Convict, Yellow and Achilles Tangs
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Convict Tangs often swim in schools of thousands. There are two reasons why they have large schools. First, It helps them escape predators. When a large fish attacks a school, they scatter like an explosion. This move confuses the predator and the prey escape. Each convict tang has another chance at life if they stay with the group.
Convict Tang (Manini)
In Hawaii, The Manini, or Convict Tang, is the most abundant member of the fish family called the surgeonfishes or tangs. It is pale greenish-white in color with black vertical bars that run from the base of the dorsal fin all the way to the belly. As a member of the Family Acanthuridae, the convict tang (Acanthurus triostegus) exhibits all of the features characteristic of the group. Roughly oval in outline, it is highly compressed laterally (from side to side), has a small mouth and eyes set high on the head.
Surgeonfishes are named for the sharp blades they bear on either side of the tail. The blades can be exposed by flexing the tail, and are used in competition and defense. In the manini, these blades are only weakly developed and are visible only on very large specimens. Manini probably gain protection from schooling and from their color pattern, the bars that give them their common English name, convict tang. These vertical bars are a kind of "disruptive coloration" and may serve to break up the body outline, making it harder for a predator to target an individual fish.
The convict tang can be found in nearly all nearshore habitats, from tidepools and reef flats to deeper waters, 150 feet (45 m) down the reef slope. During the day, manini are seen individually, in small groups, or in large schools, grazing on fine algae that grows over rock and coral surfaces. The small, slightly down-turned mouth of the manini contains flexible, comb-like teeth well adapted to grazing on the algae that makes up its diet. Like other herbivores, it spends a great deal of its time feeding and so will usually be found picking seaweed from the rocks and reef framework. Algae feeders play a crucial role in coral reef ecosystems. By keeping algae in check, they prevent fast growing seaweeds from choking out more slowly growing corals
The Yellow Tang (Zebrasoma flavescens) is a saltwater fish species of the family Acanthuridae. It is one of the most popular aquarium fish.
Yellow tang are in the surgeonfish family. Adult fish can grow to 20 centimetres (7.9 in) in length, and 1–2 centimetres (0.39–0.79 in) in thickness. Adult males tend to be larger than females. All individuals of this species are bright daffodil yellow in color. At night, the yellow coloring fades slightly and a prominent brownish patch develops in the middle with a horizontal white band. They rapidly resume their bright yellow color with daylight.
They have an arrow-like shape due to their dorsal and ventral fins being almost an extension to their bodies, and a long snout-like mouth used (as with other tangs) to eat algae. They also have a sharp spine located near their tail. They have become a popular fish for marine aquarists of all skill levels, as the fish tends to be active, hardy, and nonaggressive when kept with dissimilar species.
The Achilles Tang, also known as the Red-tailed Surgeon, or Achilles Surgeonfish, is very dark brown to purple. It has bright highlights of white and orange around the dorsal, caudal, and anal fins. A white marking is also present on the gill covers and a striking orange teardrop is found near the caudal fin. The juveniles of this species have an orange marking by the tail in the shape of a streak instead of being teardrop in shape.