Surge wrasse
A colorful reef wrasse found in the surge zone of Indo-Pacific waters.
The surge wrasse (Thalassoma purpureum), also called the green-blocked wrasse, purple wrasse, or red and green wrasse, lives in the southeast Atlantic Ocean and across the Indian and Pacific Oceans. It sticks to reefs and rocky shores where waves crash hard, usually in water no deeper than 10 meters. People catch it for food in small local fisheries, it’s a popular game fish, and it also turns up in the aquarium trade.
This fish has 8 spines and 12 to 14 soft rays in its dorsal fin, while its anal fin has 3 spines and 10 to 12 soft rays. It can reach 46 centimeters long and weigh 1.2 kilograms. Its body is fairly deep and flattened from side to side, and it has a pair of canine-like teeth at the front of its lower jaw. Females are greenish with a dark red V-shaped mark on their snout. Males are greenish-blue with two bright reddish stripes along their sides, plus a large head and a blunt snout that is greenish-blue with pinkish-purple markings. The surge wrasse looks a lot like the ladder wrasse (Thalassoma trilobatum), especially the females, but it has a bigger head and no spots on its head.
Its range is wide: from the Red Sea south to South Africa, east through Indian Ocean islands and Asian coasts, then into the Pacific as far north as Japan, south to Lord Howe Island, the Kermadec Islands, and Rapa Islands, and east all the way to Panama in the eastern Pacific. It also reaches the southeastern Atlantic along South Africa’s coast.
As its name hints, the surge wrasse lives in the surge zone on outer reef flats and along reef edges of coral and rocky reefs, usually shallower than 10 meters. Females gather in groups spread over large reef areas, with a few much larger males dominating them. It eats small invertebrates like crabs, sea urchins, brittlestars, and molluscs, plus small fish and polychaete worms. It is a protogynous hermaphrodite—females can change into males—and it spawns in open water.
The Swedish explorer and naturalist Peter Forsskål first described this species as *Scarus purpureus* in 1775, giving the type location as Jeddah. When William Swainson created the genus *Thalassoma* in 1839, he picked *Scarus purpureus* as the type species.
Quick Facts
- Taxon
- Thalassoma purpureum
Facts from the source article.
Lore & Background
The surge wrasse was first formally described as Scarus purpureus in 1775 by the Swedish explorer, orientalist and naturalist Peter Forsskål, who gave the type locality as Jeddah. When William Swainson was describing the genus Thalassoma in 1839, he designated Scarus purpureus as its type species. The species has a wide Indo-Pacific distribution that extends marginally into the south-eastern Atlantic along the coast of South Africa. Its main distribution in the Indian Ocean ranges from the Red Sea south to South Africa, east through Indian Ocean islands and coasts of Asia to the Pacific Ocean, where it extends north to Japan and south to Lord Howe Island, Kermadec Islands, and Rapa Islands, and east as far as Panama in the eastern Pacific.
This wrasse has a rather deep, laterally compressed body and a pair of caniniform teeth in the front of its bottom jaw. Females are greenish with their snout marked with a dark red V. Males are greenish-blue with two bright reddish stripes along their flanks and a large head with a blunt snout that is greenish-blue with pinkish-purple markings. It is very similar to the ladder wrasse (Thalassoma trilobatum), especially the females, but the surge wrasse has a larger head and no spots on the head.
The surge wrasse lives in groups of females spread out over large areas of reef and dominated by a few males that grow much larger than females. It is a carnivorous species that preys on small invertebrates such as crabs, sea urchins, brittlestars and molluscs, as well as small fishes and polychaete worms. It is a protogynous hermaphrodite—females change sex to become males—and it is a pelagic spawner.
Reader's Guide
The surge wrasse holds a modest but notable place in human activities, being of minor importance to local commercial fisheries and popular as a game fish, while also appearing in the aquarium trade. Its wide distribution across the Indo-Pacific and into the southeastern Atlantic makes it a familiar species on reefs and rocky coastlines subject to heavy wave action. Ecologically, it plays a role as a carnivore, preying on a variety of small invertebrates and fishes, and its protogynous hermaphroditism—where females can change sex to become males—adds to its biological interest. The species is also taxonomically significant: it was the original type species for the genus Thalassoma when William Swainson described that genus in 1839, based on the earlier description by Peter Forsskål. Its similarity to the ladder wrasse, particularly among females, has been noted, with the distinguishing features being the surge wrasse's larger head and absence of spots on the head. Overall, the surge wrasse is a colorful and resilient inhabitant of the surge zone, contributing to both local fisheries and the aquarium hobby.
Did You Know?
- The surge wrasse was first described as Scarus purpureus by Peter Forsskål in 1775, with the type locality given as Jeddah.
- It is a protogynous hermaphrodite, meaning females can change sex to become males.
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