Saddle Butterflyfish Chaetodon ephippium

Saddleback Butterflyfish
Saddle Butterflyfish
Saddle Butterflyfish
The Saddle or Saddleback Butterflyfish is named after the saddle-shaped black patch on its back which makes it look half-eaten to predators, especially with the extended string of dorsal fin. It is native to tropical reefs of the Indo-Pacific from Sri Lanka to Hawaii. The fish can grow to 30cm long, large for a butterflyfish.
Butterflyfish Butterflyfish can blanch their yellow colours at night or when stressed for camouflage. Could this be a blanched Saddleback? Or a juvenile/subadult (but threadfin quite long) or hybrid (it is said they hybridize with Threadfin and Yellowhead Butterflyfish)?