The Yellowtail Blue Damselfish (Chrysiptera parasema) is a small marine (saltwater) fish. It is also known as the Goldtail Damselfish or Goldtail Demoiselle. 

The Yellowtail Blue Damselfish has a laterally compressed blue body with a distinctive yellow caudal (tail) fin. 

It grows to about 8 centimetres (3 inches) in length. 

The Yellowtail Blue Damselfish is native to the tropical waters of the Indian and Pacific Oceans (the Indo-Pacific region). It prefers coral reefs and sheltered lagoons. 

It feeds on plankton, algae, and small crustaceans, such as crabs and shrimp.

It is often found alone or in pairs. 

It is territorial, defending its territory from other fish. A male will look after the eggs of several females – often up to 10,000 eggs in his territory. Each female lays around 300 eggs. The eggs hatch after about 4 days. The male looks after the young fish, called fry. 

Photographer: Martina Nicolls

Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM