Harlequin filefish

The harlequin filefish, also called the orange spotted filefish, is a small, brightly patterned reef fish from the Indo-Pacific. It depends almost entirely on live coral to survive, which makes it vulnerable when reefs are damaged.

Also known as: oxymonacanthus longirostris, beaked leatherjacket, coral filefish, longnose filefish, longnosed filefish

Look for a small fish with a long, pointed snout and bright orange spots scattered over blue-green skin — a pattern that stands out clearly against a coral background even without a close look.

Its skin is blue-green, covered in bright orange spots, even across the eyes. It has a long, thin snout with a tiny mouth at the tip, and its teeth are fused into a small hooked beak. Instead of paired fins on its belly, it has a single flap bordered in black with white spots. Its tail is pale with a black spot that disappears when the tail fin opens. It grows to about 12 cm. Males are a slightly darker blue-green with a brighter orange patch on their belly flap, while females have a duller, smaller patch, or none at all.

This filefish lives on shallow coral reefs across the Indo-Pacific, in clear lagoons and on seaward reef slopes, down to about 35 m. It stays close to branching Acropora coral, the staghorn-type coral it depends on for both food and shelter.

It is a picky eater, feeding almost only on the polyps of one or two preferred Acropora coral species, even when other corals are more available nearby. It forages by lunging quickly at a coral branch and pulling back, doing this throughout the day but less so in the evening. Pairs stay together to mate and raise young.

harmless

The harlequin filefish is listed as Vulnerable, with a declining population. Because it relies so heavily on live Acropora coral, bleaching events linked to warming seas hit it hard — one bleaching event in Japan lowered its growth and survival and even shortened its breeding season, and it has disappeared entirely from some reefs after major bleaching.

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