Bluewater Hunting and Freediving
to Europe. One reason these fish are able to travel such long distances and enter cold water is a special physiological adaptation that allows them to retain and accumulate body heat.
The bluefin’ s heat retention capability is unique among the tuna, and most other fish species as well. Bluefin produce heat in their red muscles( those muscles responsible for slow swimming) and in their stomachs. They conserve this heat with a special capillary system that works as a heat exchanger. The blood-carrying heat, carbon dioxide and metabolic byproducts in most fish are ducted into the gills, where respiration takes place. Bluefin blood first makes a trip through a special set of blood vessels called“ retes,” which remove some of the heat otherwise lost to the water through the gills.
The significance of all this is that the animal’ s white muscles( those muscles responsible for sprint swimming) are supercharged with the extra heat and become capable of greater speed. Furthermore, the extra heat allows the larger fish( those over 300 pounds) to extend their range into waters as cold as 45 degrees Fahrenheit. The metabolic price for this adaptation must be expensive because bluefin are voracious feeders, consuming as much as 25 percent of their body weight a day.
The Pacific bluefin travel a similar transocean pattern, from the West Coast of North America to their breeding grounds in the Philippine Sea and the Sea of Japan. I believe the disappearance of large bluefin off North America is due to overfishing in their breeding areas. Japan consumes 86 % of the world catch.
Pacific bluefin are fished heavily by line fishermen about 200 miles from the shores of California and Mexico. They find deep fish using depth sounders and attract them to the surface by casting out chum bait. Sometimes a kelp paddy will hold schools of fish. Until recently it was rare to find them there. Bluewater divers find most of their fish on the edge of steep drop-offs, usually up-current, and usually in association with bait. Spotting yellowtail in the area is a good sign because they frequently associate with bluefin. Hunt the water 50 to 100 feet further out
to sea, past the yellowtail concentrations.
Bluefin often swim with such speed( up to 55 miles per hour) that you need to aim at least one-third of a fish-length ahead of them, and on the level of their lateral line. While I suggest using a big gun and three floats, the European divers use a very different system.( The European system is described in the chapter on gear.) Actually, the European bluewater tuna divers are different themselves. Many are tough, nomadic, commercial fishermen who follow the fish around the European continent. Secretive about their catches and their methods, they fish the north coast of France for fish 60 to 90 pounds. The best bluefin fishing is off the Azores in the mid- Atlantic, where divers hunt fast-moving shoals.
Until just recently, many of the largest bluefin speared have been taken from the waters surrounding Guadalupe Island, Mexico. Noted bluewater diver and researcher Jim Stewart, of the Bottom Scratchers Club based in San Diego, reported seeing the first giant bluefin tuna in 1954. Carrying just a small single-banded gun, and overwhelmed with the size of the hundreds of fish that circled him, he hurried back to his boat. In 1962, Ron Merker went to Guadalupe for bluefin. His 57-pound record held for 20 years. Ron, a veteran of 5,000 documented dives, says he’ ll never forget the power of that fish as it dragged him under the water multiple times. Asked why he did not return to Guadalupe, Ron replied that he had seen some very large shark fins in the area as well.
I’ ll never forget my own Guadalupe Island trip, in 1982, when I speared the largest Pacific bluefin to date.
Bait fish began to gather over the rocks, stepping from 60 to 90 to 120 feet below. I had that special feeling experienced divers get when they know conditions are favorable for big fish. Sure enough, big yellowtail appeared in schools. I yelled to my Hawaiian friend and teammate Dennis Okada,‘ Don’ t shoot the yellows, I think tuna will show!’ Two dives later, in the 150-foot visibility water I watched Dennis try to ignore a 40-pound yellowtail swimming toward him. Unable to resist,
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