A long flat olive fish scrawled over with blue lines and black dots, with a broom of a tail and a habit of hanging head-down beside a coral head. Up to 1.1 m (43 in), which makes it the largest filefish in the sea and considerably bigger than the fish most divers assume they are looking at.
The posture is camouflage. Head-down, drifting with the surge, a scrawled filefish reads as a piece of weed or a bleached branch, and it can hold the pose while feeding on whatever it is inspecting - hydroids, algae, seagrass, small invertebrates and, occasionally, stinging things nothing else will touch.
The first dorsal spine is a lock, as in the triggerfishes it is related to: raised, it is held upright by a second small spine and lets the fish jam itself into a crevice.
Juveniles live in drifting sargassum out in the open ocean, patterned to match it, and only settle onto a reef once they are large. That is why a small one is a rarity on a dive and a large one is not.
The species. Aluterus scriptus (Osbeck 1765) - written. ETYFish
- long flattened olive body scrawled with blue lines and black dots
- broom-like tail, often held spread, longer than expected for the body
- drifts head-down beside coral or in open water, moving with the surge
- length up to 1.1 m
