Stegastes adustus, also known as the dusky damselfish or scarlet-backed demoiselle, is a species of damselfish in the family Pomacentridae.

It is found at one- to three-meter depths on surging and wavy coral reefs in the Caribbean Sea, the tropical waters of the western Atlantic Ocean, and the Gulf of Mexico.

[2] Adults feed on algae, plants, and detritus.

S. adustus exhibits different feeding behaviors between those that live in coral rubble and patch reef habitats.

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