From the Tropical Seas
These algae-eating flamboyant genderfluid fish abound in the shallow waters across the world. Welcome to the world of the parrotfish, with about 95 species of parrotfishes found in the Indo-pacific coral reefs and shallow sea-grass beds.
Take the beak of a parrot and stick it on a colourful fish body. Add some awkward pectoral fins that flap up and down like the little wings of an energetic bird, and it quickly becomes clear why somebody in the course of history looked at one of these fish and thought, “Hmmm. That fish looks awfully like a parrot!”
Parrotfish are ubiquitous in shallow tropical waters across the world, with the highest number of species found in the Indo-Pacific region. These brightly coloured fish can be easily observed along coral reefs, rocky coasts and sea-grass beds, often forming bustling communities.
The taxonomic position of this group of fish is under debate. Traditionally, parrotfish were nested under the family Scaridae. However, some taxonomists suggest that they are a subfamily (Scarinae) under the closely related family of wrasses, Labridae. But all taxonomic arguments aside, these robust assemblies of fish are an integral part of our reefs and play an interesting role in bio-erosion and in the constant tussle for space between coral and algae.
Algae – the primary food source of the parrotfish – are a plentiful and rapidly renewable food resource. Many individuals of different species, therefore, share the same feeding grounds with few territorial disputes. In doing so, they help to check the spread of turf algae that might otherwise suffocate coral or reduce the available area for successful coral growth. While parrotfish are generally considered herbivores, their average diet includes the soft, non-calcified tips of algal bushes, seagrass blades, occasional crustaceans, coral polyps and other organisms.
Most parrotfish go through a series of changes in colour, markings and body shape as they progress towards adulthood. The less colourful females form “harems” that are led by a larger, more colourful male. Within harems, a size-specific pecking order determines social rank. When the dominant male in the group disappears, the largest female in his harem undergoes a sex change to become the dominant male leader. This two- to three-week metamorphoses results in the ovaries changing to testes and a bright new colouration on the recently transformed female!
Many divers have their closest encounters with parrotfish at night. The fish wedge themselves into holes and crevices on the reef before falling asleep, allowing us to approach them much more closely than during their daytime activity. Macro photographs of their beautiful eyes, beaks and scales are far easier to achieve after dusk when the fish is asleep. At night, a number of species cocoon themselves in a membrane of mucous, which they extrude from their mouths. This “blanket” is thought to mask the scent of the sleeping fish from nocturnal predators like reef sharks and moray eels. Some research also suggests that the mucous cocoon provides an early warning system, allowing the fish to flee when it detects a predator disturbing the outside of the membrane. In recent years, there seem to be declining observations of this behaviour of nocturnal mucous secretion in both the Andaman and Lakshadweep waters. This could be because of the diminished number of parrotfish predators on the reef, due to greatly increased shark fishing in these waters.
During the day, groups of parrotfish can be seen hurrying about the reef with the almost bird-like flapping of their pectoral fins. Their teeth have fused into powerful, parrot-like beaks. They stop above patches of coral or algae-covered rock and shave chunks off the substrate. Most mouthfuls that a parrotfish rasps off the reef include the underlying reef structure – calcium carbonate. This inedible portion goes undigested and is then excreted, as what you and I would call sand! This process of bio-erosion, when scaled up to include all the parrotfish on a reef, contributes significantly to the production and distribution of coral sand across tropical reefs and beaches. So the next time you are a part of that idyllic picture postcard – sipping your cocktail while lying on a white sandy beach – say a little thank you to our colourful fish friends and raise a toast to the parrotfish poop that you are lounging upon!
Read also: Junglimericks: In the Crazy Wilds of India
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