Classification of the trophic categories of fishes associated with coral reefs has been done by a few workers, i.e., Hiatt and Strasburg (1960) in the Marshall Islands, Randall (1967) in the West Indies, and Vivien (1973) in Madagascar (Table 2), As noted by Smith (1978), such classifications arc somewhat different in each locality. We classify the reef fishes examined at Minatogawa into the following eight categories on the basis of gut content analysis, and furthermore subdivide some categories into the two or three groups. Species in each category are listed in Table 3.

A. Herbivores

This category can be segregated into two groups, grazing and browsing herbivores, based on the feeding mechanism and diet composition.

A-1. Grazing herbivores
Grazers obtain algae by scraping or rasping the surfaces of substrata such as dead coral branches or rocks, so that large amounts of calcareous material arc contained in the digestive tracts, along with algae (Hiatt and Strasburg, 1960; Keenleyside, 1979).

A-2. Browsing herbivores
These fish bite or tear off pieces of algae growing on the substrata without (or at least rarely) ingesting any of the inorganic material (Hiatt and Strasburg, 1960; Jones, 1968; Keenleyside, 1979).

B. Zooplankton-feeders

This category can be subdivided into the following two groups.

B-1. Midwater zooplankton-feeders
This group includes predators that pick individual zooplankters, especially calanoid copcpods, in midwater above the reefs during the day. Filter-feeding predators, which strain the zooplankters from midwater by gill raker apparatus, were not found among the species that we examined.

B-2. Demersal zooplankton-feedera
These predators feed dominantly on demcrsal zooplankters that swarm in reef caves and crevices and coral heads or hide in or on the substrata during the day and disperse above the reefs at night. Their diets consist mostly of copepods (especially harpacticoids), mysids, gammaridean amphipods, cumaceans, isopods, tanaids, ostracods, polychaetes (in part), and various larval forms. Both diurnal and nocturnal predators are recognized in this group; the former includes syngnathids, pseudochromids, pomadasyids, callionymids, gobiids, and labrids, whereas the latter is made up of apogonids.

C. Benthonic animal-feeders

This category has often been subdivided into several groups (Table 2), because the species involved in this category hunt a great variety of prey by various feeding strategies. For example, in the West Indies Randall (1967) classified this category into three groups. The first group was sessile animal feeders that subsist primarily on sponges, anthozoans, tube-dwelling polychaetes, gorgonians, and tunicates. The second was "shelled"-invertebrate feeders that prey by crushing mostly gastropods, pelecypods, eehinodcrms, crabs, and hermit crabs with their jaws or pharyngeal teeth. The third was generalized carnivores that capture a variety of mobile benthonic animals such as crustaceans, worms, and small fishes. We can also segregate this category into two groups-mobile benthonic animal-feeders and sessile animal-feeders-according to the degree of prey mobility.

C-1. Mobile benthonic animal-feeders
On Minatogawa reefs, a great number of species has this food habit. These carnivorous predators mainly snap up small invertebrates such as decapods and stomatopods adapted to avoiding predation by quickly moving to refuge or resting places, e.g., crevices among the corals. But these predators sometimes hunt small fishes, gastropods, and dcmersal zooplanktera such as gammaridean amphipods.

C-2. Sessile animal-feeders
This group includes predators that pluck or anip off mostly spongca, sedentary polychaetes, sea anemones, octocorallian cords, and chitons. Most of these prey possess the ability to avoid prcdation by firmly adhering to the substrata or quickly withdrawing into their heavy defensive armor at the approach of danger. Furthermore, species that feed largely on slow-moving forms such as errant polychaetes and gastropoda are also categorized in this group.

D. Omnivores

All species in this category contain both algal and animal diets in their digestive tracts. We can subdivide it into three groups according to the relative abundance of these two types of prey.

D-1. Omnivores feeding largely on algae rather than animals
These fish contain an animal diet in an amount of 6-20% of the total diet volume, and the remaining items are algae.

D-2. Omnivores feeding largely on animals rather than algae
Algae form 6-20% of the total diet volume of these predators, and the remaining items are animals.

D-3. Generalized omnivores
Most omnivorous predators fall into this group. They feed on both algae and animals in about equal amounts.

E. Coral polyp-feeders

These predators feed selectively on only scleractinian coral polyps. In the Marshall Islands Hiatt and Strasburg (1960) subdivided this category into three groups. The first group was "browsers" that bite off individual polyps with protruding snouts and teeth projecting from small mouths. The second was "grazers" that scrape off the surfaces of living coral tips. The third was "feeders on branching coral tips" that break off living tips of branching corals with strong or fused teeth. In the present study most coral polyp-feeders have browsing habits, but the blenniid Emllias brevis and the tetraodontid Tetraodon nigropunctatus are placed in the second and third groups, respectively.

F. Ectoparasite-feeders

This category is represented by only the cleaner labrid Labroides dimidiatus which removes crustacean ectoparasites from the body, fins, gills, or mouth of other reef fishes.

G. Fish skin-feeders

These fish have a highly specialized feeding strategy: They form mimetic associations with harmless or nonpredatory reef fishes and feed by tearing pieces from the body or fins of other fishes.

H. Piscivores

This category includes predators that hunt only small fishes by ambushing or stalking. In the present study, species that capture both fishes and crustaceans such as decapods are categorized as mobile benthonic animal-feeders.