Humbug damselfish

The Humbug damselfish (Dascyllus aruanus), also known as the Threestripe dascyllus, is a small ray-finned fish belonging to the damselfish family (Pomacentridae), order Perciformes. Typically, the size of this fish does not exceed 6 cm, although there are reports of specimens reaching 10 cm in body length. Males are larger than females and more aggressive. Conflicts occur between adult individuals unless they are a male-female pair.

It has a characteristic appearance distinguished by its black and white coloration. The body is predominantly white with three vertical black bars: one runs through the eye, another across the middle of the body, and one more at the base of the tail. The tail is entirely white, which is a distinctive feature. The fish's body is laterally compressed, giving it a somewhat oval shape.

The Threestripe dascyllus inhabits the tropical waters of the Indo-Pacific region and is commonly found throughout the Red Sea. They typically live at depths ranging from 1 to 12 meters. These fish prefer to stay close to branching corals, which provide them with protection and shelter from predators.

The Humbug damselfish reproduces through external fertilization. Males build a nest and invite a female to spawn, accompanying their actions with courtship displays and a 'dance' above the nest. Females lay adhesive eggs, which the male guards until the larvae hatch. During this time, the fish become very aggressive and drive other fish away from the nest. The larvae hatch 3-5 days after laying, usually at night, which increases the survival rate of the fry and aids their dispersal across the reef. The fry lead a pelagic lifestyle and feed on plankton.

Dascyllus aruanus primarily feeds on plankton and small invertebrates. They also consume algae and detritus, making them omnivorous. They often feed in small groups, taking advantage of the protection offered by numbers.

The Threestripe dascyllus poses no danger to divers. They are usually curious and may approach divers, but they pose no threat. Their small size and generally peaceful nature make them harmless to humans.