PARROTFISHES ARE SO COLORFUL, SO RELATIVELY APPROACHABLE AND SO ABUNDANT ON TROPICAL REEFS that it’s easy to take them for granted and focus on looking for “exciting” animals like sharks, frogfishes and seahorses. It doesn’t help that, often, they’re hard to pin down as to species. In reality, parrotfishes live complex lives that can involve changes of colors, patterns, size and gender.
At one time naturalists thought there were about 350 parrotfish species, based on appearances.
Actually, there are about 80. The inflated number resulted from perceiving their varying phases as differing fishes. About three times as many species inhabit the Indo-Pacific basins as the Caribbean/tropical Atlantic (although, as a personal, unscientific observation, Caribbean reefs I’ve dived seemed far more densely populated in terms of parrotfishes than those in the Indo-Pacific).
Whatever, they all largely share the same characteristics of swimming primarily with their pectoral fins and having beak-like jaws of fused teeth that give them their parrotfish nomenclature. Their dental arrangement supports lives spent relentlessly scraping algae off (mostly) dead coral – the primary nutrition source for nearly all species.
The side effect is that along with the algae they tend to ingest a fair amount of the coral’s calcium carbonate material – it’s estimated that as much as three-quarters of the contents of a working parrotfish’s digestive tract at any given time is inorganic sediment.
Teeth-like plates in their throats (“pharyngeal teeth”) let them grind the calcium carbonate into sand-like particles, which are excreted. Actually, it’s not that they grind it into sand-like particles; they grind it into sand.
It’s true: Parrotfishes poop out sand – a very fine white form that makes up much of the seafloors and beaches of coral reef environs. It’s estimated that a large fish can produce more than a ton of sand in a year. And, in fact, this bio-erosion activity plays a big part in the healthy reef dynamic of being constantly built up and worn down.
MOSTLY CORAL REEF DWELLERS
Parrotfishes have traditionally been located in Family Scaridae, although some sources now consider them a subfamily of the wrasses (Family Labridae). In any event, they’re primarily found on coral reefs and seagrass beds. But some species are found away from reefs in subtropical waters, including on rocky coasts in the Gulf of California and the Mediterranean.
The Caribbean and tropical Atlantic are home to about a dozen species in the genera Scarus and Sparisoma. The most familiar are the queen (Scarus vetula), princess (Scarus taeniopterus), striped (Scarus iserti), stoplight (Sparisoma viride) and yellowtail (Sparisoma rubripinne) parrotfishes, depending on the site. But while described as occasional, blue (Scarus coeruleus), midnight (Scarus coelestinus), and rainbow (Scarus guacamaia) parrotfishes are not unfamiliar. About 40 species are found in the Indo-Pacific, in some half-dozen genera, including genus Scarus. But not Sparisoma – they’re found only in the Caribbean and tropical Atlantic.
Do genus and species really matter (besides to the parrotfishes)? The distinction between Scarus and Sparisoma can help us understand their life cycles and perhaps what we are seeing.
THE UNBEARABLE APPETITE (AND WRIGGLYNESS) OF PARROTFISHES
For discussion purposes, this article focuses on Caribbean species. Also, because I only have a few decent photos of them – far fewer than I would like. Which brings up a point: Parrotfishes rarely stop moving during the day (I said at the top that they’re relatively approachable; they don’t pose very well). Once filled with prey, piscavores like sharks and groupers can go for long periods without having to eat again.
For herbivores and plankton pickers, finding sustenance is pretty much a full-time job. Schools of blue tangs rush around a reef scarfing down algae like little Labrador retriever puppies. Parrotfishes are always in motion, twisting and turning to get a good angle on the coral. It makes one wonder about the wisdom of their strategies, considering the energy they have to put into constantly scraping up nourishment.
And scraping is what they do: Rather than targeting individual plants, they graze the surface, taking off detritus and sediment along with the thread-like turf algae present on the surface. Scarus species tend to bite at a rate two to four times faster than Sparisoma species. But Sparisomas tend to bite into the coral more deeply, leaving noticeable marks.
