Damselfish: Small, Shy, Feisty

 Damselfish like Threespot, Dusky and Bicolor Damsels don’t have the celebrity status of more charismatic members of Family Pomacentridae like Clownfish or the in-your-face visibility of Sergeant Majors. But they’re feisty little guys who deserve attention – and, in fact, encountering Threespot Damsels (and the Damselfish Stare of Intimidation) are among my favorite things on the reef.

threespot damselfish Stegastes partitus
Threespot Damselfish, on patrol.

EVERYBODY KNOWS ABOUT CLOWNFISH AND SERGEANTS BUT OTHER MEMBERS OF THE DAMSELFISH GROUP – like Blue and Brown Chromis, Bicolor Damselfish, Threespot, Dusky and Cocoa Damselfish – get less attention, even though they’re pretty much ubiquitous on the reef. Perhaps they’re so abundant and low key that they’re taken for granted. All told, Family Pomacentridae encompasses more than 250 species of damsels worldwide, most in the Indo-Pacific. But damsels have a strong presence in the Caribbean, in physical numbers if not species diversity.

One reason damselfish don’t stand out may be that adults of many species are pretty muted in coloration. And, they tend to be somewhat shy and evasive when divers approach – with one significant behavioral exception. In contrast, juvenile damsels often are colorful, fading into drab shades as they mature.

Damsels like Threespots and Bicolors tend to make their homes around areas of dead coral – prime territory for the growth of the hair-like microalgae that make up the greater part of their diets. Others are plankton eaters, catching tiny copepods and other zooplankton from the currents. But even the herbivores will supplement their food supply with benthic copepods and other crustaceans.

They’re all benthic egg layers. The male prepares a nest on a suitable subsurface for the female to deposit eggs for fertilization. And then the Daddy Fish spends enormous energy ferociously warding off predators and intruders (the aforementioned non-shy behavioral exception).

DAMSELS NOT CALLED DAMSELFISH:

Anemonefish:

False clown anemonefish (Amphiprion ocellaris)
False clown anemonefish (Amphiprion ocellaris)

Whether people realize that Clown anemonefish are members of the damselfish family or not, they’re the superstars of Damsel World. They’re discussed separately in Shades of Orange. Found only in the Indo-Pacific, they encompass some two dozen species, mostly but not always orange. Only one is actually called a Clownfish (Amphiprion percula). The one at left is a False Clownfish (Amphiprion ocellaris) – it lacks the black motifs of true Clowns. Planktivores, they live with sea anemones, finding protection in the anemones’ tentacles. They help the anemones by eating parasites and enriching anemone food supplies with poop.

Chromis:

Brown Chromis (Chromis multilineata)
Brown Chromis hang out in strategic locations above the reef to capture plankton swept along in the currents.

Chromis are another variety of damselfishes identified by their own damsel-less common name. The chromis genus encompasses more than 100 species worldwide but in the Caribbean, Blue Chromis (Chromis cyanea) and Brown Chromis (Chromis multilineata) are the little guys you’re most likely to encounter, at least in the Caribbean.

Blue Chromis are constantly swimming and hovering off the reefs to sweep in zooplankton carried by the currents.

They differ from other damsels with longer bodies and more deeply forked tails. They’re the plankton feeders who hover above coralheads, generally facing into the currents picking zooplankton from the passing waters. Brown Chromis are likely to be found in large aggregations, as at left. Blue Chromis generally make up smaller groups and stay closer to the reef.

Sergeants:

Scissortail Sergeant, Abudefduf sexfasciatus)
Scissortail Sergeants on the Great Barrier Reef.

Sergeants (Genus Abudefduf) are the little damsel-shaped fishes with sergeant’s stripes – the genus names means “the one with prominent sides.”  Most of the 20 or so Abudefduf species are found in the Indo-Pacific (like the Scissortail Sergeant, A. sexfasciatus), but the Caribbean’s Sergeant Major (A. saxatilis) is probably encountered by more divers than any other single species. The only other Caribbean species, the Night Sergeant (A. taurus), is less common throughout the region.

Sergeant Major (Abudefduf saxatilis)
Sergeant Majors at Bonaire.

Sergeant Majors stand out not because they’re colorful – they are, after all basically gray with black and white stripes tinged with yellow – but because their sergeants’ stripes do give them a clear stage presence. And, they insist on building their egg nests out in the open and then guarding them ferociously, so they’re kind of an in-your-face, not-easy-to-miss variety of fish.

Sergeant Majors plant their egg nests right out in the open – and then protect them aggressively.

