(Business 2.0) – Mackerel has always been a poor man's fish in Japan. Called saba in Japanese, the oily species spoils so rapidly that "it starts stinking while it's still swimming," according to an old saying. Even at upscale supermarkets, it goes for less than $10 a head.

Unless, that is, there's a tag on its body bearing an ideograph pronounced "se-key." Then the saba can sell for nearly $60. "We knew if we could differentiate, we could charge a higher price," says Kishichiro Okamoto, head of the Saganoseki branch of the fishermen's cooperative in Japan's Oita Prefecture. Okamoto used tradition and quality control to make a premium brand out of a wild fish that, in many ways, is just like every other mackerel on the market.

Even Japan's most adventurous sushi fans balk at raw saba: Chefs typically cure it in vinegar or salt. But the fishermen of Saganoseki have long eaten saba fresh from the water without getting sick. One explanation: Saganoseki sits on Japan's Inland Sea, where strong currents are believed to whip fish into shape, lowering their fat content. Another is a local preservation technique, known as ikejime, that involves puncturing holes near the gills and tail to quickly drain blood.

In 1988, with Saganoseki's fishermen desperate for new revenue, Okamoto hatched a plan to market local saba to high-end restaurants as the unthinkable: raw, unpickled sashimi. He came up with the Seki brand name--linking the fish to the Saganoseki area--and created a list of rules for distributors: 1) Only saba caught with rods can be Seki saba, because nets damage the fish. 2) All Seki saba must be killed by ikejime. 3) To prevent excessive handling, the fish can't be weighed or measured; instead, wholesale patrons must engage in "face buying"--negotiating simply by looking at the fish.

Top restaurants rebuked Okamoto at first, afraid that raw saba might poison customers. But after showing off his saba sashimi at major fish markets for four years, he got Osaka's New Otani Hotel to try it. By the mid-1990s, Seki saba was showing up in high-end sushi joints around Tokyo. "It has a light but firm texture," says Toru Hashimoto, owner of the top Tokyo restaurant Toyoda. Okamoto's co-op recognizes 50 restaurants in Japan as official dealers.

Today, Seki saba brings in more than $3 million a year for Saganoseki, and the company's branded horse mackerel--Seki aji--sells $2 million at wholesale. The success has inspired copycats: Akashi, a town in Hyogo Prefecture, is branding its octopus, and Rishiri, in Hokkaido, markets a trademarked kelp. Even Saganoseki has expanded, launching Seki isaki--grunt--in September. "With Seki saba we proved that a brand is really about building credibility," Okamoto says.

"The waters around here are full of marketing opportunities."

Regular mackerel $9 per fish

Seki saba mackerel $58 per fish

Sources: Rakuten; Tokyo market prices