Adult blue surgeonfish (Paracanthurus hepatus) have a sharp caudal spine, and it is only out when the fish experiences excitement of some form.
Indo-Pacicfic, East Africa to Indonesia, Micronesia, Samoa, New Caledonia. Also southwest Japan to the Great Barrier Reef.
Just like all reef dwelling creatures, protection of coral reef ecosystems is essential to continued abundance.
They can be solitary or form groups, with the young preferring to hide in branching corals.