Bearded Filefish (Anacanthus barbatus)

The filefish family is filled with no shortage of strange species. Compared to their close cousins, the triggerfishes, monacanthids are far more variable in their morphology. There are tiny circular species, like Rudarius. There are species with giant, fan-shaped pelvic fins, like Monacanthus. There are specialized coral-eating forms with elongated mouths, like Oxymonacanthus. And their are semi-pelagic giants, like Aluterus scriptus, which can grow to over 3 feet in length! But one of the most peculiar and poorly understood of these is the Bearded Filefish, Anacanthus barbatus.

There is absolutely no mistaking the Bearded Filefish. The species is by far the most slender in the family, roughly equaling the size (up to 35cm) and shape of a mangrove pod. This is, of course, no mere coincidence, as this fish has likely evolved the resemblance quite purposefully. Even the swimming style of Anacanthus reminds one of a mangrove pod gently bobbing about in the ocean, tilted downwards at an oblique angle. And at the tip of the jaw is a long, fleshy appendage (the “beard”) that serves to further disguise this filefish.

There’s only one species of Anacanthus and you’ll only find it in shallow sandy habitats or around muddy coastal waters of the Indo-Australian Archipelago, sometimes in brackish conditions. Specimens are often observed swimming near to manmade objects like rope or near long, stringy sponges and gorgonians or simply drifting along near to the bottom. Like most filefishes, the diet is likely formed of various invertebrates, though little seems to have been documented on this.

We know very little about where this unique species fits within its family. The few morphologists who have studied the group have hypothesized that the Mimic Filefish (Paraluterus) might be its closest relative, though that seems unlikely to be accurate. The two look little alike and are quite different in their behavior and ecological preferences. Genetic studies into this group have so far not included this species, illustrating just how uncommon it can be to encounter one in the wild. What little data does exist points toward Aluterus and Monacanthus, both groups that possess elongated species and tend to drift around.

Aquarium specimens of Anacanthus are few and far between, though this filefish makes for a fairly undemanding addition to a peaceful tank. The species is coral safe, though probably less trustworthy with small crustaceans. It’s tranquil personality could render it vulnerable to overly aggressive tankmates, at least, those that manage to even recognize this swimming mangrove pod as being an actual fish worth bothering. Males are reported to quarrel in captivity, but are otherwise quite peaceful.