These fishes have considerable variation in both feeding methods and diet. Although most direct their attention towards bottom feeding or planktivory, in which they feed upon phytoplankton or Zooplankton in the water column, there are some remarkable exceptions. Goatfishes utilize their barbels, which bear chemosensory organs, to stir up the bottom and
detect prey. They also feed upon smaller invertebrates in sand, rubble, algal beds, or on coral pavement, and some species may take small fishes that they disturb. Archerfishes swim near the surface of the water and can detect visually, with a correction for light refraction, terrestrial prey on overhanging branches of trees and shrubs or blades of grass at the water's edge. Upon detecting the prey, usually an insect, archerfishes direct a stream of water drops toward that prey, knocking it to the water where it can be captured with the mouth and consumed. The drops are formed by compression of water by the gill covers and shot by forcing them along a groove formed by the tongue and palate. Archerfishes also consume floating fruits and flowers. Although galjoens have small mouths, they are capable of preying upon ascidians, mussels, barnacles, and other crustaceans. Galjoens also consume seaweeds. The sea chubs have a mixed feeding strategy and diet. Members of the subfamilies Kyphosinae (except the genus Gras) and Girelli-nae graze or pluck algae. Those in the subfamilies Scorpidi-nae and Microcanthinae are carnivores that feed upon benthic invertebrates. The jutjaws strain zooplankton from the water column. The sicklefishes feed upon small invertebrates they extract from soft sediments, usually mud. Monos have small, obliquely positioned mouths with a combination of brushlike teeth on their jaws, villiform teeth on the vomer, and palatines within the mouth. They use this combination to capture and feed upon small fishes, invertebrates, or plankton. The but-terflyfishes have been collectively described as microcon-sumers. Some species feed exclusively upon coral polyps, others upon small invertebrates on corals, rocks, coral pave ment, or crevices, and still others, such as Hemitaurichthys polylepis, forage for zooplankton in the water column. There is some plasticity in diet for a number of species. While Chaetodon trifascialis feeds only upon acroporid corals, C. punc-tatofasciatus will feed upon a variety of benthic invertebrates, corals, and even filamentous algae. The forcepsfish (Forcipiger flavissimus) uses its tubular snout to feed upon hydroids, fish eggs, and small crustaceans, and to excise pieces of the tentacles of polychaete worms, the tube feet of starfishes, and the pedicilaria of sea urchins. On the other hand, the longnose butterflyfish (F. longirostris), with its longer snout, feeds mainly upon small crustaceans that are taken whole. Angelfishes also
A pair of yellow goatfish (Mulloidichthys martinicus) foraging in bottom sediments for food. The barbels situated under their chins have chemosensory organs that allow goatfishes to detect potential prey. (Illustration by Joseph E. Trumpey)
have considerable plasticity in their diet, although perhaps less so compared to butterflyfishes. Pygmy angelfishes (Centropyge spp.) feed mostly upon filamentous algae, while Genicanthus angelfishes forage mainly for zooplankton in the water column and supplement their diet with benthic invertebrates or algae. Others in the family feed upon sponges, small soft-bodied invertebrates, fish eggs, and algae.
Little is known about the feeding habits and diets of the old-wife, boarfishes, and armorheads, but they appear to feed upon benthic invertebrates and fishes. Leaffishes, which can conceal themselves even in open water thanks to their ability to mimic leaves downed in water, are remarkably good predators upon fishes and invertebrates (mostly crustaceans, insects, and worms). However, one larger species from Southeast Asia, the catopra (Pristolepis fasciata), is primarily a herbivore that feeds upon filamentous algae, submerged land plants, seeds, and fruits, but will also take crustaceans and aquatic insects. Knife-jaws use their parrotlike beaks to break open and feed upon barnacles and mollusks. The hawkfishes feed upon small crustaceans and fishes they ambush from a perched position on a coral or rock, or from a resting position on the bottom. One species, Cyprinocirrhites polyactis, plucks zooplankton while hovering in the water column, and a second species, Cirrhitichthys aprinus, has been observed taking zooplankton as it darts out from soft corals into the water column along current-swept reef walls. Kelpfishes exhibit feeding behavior similar to hawkfishes and feed upon small invertebrates. The seacarps feed upon algae and other seaweeds they grab from the bottom with their mouths. The small mouths and thick lips of morwongs are used to feed upon small benthic or pelagic invertebrates, such as polychaete worms, crustaceans, mollusks, and echinoderms, or in some species, algae. At least one species, Chirodactylus grandis, feeds upon squid and small fishes. Trumpeters feed upon benthic invertebrates, although the members of the genus Men-dosoma feed upon zooplankton.
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