Atlantic Bluefin Tuna Biology
The Atlantic bluefin tuna is one of the biggest fish species in the world (4). They typically range from .5-3 m in length and 136-680 kg; however, the latter is becoming more rare due to overfishing (5, 6). In the 1970s the average weight was 544 kg, and the latest poll of the Bluefin shows the average weight to be half of what is was in 1970 (5, 6, 7). They tend to live 15-30 years, and occasionally nearing 40 (4, 5). As they are warm-blooded, they can tolerate both warm waters, such as in the Gulf of Mexico where they spawn, as well as off the nutrient-rich coast from the Gulf of Mexico, Newfoundland, Iceland to the Canary Islands, and Canada (1, 5). There are two stocks of Atlantic bluefin tuna: the western Atlantic stock, which spawns in the Gulf of Mexico and the eastern Atlantic stock, which spawns in the Mediterranean Sea (6). Despite this, both typically grow and feed off the east coast of the United States and Canada, as well as a large part of the North Central Atlantic Ocean, and are categorized as one species (6). Atlantic bluefin tuna eat several kinds of fish including herring, anchovies, sardines, bluefish, and mackerel; squid; and crustaceans (1, 5). The females, who, from mid-April to June, release about 10 million eggs, of which only a few live, reach sexual maturity at about 8 years old (4). Their torpedo-like shape, along with their retractable pectoral fins, permit them to swim up to 65 km/h and swim nearly 8,000 km across the Atlantic (4, 6). Despite staying near the surface for most of the time, they can swim down up to one kilometer (1). They also are able to return to the place where they spawned, even after migrating several thousand miles (1).
Bluefin Tuna Anatomy
As mentioned above, the physical attributes of the bluefin tuna allow it to have their amazing abilities. They are dark-blue to black on their dorsal (upper) surface, and a lighter silver/white color on the ventral (bottom) surface (1, 5). The structure of their eyes allow them to see well in dark nutrient-rich waters (5).
Table 1: Bluefin tuna size class categories.
Table 1: Bluefin tuna size class categories.