing I learned early on is that pollution isn't the biggest problem facing the oceans, though it is certainly important.
It's overfishing. We're just taking too many fish out of the sea.
Since 1950, 90% of the big predator fish - your swordfish, your shark - have disappeared.
This summer, Oceana launched a new campaign and a new research boat, the MarViva Med, dedicated to saving the northern bluefin tuna, or Thunnus thynnus.
This is your elite fish, the kind that sells for $100 per pound (£125 per kg) or more in Japanese fish markets.
Unfortunately for the bluefin, it's not only one of the world's most coveted seafood species - it's also one of the most threatened.
Since the mid-1990s, tuna populations have spiralled downward, and scientists warn that an immediate moratorium on fishing is the only way to avoid an irreversible collapse.
In June, the European Union closed the bluefin tuna season for most ships two weeks early, but that's only a stop-gap measure.
Time is running out to save these sleek and powerful fish.
Tiger tamed
Conservationists often refer to the bluefin tuna as the "tiger of the sea", but in truth a mature bluefin outweighs, outgrows and outpaces even the heftiest wild cat.
Bluefin can weigh up to 1,400lbs (635kg) and measure 15ft (5m) long, and can sustain bursts of speed up to 60 mph (100 km/h) in pursuit of prey.
Warm-blooded, they migrate across oceans, and females produce up to 30 million eggs each spawning season.
Bluefin tuna have fascinated and fed humans for ages. The first evidence of bluefin fishing in the Mediterranean dates to the 7th Millennium BCE when the Phoenicians established fisheries using hand-lines and primitive seine nets.
Aristotle studied tuna in his History of Animals, written in 350 BCE, and contended that the enormous fish gorged for two years before bursting from overeating.
Four hundred years later, Pliny the Elder recommended eating tuna to treat ulcers, suggesting the neck, belly and throat as the finest pieces that must be eaten fresh even though "they cause severe fits of flatulence".
But it wasn't until the late 20th Century that that tuna became a global business.
In recent years, sushi and sashimi have exploded in popularity in Japan and around the world, and consumers tout the fatty flesh of the bluefin as the most prized meat.
Purse seine ships, which close drawstring nets around schooling fish, became larger and more sophisticated, and fattening cages dotted the seas starting in 1996.
These cages, which can measure 50m (165ft) across, may represent the biggest threat to bluefin survival.
Tuna, often juvenile, are captured and dumped in the cages - or "ranches" - for months to fatten up, with all the associated problems of aquaculture: disease, waste and overfishing of the smaller fish used to feed the bluefin.
Fishing for giant bluefin has become hugely profitable.
In the 1960s, its meat sold in the US for seven cents a pound. This season, the first bluefin sold in Taiwan netted $105 a pound.
Quota of ignorance
Despite this booming business, we barely understand how tuna populations work.
Several bluefin fisheries have cropped up in the Atlantic, only to collapse within a few years. The North Sea fishery collapsed in 1963, and a Brazilian fishery appeared in the early '60s only to vanish by 1967.
No-one knows why.
Current catch quotas set by the International Commission for the Conservation of Atlantic Tunas (Iccat) are nearly impossible to enforce, as fewer than 5% of catches have been sampled independently in the last decade.
Some conservationists estimate that the fishing industry took 50,000 tonnes of bluefin from the Mediterranean by mid-June of this year - and the quota was set at 28,500 tonnes.
Iccat has set a declining quota for Atlantic bluefin over the next few years as part of a 15-year recovery plan, reducing the total allowable catch to 25,500 tonnes in 2010.
But it isn't enough. Bluefin need a generational breather to prevent total collapse.
In the meantime, the data gathered by researchers aboard Oceana's MarViva Med tells us that the quotas that are in place are not effectively enforced and are ignored by the tuna fleet.
Even as a lay person, not a scientist, it's abundantly clear to me that overfishing is pushing our oceans towards an irreversible collapse.
Bluefin tuna is just one species that's already at the brink of extinction. We can bring the tuna back, but only if we act now.
Ted Danson is an Emmy- and Golden Globe-winning actor who has appeared in more than 25 films. He is a founder and board member of Oceana, which researches and campaigns on marine issues
The Green Room is a series of opinion articles on environmental issues running weekly on the BBC News website
