As most of Tokyo sleeps, men in rubber boots haggle over tuna in the cavernous halls of Tsukiji market.

The clang of a bell around 5:30 am kicks off the action at the world's biggest fish emporium. Traders flash hand signs and bellow out prices as they buy and sell what will soon end up on plates in the Japanese capital and beyond.

Fins are lopped off to expose the red flesh among rows and rows of the hulking tuna carcasses, which are still moved around the market by wooden cart.

In all, about $18 million worth of fish, seafood and vegetables -- over 2,900 tons -- change hands each day at the market.

"Do you see how we use hand signs?" asks one bidder, seconds after another man violently rings the bell and starts yelling out bids.

"This is exactly how people used to trade stocks in the old days."

Major stock markets have shifted to computer trading while Tokyo mushroomed into one of the world's biggest cities over the decades, but little has changed in the way business is done at Tsukiji since its opening in 1935.

Now, almost 80 years later, the city plans to move the market to a new location and give the popular tourist draw what advocates say is a badly-need technological update.

But not everyone is happy about the move away from prime-real estate in the centre of the teeming metropolis.

Relocating the market and building to a modern facility about 40 percent larger with state-of-the-art refrigeration will cost upwards of $3.8 billion.

And the move, now scheduled for 2016, has been marred by revelations of heavy soil contamination at the site, once formerly a gas plant about 2.3 kilometres away (1.4 miles).

That has saddled Tokyo with more than half a billion dollars in cleanup costs at the less-than-central location.

It is unclear what will happen to the current site beyond building a new road linking downtown with some 2020 Olympic Games venues.

'Totally outdated'

Hiroyasu Ito, chairman of the Seafood Wholesalers' Association, insists the move is crucial for Tsukiji to handle modern-day demands for freshness.

"Railroad freight cars used to roll into the market and unload fish and goods right here," he says, pointing to a large picture in his office that gives a birds-eye view of Tsukiji's layout.

"We don't use the rail cars anymore. Now refrigerated trucks drive around instead."

Key to ensuring perishable goods stay fresh is a so-called cold chain which maintains produce at a consistent temperature until consumers buy it, something the market is ill-equipped to do, Ito says.

"Customers want fresher and fresher seafood so that they can eat it raw, which puts pressure on us. Delivery people have had to come up with high-tech cooling methods," he says.

"We have managed to keep the fish cold in high-quality foam coolers. But we're pushing the limit -- Tsukiji is totally outdated.

"In the new facility, we plan to shut out air from the outside and keep the fish section at a steady temperature."

But the move to a scrubbed-clean market farther away from downtown is not popular with some shoppers.

"The messy and crowded scenes at Tsukiji are what makes the place attractive," said out-of-town visitor Tetsuya Kojima, who added that he was unlikely to visit the new site.

Some of the old guard are not about to leave quietly either.

Union member Makoto Nakazawa, a leader in the fight to stop Tsukiji's move, lashes out at what he sees as profit trumping all else.

"Tokyo wants to move the market to satisfy the greed of real-estate interests here -- I cannot think of another reason," says Nakazawa, who has organised small demonstrations in protest.

Soil contamination, whopping bills

The 40 hectares of land earmarked for the new market is soaked with toxic chemicals, the legacy of its previous life as a gas plant.

Opponents have filed lawsuits over the city's purchase of the land without requiring Tokyo Gas to clean up its former site. That means taxpayers will shoulder the hefty 58.6 billion yen cleanup.

And the bill could still grow.

Labour and materials prices are shooting up with contractors in short supply as they focus on quake-tsunami disaster reconstruction projects and building for the Olympics in seven years.

Still, the municipal government says it is pushing ahead with plans to uproot Tsukiji and erect the new market by March 2016, about a year later than previously scheduled.

"We are aware of a number of difficulties," says Masataka Shimura, a Tokyo official leading the new market project.

"But we're still planning to do the move as scheduled."