Razor Surgeonfish

Family: Surgeonfishes (Acanthuridae)
Size: Up to 60 cm (24 in) | Common: 30 cm
Depth: 3 – 30m (10 – 100ft)

Distribution: Eastern Pacific (Costa Rica to Colombia and Ecuador, including the Galapagos and Malpelo).

Identification: A fast-moving grazer with built-in weaponry.

• Coloration: The oval-shaped body is typically a solid, uniform grey, bluish-grey, or brown. The standout feature is its vibrant, bright yellow tail.
• The Razors: Look closely at the narrow base of the tail (the caudal peduncle). You will see a horizontal row of 3 to 6 distinct black spots. These are actually sharp, bony plates (scutes).

Behavior: The lawnmowers of the rocky reef.

• Diet & Schooling: They are strictly herbivores. They frequently form massive, fast-moving schools that wash over the rocky reefs like a wave, rapidly grazing on benthic algae before moving on.
• Defense: Those black bony plates near the tail aren't just for show. They act like literal scalpels. When threatened by a predator or a rival, the fish will thrash its tail to slash its attacker.