Silver, speckled black, with fins in a blue so saturated they look artificial. Up to 1.1 m (43 in), and a fish that arrives suddenly, crosses a reef at speed and is gone.
It hunts by following. Bluefin trevally shadow octopus, morays and other bottom hunters, taking the fish that bolt out of holes as the forager works through them, and they will follow a diver for the same reason. The partnership is one-sided but real: the trevally catches more this way than alone, and the forager loses nothing it could have caught.
Color is a hunting tool. The fish flushes dark, almost black, during an attack and pales again afterward within seconds; the change appears to signal intent to other trevally rather than to the prey, and hunting groups coordinate with it.
It is a prized game and food fish, and large individuals carry ciguatera in parts of its range - a common tax on reef predators that live long enough to accumulate it. The blue fins fade almost immediately after death, which is why a fish on ice never looks like the animal in the water.
The species. Caranx melampygus Cuvier 1833 - mela- (black) + pygus (rump or buttock). ETYFish
- silver body speckled with small black spots, electric blue fins
- steep forehead and a deeply forked tail
- flushes almost black while hunting, then pales again
- length up to 1.1 m
