Family: KYPHOSIDAE, Sea-Chubs, Half Moons, Nibblers, Opaleyes, Rudderfishes
SEA-CHUBS, HALF MOONS, NIBBLERS, OPALEYES, RUDDERFISHES
The sea-chubs are medium sized fishes (to 78 cm) with body moderately deep, oval, compressed; head small; mouth small, horizontal and opens at the front; the top jawbone slips partially under the under-eye bone when the mouth is closed; teeth incisiform, bases set horizontally in mouth, rounded tips and a curved, hockey-stick shape; dorsal fin continuous, XI-XIV spines that fold down into a scaly groove, no notch after spines; anal fin III spines; tail fin concave to forked; pectoral and pelvic fins relatively short; origin of the pelvics behind the base of the pectoral fin; scales small, thick and rough, covering the body and head (except the snout) and soft portions of the median fins.
Most of these fishes are omnivorous, but feed mainly on benthic algae; their digestive tract is very long, as would be expected from their plant-feeding habits. However one eastern Pacific species is a mid-water feeding zooplanktivore. They sometimes occur in huge aggregations that swarm over the reef"s surface.
The family is found circumglobally and contains about 56 species in 15 genera. It is divisible into two subfamilies, the Kyphosinae and the Girellinae (sometimes regarded as separate families). The latter group is mainly subtropical or temperate in distribution. In our region there are 9 endemic species from 5 genera (1 endemic).