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Home › Sea Life Facts › Marine Species › Vertebrates › Damselfishes

Interesting Facts about Damselfishes

[Boxfish Phylum: Chordata] [Class: Actinopterygii] [Order: Blenniiformes] [Family: Pomacentridae]

No matter whether you call them damselfish or damsels, these brightly-coloured tropical marine fishes are a joy to watch when they're dancing around shallow coral ecosystems.

Yet, one of the funniest facts about the damselfish family (Pomacentridae) is how aggressively these medium-sized marine fish defend their territories against perceived threats and intruders.

Damselfish Habitat and Geographical Range

Damselfish are one of the most widespread (cosmopolitan distribution) of all marine vertebrates, but especially:

• Eastern Pacific (e.g. the Galápagos Islands, Gulf of California, Central and South America)
• The Indo-Pacific regions (e.g. Australia, the Coral Triangle, Philippines, Indonesia, East Africa)
• Most parts of the Western Atlantic (including Florida, Bahamas, and the Caribbean Sea)
• Some regions in the Eastern Atlantic (e.g. Canary Islands, Cape Verde)

Put another way, you might say that damselfishes are resident in almost all of the tropical and subtropical oceans around the world.

Even so, they have a distinct preference for certain kinds of habitats. Besides being closely associated with coral reefs and reef flats, they also thrive in lagoons, around rocky coastlines, and in seagrass meadows.

Damselfish Characteristics and Behaviour

Most species of damselfish are extremely territorial and they will viciously defend their particular dwelling and nesting site, usually a collection of corals or rocks.

Besides that, damselfishes fulfill an important role in reef maintenance, especially in the cultivation of overgrown patches of algae on sensitive coral structures.

For the most part, damselfish live in a depth range between one (1) and fifty (50) metres (164 feet) - even though some species thrive well in deeper environments.

But wait - there's more:

It's fair to say the most notable features of damselfishes (family Pomacentridae) are the vibrant colours. The body colouration of the juveniles is often a stunning mix of yellow, oranges, and different shades of blue and black.

Some species have a continuous dorsal fin, and others have a forked tail. Yet, almost all have rough, "teeth-like", fish scales (known as ctenoid scales) that cover most of the body.

Compared with the laterally compressed body shape of many vertebrate fish families, their physical size is fairly small. Thus, the average size of damselfish is around nine (9) centimetres in length (4 inches).

Yet, one of the biggest of the species is the giant damselfish (Microspathodon dorsalis) which can grow up to thirty six (36) centimetres long (almost 15 inches).

What Do Damselfish Eat?

Most of the schooling damselfishes are diurnal omnivores that consume large amounts of plant and animal matter.

Even though most will pick off scraps of plankton and detritus, herbivorous species are algae-farmers with a distinct foraging behaviour.

In the main, damselfish will include a combination of planktonic organisms, small invertebrates, and crustaceans in their daily diet (especially copepods, polychaetes, and caridean shrimp).

Interesting Fact: Studies show the male cortez damselfish (Stegastes rectifraenum) engages in filial cannibalism, and may actually consume more than 25% of its clutches.

Damselfish Species List

How Do Damselfish Reproduce?

Because they are an oviparous species (e.g. egg-laying), damselfish reproduction involves several distinct phases, including courtship, preparing a nest, spawning, and subsequent parental care, almost always undertaken by the male.

The majority of the species reach sexual maturity between the age of one and two years old. Moreover, exhibitions of sexual dimorphism means the males often become more brightly coloured than their female counterparts during the breeding season.

Courtship Behaviour

Once a male establishes a nesting territory, usually a flat rock or an open patch of substrate, he will defend it with fervent aggression and unwavering tenacity.

Courtship begins when a male either chases his chosen female, or when he displays darting movements, to attract one into his nest. It's also common to hear buzzing or clicking sounds during this part of the mating ritual.

Spawning

After selecting the nest, the female will lay a dense patch of many hundreds of adhesive eggs onto the designated substrate.

Then...

The male fertilises the thick layer of eggs externally. Following that, he guards them by chasing away any potential predators (including inquisitive scuba divers), and uses his fins to fan the eggs. Doing so helps to increase oxygen, keep them clean, and prevent fungal growth.

Incubation and Hatching

In most cases, the eggs need up to seven (7) days for incubation, determined by species and the temperature of the water.

These hatchlings drift with ocean currents for several weeks before eventually settling around a suitable reef and developing enough to begin life as juvenile damselfish.

Fun Fact: Damselfish have active reproduction cycles and may spawn several times per season, especially if the water is warm.

Threats and Predators

Even though damselfishes can enjoy a healthy lifespan up to fifteen (15) years in the wild, the ones kept as marine aquarium pets tend to have shorter lifetimes.

On top of that, they face some significant threats from predatory fish species outside of captivity. For instance, the main hunters of damselfish are:

• Barracudas
• Blennies (egg predators)
• Crabs (preying on juveniles)
• Gobies (raiding the nest)
• Groupers
• Lionfish
• Moray eels
• Octopuses (during the night-time)
• Sea birds (especially diving birds)
• Snappers
• Large wrasse species

Other contributing factors for the decline in a few vulnerable areas include certain types of human behaviour (e.g. coral reef destruction and degradation, overfishing).

Pro Tip: According to a 2007 assessment issued by the IUCN Red List of Threatened Species, the conservation status of most damselfish species is "Least Concern" (LC). However, they list the clarion damselfish (Stegastes redemptus) and the guardian damselfish (Altrichthys curatus) as "Vulnerable" (VU).

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