(FORTUNE Magazine) – No one seems to remember just who, in the mid-1970s, first had the idea to ship a giant bluefin tuna from New England to Japan by airfreight, but in that moment was born a trade to gladden the flintiest Yankee heart. Until then, the bluefin (Thunnus thynnus, from the Greek word thuno, meaning "rush") had been considered a giant nuisance--a wrecker of nets and gear, fit for cat food. Now, of course, it is the object of a seasonal piscatorial gold rush.

The highest price paid for a New England tuna exported to Japan this year was $14,920; more commonly, a bluefin might fetch $8,000. The fish's fat content, more than anything, determines its value on the Japanese market (the fattier the better). At just about this time of year, as they conclude their long feeding run up the East Coast, the bluefin arriving at Cape Cod and the Maine coast are reaching a state of optimum sashimi. In the pages that follow, FORTUNE chronicles the mad rush to market.

--Timothy K. Smith

REPORTER ASSOCIATE Sheree R. Curry