New York - Think Wall Street trading is brutal? Head up to the grittiest part of the South Bronx, where cutthroat deals are made in the dead of night on a massive concrete floor that reeks of fish guts.

The New Fulton Fish Market is the nation's largest seafood market, and second in the world to Tokyo's. Here, in a refrigerated building the size of six football fields, fishmongers are filleting, selling and packaging seafood - 200 million pounds a year worth close to $1 billion by some estimates. It is headed for restaurant tables, stores and mouths across America.

Glistening under the fluorescent lights is just about every sea creature. Most come in by truck, but about half are flown in from the ends of the Earth: Arctic char from Iceland; mahi-mahi from Ecuador; hamachi from Japan; branzino from Greece; salmon from Scotland; cockles from New Zealand.

Experienced buyers negotiate prices in seconds, judging quality on a look, a touch, a smell and often a raw taste.

"You know right away if fish is fresh. It's like looking into a woman's eyes - you know what's there," says Roberto Nunez, a 44-year-old Peruvian immigrant who started out as a dishwasher and has been the buyer for more than a decade for celebrity restaurateurs Lidia Bastianich, her son, Joe Bastianich, and their partner, Mario Batali.

Five nights a week, Nunez shows up at 1 a.m. to purchase as much as $15,000 worth of seafood, enough to meet the demands of 10 restaurants. What's available on any given night depends on a variety of often unpredictable factors, such as severe weather that keeps fishing fleets in port or a spotty catch in an overfished ocean.

"This is not like ordering tomatoes or potatoes," Nunez says. "Seafood is wild."

By 2:30 a.m., one of the key items on his handwritten list of orders - 400 pounds of striped bass - remains unfilled from among dozens of vendors.

"I'm getting nervous," he says.

The day's hundreds of offerings - including crabs, clams, mussels, slimy squid, octopus and caviar - are spread out across the floor in ice-lined boxes, a shimmering spectrum of silvers, pinks, reds and browns. Buyers, some vying for the same, scarce items, point to a specific box and cry out, "That's mine!"

All night, dozens of men in coats and wool caps work to the soundtrack of mini-forklifts whizzing around, honking and spewing exhaust as they move seafood-laden pallets. The smell is a mixture of the fishy and the fresh scent of the ocean.

Nunez finally spots some striped bass. But when he lifts the gills, "it's no good; they're brown," he says dejectedly. (The gills should be bright red). Plus the skin is dry, the eyes are cloudy, and it smells funky.

The hunt continues for the rest of his list: scallops, shrimp, squid, monkfish liver, fluke, shad roe, blowfish.

He spies black sea bass from New Jersey at $6.75 a pound. "How many do you have?"

"One hundred pounds," says vendor John Dias.

"How about $5.50?" Nunez asks.

Dias relents.