A tuna is a saltwater finfish that belongs to the tribe
Thunnini, a sub grouping of the mackerel family which together with the tunas,
also includes the bonitos, mackerels, and Spanish mackerels. Thunnini comprises
fifteen species across five genera, the sizes of which vary greatly, ranging
from the bullet tuna, weight: 1.8 kg up to the Atlantic bluefin tuna. The
bluefin averages 2 m, and is believed to live for up to 50 years. Their
circulatory and respiratory systems are unique among fish, enabling them to
maintain a body temperature higher than the surrounding water. An active and
agile predator, the tuna has a sleek, streamlined body, and is among the
fastest swimming pelagic fish the yellowfin tuna, for example, is capable of
speeds of up to 75 km/h. Found in warm seas, it is extensively fished
commercially and is popular as a game fish. As a result of over ishing, stocks
of some tuna species, such as the Southern bluefin tuna, have been reduced
dangerously close to the point of extinction.
