Natural History

Sea-Faring Butterflies

spotfinbutterflypair

Flitting about the reef for food and courtship, butterflyfish swap wings for fins.

Story By Suzanne Gerber ~ Photos By Barbara Shively

English speakers call this colorful, delicate and playful species of fish by a poetic name — butterflyfish — but its scientific name tells a different story. Chaetodontidae, pronounced key-toe-DON-ti-day, comes from the Greek words chaite (“hair”) and odontos (“tooth”). This far more prosaic appellation derives from the fish’s rows of bristly teeth. Even if this thin, colorful fish didn’t flit around underwater landscapes in his search for food, Barbara and I would stick to the name butterfly.

Worldwide, there are some 114 different families of butterflyfish (scores of them in certain Pacific regions), but here in the Caribbean we usually encounter just half a dozen, four of which Barbara has captured on film (and now digital memory cards). But don’t ask her how long it can take. One elusive type, the longsnout, managed to avoid her lens for three years!

With their impressive array of colors and patterns, butterflyfish are among the most common sights on any reef. They have thin, laterally compressed bodies that resemble their handsome cousins, the angelfish. Like their winged namesakes, butterflyfish spend their days hunting with their needlelike snouts in search of coral polyps, worms and other tasty treats.

There are few drab varieties, but most butterflyfish display striking patterns with backgrounds of blue, red, orange or yellow. A commonality among them is a dark band across their eyes and round, eye-like dots. Both of these markings are camouflage. The eyeband hides their real eye while the “false eye,” near the tail, confuses predators, who consequently don’t know which end to attack. And when they do chomp down on the rear end, the damage is far less severe than a blow to the head would be.

Butterflyfish, like their close relatives the angelfish, have laterally compressed bodies (extremely thin when viewed from the front). This body style gives them great maneuverability to negotiate the coral reefs and sea grass beds they inhabit. If you are looking at one directly from the front, top or back, it is so thin it almost disappears from view.

Juveniles are usually solitary swimmers (occasionally taking on the reef role of “cleaner fish”), though as they age they sometimes travel in small schools. Most frequently, however, adults are observed in pairs. Given that the average lifespan is about three years and the fact that researchers have tracked the same stable pairs for at least that length of time, it’s fair to say these little guys mate for life. A sweet behavioral characteristic: since butterflyfish use vision to find their prey, couples’ communication is visual too. If a pair becomes separated, one may swim upwards so they can find each other.

Research is limited, but the common wisdom is that butterflyfish reproduce through seasonal spawning, usually at dusk. Depending on where they are, that could mean winter and early spring, midsummer, or at random times throughout the year. It’s quite the scene, if you’re lucky enough to catch it. Females look visibly pregnant until they are ready to drop the eggs, at which time the male swims behind and below her, putting his snout to good use nudging her belly. All this is happening as the parents rise up in the water column, but  the moment the female releases a white cloud into the ocean, the adults descend to the bottom. (In one species it’s more of a cartoon-fish scene, with the male chasing his bride around a large sponge.)

Banded butterflyfish

You don’t have to be a marine biologist to figure out how this variety got its name. Banded butterflies sport two dark midbody bands, including one that paints a stripe along the eye line. Like most butterflyfish, the bandeds are usually solitary or in pairs, found in shallow waters around coral reefs, active by day and at night heading for shelter since they are particularly vulnerable to night predators like sharks and moray eels. Babies are adorable, with a large, ringed black spot at the base of the dorsal fin. Even as juveniles they have four vertical bars, but their coloring is brownish-yellow rather than white.

If threatened, banded butterflyfish will turn and face its aggressor, lower its head and raise its doral spines fully erect. This is to intimidate the aggressor and to remind it that the butterflyfish is much too spiny to make an easy meal.

Spotfin butterflyfish

bandedbutterflypairverticalThough not uncommon in the Caribbean, this species is a more frequent sighting on the shallow reefs around Florida. They, too, are usually seen in pairs or small groups (maybe four or five but rarely in schools). One of the spotfins’ main distinctions among butterflyfish is that it swims and feeds over bare, sandy bottoms. (They also fancy dining on anemones, which their kith and kin don’t.)

The way to recognize the spotfin is from, well, the spot on its (dorsal) fin. Look for a white body featuring a black bar that runs vertically through the eye and across the head as well as a thin yellow bar stretching from the gill opening to the base of the pectoral fin. (In juveniles, a second black bar runs from the base of the dorsal fin to the base of the anal fin, with an additional spot there.)

Foureye butterflyfish

This variety exhibits typical butterflyfish behavior and differs mainly in appearance, which as with its compadres, is what gives the foureye its name. It’s the large, dark spot on the rear portion of the body, surrounded by a brilliant white ring (the spot serving as a false eye). A black vertical bar on the head runs down the actual eye, obscuring it from predators. The adult foureye is handsomely patterned: a white body with dark, thin lines radiating diagonally from the middle of his body to the top and the bottom. It is the only butterfly species with these converging lines. While foureyes usually mate for life, sometimes they can be seen in groups of up to 15.

The isopod pictured on the foureye butterflyfish on the previous page can be found on most of the Caribbean butterflyfish types. According to Marilyn Schotte at the Smithsonian Institution’s Natural History Museum, isopods are parasites and each type of isopod has a favorite host species to which it will attach. As juveniles they are not discriminating but will grab onto pretty much any handy fish. As they mature they will switch to their preferred species, usually attaching to  the mouth or around the gills. Isopods all start out as juveniles, become males next and then, if there are few or no females around, some of them turn into females.  In some species the female is non-feeding, living off its reserves long enough to reproduce. The juvenile and male isopods suck the blood of the host fish — but do not kill their hosts.

Longsnout butterflyfish

The fish that so long eluded Barbara tends to inhabit deeper parts of the reef (and walls) than its peers, which may explain why its image is so hard to capture. The longsnout is more of a loner, usually pairing up only to breed, and never deigns to take on the role of cleaner fish. And, the longsnout looks totally different from its brethren. It’s a good bit smaller (two to three inches, whereas most others are six), with a tall and narrow body, not disc-shaped. The upper half is yellow-orange, darkening into a blackish dorsal fin. The lower half is white, it sports orange bands on its head, and the snout is longer than others’, relative to the rest of its body. Favorite snacks are sea urchins’ tubelike feet and the tentacles of tubeworms.

New York-based Suzanne Gerber writes about scuba, travel and health for a variety of publications. Book your next dive trip by contacting Suzanne at suzanne@worldofdiving.com.

Avid underwater photographer Barbara Shively discovered Grand Turk diving in 1997 and has returned every year. It is her passion to share the coral reefs’ beauty through her photographs. A variety of her prints are on sale at Art Provo, located in The Regent Village, Providenciales.



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