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 ,