Description & Behavior

Sergeant majors, Abudefduf saxatilis (Linnaeus, 1758), aka damsel fishes, five fingers, pilotfishes, are named so because of the military stripes that their pattern resembles, are small marine reef fish belonging to the family Pomacentridae (damselfish). Known also as ‘píntano’, they are compressed laterally with a forked caudal (tail) fin and have a single nostril on each side of the snout. This species grows to a maximum of approximately 23 cm in length and up to 200 g in weight.

The yellow coloration on their upper bodies fades to a green/grey color towards their lower body and is banded in five distinctive black vertical stripes. Males become dark blue/purple in color during mating season when guarding eggs.

These fish exhibit social behaviors and school together during feeding then disperse at night to hide from large reef predators that hunt at this time. They have been shown to display aggression towards other fish but territories are only established for spawning and broodcare. They also do not seem to be afraid of divers and are attracted to those that feed them.

World Range & Habitat

Sergeant majors, Abudefduf saxatilis, are strictly an Atlantic species, abundant in warm waters ranging from Rhode Island in North America, to the Caribbean Sea and to Uruguay in South America. They are also present along the west coast of Africa from Cape Verde to Angola.

Often found inhabiting shallow coral reefs, this species can be found as deep as 15-20 m but can also be found within seagrass and mangrove habitats. Juveniles, especially, are a common presence in both seagrass beds and around mangrove roots utilizing them as nurseries that provide food and shelter. When the fish become too large to benefit from the protection these habitats provide, they migrate back to the coral reef where they first hatched.

Feeding Behavior (Ecology)

Sergeant majors, Abudefduf saxatilis, form large organized feeding aggregations consisting of a range of size classes as well as other fish species. They are generalist feeders that forage arrow-worms, Hydromedusae, planktonic polychaetes, salps, algae and pelagic mesocrustaceans (including krill and copepods).

Also, juveniles may hold cleaning stations together with the doctorfish (Acanthurus chirurgus) and the blue tang (Acanthurus coeruleus) and graze algae as well as pick molted skin and parasites from green turtles (Chelonia mydas). This behavior is preceded by a characteristic inspection usually followed by feeding nips on the turtles’ skin (head, limbs, and tail), as well as on their carapace. The most inspected and cleaned body parts are the flippers.

Predators include Leopard coralgroupers, Plectropomus leopardus, Blueheads, Thalassoma bifasciatum, Graysbys, Cephalopholis cruentata, Nassau groupers, Epinephelus striatus, Yellowfin groupers, Mycteroperca venenosa, and Cobia, Rachycentron canadum.

Life History

Sergeant majors are an oviparous species (producing young by means of eggs) that breed in distinct pairs. Spawning can occur year round depending on the region (November to February in Brazil and April to August in the Red Sea). Typically, spawning begins during night time and is completed by morning.

During spawning, a single female can deposit up to 20,000 eggs which are red in color, oval-shaped and adhere to the substrate on which they are laid. After fertilization, the males will guard the eggs for about a week until they hatch.

The average life-span of this species is around 6 years in the wild and up to 15 years in captivity.

Oviparous: produces eggs that develop and hatch outside the body of the female.

Viviparous: embryo develops inside the body and gains nourishment from the female.

Ovoviviparous: eggs are retained within the body of the female in a brood chamber where the embryo develops, receiving nourishment from a yolk sac. This is the method of reproduction for the “live-bearing” fishes where pups hatch from egg capsules inside the mother’s uterus and are born soon afterward. Also known as aplacental viviparous.

Conservation Status & Comments

Sergeant majors  are currently listed as ‘Least Concern’ by the IUCN Red List with a ‘Stable’ population trend.

There are currently no species-specific conservation measures and no CITES legislation in place for this species.

Resilience to fishing pressure: Medium, minimum population doubling time 1.4 – 4.4 years.

Extinction vulnerability to fishing: Low to moderate vulnerability (31 of 100).

References & Further Research

Their scientific name ‘Abudefduf’ translates to ‘father’ and ‘saxa’ to ‘living among rocks’ which denotes their position on the reef.

These fish are only of minor importance to commercial fisheries but are highly prevalent in the aquarium trade. Despite their hardy nature, they can be difficult to rear; requiring a lot of space, plenty of places to hide and can be picky with their food choices.

Sergeant Majors, Abudefduf saxatilis, have also been observed cleaning parasites off of larger marine creatures creating symbiotic relationships that benefit both the fish itself and the client organism.

Primary Researcher: Shelby-Jay Lewis

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