The damselfish is the most popular member in the family of reef fish. They consist of nine species which are identified based on color. It is territorial and stays on one part of the reef where it maintains farms of algae, which is its food.
On every snorkeling adventure, you will undoubtedly spot many different types of damselfish. They are among the most popular families of reef fish, which also include gobies, angelfish, butterflyfish and wrasses. There are nine well-known species in the damselfish family (Pomacentridae) – three are shown here: the Threespot Damselfish (Stegastes planifrons), Yellowtail Damselfish (Microspathodon chrysurus) and Bicolor Damselfish (Stegastes partitus). While some of the species are fairly distinct and easy to identify, others are very similar in appearance.
Damselfish appear to have an elaborate system of inter and intra species identification and communication. These fish use both color and sound to signal behavior changes to predators and each other. In any case, the behavior of damselfish is a fascinating glimpse of the complex interaction that takes place on a shallow coral reef.
Damselfish are territorial fish, staking claim to a certain part of the reef (usually in stands of Elkhorn, Staghorn and Fire Coral) and vigorously defending it. The fish stakes out this territory in order to allow algae to grow and has actually been observed inflicting wounds in the coral itself to allow the algae to take up residence. The algae then become food for the damsels and a variety of other fish as well.
The damselfish maintains farms that range from a few square feet to 500! Considering the small, four to seven inch size of the damselfish, its ability to stake out, farm and defend a substantial area of reef is pretty astounding.
The damselfish’s pugnacious defense of its territory has earned it the reputation of the most aggressive fish on the reef. Its role as a reel fighter can be frequently observed during a leisurely snorkel outing. The damselfish appears to be fearless, challenging larger fish and even nipping at snorkelers who get too close to its territory. While the nip is harmless to humans, it shows the belligerence of a fish that is willing to take on an opponent ten times larger than itself.
The damselfish has had to learn some unique defensive tricks to fight off its larger adversaries. When defending its territory, it attacks both the fins and the eyes of larger fish, which have learned to shy away from combat with a damselfish, since damage to either of these very important body parts could lead to the fishes’ demise.
If you spend some time watching a damselfish and its algae patch, you will see it invaded by schools of Blue Tangs and parrotfish, which use the protection of numbers to overwhelm the damsel. Since the damsel can’t decide which one to drive off, the tangs and parrots steal a quick meal and depart.
The damselfish recognizes the behavior of different reef fish and establishes a defense system for each. It will let small carnivorous fish that do not eat algae very close before chasing them away. But if an herbivorous fish merely turns in the direction of the damsel’s algae patch, a much more vigorous defense is mounted!
If a damselfish seems particularly aggressive, it’s probably defending a cluster of eggs deposited in the algae by a female damselfish. Guarding the eggs becomes the job of the male damsel and, during this time, it becomes even more aggressive!
Juvenile damselfish can be found in mangrove systems and in the shelter of the reef, biding their time while growing large enough to establish their own farms. In this stage of life the juveniles’ color and markings are dramatically different from the adults, making them easy to distinguish.
The best way to observe a damselfish is to remain as motionless as possible at a safe distance of about five feet, so as not to trigger any defensive behavior and to let other fish approach its territory. Then it’s a show as the reef farmers turn into fighters and defend their farms.