Chaetodon auriga
Cross-stripe butterfly
(Also: Diagonal butterflyfish; Threadfin; Threadfin butterfly; Threadfin butterflyfish; Threadfin coralfish; Whip butterflyfish)

Threadfin butterflyfish are found throughout the Indian and Pacific Oceans. They are found in the Red Sea and the coast of eastern Africa, off the coasts of Australia and New Guinea, east to the Hawaiian, Marquesan, and Ducie islands, as far north as southern Japan, and south to the Lord Howe and Rapa islands. (Capuli, 2006; Nelson, 1984; Steene, 1977)

Threadfin butterflyfish are found in tropical coral reef habitats (Nelson 1984; Herald 1975; Jobling 1907). Although they are usually found where there is abundant coral, they are occasionally found in areas with sparse coral as well (Steene 1977). Chaetodon auriga are found at water depths between 1 and 35 meters (Capuli, 2006). (Capuli, 2006; Herald, 1962; Jobling, 1995; Nelson, 1984; Steene, 1977)

Threadfin butterflyfish are small, boldy colored fish (Findley and Findley 1985). They have a dark band running across the eye from the top of the head to the jaw, and a dark eyespot on the posterior part of the body (Nelson 1984). They have black lines and a yellow coloration on the posterior part of the body. They have broad, laterally compressed bodies and elongated snouts with small, sharp teeth (Moyle and Cech 2000). Adults can reach up to 23 cm (Steene 1977). Although young have patterns similar to adults, adults have a long filament extending from their dorsal fin (Steene 1977). (Findley and Findley, 1985; Moyle and Cech, 2000; Nelson, 1984; Steene, 1977)

Butterflyfish release eggs into the water column, which are externally fertilized (Hourigan 1989). Embryos hatch approximately 30 days after spawning and the larvae then spend about 40 days floating in the water column as plankton before they metamorphose into juveniles (Hourigan 1989). (Hourigan, 1989)

Chaetodon auriga are monogamous, they mate with one partner and maintain this partnership for many years (Jobling 1995; Paxton and Eschmeyer 1998; Roberts and Ormond 1992). Low rates of adult mortality enable these monogamous relationships to last for many breeding seasons. However, if an individual loses a mate, they will find another (Roberts and Ormond 1992; Hourigan 1989) (Hourigan, 1989; Jobling, 1995; Paxton and Eschmeyer, 1998; Roberts and Ormond, 1992)

Female C. auriga release hundreds of thousands of eggs at a time (Hourigan 1989). Threadfin butterflyfish spawn frequently throughout their long breeding seasons (Roberts and Ormond 1992). They can be sexually mature at sizes of 13 cm (Capuli, 2006). (Hourigan, 1989; Jobling, 1995; Paxton and Eschmeyer, 1998; Roberts and Ormond, 1992)

There is little information available on parental investment of Chaetodon auriga, however other species of butterflyfish do not invest in parental care (Roberts and Ormond, 1992). Once the eggs are fertilized in the water column, there is no further parental involvement. (Capuli, 2006; Roberts and Ormond, 1992)

There is little information known about the lifespan of butterflyfish.

Threadfin butterflyfish are found in pairs, but are sometimes found singly or in large feeding groups (Steene 1977). Threadfin butterflyfish use their tubular snout to poke into coral holes and crevices in order to find prey (Norman 1975). They can also feed by scraping the surface of coral (Moyle and Cech 2000). They are active during the day and are non-migratory. (Capuli, 2006; Moyle and Cech, 2000; Norman, 1975; Steene, 1977)

There is no information on home range in threadfin butterflyfish.

Threadfin butterflyfish are visual predators, and they use their appearance to fool potential predators. Little additional information is available on how they communicate with one another (Nelson 1984). (Nelson, 1984)

Chaetodon auriga are benthic feeding fish that feed mostly on plankton (Pratchett 2001). However, they are omnivorous, and also feed on coral polyps, algae, shrimp, gastropods, nemertime worms, and polychaetes (Steene 1977). Threadfin butterflyfish have elongated snouts, with small protractile mouths that are filled with many small, sharp teeth (Moyle and Cech 2000; Herald, 1962 Jordan, 1907). They are able to use their elongated snouts in order to scrape the surface of coral to obtain algae and other small prey (Moyle and Cech 2000). (Herald, 1962; Jordan, 1907; Moyle and Cech, 2000; Pratchett, et al., 2001; Steene, 1977)

There are few documented predators of threadfin butterflyfish (Jordan 1907). Their spiny fins and quick speed make them difficult prey (Norman 1975; Jordan, 1907). Threadfin butterflyfish have mechanisms in order to deter and avoid potential predators. The dark bands over their eyes, as well as the posterior eyespot are probably mechanisms to confuse potential predators, making their tails seem to be their head and their head seem to be a tail (Nelson 1984). Other butterflyfish species have been reported swimming short distances tail first, and then rapidly swimming off in the opposite direction in order to confuse and escape potential predators (Norman 1975). (Jordan, 1907; Nelson, 1984; Norman, 1975)

Butterflyfish are dependent on coral reefs to obtain much of their food. The number of butterflyfish in an area is largely dependent on the amount of coral in a particular reef ecosystem (Ohman et al. 1998). In addition, butterflyfish are important in reducing the amount of algae that accumulates on coral (Moyle and Cech 2000). Butterflyfish and their eggs and larvae are important food items for marine predators. (Moyle and Cech, 2000; Ohman, et al., 1998)

It may be possible to use butterflyfish, such as threadfin butterflyfish as bio-indicators in order to monitor coral reef ecosystems (Brokovich and Baranes 2005; Ohman 1998). Chaetodon auriga are also kept in aquaria as pets. (Brokovich and Baranes, 2005; Ohman, et al., 1998)

Chaetodon auriga are not known to negatively affect humans.

Chaetodon auriga is not threatened at this time. However, it is believed that the density of butterflyfish correlates with the amount of live coral in a particular region. If reef habitats are destroyed, this will threaten butterflyfish populations (Ohman et al. 1998). (Ohman, et al., 1998)