The Harlequin Sweetlips (Plectorhinchus chaetodonoides), also known as clown sweetlips, spotted sweetlips, or many-spotted sweetlips, is a type of marine fish in the sweetlips family (Plectorhinchinae), which is part of the grunt family (Haemulidae).
The Harlequin Sweetlips is known for its rapid growth and dramatic transformation from juvenile to adult. Witnessing this transition is absolutely fascinating!
Juvenile
Juvenile Sweetlips, starting at about 2.5 cm, are brown with large, round, black-ringed white spots and white-edged fins. They swim in a distinctive, erratic pattern often described as a drunken dance, flapping their dorsal fins and undulating their bodies in constant motion.
This behavior mimics noxious flatworms, helping them avoid predators. Solitary by nature, they take shelter in corals. Juvenile Sweetlips are carnivores, feeding mainly on small invertebrates like crustaceans and plankton, which they hunt at night among coral reefs and rocky substrates.
Adult
As they mature, Harlequin Sweetlips grow quickly to around 60 cm and undergo a significant color change. Juvenile spots evolve into a more subdued pattern of brown spots over a white base, with a pale cream or yellow background color, dark spots on the upper and mid-body, and clear markings on the belly. Their rubbery lips, tail, and dorsal fin are spotted, while the pectoral and ventral fins are dark. Adults have a streamlined body with a prominent, rounded head and large eyes, and their swimming style becomes more graceful and powerful.
They can also produce a 'grunt' sound by grinding their teeth, which is amplified by their swim bladder, aiding in communication and dominance. Adult Harlequin Sweetlips are solitary, often found near and under ledges or caves during the day. As carnivores, they feed on benthic invertebrates like crustaceans and mollusks, as well as small fish, which they hunt at night.
Reproduction
Sweetlips reproduce by spawning in pairs or small groups, typically during warmer months. They synchronize the release of eggs and sperm into the water, where fertilization occurs externally. After fertilization, the eggs develop into larvae that drift with the currents before settling on the reef. As the larvae grow, they eventually settle into their reef habitat as juveniles, continuing their life cycle.
Predators
Both juvenile and adult face various predators in their reef environment. Juveniles are particularly vulnerable to larger fish like groupers, snappers, and barracudas. Adults are at risk from large predators such as sharks and bigger groupers. To defend themselves, Sweetlips use behaviors like mimicking noxious flatworms and producing a grunting sound. Humans also pose a threat: adults are caught for food, and small, colorful juveniles are collected for the aquarium trade, leading to overexploitation in some areas. Overfishing and habitat damage further threaten their populations.
Where to Find Harlequin Sweetlips on Koh Tao
You can spot Harlequin Sweetlips at many dive sites around Koh Tao, check out these locations:
Chumphon Pinnacle,
Sail Rock,
Laem Thian,
Hin Wong Bay,
Japanese Gardens,
Twin Peaks,
White Rock,
Mango Bay,
etc...
