Eggs
The female glues her purple eggs onto a rock cleaned by the male.
Four-stage life cycle
Sergeant major
A small striped fish living in groups near the reefs
Recognisable by its five black bars on a yellow and silver body, the sergeant major forms lively clouds above reefs and wrecks.
Life cycle (4 stages)
Larva
Larvae hatch after a few days and drift in the plankton.
Juvenile
Young fish gather in small groups in very shallow water.
Adult
It lives in dense schools and becomes territorial during breeding.
Physical changes
- Five vertical black bars on a silver to yellow body.
- Adult size around 15 to 20 cm.
- The male turns bluish while guarding the nest.
- Oval body and short fins adapted to fast swimming.
Habitat
- Coral reefs
- Wrecks
- Piers and rock armour
- Lagoons and reef flats
Diet
- Zooplankton
- Algae
- Small invertebrates
- Fish larvae
Survival adaptations
- Schooling for protection against predators.
- Aggressive nest defence by the male.
- Highly opportunistic diet.
- Tolerance of rough shallow water.
Ecological importance
- Transferring plankton energy to reef predators
- Controlling algal growth
- Providing essential biomass for trevally and grouper
Importance
- Type : Reef bony fish (Pomacentridae family)
- Habitat shift : Eggs on rock → Planktonic larvae → Juveniles in shallow water → Schooling adults
- Role : Abundant link in the reef food chain.
- Its density reveals the productivity and balance of a reef.
Did you know?
The male sergeant major cleans his rock, attracts several females and then guards thousands of purple eggs, fanning them relentlessly.