Scrawled filefish: weird. wonderful and worldwide

Sailing thousands of miles across vast oceans introduces us to ecosystems alien in many respects to our home waters of south Florida. Departing the tropical and subtropical waters of the western Atlantic and Caribbean for the Indo-Pacific, for example, one encounters a rich increase in marine species. Many of the fundamental elements are the same, but higher degrees of specialization result in numerous additional species and, indeed, entire families of corals, crustaceans, fishes and other marine life. In the case of inshore fishes, we’re talking about going from 500-odd species on the Florida Reef Tract to approximately 2,700 species in Indonesia, which scientists believe to be the approximate epicenter of coral reef organism evolution.

After traversing the species-poor outposts of the eastern tropical Pacific, like Cocos Island, the Galapagos and the Marquesas, the variety of colorful tropical reef fish steadily increases westward through the Society Islands, Samoas and Tonga, Fiji, Vanuatu, and points west and northwest. Yet select inshore fish species, not particularly fast, not especially common, somehow manage to inhabit a broad band of the world’s oceans. Therefore, it’s entirely possible to splash into the clear, warm shallows of a Fijian reef out of one’s dinghy and come face to face with an old friend from Florida.

Such was the case one sunny afternoon at Wilkes Pass, an outer reef area west of Malololailai Island, Fiji. I had been surfing with two fellow sailors at the northern offshore corner of the pass until the incoming tide finally flattened out the breaking waves and it was time to go. Alas, the dinghy anchor was wedged firmly under a ledge, and as we free dove to clear it, I got to the sea floor up-current of the rocky undercut. Mesmerized by the menagerie of marine life, I drifted slowly along the bottom through clouds of iridescent damselfish. A large, familiar form materialized in the gloom — nearly 30 inches in length, elongated face terminating in a small, puckered mouth, decorated head to tail in brilliant neon-blue dots, lines and squiggles, interspersed with black dots, all over a mottled-tan background.

The scrawled filefish (family Monacanthidae, species Aluterus scriptus) felt my stare and abandoned a motionless attempt at camouflage, slowly undulating its transparent second dorsal and anal fins and disappearing majestically into a small dark pocket deep under the ledge.

Scrawled filefish certainly rank among the most lovely and bizarre fish species on the planet, as well as one of the more versatile. These fish are very thin and compressed. Their skin feels like 220-grit sandpaper. Their bodies taper back to a large, expansible, paddle-shaped tail. A pronounced dorsal spike sprouts vertically from atop the head, over the eye, to complete the improbable profile. These filefish inhabit temperate to tropical seas worldwide, in places as different as Nova Scotia and equatorial Pacific atolls. They may be found in depths and locations anywhere from a few feet of water inshore to outer reef and shore slopes at 250 feet or more. An ability to live far at sea among floating weeds and debris certainly helps their wide distribution. Pull up to a floating log, pallet, ship’s hawser or clump of Sargasso weed offshore during a passage, and you are very likely to find well-camouflaged juvenile scrawled filefish, and sometimes adults, hovering close to the habitat. They will readily take a small baited hook, best fished with light wire leader (No. 2 single-strand stainless steel) to protect against their sharp teeth. The fillets are thin, but the meat is firm, white and delicious.

A flexible diet also helps these fish live in a variety of habitats and water temperatures around the world. As omnivores, scrawled filefish use their concave, tapered snout and small mouth to clip off bits of algae and seagrasses as well as a wide variety of soft, bottom-dwelling invertebrates, including sponges, tunicates, and polyps small and large — soft, branching corals, hydrozoans, or anemones. They’re not above taking free-drifting invertebrates and occasional small, slow-moving fishes as they cruise in midwater, and I’ve even seen them picking at the ends of dangling tentacles of Portuguese men-of-war and other jellyfish.

The best areas to observe large, adult scrawled filefish are seaward fore reef and terrace areas covered with gorgonians. Snorkel or scuba dive slowly over the soft coral forest. Pairs and single filefish will first freeze, often in a near-vertical pose, changing color pattern to mimic their surroundings. Approach carefully, and you can get quite close before they begin to ease off, particularly if you keep your mask averted and look out of the corners of your eyes.

By Ocean Navigator