Bluefin tuna, distributed worldwide, are one of the largest gamefish available to the bluewater hunter. In the Atlantic, they reach weights of 1,700 pounds (770 kilograms), while the largest Pacific bluefin, netted in 1989, weighed 1,008 pounds (457 kilograms). My world record of 398 pounds (180.7 kilograms), taken in 1982, still stands but I feel confident it will be broken many times over if we, as a world community, can work together for improvement in resource management.
An international tuna commission, the International Commission for the Conservation of Atlantic Tuna, attempts to regulate Atlantic bluefin stocks. Because of their great value (my fish, freshly caught, if jetted to Japan, would have been worth $25,000) and rapidly decreasing stocks, there is always a lively dispute between scientists and fishermen. The scientists, intent on management, caution us against overfishing. Fishermen, intent on feeding their families, insist that things have never been better. The fact is that overfishing by purse seiners in the 1960s severely jeopardized future populations of bluefin tuna by wiping out complete year-classes of these fish.
The situation is even worse in the Pacific, where no functioning plan is in place. In the fall of 1989, night squid netters directed by spotter planes observing mysterious phosphorescent contrails on the surface (giant bluefin tuna disturbing the plankton) started a California bluefin bonanza yielding many fish weighing 600 to 800 pounds. Several netters became millionaires in the space of three months while their deckhands, sharing in the catch, bought new cars.
It is disheartening to think that this marvelous and mysterious migration of huge breeding tuna, perhaps repeated over millennia, was decimated in the span of a few months by man using his highly sophisticated methods. Because of their timidness and great speed, bluefin stocks are at little risk with bluewater hunters who, to date, have taken less than 100 individuals worldwide.
Atlantic bluefin are found off the eastern United States, Canada and the west coast of Europe. Northern Pacific bluefin traverse the ocean from North America to Japan. The Atlantic and North Pacific bluefin are considered to be subspecies of the same species. Southern bluefin, considered a separate species, roam the South Atlantic, the South Pacific and Indian Oceans.
Prolific breeders, capable of producing 10 million eggs per year, they have been known to reach 30 years of age_my 398-pound bluefin was scientifically calculated to be 11 years old. In the Atlantic, bluefin tuna cannot breed until they are at least six years old (about 100 to 120 pounds). They are not effective breeders until they weigh over 500 pounds, typically at age 15 to 16.
Traveling up to 150 miles per day, these fish regularly make the trip from warm Caribbean waters northward to the cold waters off Nova Scotia and, in some cases, even cross the Atlantic 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.
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