Family: POMACENTRIDAE (Damselfishes)
The sergeant major has a compressed ovoid body, and a single continuous dorsal fin. The coloration is very notable with five distinctive black stripes on a silvery-white body tinged with yellow. Damselfish differ from most other families in having only a single nostril on each side of the snout. They are about 22.9 cm (9 inches) long.
Range and Habitat
The sergeant major's range extends from the Gulf of California to Peru, including offshore islands. They occur in large groups around and over reefs and wrecks to depths of about 30 m (100 feet). They are abundant in the Gulf of California, though their number is reported to be reduced during winter months in the Bay of La Paz.
During the spring and summer, the male clears a nest site of algae and other growth from a rocky surface in preparation for the female to lay eggs. He fertilizes them and guards them until they hatch. Females reproduce with several males using several nest sites during a single breeding season.
The Ocean Oasis film features a male sergeant major swimming back and forth over the nest. The eggs look like purple patches over the rock. It is amazing to observe the energy of this fish, constantly chasing off predators to protect the eggs. It seems like an endless task. The male spends weeks guarding the nest until the eggs hatch. Sergeant majors produce few eggs, so they need to spend more time protecting them.
The attentive care shown by this species is in sharp contrast with the reproductive strategy of the creolefish, which produce large quantities of eggs and then leave them to their fate. Both strategies have proven successful.
The sergeant major feeds during the day on surface and midwater plankton; it also grazes on bottom-living invertebrates and algae attached to the rocks.
Text by Patricia Beller
Photograph © Gini Kellogg
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