Sixbar wrasse
A reef-dwelling wrasse known for tool use in aquaria.
The sixbar wrasse, also called the six-banded wrasse (Thalassoma hardwicke), belongs to the Labridae family and lives naturally in the Indian Ocean and western Pacific Ocean. It sticks to reef areas, from the water’s surface down to about 15 meters deep. While it can reach 20 cm in total length, most individuals stay under 15 cm. Local fisheries catch it in small amounts, and it also turns up in the aquarium trade.
This fish is greenish, with four dark bars across its upper body and two more saddle-like bars near the tail base. Its dorsal fin has 8 spines and 12 to 14 soft rays; the anal fin has 3 spines and 11 soft rays. Larger adults develop pink streaks radiating from around the eye. The species ranges across the tropical Indo-Pacific, between 30°N and 32°S, from East Africa and Madagascar to Japan, Indonesia, the Philippines, northern Australia, and various western Pacific islands. It lives on coral reefs, reef slopes, and in lagoons, down to at least 15 meters deep.
Active during the day, the sixbar wrasse claims a home range larger than 1,000 square meters. It forms small groups and eats planktonic and bottom-dwelling crustaceans, foraminiferans, small fish, fish eggs, and fish larvae. During breeding season, males and females pair up; males then show brighter colors and a black spot in the middle of the tail fin. One aquarium individual was seen using a rock as an anvil: it carried hard pellets too big to swallow to a particular rock, broke them into pieces, and repeated this behavior with the same rock, showing it could remember how to solve the problem.
In aquariums, the sixbar wrasse needs a large tank with a sandy bottom and plenty of rocks offering caves and crevices for hiding and hunting. It may move objects around to find tubeworms, mollusks, and other invertebrates underneath. It also eats shrimp, crabs, and small fish, smashing larger prey against rocks. It can jump out of the tank and will bury itself in the sand when scared.
The sixbar wrasse is common across a wide range. Though sometimes collected for the aquarium trade, this is only locally significant, and no major threats have been identified. The International Union for Conservation of Nature lists it as a species of least concern.
Originally described as *Sparus hardwicke* in 1830 by English naturalist John Whitchurch Bennett, the type location is the south coast of Ceylon.
Quick Facts
- Taxon
- Thalassoma hardwicke
Facts from the source article.
Lore & Background
The sixbar wrasse was originally described as Sparus hardwicke by John Whitchurch Bennett, with the type locality given as the south coast of Ceylon. The specific name honors Bennett's friend and fellow naturalist, Major-General Thomas Hardwicke. The species is greenish with four dark bars on its upper body and two more saddle-like bars over the caudal peduncle; larger adults have pink streaks radiating from near the eye. It is diurnal and has a home range exceeding 1000 m², forming small groups that feed on planktonic and benthic crustaceans, foraminiferans, small fish, fish eggs, and fish larvae. During the breeding season, males and females pair, with males developing a gaudier color and a black spot in the center of the caudal fin. In aquaria, one individual was observed using a rock as an anvil to break hard pellets, demonstrating memory and problem-solving ability.
Reader's Guide
The sixbar wrasse is a common species with a wide range across the tropical Indo-Pacific, from East Africa and Madagascar to Japan, Indonesia, the Philippines, northern Australia, and various western Pacific island groups. It is found on coral reefs, reef slopes, and in lagoons. Although sometimes collected for the aquarium trade, this is thought to be of only local significance, and no other major threats have been identified; the International Union for Conservation of Nature has assessed its conservation status as being of least concern. In aquaria, it appreciates a large tank with a sandy base and rocks for shelter and hunting. It may move aquarium objects to discover tubeworms, molluscs, and other invertebrates, and it feeds on shrimps, crabs, and small fish, bashing larger prey on rocks. It is capable of jumping out of the aquarium and will submerge itself in the sand when frightened. The species' observed tool use—carrying hard pellets to a specific rock to break them—highlights a notable cognitive capacity, though this behavior is documented only from a single aquarium specimen.
Did You Know?
- The sixbar wrasse can grow to 20 cm in total length, but most individuals do not exceed 15 cm.
- Its specific name honors Major-General Thomas Hardwicke, a friend of the original describer.
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