Designed as they are to graze filamentous algae, parrotfishes are actually omnivores – they’ll eat anything if the opportunity presents itself, stalks of bushy, uncalcified algae, blades of sea grass, small crustaceans and bits of sponge. Stoplights and queens appear to go for living coral polyps as well as well as the algae on dead corallite structures.
The Florida Museum of Natural History suggests that differing species can be distinguished by their upper and lower teeth structures, although it does not indicate how to hold them comfortably while you do so. Largely this means that members of genus Scarus are characterized by upper beaks that overlap their lower jaws, members of genus Sparisoma by upper jaws that fit inside the lower ones.
In size, adult parrotfishes range from as small as three inches – bucktooth (Sparisoma radians) – and as large as four feet – the rainbow (Scarus guacamaia). Most species reach adulthood in two to four years. Some have lifespans of up to 20 years.
Mostly, to the casual observer, we rely on colors and patterns to identify them – potentially a problematical exercise since many species tend to change dramatically as they pass through phases. Scientifically, they’re termed both diachromatic (members of a species can exhibit more than one color pattern) and protogynous hermaphroditic (they can change sex from female to male).
THE DIACHROMATIC FACTOR
During their lives, most parrotfishes pass through a series of phases involving significant changes in colors, patterns and body shapes – juvenile phases, initial phases and terminal phases (terminal-phase fishes used to be referred to as supermales). They tend to be larger in size, brighter in colors and more aggressive in behavior. Since parrotfishes typically live in harems in which a terminal-phase male will oversee two to seven mostly initial-phase females (and juveniles), terminal phase males are relatively few in number among the parrotfish population.
THE HERMAPHRODITIC FACTOR
Species in the genus Scarus (think princess, among others) have two types of males – those born male (primary males) and those born female (secondary males). All Scarus females who live long enough will eventually change color patterns and transition to males.
In the genus Sparisoma (think stoplight) all males are secondary – and many females in some species don’t ever make the transition to male. Perhaps they like to think big – In some species, Sparisoma females tend to be larger than either initial or terminal phase males.
The transition to supermale status reflects the needs of the setting. Generally, if a dominate terminal male dies, the largest initial-phase individual will make the transition to terminal phase to assume the supermale duties. Gonads are transformed from ovaries to testes and colors become brighter over a period of several weeks.
Parrotfishes reproduce by broadcast spawning, and it’s often a daily activity – at an established time (usually early morning or late afternoon) the fishes
journey to fixed spawning areas, usually on the edges of reefs where the current will carry eggs away from the clutches of likely predators. In some species, the males mate only with females in their harems; in others males and egg-laden females just show up.
They typically spawn in pairs, doing elaborate courtship routines of darting and weaving around each other, eventually rising in the water column and releasing sperm and eggs in a cloudy aggregation, maximizing their gametes’ chances of achieving fertilization and escape into the current. Some species with large numbers of initial-phase males may spawn in groups. And it’s not unusual for initial-phase males to lurk about a supermale’s spawning site to rush in and contribute sperm to the egg/sperm cloud.
SLEEPING WITH THE (OTHER) FISHES
In search of a good – and safe – night’s sleep, parrotfishes mostly return to their reef territories and seek to stuff themselves into crevices in the corals. Some bury themselves in the sand, some rely on night colors for camouflage. And some like the queen parrotfish secrete a mucous membrane from their mouths to envelop themselves and, presumably, mask their smell from hunting predators.
Principal Sources: Reef Fish Behavior, Ned DeLoach; Indo-Pacific Coral Reef Field Guide, Gerald Allen, Roger Steene; Reef Fish Identification, Tropical Pacific, Gerald Allen, Roger Steene, Paul Humann, Ned DeLoach; Encyclopedia of Fishes, John Paxton and William Eschmeyer; Fishbase.org, www.fishbase.org; Florida Museum of Natural History, www.flmnh.ufl.edu; Shedd Aquarium, www.shedaqurium.org.