Stegastes planifrons

Lore & Background

The adult threespot damselfish is a brownish-grey, bony fish with a dusky yellow sheen and a large black spot at the base of the pectoral fins. It grows to 13 cm in length. The large dorsal fin has 12 spines and 15-17 soft rays; the anal fin has two spines and 13-14 soft rays. Neither the pectoral nor pelvic fins have spines. Juveniles are a much brighter yellow, with a few tiny blue spots on the head and upper body, including one on the upper iris. They have three distinctive black spots: one at the junction between the dorsal fin spines and the soft rays, one dorsally on the caudal peduncle, and a third smaller one just above the base of the pectoral fins. These spots tend to have a faint blue rim, and the pectoral spot is absent in very young juveniles, becoming more prominent as the juvenile grows.

Reader's Guide

The threespot damselfish is found down to about 30 m in the western Atlantic Ocean, ranging from Florida through the Caribbean Sea to the Bahamas. It is a demersal fish, favouring inshore and offshore coral reefs, often among staghorn coral, and at night may be found in caves. Its diet consists mainly of seaweed, but also includes copepods, gastropod molluscs and their eggs, hydroids, marine worms, and sponges. Adults vigorously maintain large territories, chasing away and nipping intruders, including humans. A male and female form a breeding pair; the female lays eggs that stick to objects on the seabed, and the male guards and oxygenates them by fanning with its fins. Its occasional presence in the aquarium trade is noted, but the article provides no further details on its significance in that context.

Did You Know?

• The threespot damselfish grows to 13 cm in length.
• Juveniles have three distinctive black spots, often with a faint blue rim.
• Adults vigorously defend large territories, even nipping human intruders.
• The male guards and fans the eggs to oxygenate them.