Abudefduf saxatilis – Sergeant Major
Abudefduf saxatilis has been described by Linnaeus as early as 1758. The genus name Abudefduf is derived from Arabic and means “father”. Saxa means “lives among rocks and tilus means” coloured like a tile “. This genus derives its name father from their bossy, aggressive behaviour towards other fish on the reef.
The common name for this species is Sergeant Major. The bossy behavior of this generation is reminiscent of the drill sergeant who is allowed to train the soldiers, combined with the vertical stripes.
This damsel can become a big fish. Abudefduf saxatilis can reach a maximum length of about 23 centimetres, but on average adult, specimens are about 18 centimetres in length.
The colour of the fish depends on the phase it is in. This species has two phases: the light and dark phase.
The Sergeant Major takes on the light phase when they swim over light-coloured sand or over the reef. The overall colouring is light. The back turns a light yellow which sometimes tends to green. The bottom half of the fish is light grey, just like the head. Four to five distinct black vertical stripes are visible on the flank. Sometimes a sixth faint line can be found on the tail root.
They take on the dark phase when they move between rocks and corals in the dark. Abudefduf saxatilis then becomes much darker and the colour changes from light grey to dark blue. The males also assume this colour when guarding a nest with eggs.
The habitat of Abudefduf saxatilis is around the Atlantic Ocean and the Caribbean. They occur from Rhode Island, Canada to Uruguay. They occur in large numbers in the Caribbean. They also occur on the other side of the Ocean. From Cape Verde to Angola.
They inhabit the rock formations and reefs at a depth of 0 to 20 meters. Sometimes the adults form very large schools. Such a school may consist of several hundred fish.
This species does not occur in the Indian and Pacific Oceans (Indo-Pacific). There their place is taken by the closely related and similar-looking Abudefduf vaigiensis.
The Sergeant Major Damsel’s diet is versatile. In the wild, this omnivore feeds on algae, invertebrates, zooplankton and small fish.
In the aquarium, they can be fed with spirulina, zooplankton such as cyclops, pods and small invertebrates such as brine shrimp, krill and mysis.
Abudefduf saxatilis is fairly territorial and can grow quite large. They, therefore, need a large aquarium from about 1,000 litres. Because they can sometimes be very aggressive towards other fish, it is advisable to keep them solitary. Provide many hiding places for the aquarium.
Feed them regularly to distract them. This species is usually considered reef safe but does eat invertebrates and sometimes soft coral.
Due to their active and aggressive nature, it is better not to combine them with all too calm and fragile species.
Breeding Abudefduf saxatilis
Abudefduf saxatilis lays the eggs on the bottom between the coral or rocks. They build nests of up to 200,000 eggs. The eggs are salmon to red coloured and glued to the bottom with a filament thread. The male is guarding the eggs. While guarding the eggs, the male turns dark blue.
Fertilized eggs turn greenish after about 96 hours. The eggs hatch after about 6.5 to 7 days. The larvae then float in the water column and form part of the zooplankton until they are somewhat larger. The fry are often found in tide pools.
Breeding in the aquarium is possible but very difficult. It is commercially cultivated, but in the home aquarium this is virtually impossible.
John de Lange