Mediterranean damselfish

The Mediterranean damselfish is uniformly colored with a predominantly black and grey body. Juveniles are bright blue.

The body is oval, the mouth is protractile. The pectoral and pelvic fins are translucent. The dorsal and anal fins are black with a bluish sheen. The caudal fin is black, homocercal, and forked.

The scales are marked with grey to coppery color. The belly is lighter than the back.

Chromis chromis is a schooling fish that resides near reefs. It is a diurnal species with a lively temperament. Males become territorial during the breeding season. Females remain gregarious. Juveniles gather in small schools near cavities where they seek refuge in case of danger.

The Mediterranean damselfish is a carnivorous species that feeds on small benthic or pelagic invertebrates.

The breeding period extends from late May to early September, as the water warms up. During this period, males establish a territory that they fiercely defend.

Each prepares a nest by cleaning an area between rocks, in seagrass beds, or sand. It then launches from the nest to the female group, making back and forth trips. Once a receptive female is found, she follows the male to the nest to deposit her eggs, which are immediately fertilized. The female then stays for a few days to guard the eggs before abandoning the nest. The male remains throughout the incubation period and defends the eggs until they hatch a week later.

Juveniles are bright blue and remain in a tight school near rocky outcrops. They change color from blue to black at a size of 15 mm. Growth is rapid thereafter, tripling in size by the end of summer.