Fish are gill-breathing vertebrates (animals with backbones) that typically have scales and fins. Of the estimated 20,000 species of fishes living on the earth today, about 60 percent are marine (live in saltwater), and most of these inhabit the continental shelves of warm seas (Cohen 1970). Based upon lists by Dahlberg (1975), Scott (Unpub.) and Gilligan (Unpub.), it is likely that there are over 300 exclusively marine fish species in Georgia's coastal, inner-shelf, and midshelf areas. Roughly one-third of these are considered reef fishes and many others are indirectly associated with reefs.

The systematic checklist (page 69) contains 150 species in 52 families, 12 orders,and 2 classes. The list contains all the fish species known to occur at Gray's Reef National Marine Sanctuary and species that are known to occur along the Georgia coast at the depth of Gray's Reef but have not yet been reported at the Sanctuary. Species that have been collected, photographed or observed at Gray's Reef are annotated with symbols that are explained in a key at the beginning of the list. Species that were collected or photographed during the study and which have not been previously reported from the inner- and midshelf of Georgia are also included in the list.

The fishes that inhabit Gray's Reef encompass a wide variety of sizes, forms, and ecological roles. Often, the designation of species as a 'reef fish' is unclear because species vary widely in their degree of association with reefs and hard bottoms. It is clear, however, that after their arrival as larvae or juveniles, some fish species are totally dependent upon the reef for food and cover, rarely venturing away from it during their life. Examples include angelfishes, damselfishes, and sedentary reef dwellers such as the seahorse, the soapfish, blennies, and gobies. Though most are day-active, many are nocturnal, seeking refuge within the structure of the reef during the day and emerging at night to feed. These include the bigeyes, cardinalfishes, squirrelfishes, and morays.

Some pelagic (open-water rather than bottom-dwelling) species aggregate near reefs in search of prey. These include the jacks, mackerels, bluefish, cobia, barracuda and schooling fishes. Many gobies, some wrasses, basses, and porgies inhabit the sand near reefs. Finally, some species live in or on other species. Examples include the pearlfish which lives in a sea cucumber, the sharksuckerand the pilotfish, that 'hitch rides' on large animals and the silver driftfish, which lives in association with jellyfish.