Pacific double-saddle butterflyfish (Chaetodon ulietensis)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Chordata · Class: Teleostei · Order: Acanthuriformes · Family: Chaetodontidae · Genus: Chaetodon.

Accepted name: Chaetodon ulietensis · Authority: Cuvier, 1831 · Taxonomic status: accepted · AphiaID: 218717.

Synonyms and superseded combinations recorded for this taxon: Chaetodon aurora De Vis, 1884; Chaetodon ulientensis Cuvier, 1831; Chaetodon ulietensis confluens Ahl, 1923; Rabdophorus oxychaetodon ulietensis (Cuvier, 1831).

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218717 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (FishBase)

Measured values published by FishBase for Chaetodon ulietensis. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Maximum length: 15 cm · Depth range: 0–40 m · Habitat zone: reef-associated · Body shape: short and / or deep · Vulnerability index: 10 of 100 · Fishery importance: minor commercial · Aquarium trade: commercial.

FishBase notes: Occur in coral-rich areas of lagoon reefs and less commonly in seaward reefs. Juveniles in harbors and estuaries (Ref. 48636). Benthopelagic (Ref. 58302). Usually solitary, in pairs or in small groups.

Feed on plant and animal material. Oviparous (Ref. 205), monogamous (Ref. 52884). Form pairs during breeding (Ref. 205). Can be easily maintained in tanks.

Source: FishBase species summary (SpecCode 5580) — https://www.fishbase.se/summary/Chaetodon-ulietensis.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

4,556 georeferenced occurrence records for Chaetodon ulietensis are published through GBIF from 37 countries or marine areas. The map above plots 304 distinct locations from a sample of 3,000 records, omitting 20 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Australia (1,088); French Polynesia (838); New Caledonia (432); Tonga (311); Fiji (290).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 2385416) — https://www.gbif.org/occurrence/search?taxon_key=2385416&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=218717 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Conservation status (IUCN Red List)

The IUCN Red List assesses Chaetodon ulietensis Cuvier, 1831 as Least Concern (code LC). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 165665) — https://www.iucnredlist.org/species/165665/0; GBIF IUCN Red List category endpoint (taxonKey 2385416) — https://api.gbif.org/v1/species/2385416/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

These fish can reach a size of 15 cm. They are white with vertical thin black lines down the body and two dark saddles on the fore and hind back, which softly grade into the background colour caudal gradient. Immediately after the hind quarter saddle, the body and tail is bright yellow with a black spot on the caudal peduncle.

The dorsal fin has a streak of yellow from the crown of the head to the tail. Like most of its relatives, this species displays a black eye band like a mask. As in most butterflyfish, the Pacific double-saddle butterflyfish is prone to blanching at night and when startled.

C. ulietensis belongs to the large subgenus Rabdophorus, which might warrant recognition as a distinct genus. In this group, it is sister to the similar-looking black-wedged butterflyfish, C. falcula. Other fairly close relatives are the quite differently-shaped but similarly-coloured lined (C. lineolatus) and spot-naped butterflyfishes (C. oxycephalus), while the blue-cheeked butterflyfish (C. semilarvatus) is the sister species to all of these. Vertical lines are present in all of these species, while a white body with yellow behind and black on back and caudal peduncle are shared by all but C. semilarvatus.

Ecology

Chaetodon ulietensis is often found singly or in pairs on coral-rich reef systems, foraging on sessile invertebrates and algae. It is not a territorial species that freely grazes throughout a wide range within reefs, lagoons and harbors, and every now and then large groups congregate at rich feeding spots. It is rarely ever observed in a deep reef environment or the open sea; juveniles are typically reared in shallow lagoons, estuaries or harbors.

An opportunistic omnivore, diet consists mainly of microscopic algae, other plankton, and small sessile invertebrates. As a measure of defense, they typically wedge themselves in tight crevasses to escape predators.

In the aquarium

Although common in the wild, it is rarely imported by the aquarium trade. In aquarist terms, it is considered a hardy Chaetodon and beneficial for the control of nuisance pests. The Pacific Double-saddle Butterflyfish has been observed as a beneficial predator of Aiptasia and Majano sea anemones.

Like most Raccoon Butterflyfish (C. lunula), C. ulietensis will eliminate this nuisance within a 2- to 6-week period depending on the anemone population and size of the tank. And unlike most raccoon butterflyfish, this species rarely feeds on ornamental corals. The Pacific Double-saddle Butterflyfish readily accepts most prepared frozen and dry foods, thus it can easily make the transition to aquarium life, unlike the Copperband Butterflyfish (Chelmon rostratus) or other less hardy Chaetodon species.

Source: Wikipedia: Chaetodon ulietensis — https://en.wikipedia.org/wiki/Chaetodon_ulietensis (CC BY-SA 4.0). Accessed 2026-09-25.