Males prepare the nests of purple eggs by clearing off spots on open surfaces – pier pilings and the hulls of wrecks are quite popular. They then work to entice females to contribute eggs – but not just one female. Male Sergeant Majors play around and a single nest’s eggs may include contributions from as many as five females. And, there may be multiple nests along a hull surface, each guarded by its own frantic fish daddy, each swimming back and forth, both aerating the eggs and challenging anybody or anything that may get too close. Many a diver has been nipped, harmlessly, by a determined Sergeant Major.

DAMSELS THAT ARE CALLED DAMSELFISH:

Bicolor Damselfish:

Bicolor Damselfish (Stegastes partitus)
A pair of Bicolor Damsels cruises just off a coral formation. At upper right, a juvenile Threespot Damselfish.

Bicolor Damselfish (Stegastes partitus) are often overlooked both on the reef and in damselfish descriptions. Found only in the tropical Atlantic/Caribbean basin, these plankton-eaters are small and the opposite of colorful: dark gray or black in their front halves, whitish in their rear halves, sometimes with yellow patches on their sides.

And they’re shy, living in groups of a dozen to 20 members that stay close to coral structures and adept and disappearing into nooks and crannies if they think they’re getting too much attention. Actually, they’re hard to photograph decently due to skilled elusiveness.

Juvenile Bluehead Wrasses are famous for their raids on Bicolor Damsel egg nests, and Bicolor Damsels for defending their egg caches. Click on the screenshot to view a video of a raid – and a Bicolor defensive struggle.

All egg nests are vulnerable to predation by other fishes and bluehead wrasse juveniles are notorious for raiding bicolor nests. The little fishes lay their eggs in protected areas under ledges but they’re still vulnerable to attack. Once a nest is laid, the males guard them and fight ferociously to protect them.

Threespot Damselfish:

Threespot Damselfish (Stegastes partitus)
A Threespot Damselfish’s Stare of Intimidation.

An exception to damselfishes’ reticence thing is the Three-spot Damselfish (Stegastes planifrons), feisty little guys three to four inches long that sometimes find you before you find them. The same could be said about Dusky Damselfish (S. adustus), Cocoa Damselfish (S. variabilis) and Longfin Damselfish (S. diencaeus).

Like most juvenile damselfish, this young Cocoa Damsel at front center sports flashy colors, which fade to muted brown/green as they mature. See the Bicolor Damselfish photo above for a juvenile Threespot Damselfish.

They’re herbivores – algae eaters – who “farm” patches of microalgae for their personal consumption. They constantly weed out the algae they don’t want, to make room for the stuff they want to encourage.

And they guard their little gardens ferociously, nipping at and chasing off intruders much bigger than they are – whether parrotfishes or divers. You do see a lot of them on the reef, patrolling their little areas of coral, but sometimes you pass by a little coralhead and the first indication you have of the damselfish’s presence is being nipped on the hand. Not serious but noticeable.

A Threespot Damsel passes back and forth, warding off an intruder – namely, me.

Nipping or not, they dart around frantically and likely give you the Damselfish Stare of Intimidation when you get too close. Until you go away, which you always do. Still, as they patrol back and forth, often disappearing behind a coralhead, they otherwise fit the shy mode.

Yellowtail Damselfish:

Yellowtail Damselfish (Microspathodon chrysurus)
A pair of Yellowtail Damselfish prepare a nest in a process called finning.

Yellowtail Damselfish (Microspathodon chrysurus) are fishes of a different color – several of them. With an overall body color ranging from black/blue to dark brown, they’re easy to distinguish by their yellow tails. Typically, their heads, backs and dorsal fins are speckled with iridescent blue dots.

The darkness of Yellowtail Damselfish highlight the iridescent blue dots adorning their bodies.

Like other damsels, M. chrysurus maintain a small territory where they feed largely on algae, supplemented by coral polyps and other invertebrates. Unlike other damsels, they’re not especially aggressive about its terrain and can be closely approached.

PRINCIPAL SOURCES: Reef Fish Identification Florida, Caribbean, Bahamas, Paul Humann, Ned DeLoach; Reef Fish Identification, Tropical Pacific, Gerald Allen, Roger Steene, Paul Humann, Ned DeLoach; Marine Life, Caribbean, Bahamas, Florida, Marty Snyderman & Clay Wiseman; Reef Fish Behavior, Ned DeLoach; Small-Man’s Complex: The Genus Stegastes, Reefkeeping.com; Sergeant Major, Florida Museum, Bicolor Damselfish, International Union for Conservation of Nature’s Red List; Damselfish, Marine Species Identification Portal; Damselfish, Abudefduf, Et.al., Wikipedia. 

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