Novaculichthys taeniourus (Rockmover Wrasse, Dragon Wrasse or Reindeer Wrasse) is a wrasse that is mainly found in coral reefs and lagoons in the Indo-Pacific region. These include those of the Gulf of California to Panama; tropical Pacific Ocean islands including Hawaii; the Philippines, Indonesia and Australia; and the Indian Ocean to the east coast of Africa. The common name, "Rockmover Wrasse", comes from their behavior of upending small stones and reef fragments in search of prey.^[1]

Description

Juvenile in Kona

The Rockmover Wrasse is a colorful fish, 27–30 cm (10.6–12 in) in length.^[2] It has an oblong, laterally compressed body and a wedge-shaped head. Except for two scales on the upper part of the gill coverings and an almost vertical row of small scales behind each eye, their head is scaleless.

There is a marked difference in appearance between juveniles and adults. In juveniles the first two dorsal fin spines are long and extended, drooping over the fish's forehead to form a "cowlick". As the fish mature, the elongated rays are lost. Adult fish have a dark greenish-brown body with an elongated white spot on each scale. Their head is gray-blue with brown lines radiated from their eyes. There are two black spots in front of the dorsal fin and a wide vertical white bar on base of the caudal fin. The posterior part of their caudal fin and pelvic fins are black. Juveniles found in Hawaii are usually green and those in the western Pacific are burgundy to brownish. Both are spotted in white.

The difference in appearance between juvenile and adult Novaculichthys taeniourus is so striking that the common name "Rockmover Wrasse" is used for adult Novaculichthys taeniourus and "Dragon Wrasse" for juveniles.^[1][3]

Habitat

Adult fish live on shallow semi-exposed reef flats and in lagoons and seaward reefs to depths of 14–25 m (46–82 ft). They prefer hard-bottomed grassy areas of mixed sand and rubble where there is exposure to a mild surge. Juveniles favor shallow areas on rubble among large patch reefs or protected open patches on reef crests.^[2]

Juvenile in Kona

Reproduction

Although little is known about reproduction of these fish, it is believed that, like other wrasses, they probably are able to change sex and are pelagic spawners, broadcasting eggs and sperm into the water column.^[3]

Behavior

These fish are highly territorial. Large adults, usually in pairs, move over their large section of a reef. One fish turns or shifts large pieces of debris or rubble grabbing or pulling it with its mouth or pushing it with its snout. When the working member of the pair has revealed the prey, the other fish quickly grabs and eats it. Juveniles do not usually work in pairs, doing all the work themselves. Facing danger, these wrasses quickly dive into the sand for protection. Juveniles resemble algae and mimic the movements of detached, drifting seaweed by swaying back and forth in the currents.^[2]

Distribution

They are widely distributed in tropical Indian Ocean and Pacific Ocean reefs and lagoons.

References