Blue tang change color as they mature.
A Fish that Goes by Many Names
One of over 70 species of surgeonfish, the blue tang lives in coastal waters, coral reefs and inshore rocky or grassy areas between 6-131 feet deep. They can be found in waters from New York to Brazil and as far east as the remote Ascension Island.
The blue tang goes by several aliases, including blue barber, blue doctor, blue tang surgeonfish, yellow barber and yellow doctorfish. The terms "barber," "tang" and "doctor" refer to the extremely sharp spines on each side of the fish’s tail, which are said to resemble surgeon’s scalpels. They usually remain flat against the fish’s body, extending only when it is threatened or alarmed. As the tail thrashes from side to side, the fish is capable of inflicting serious damage to an enemy.
Yellow and blue refer to the fish’s color, which changes as the fish matures. Young fish are bright yellow with blue spots near their eyes. As they mature, they become blue over most of their body with a yellow tail. Full-grown adults are a rich blue from head to tail, with narrow dark lines running the length of the body.
Adults average 12 inches in length and live singly, in pairs – or sometimes in groups as large as 10-12. Occasionally, they form larger groups on reefs. The blue tang feeds on algae, using its sharp teeth to rip it from rocks and coral. This diet is important not only for the fish, but also for the health of reefs as it prevents the algae from overgrowing and suffocating the coral. On reefs, the blue tang rests in narrow holes and crevices, protected from predators such as tuna, bar jacks and tiger groupers.