In the field, fish are caught using rod and reel and brought aboard the fishing vessel, where tags are externally attached, or surgically implanted inside the tuna. Each tag, ranging in price from US$1,500-$3,500, records sunrise and sunset, pressure (or depth), water temperature and body temperature. When months or years later a fisherman catches the tagged tuna, the fisherman receives a handsome reward for returning the electronic tag to scientists who then download the data into a computer for analysis.
Some tags do not even need to be physically retrieved but rather transmit their data to researchers via satellite. Using astronomical techniques similar to those used by 17th century mariners, the tuna's position on earth can be calculated from sunrise and sunset data, revealing the migratory track of individual fish as they swim throughout the North Atlantic Ocean and adjacent seas. The longest migration recorded to date was from a fish caught, tagged and released in North Carolina that over the course of 4.8 years traveled across the North Atlantic and into the Mediterranean.
Bluefin tuna are often described with superlatives: largest, fastest, most powerful. They are long-lived, among the largest fish on earthweighing up to 1,500 lbsand make trans-oceanic migrations in as few as 20 days.
The same muscles that power their locomotion across ocean basins are at the heart of the sushi economy that has made the bluefin so prized by diners. Global demand for bluefins has grown dramatically in recent years, and sushi connoisseurs revere bluefin tuna above all else. A single fish sold at auction in Japan for $173,000 pricing that has fueled industrial fishing pressure and has led to the near-collapse of bluefin populations in both the West and East Atlantic.
Tag-A-Giant research is providing fisheries managers with the information needed to design and implement sustainable limits for commercial
|Contact: Randy Kochevar|
Tag-A-Giant Foundation (The Ocean Foundation)