Went snorkeling and spotted a strangely shaped fish? If it had a pointy mouth, fan-like tail, and psychedelic black and neon-blue pattern, you probably ran into the scrawled filefish (Aluterus scriptus). Closely related to pufferfish, these filefish have an unusual trick up their sleeve.
Below, find everything you need to know about the scrawled filefish, including where it can be found, what it eats, and its fascinating color-changing abilities.
| Name (common, scientific) | Scrawled filefish, scribbled filefish, broomtail filefish, Aluterus scriptus |
| Family | Monacanthidae |
| Spread | Tropics and subtropics around the world |
| Habitat | Reef |
Scrawled filefish appearance
Where do I start? If you’ve seen one photo of a scrawled filefish, you’re unlikely to ever fail to identify it again—they really are quite strange. This species is a member of the order Tetraodontiformes, which also houses the pufferfish, boxfish, blowfish, triggerfish, and trunkfish families.
Filefishes, which belong to their own family called Monacanthidae, are named for their rough, slightly spiked scales, similar in feel to a shark’s sandpaper-like skin. They can be recognized by their laterally compressed (flat) bodies, snout-like mouths, fan-like tails, and often elaborate patterns. They also sport a spine on their heads that they can raise and lower at will.
The scrawled filefish is the largest of its family, reaching up to 1m (3.3ft) in length. This species is yellowish-brown to grey in color, with a unique pattern of black dots and neon blue scribbles—hence the name. A dark honeycomb pattern is sometimes visible beneath the scrawls.
Planning your next snorkel trip?
Scrawled filefish natural habitat
The scrawled filefish has a circumglobal distribution. It’s naturally found in a wide band that spans all across the globe, including the tropics, subtropics, and even into temperate waters. It’s not picky when it comes to temperature, that’s for sure!
In its natural range, this species mostly prefers reef environments. Juveniles tend to stay in shallower waters than adults; I’ve seen plenty of small scrawled filefish while snorkeling, but larger specimens only while diving. They’ve actually been spotted as deep as 120m (almost 400ft), though they generally prefer to stay around 20m (65ft).
Juvenile and even sometimes adult scrawled filefish are also associated with floating objects, like driftwood or seaweed, in the open ocean. They tend to eventually settle on the reef, but can end up pretty far away from where they started their lives in the meantime.
Filefishes are diurnal (active during the day). At night, they may “moor” or “park”. This involves finding a sheltered spot away from the worst of the water current. One interesting 1998 paper mentions a scrawled filefish using its mouth to hold on to a piece of sponge attached to an offshore platform, effectively anchoring itself in a low-flow spot.
Did you know? The IUCN Red List considers Aleturus scriptus to be a species of Least Concern. The organization notes the species is common in much of its very wide range.
Scrawled filefish facts
Diet
Their snout-like mouth and powerful teeth reveal what scrawled filefish eat: they graze the reef. Omnivorous in nature, they’re not picky about their meals and will consume anything from crustaceans to algae, sponges, hydrozoans, anemones, seagrass, hydroids, and corals.
Color changes
Yes, this fish can change color! Some members of the order Tetraodontiformes, including many filefishes, can adjust their colors and patterns based on their surroundings and mood. You’ll see one, look away for just a second (literally), and suddenly it’s much lighter or darker.
The mechanism works in a manner that’s pretty similar to how cephalopods (like my favorite, the amazing Caribbean reef squid) and chameleons shift their hues, although the scrawled filefish definitely can’t do it as quickly and flawlessly as something like an octopus. Still, it’s pretty impressive!
Check it out:
Edible?
That depends, how brave are you? Some folks fish for scrawled filefish, state that they’ve eaten it many times with no ill effect. In fact, there are people who note this species to be particularly delicious. However, I can tell you I absolutely wouldn’t risk it myself.
Filefish are reef grazers. Many creatures on the reef are toxic, and while the fish aren’t affected by the toxins in question, they can still absorb them into their tissues. Their gastrointestinal tracts have been noted to contain palytoxin, an extremely toxic substance they get from eating corals. Sure, you can carefully gut and clean the fish, but there’s another issue.
The species’ tissues in general can contain ciguatoxins that cause ciguatera poisoning, produced by a dinoflagellate present on reefs called Gambierdiscus toxicus (it’s in the name!). Ciguatera is not uncommon after eating reef fish, and proper cleaning unfortunately doesn’t completely eliminate the risk.
If you have any more questions about the scrawled filefish, or if you’d like to share where you spotted this fascinating species, don’t hesitate to leave a comment below!
Sources & further reading
Kuiter, R. H. (1996). Guide to sea fishes of Australia. Frenchs Forest, New South Wales, Australia: New Holland Publishers.
Lieske, E., & Myers, R. F. (1994). Coral reef fishes: Caribbean, Indian Ocean and Pacific Ocean including the Red Sea. (No Title).
Mak, Y. L., Wai, T. C., Murphy, M. B., Chan, W. H., Wu, J. J., Lam, J. C., … & Lam, P. K. (2013). Pacific ciguatoxins in food web components of coral reef systems in the Republic of Kiribati. Environmental science & technology, 47(24), 14070-14079.
Myers, R. F. (1999). Micronesian reef fishes: A comprehensive guide to the coral reef fishes of Micronesia. Coral Graphics.
Sudo, K., Maehara, S., Nakaoka, M., & Fujii, M. (2022). Predicting future shifts in the distribution of tropicalization indicator fish that affect coastal ecosystem services of Japan. Frontiers in Built Environment, 7, 788700.