TOKYO – A group of Mainers learned Friday that very little can prepare anyone for the Tsukiji fish market. To call it immense would be to call Mount Katahdin a hill.

Tsukiji, the common name for the Tokyo Metropolitan Central Wholesale Market, is the largest fish market in the world, handling about 41/2 million pounds of seafood a day. Stretching for 55 acres along the Sumida River, it brings together thousands of wholesalers and buyers and a few bleary-eyed tourists beginning at 3 a.m. almost every day.

Four members of the weeklong Maine gubernatorial trade mission to South Korea and Japan rose early Friday to tour Tsukiji with Tomohiro Asakawa, a fisheries commercial specialist with the National Oceanic and Atmospheric Administration and one of only a few U.S. government workers overseas charged with promoting U.S. seafood exports.

The group consisted of Ben Metivier, sales manager for Atwood Lobster Co. of Spruce Head; Ned Porter, deputy commissioner of the Maine Department of Agriculture, Food and Rural Resources; Wade Merritt, director of operations at the Maine International Trade Center; and Jeffrey Porter, senior international trade specialist with the U.S. Department of Commerce office in Portland.

A brief cab ride from the ANA International hotel brought them to the outskirts of the dimly lit market, which was bustling with pushcarts, trucks and workers stacking millions of plastic foam boxes of fish. For the most part, the market is contained in warehouses and buildings that look like empty parking garages. On the outskirts of the market are open-air booths and shops where venders sell knives and other kitchen products.

The group was immediately overwhelmed by the sheer number of the shoe-box-size containers being stacked, each hiding one of every kind of seafood imaginable – from Portuguese sardines to Norwegian salmon to Alaskan king Crab. Rows upon rows of boxes stretched as far as the eye could see.

“By 10 a.m., it will all be gone,” Asakawa said. Jaws dropped. Everything sold in fewer than six hours? It seemed impossible, the group said.

After being caught or harvested, seafood is sold to a middleman, or wholesaler, Asakawa said. It then is shipped to the market and sold at auction to authorized buyers and intermediate wholesalers. Authorized buyers sell directly to consumers, and intermediate wholesalers sell to stock purchasers, who then sell to consumers.

The first stop was the sea urchin market, where wholesalers took stock of thousands of boxes of urchin innards, which resemble little orange tongues. Representatives of the auction houses, called “gyousha,” scrawled notes, estimating values by pressing the tops of the boxes to test firmness and observing color. Licensed buyers milled about, deciding what to bid on at the day’s auction.

Asakawa pointed out a long row of Maine sea urchins, which were impossible to distinguish without his help, as all urchins are repackaged in uniform boxes in Japan. The most prized sea urchins come from Hokkaido, a northern Japanese island, and bidders pay up to 7,000 yen, about $60, for a 260-gram box, or 9 ounces, Asakawa said. Maine sea urchins fetch about 1,000 yen per box, about $9.

Asakawa led the group to the Tsukiji’s main attraction, the tuna auctions, by way of the shellfish, sardine and crustacean markets. Metivier stopped and stared incredulously at an Australian lobster that had been shipped in sawdust instead of water.

“I can’t believe that,” he said, watching as the creature still crawled in its box.

Eel, squid, octopus, sea cucumber and a few unrecognizable organisms writhed in their close quarters. For better or worse, they are kept alive for as long as possible before their sale.

The group also expressed surprise at the absence of fish smells in the air and the cleanliness of the ground. Hoses spewed fresh water constantly and supervisors employed by the market were ubiquitous, recognizable by their rubber boots and canvas jumpsuits. As vigilant as they were about cleanliness, many had cigarettes clamped between their lips.

The next stop, at around 5 a.m., was the frozen tuna market. Upon entering, each person gasped at the sight of the roughly 200 enormous, headless, frozen fish arranged on rows of wooden palettes. Dry ice emitted an eerie mist that hovered above the ground and around the fish. About a half-hour from auction time, inspectors and potential bidders lifted gills and peered inside the 400-pound carcasses with flashlights. A market employee poured hot water from a copper kettle onto the rear of the tuna so that a second worker could cut slices for display. Chatter filled the room and many buyers relayed findings on cell phones.

The fresh tuna market was more lively, packed with about 500 buyers and inspectors who moved quickly around the fish. Buyers straddled the animals, digging inside to rip out small pieces and rub them between their fingers.

“They’re looking for high fat content and bright, red color,” Asakawa said.

The price of frozen tuna averages 3,000 yen per kilogram, Asakawa said, about $12 a pound.

On a given day, sashimi-grade fresh tuna goes for about 20,000 yen per kilogram, or $23 a pound, Asakawa said. That’s a $10,000 fish.

“You could buy a Porsche,” Asakawa said, gesturing at the rows of fish.

At 5:30 a.m. sharp, seven auctioneers rang hand bells and shouted to signal the start of the auction. The floor immediately cleared as buyers rushed to the back of the room. Auctioneers stood above each fish and called bids until a price was reached. After the purchase, buyers wheeled their tunas out of the market on large carts and brought them to the stalls. There, the fish were filleted and sold.

Asakawa led the group to one tuna stall where a man mustered all his strength to push and pull a 4-foot-long saw through the body of his fish, halving it in little more than a minute.

Those allowed to shop at the stalls are authorized buyers and sell to restaurants and retail operations. But Tsukiji does not exclude those seeking a bite to eat. Asakawa brought the group to the outskirts of the market where vendors sold kitchen products, fruits and vegetables. There, a cluster of tiny restaurants had opened at 5 a.m.

“I’ve never had sushi for breakfast, but I guess I’m about to,” Metivier said. Porter never thought he would try sushi, but decided he was up for it.

Asakawa selected a restaurant that consisted of a bar and eight seats around it. For 2,100 yen, about $18, the group dined on miso soup with clams, sashimi, or pieces of raw fish on white rice, a small omelet, sushi rolled in rice and seaweed, and green tea.

“It doesn’t get any fresher than this,” Jeffrey Porter said. Porter couldn’t get enough of the wasabi, the hot, green Japanese condiment.

Everyone in the group agreed that the visit to Tsukiji was a high point on the trade mission. They said their only hope for next time is to patrol the market and find more Maine products prominently displayed.