Whynott takes readers out to sea with ""the true sons of the whalers of old"" -- the men who make their living harpooning bluefin tuna in the Atlantic Ocean from Cape Cod to Maine. Only 200 harpoon permits are issued to East coast fishermen each year, and about 30 of their boats, says Whynott (English/Mount Holyoke; Following the Bloom, not reviewed), actually harvest any fish. There is no daily limit for harpoon fishermen (regular permit-holders are allowed but one tuna per day), but the total quota for the entire western Atlantic is 53 tons -- about 240 fish. Whynott followed the fortunes of Bob Sampson and his son, Brad, for the 1992 and 1993 seasons. Like most harpoon fishermen based on Cape Cod, the Sampsons employ a spotter plane to locate schools of giant bluefin. The pilot will sometimes watch for humpback whales, which, like tuna, feed on herring and mackerel. When a school is spotted, the boat races to the area and one man climbs into the pulpit wielding a 12-foot-long harpoon, usually of aluminum, with a bronze ""dart"" wired for 800 volts. Thanks to the sushi boom, one throw can bag a fish that will bring as much as $50,000 at the Japanese auction houses. Bluefin tuna can grow up to 10 feet long and weigh as much as 1,500 lbs., but most are in the 300- to 500-lb. range. The Sampsons, who helped organize a group of Cape Cod fishermen to deal directly with the Japanese, got an average of $16.50 per pound for their fish in 1992; they grossed almost $200,000 for the 1993 season. Not bad, notes Whynott, for a fish that just 20 years ago was sold as cat food for five cents a pound. Whynott's natural history of the giant bluefin tuna, its mating and migratory habits, and his profiles of the Cape Cod fishermen and their lifestyle, is engagingly rendered.