Tunas are streamlined, spindle-shaped open-water fishes with two dorsal fins that fold into grooves and finlets between the second dorsal and their deeply forked or lunate tails. At least two small keels extend from each side of the narrow tail base. Their upper bodies vary between shades of silvery iridescent blues and greens with countershadings of white on the belly. Pelagic species, built for speed and endurance are rapacious predators of squids and fishes in the near-surface zone of the open ocean.
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