Pacific Bluefin Tuna
Bluefin tuna are the largest of the tuna species, reaching upwards of 680 kg. There are three species in each of the Pacific, Atlantic and Southern Oceans. In all oceans bluefins are known for their impressive migrations, routinely crossing ocean basins. In the Pacific, tagging studies indicate there is only one stock with a spawning ground off southern Japan. In the first few years of life some young tuna make the extensive migration from Japan to the eastern Pacific off California and Mexico. Their decision to come east has been linked to the abundance of prey off Japan. Off California and Mexico their annual movements and preferred habitat are poorly understood.
Like all tunas, bluefin are endothermic and can regionally elevate body temperature above ambient water temperature. Comparing results from bluefin with yellowfin and albacore tuna will provide important insights into how endothermy influences movements and habitat selection.
In addition to being the largest, blue fin are the most highly prized tuna on the Japanese sashimi market. As a result of the associated fishing pressure, populations if Atlantic and Southern Bluefin are 15-20% of historic levels.