The sergeant major (Abudefduf saxatilis) is a member of the damselfish family (Family Pomacentridae) that lives on coral reefs around the world.

Sergeant major. Source: Florent Charpin/www.reefguide.org

Scientific Classification Kingdom: Animalia (Animals) Phylum:--- Chordata Class:------ Osteichthyes (Bony Fishes) Order:-------- Perciformes Family:-------- Pomacentridaedae (Damselfishes) Genus:----------Abudefduf Species:----------Abudefduf saxatilis (Linnaeus, 1758)

Physical Description

Sergeant majors are small (10 to 20 centimeters in length) marine fish with an oval shape.  They derive their common name from their striped coloration evoking the associated military rank. Their bodies are usually silver with yellow on the upper body. The five dark bands resemble "sergeant stripes". 

Distribution

Distribution of sergeant majors. Florida Museum of Natural History Sergeant majors have a wide distribution.  They are found in the Atlantic Ocean from 40.9°N and they are abundant in the Caribbean Sea.  They are also found around islands of the mid-Atlantic, Cape Verde, along the tropical coast of western Africa south to Angola, in Madagascar, Seychelles, and the Red Sea.

Habitat

They are usually found in shallow waters to around 15 meters in depth. Juveniles are common in tide pools while adults typically school over shallow reef tops.

Feeding Behavior

They are generalist opportunistic feeders who eat plankton, algae, small invertebrates, other small fish, and eggs. They tend to feed in large loose aggregations above the reef.

Behavior

Adults frequently form large feeding aggregations of up to several hundred individuals.

Reproduction

Males prepare nests on walls, beneath overhangs, or in the sand, by clearing away living organisms, debris and silt from a site.  Courting males change colors to a very dark blue coloration and become very aggressive.  They attract females by swimming in small loops 0.5 to 1.5 meters above the benthic substrate.  Male may attract one to several females to lay eggs in their nests. One female can deposit as many as 2000 purple eggs, depending on their size, that are  attached to the substrate by an individual holdfast. The males care and protect the eggs, fanning them to increase circulation of oxygen carrying water, for six to eight days.  After hatching the larvae enter the pelagic stage. Sergeant major larvae start as tiny (2.5 millimeter) fish with large heads and jaws that are capable of swimming and capturing small prey.  After 17 to 20 days when the larvae have reached a size of about 13 millimeters the juveniles move to tide pools, mangroves, or floating mats of Saragassum algae where they remain for a few months before moving to the reef.

Conservation Status

Sergeant majors are widespread and abundant, such that the species is not considered to be a species at risk.

References and Further Reading

• Encyclopedia of Life. 2011. Abudefduf saxatilis (Linnaeus, 1758)
• Cathleen Bester. Abudefduf saxatilisFlorida Museum of Natural History
• Fishbase. 2011. Abudefduf saxatilis, Sergeant major
• P.Humann and N.Deloach (Editor) 1994. Reef Fish Identification: Florida, Caribbean, Bahamas. New World Publications, Inc. Jacksonville, FL. ISBN: 1878348078
• N.Deloach. 1999. Reef Fish Behavior, Florida, Caribbean, Bahamas. New World Publications, Inc. Jacksonville, FL. ISBN: 1878348280