The dusky farmerfish (Stegastes nigricans) is a species of damselfish found around coral reefs at a depth of one to 12 meters, in tropical climates between 30°S and 30°N. They are known for farming monocultures of algae such as cyanophores and rhodophytes.
Short description - Dorsal spines (total): 12; Dorsal soft rays (total): 15-17; Anal spines: 2; Anal soft rays: 12 - 14. Diagnosis: Adults generally brown; dorsal part of head and nape darker, grading to tan on lower part of head and breast. The scales have darker brown margins. The lips are whitish lips; the suborbital is mostly blue; the preopercle and opercle scales with blue centers. The median and pelvic fins are brown; the pectorals are dusky; a well-defined dark brown or blackish spot is sometimes present at base of posteriormost dorsal rays, which distinguishes it from S. lividus where the spot is diffuse. Males in courtship or guarding eggs with broad white bar across middle of body and pale blue stripe from mouth to upper part of pectoral fin.
Max length - 14.0 cm TL male/unsexed; common length : 9.0 cm TL male/unsexed.
Dusky farmerfish's Behavior & Ecology
Adults inhabit reef flats and lagoon reefs. Frequently occur in colonies associated with live or dead branching staghorn coral (Acropora). Feed on algae, gastropods, sponges, and copepods. Territorial, maintain and 'weed' filamentous algae patches growing on dead coral. Particularly aggressive during reproductive periods. The species emit clicking noises during aggressive encounters. Oviparous, males tend the nest visited by several females.
Dusky farmerfish's Reproduction
Oviparous, distinct pairing during breeding. Eggs are demersal and adhere to the substrate. Males guard and aerate the eggs.