This is a Garibaldi. A Garibaldi is a type of damselfish. Like other damselfishes, Garibaldis are territorial. An adult male Garibaldi will defend a patch of the rocky sea floor and keep other Garibaldis away. This territory is several square yards of area. Within its territory, the Garibaldi eats red algae that grow on the sea floor. The Garibaldi also prepares a nest in the algae. The Garibaldi keeps the algae in its nest trimmed to a height of one to two inches by nipping at the tops of the plants.
Garibaldis are very precise about the boundaries of their territories. Two neighboring Garibaldis may graze peacefully together at the edges of their territories within a few inches of each other. But they will face each other head to head and rapidly wave their tail fins whenever their neighbor gets too close to their territory.
Garibaldis are a brilliant orange-yellow color. But juvenile Garibaldis are also covered by small blue dots. As long as a juvenile has blue dots, other adult Garibaldis will tolerate its presence within their territories. But when the juvenile reaches 3 to 6 years old, the blue dots fade away. After this, it must claim and defend its own territory, and is not permitted in the territories of other adults. Wild Garibaldis may live as long as 12 years.
Garibaldis are found in the Pacific Ocean in shallow water near the coasts of southern California and Baja, Mexico.
You also can see some purple spiny sea urchins on the rocks below and to the right of the Garibaldi in this photograph.
Diana Reischel took this photograph. Diana was a marine biologist for ReefNews in 1999.