Blackback Butterflyfish

The fish in the image appears to be a Blackback Butterflyfish (Chaetodon melannotus) due to its striking black and yellow coloration. It has a yellow body with dark diagonal lines extending from the back towards the belly. A prominent black patch covers the back, extending into the dorsal fin, and a broad black bar passes vertically through the eye. There is often a white patch or spot behind the eye, which is visible in the image. The caudal fin (tail fin) is typically yellow, and the overall body shape is compressed and disc-like, typical of butterflyfishes.

This species is typically found in marine tropical waters, particularly in coral reefs and rocky areas. They inhabit a wide depth range, usually from 2 to 20 meters, but can be found deeper. Their distribution extends across the Indo-Pacific region, including the Red Sea, East Africa, the Maldives, Southeast Asia, Australia, and various Pacific islands.

Blackback Butterflyfish are largely nocturnal feeders. They primarily feed on soft coral polyps (especially alcyonaceans), small invertebrates, and algae. They play a role in coral reef ecosystems by grazing on corals and algae, which can help maintain the balance of the reef. They are generally solitary or found in pairs. Their conservation status is 'Least Concern' by the IUCN, indicating stable populations, but they can be vulnerable to coral reef degradation.

Other similar-looking butterflyfish species include the Yellowhead Butterflyfish (Chaetodon xanthocephalus) which has a yellow head but lacks the distinct black back and eye bar, and some other Chaetodon species with black markings. However, the combination of the black back, black eye bar, and yellow body with diagonal lines is characteristic of the Blackback Butterflyfish.