Wherever they’re buying fish from, the suppliers and chefs have one thing in common: speed. With a food that spoils this quickly, nobody can sit around dithering; decisions to buy thousands of dollars’ worth of fish are made in the blink of an eye.

One morning, I visit Pierless Fish, another top-rated local wholesaler, in the Brooklyn Navy Yard, and find owner Robert DeMasco barking buy-and-sell orders into a phone while frantically clicking away on his computer. At a nearby desk, his partner haggles with a Maine fisherman over an order of striped bass. “How much does he want?” DeMasco asks.

“He wants $4.50.”

“Fuck him! Tell him $4.”

His partner shrugs. This fisherman’s a good source, so the partner doesn’t want to piss him off and risk losing the guy’s support if they need striped bass later in the month. DeMasco gives in and agrees to $4.50. “There’s a lot of deal-making,” he tells me.

The sheer value of an individual purchase can be astonishing. We wander over to a six-foot-long box, and DeMasco heaves off the cover. Inside is a massive bluefin tuna, as thick as a tree trunk. He’ll cut it up into some fish fillets and block-pieces of sushi. Bluefin costs $9 a pound, and this one weighs almost 500 pounds. It’s a $4,000 fish.

For a new chef, cracking into the elite fish network is not easy. “What makes the Fulton Fish Market unique,” says Dan Kim, partner of Alaskan Feast, a Fulton wholesaler, “is that you come to us—we think about it.” (The market is set to move to the Bronx any day now, but its social structure surely will remain intact.)

Rick Moonen, the chef who cooked at Oceana and ran Restaurant RM in New York (before decamping last year for Vegas), recalls how difficult it was, when he first started in the business, to get Samuels to give him access to the top-tier fish. Moonen was buying from Louis Rozzo, a competing Fulton wholesaler, so Samuels wouldn’t have anything to do with him. “The first couple of times I tried to get him to sell to me, he was like, ‘Nah,’ ” Moonen says. But Moonen kept on visiting Samuels’s operation and talking to his staff. He promised to pay cash up front for all his purchases. “After a while, I was down around the fish market often enough, it showed I was serious. So finally we went into the back room for a talk and he agreed to work with me.”

Once a chef has a trusted supplier, he tends to stick with him. That’s because a good supplier isn’t merely a source of fish; he’s a source of information about what’s fresh, what to go for, and what to avoid. Indeed, suppliers practically dictate the menu at the top restaurants. Eric Ripert uses Samuels exclusively; Daniel Boulud relies heavily on Rod Mitchell of Browne Trading Company up in Portland, Maine, who is renowned for having the best New England fish. Over at Sea Grill, Ed Brown also uses Browne Trading for about 30 percent of his fish; 60 percent comes from Rozzo, who, as Brown avers, gets the best snapper from Florida.

“He puts his hands on guys with day boats, and he’ll say, ‘I’ll take the entire boat. Pack it up, and fly it up to Newark.’ He’s got that kind of power,” Brown says. “And he’ll pick out the golden pieces and send them to me, the best three pounds he’s got. Whereas if you’re Joe Smith the chef, he’s like, ‘Yeah, I’ll get you three pounds—from the bottom of the box.’ ”

Another big player in fish networks is, improbably, FedEx. It has transformed the industry, giving chefs instant global access to individual fishermen worldwide, thus allowing the chefs to opt out of local machinations. At Esca, chef David Pasternack gets his top sockeye salmon by ordering directly from boats in British Columbia and Alaska. “I call ’em in the morning, see what they got, and if it’s good enough, they overnight it to me. It’s literally right off the boat,” Pasternack says. (Other fish he buys from Samuels.) Over at Oceana, Gallagher buys his fish exclusively from a FedExed network of twenty handpicked fishing companies worldwide. One of them, Scottish Wild Harvest, in western Scotland, sends him ten-pound boxes of langoustines, packed in a remarkable fashion: They’re in a dark tank for a few days to recover from the stress of being caught, then shipped to New York in temperature-controlled boxes.

“They’re literally still alive when I open the box here,” Gallagher marvels. “Out of 100, maybe one is dead. Whereas years ago when they shipped them, about half would be dead.”