Yet while FedEx brings in ever-more-elite fish, it also brings in ever-more-elite prices. Ed Brown often spends $100 to ship a 50-pound box of wild king salmon from Alaska, or sea trout from Tasmania. That’s another $2 per pound on the price, a hefty spike when you consider that local merchants nearly come to blows over 25-cent price differences. FedExing is thus an extra gamble for a chef, another way of eating into the already thin margins of the fish business. “If I don’t sell three portions,” he adds, “that could be my entire profit for that order.”

Sushi can be even more expensive. The best fatty tuna from Tokyo can regularly cost up to $50 a pound, so great is the Japanese demand for elite cuts. Over at Jewel Bako, owner Jack Lamb recently paid $42 a pound for big thin reef squid, coveted for its creamy taste. “At first I was like, ‘$42? This is crazy,’ ” he says. “But they said it’s the greatest squid in Japan, and when I tasted it, it was true.” Sushi has one major advantage: It is regularly “flash frozen”—a method of super-quick freezing that sometimes begins on the boat when the fish is still alive. Since sushi is frozen, a chef can stock up on excellent fish and hold it for weeks or even months, without needing to sell it instantly. It is a little jarring to learn that virtually all sushi arrives at restaurants in a cold brick that’s sawed into portions using wood-shop tools. But FDA rules require that all sushi be frozen, to kill parasites. (The exception is tuna, a naturally parasite-free fish.)

When it comes to suppliers, secrecy reigns. Many chefs won’t discuss whom they buy from, to prevent another restaurant from dipping into the same source. Gallagher was eating superb tuna at Sushi Seki, the Upper East Side sushi restaurant, and asked the chef where it came from. “He said, ‘Spain.’ I said, ‘Who’s your supplier?’ He just started laughing. And I realized I’ll never find out. Chefs’ sources are a pretty highly guarded secret. I don’t mind talking, but some of the old guard, they won’t say anything.”

What happens if a supplier screws a chef and sends him sub-par fish? With the long-term relationships, this doesn’t happen often: If Samuels and his ilk can’t find good enough halibut or monkfish for Eric Ripert or Pasternack, they’ll simply say none are available rather than foist mediocre fish on them. But sometimes a new supplier will “haze” a chef, checking to see how seriously he takes his quality. “Everybody’s gonna try to throw a couple of fish in there that aren’t very good,” says Daniel Angerer, a former co-owner of restaurants Fresh and Coast. Gallagher tells me that a supplier recently tried to “up” his order, shipping him 850-gram loup de mer when Gallagher had ordered only 800-gram fish. Gallagher sent them back, with an angry phone call. “I’m a gentleman, but I’m a ballbuster too. They’ll try to send you stuff and it’s not great, to test you. Then they find out you’re a ballbuster, and they treat you better.”

“There are companies I don’t like, but you couldn’t pay me all the money in the world to badmouth them,” Ed Brown says, laughing. “Relationships are everything, and you don’t want to break them.”

Indeed, those in the fish network are in a curiously co-dependent relationship. In a strictly economic sense, the top Fulton suppliers, like Samuels or Dan Kim of Alaskan Feast, probably don’t need the big chefs: Fancy restaurants don’t account, in fact, for much more than 10 or 20 percent of their business. Most of the business goes to mid-market restaurants and supermarkets that are willing to buy fish that’s a rung or two down the ladder, is a few days older, or has been damaged in transit. But having an elite chef as a client gives a fish seller prestige. “I know guys who get screwed on bills by big restaurants, but they don’t cut them off, because they all want to be the one saying, ‘I’m supplying so-and-so,’ ” says one supplier who asked to remain nameless. Indeed, serving a top chef can sometimes be less than profitable, as Dan Kim notes. “When I buy a fish for $10 a pound, I just look at myself and I go, ‘What am I doing?’ Handling these really expensive fish is almost more of a courtesy. You don’t make your money on it.”

Of course, chefs being chefs, outsize egos can sometimes rub suppliers the wrong way—particularly if someone is being a stickler about price. Few elite chefs will admit to serious haggling; if the fish is truly good, they claim they’ll pay almost whatever price necessary, since their wealthy customers can afford it. But suppliers tell a different story. “I remember one top guy, literally one of the top chefs in New York, was looking at some of my monkfish,” one supplier told me. “It was just amazing stuff. Line-caught, perfectly handled—it was so fresh it was still flopping around when we got our hands on it.” He asked for $5.50 a pound, but the chef refused to pay more than $4.50. “We couldn’t believe it. We’re like, ‘This is the best monkfish we’ve ever seen.’ And he’s like, ‘I don’t care. I can get monkfish elsewhere for $4.50.’ Yeah, but not as good as this. And this guy’s supposed to be running one of the best restaurants in New York?”