Hawaiian Marine Life Profiles: Fish
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Found in Exhibit:
Shallow Reef, Deep Reef
|The wrasse family has the distinction of being one of the most difficult fish to identify. Juveniles often display different patterns and colors than the adults, and again males and females sometimes have varying appearances. These variations resulted in confusion in the past, with males and females of the same species often being identified as separate species. To make identification even more confusing, females can actually change into males.
The rockmover wrasse is one species that has a very different appearance as a juvenile as it does when it is an adult. As a juvenile, it more closely resembles a drifting piece of algae than a fish. Juvenile rockmovers, which are sometimes called dragon wrasses, have long filamentous extensions on their fins and sway from side to side, appearing to drift with the currents. They are generally reddish or brown in coloration with white speckles to help them blend into the background. As they age, the fins start to diminish in size, and their color becomes a slightly more uniform brown and white until all traces of the elongated fins disappear.
Rockmover wrasses get their name from their method of finding food, by overturning small rocks in search of prey living in the sea floor. They eat small invertebrates such as brittle stars, sea urchins and worms. Rockmover wrasses are found in the Indo-Pacific region and the tropical eastern Pacific area. They are generally seen in depths of 10 to 70 feet over areas with sandy or rubble-covered bottoms. Rockmovers can also be seen following SCUBA divers in hopes that they will disturb the bottom, revealing the sought-after prey. Unlike many species of the wrasse family, male and female rockmovers have the same color pattern.
Members of the wrasse family can generally be identified by their thick lips, cigar-shaped bodies and prominent use of their pectoral fins. They will use their tail fin only when needed for speed. Wrasses are also known as one of the most territorial fish on the reef. Wrasses are also diurnal, meaning they are more active during the day. At night, the smaller species often bury themselves in the sand, while the larger ones find shelter in the reef.
As far as scientists know, wrasses are born as females, known as the initial phase, but some change into males later in life, known as the terminal phase. It is not exactly known what triggers the change to occur for all species, however, we do know that wrasses live in harems with one male and several females. When the male dies or is removed, the most dominant female will begin the change. The change not only involves internal changes, but can also include growing larger and coloration changes.
On first impression, the rockmover wrasse seems to be just another reef fish, however closer investigation reveals a world full of bizarre sex changes, fascinating camouflage and an impressive tenacity for finding food. Anyone lucky enough to be able to see a rockmover in action, carefully moving rocks from one area to another, looking for a meal and creating holes in which to hide from predators, is in for both amazement and amusement.