Abudefduf saxatilis is a member of the Pomacentridae family, which includes both the damselfishes and anemonefishes. This family is abundant in the tropical and warm temperate waters of the world. The sergeant major is a small, laterally compressed, rounded fish. A single nostril on either side of the snout distinguishes it from the butterflyfishes and angelfishes. It has a small, oblique terminal mouth. The upper part of the body is yellowish with 5 vertical black bars. A faint sixth bar may be present. There is a black spot at the upper base of the pectoral fin (Randall 1996).
A. saxatilis is often observed on shallow reefs in large feeding aggregations of up to a few hundred individuals (Randall 1996). This fish uses different color phases for camouflage. The light phase is visible from below when the sergeant major is swimming over the reef, while the dark phase allows the fish to hide in the reef when threatened. When males guard the red or purple patches of eggs in their nests, they take on a dark blue tinge. (Randall 1996).
Potentially Misidentified Species: Scissortail sergeant Abudefduf sexfasciatus Lacepede 1801Banded sergeant Abudefduf septemfasciatus CuvierIndo-Pacific sergeant Abudefduf vaigiensis Quoy and Gaimard 1825
Regional Occurrence: Abudefduf saxatilis is abundant in reef and rocky environments in the Atlantic Ocean (Molina et al. 2006). Populations have been recorded in the western Atlantic Ocean as far north as Canada, and south to Uruguay in South America, at depths ranging from 0 to 20 m. A. saxatilis is abundant on Caribbean reefs (Randall 1996) as well as on the tropical coast of Western Africa to Angola, where they form large feeding aggregations of up to a few hundred individuals. Juveniles are found in tide pools or in similar sheltered areas, schooling close to caves and shipwrecks. Adults are most common on shallow reefs.
IRL Distribution: Juveniles of Abudefduf saxatilis were recorded as one of the 10 most abundant species of fish occurring in the surveys in the Indian River Lagoon (Lindemen and Snyder 1999).
Age, Size, Lifespan: Abudefduf saxatilis grows to a maximum length of approximately 23 cm and can weigh up to 0.2 kg. Males and females reach maturity at 10 cm and 8 cm, respectively.
Abundance: Abudefduf saxatilis is abundant on tropical reefs and has been observed to rapidly increase its population size in areas of recreational disturbance, i.e. where artificial food sources are created by fish feeding and other habitat disturbances (Medieros et al. 2007).
Reproduction: Sergeant majors are oviparous. Males prepare nests for egg masses on rocks, reef outcrops, shipwrecks, and pilings. Spawning times vary depending upon region. For example, Caribbean populations do not appear to exhibit a lunar spawning pattern. Females in this region have been observed to spawn at various times throughout the month (Foster 2004). During courtship, males actively chase females in the early hours of the day and spawning takes place in the morning hours. Females release approximately 200,000 salmon- or red-colored, oval-shaped eggs, measuring 0.5 to 0.9 mm in diameter, in discrete, densely packed monolayers that adhere to the substratum (Robertson et al. 1993). Once fertilized, the eggs turn greenish (within 96 hours). The male guards the eggs until they hatch, usually within 4-5 days after fertilization, in the hour following sunset (Robertson et al. 1993, Foster 2004).
Abudefduf saxatilis larvae have a reduced pelagic stage lasting 18 to 27 days, and a post-larval pelagic stage lasting 55 days (Molina et al. 2006). The egg and larval development of laboratory-reared A. saxatilis has been exhaustively described by Alshuth et al. (1998). This study identified pigmentation, pelvic fin size, and the pectoral fin rays as the most useful characteristics for distinguishing the larvae of A. saxatilis from yellowtail damselfish (Microspathodon chrysurus) and beaugregory (Stegastes leucostictus). The sergeant major larva has a smaller and less-pigmented fin, as well as more heavily pigmented dorsal and pelvic fins.
Temperature: Temperature differences may account for regional variation in morphological traits, particularly size (Molina et al. 2006).
Salinity: Abudefduf saxatilis is not reported to exhibit significant tolerance or intolerance for hypo- or hypersaline conditions.
Trophic Mode: The sergeant major feeds on an unusually wide variety of benthic algae, small crustaceans, colonial anemones, copepods, pelagic tunicates, invertebrate larvae, and small fishes (Randall 1996).
Associated Species: Juvenile Abudefduf saxatilis may be present at green sea turtle (Chelonia mydas) cleaning stations, along with doctorfish (Acanthurus chirurgus), and blue tang (Acanthurus coeruleus). These fish inspect the turtles’ hard shells and soft tissues, and remove any algae and parasites that may be present.
Special Status: None.
Economic Importance: The sergeant major is a species of damselfish that is popular in the aquarium trade.
References: Alshuth SR, Tucker JW, and J Hateley. 1998. Egg and larval development of laboratory-reared sergeant major, Abudefduf saxatilis (Pisces, Pomacentridae). Bulletin of Marine Science 62:121-133.Fish Base (a). Abudefduf saxatilis Seargeant major. Species summary. Available online.FMNH. Ichthyology at the Florida Museum of Natural History. Available online.Foster SA. 2004. Diel and lunar patterns of reproduction in the Caribbean and Pacific sergeant major damselfishes Abudefduf saxatilis and A. troschelii. Marine Biology 95:333-343.Lindeman KC and DB Snyder. 1999. Nearshore hardbottom fishes of southeast Florida and effects of habitat burial caused by dredging. Fisheries Bulletin 97:508-525.Medeiros PR, Grempel RG, Souza AT, Ilarri MI, and CLS Sampaio. 2007. Effects of recreational activities on the fish assemblage structure in a northeastern Brazilian reef. Pan-American Journal of Aquatic Sciences 2:288-300.Molina WF, Shibatta OA, and PM Galetti, Jr. 2006. Multivariate morphological analyses in continental and island populations of Abudefduf saxatilis (Linneaeus) (Pomacentridae, Perciformes) of western Atlantic. Panama-American Journal of Aquatic Science 1:49-56.Randall JE. 1996. Caribbean Reef Fishes, Third Edition, TFH Publications, Neptune City, NJ. 512 p.Robertson DR, Schober UM, and JD Brawn. 1993. Comparative variation in spawning output and juvenile recruitment of Caribbean reef fishes. Marine Ecology Progress Series 94:105-113.