What makes them special?

 Yellowfin Damselfish subadult Photo: Jean-Paul Boerekamps

From Juvenile to Adult

Young Yellowtail Damselfish look surprisingly different from the adults. Juveniles are bright blue with numerous tiny electric blue spots, making them one of the most colourful little fish on the reef.

As they grow, the yellow colour gradually appears, starting around the tail and spreading over the rear part of the body. At the same time, the brilliant blue spots begin to fade. By adulthood, the transformation is complete, leaving a fish with a blue front and a striking yellow rear and tail.

Small but fiercely territorial

Damselfishes may be small, but they are definitely not shy. Spend a little time watching a reef and you will often see these tiny fish darting out from the coral, chasing away anything that gets too close. Some species defend a territory many times their own body length, including against fish considerably larger than themselves.

Many damselfishes are surprisingly bold. They choose a small patch of reef or algae as their territory and defend it vigorously. If another fish enters, the damselfish may rush out to chase it away, sometimes repeatedly attacking an intruder much larger than itself.

Some actually “farm” their own food

One of the most fascinating behaviours is seen in farmer damselfishes. Instead of simply eating the algae growing on the reef, they actively cultivate particular algae within their territory and protect it from other herbivores. In a sense, they have their own tiny underwater vegetable garden.

The male takes care of the eggs

In many damselfish species, the male guards the eggs after they have been laid. He carefully fans them with his fins to keep water flowing over them and removes damaged or unfertilised eggs.