ʻŌʻili ʻUwiʻuwi: The Fantail Filefish of Hawaiian Reefs

Pronunciation: An approximate syllable guide is “oh-ʻee-lee oo-wee-ʻoo-wee,” with brief catches at the ʻokina marks.

Meet the Fantail Filefish

With a spotted body and an orange tail that opens like a fan, the fantail filefish (Pervagor spilosoma) is a distinctive Hawaiian reef resident. Recorded as ʻōʻili ʻuwiʻuwi in Hawaiian fish guides, it has a prominent dorsal spine positioned above the eye.

Its appearance is only part of the story. This species is also known for dramatic changes in abundance: in some years it can become exceptionally numerous on reefs, while at other times it is much less frequently encountered.

How to Identify a Fantail Filefish

The Reef Environmental Education Foundation highlights the combination of numerous dark spots and an orange, fan-shaped tail with black edges. The body can appear yellow to white, while the Hawaiʻi Coral Reef Network describes yellow-orange coloration.

Body: Pale to yellow-orange, with numerous dark spots.
Tail: Orange and fan-shaped, with dark edging.
Spine: A conspicuous dorsal spine above the eye.
Overall impression: A spotted fish with a tail that is especially useful for identification.

Look for the full combination rather than relying on the orange tail alone. Lighting, viewing angle, and the fish’s position can change how strongly individual colors appear.

What Is Behind the Hawaiian Name?

The Hawaiʻi Coral Reef Network gives the name ʻōʻili ʻuwiʻuwi and translates it as “squealing ʻōʻili.” A fish list for Kaloko-Honokōhau National Historical Park, hosted by the University of Hawaiʻi, also records this Hawaiian name for Pervagor spilosoma.

Names can appear with different spacing and marks in older references. Pairing the Hawaiian name with the scientific name is a helpful way to keep the species clear, especially when learning about several different filefishes.

Where Fantail Filefish Live

Fantail filefish are associated with reef habitats, including shallow waters. The Hawaiʻi Coral Reef Network records them in shallow depths down to about 30 meters, while research on their population history also documents juveniles in offshore waters and fish in deeper habitats during periods of high abundance.

That range of observations is a reminder not to think of a fish’s habitat as one fixed spot. Different stages of life and different population conditions can produce different patterns of where fish are found.

What Do Fantail Filefish Eat?

The fantail filefish is an omnivore. Its recorded foods include gastropods, sponges, tunicates, heart urchins, and algae. That menu combines animal prey with plant-like food growing around the reef.

It shares some food types with Moa, the spotted boxfish, another reef resident whose diet includes sponges, tunicates, and algae. Comparing their different shapes is a useful reminder that fish do not need to look alike to share parts of a menu.

The Filefish That Sometimes Arrives in Huge Numbers

The species’ population booms are unusually striking. A 2005 study of long-term Hawaiian records documented strong recruitment events in which large numbers of young fantail filefish entered reef habitats. During these events, they could become one of the most abundant fish on Hawaiian reefs.

The study describes a major event progressing along the island chain during the 1980s, with strong recruitment recorded at different islands in different years. At the Kāneʻohe Bay study site, no other species among the 30 monitored over 20 years showed the same extremes of abundance.

These historical findings do not tell us how many fantail filefish are on reefs today. They show why a species that seems scarce on one visit can have a very different place in local observations during another period.

Learning to Watch the Reef Over Time

A single snorkel outing offers only a snapshot. Fantail filefish make a strong case for noticing which species appear repeatedly, which are occasional visitors to your field of view, and how those observations change across visits.

Enjoy watching without chasing, feeding, or handling fish. For identification, try to notice the spots, dorsal spine, and open tail while giving the fish room to move naturally.

Meet the Fish Behind the Cards

Our Hawaiian Reef Fish Playing Cards pair watercolor illustrations with Hawaiian and English names. Explore the full deck to keep discovering reef life beyond the water, one hand at a time.