Yellowtail Damselfish

There is interspecific overlap of feeding areas of M. chrysurus and two other damselfish species—Stegastes dorsopunicans and Stegastes planifrons. All three cohabitants consume the same benthic microalgae and have the same feeding cycles. In terms of defending the feeding grounds from intruders, studies have shown that M. chrysurus is less competent than Stegastes spp. at inhibiting intruders. However, yellowtail damselfish have a competitive advantage because of their size. M. chrysurus are aggressive toward their cohabitants, using their size-based dominance to obtain food.

In regards to feeding habits, adults typically graze on algae while juveniles are carnivorous. M. chrysurus is omnivorous with a gradual change in feeding habits throughout development. This change in diet is related to the distribution of adult and young adult damselfish. Gut content analysis of yellowtail damselfish shows a change is food ingested from young adulthood to adulthood. Young adults primarily feed on animal-like nematocysts and zooxanthellae. Adults tend to tend to be more selective in their feeding habits, eating blue-green algae called cyanophytes. However, if there is an abundance of another food source available those are likely to be ingested by the species.

The spawning cycle of the yellowtail damselfish starts at sunrise and lasts approximately 1 hour after male damselfish have prepared nests on dead coral surfaces. Their eggs are demersal, adhering to the substrate where males guard and aerate them. Hatching occurs the morning of the 6th day of incubation. Reproductive activity is highest during the lunar period between full and new moon. At those points in the lunar cycle, the gravitational pull of the sun and the moon are very high resulting in spring tides.