Coral Reef Fish
Of all vertebrate animals that dwell on coral reefs, it is the fishes that are by far the most numerous, varied, and critical to coral reef health.
In the Greater Caribbean region alone some 500-600 species of coral reef fish are recognized; the Indo-Pacific region houses perhaps 8-10 times that number.
While entire books can (and have) been written about these fascinating animals, here we provide an introduction to two broad aspects of the biology and ecology of coral reef fishes: (1) physical adaptations for coral reef life, and (2) feeding strategies.
Adaptations For Coral Reef Life
The coral reef environment has a physical structure that is radically different than that of the surrounding open ocean. Fishes that live in reef habitats have therefore evolved a host of specialized traits well suited to their colorful and complex homes.
Reef Fish Shape
The body shape of fishes that dwell on coral reefs differs in a number of crucial ways from that of most other fishes.
Many species have evolved thin, flattened bodies that are effective in making sharp turns. This trait greatly facilitates a fish's ability to quickly maneuver about the solid reef.
The functionality of the pancake-like body shape is further enhanced by specialized positioning of the pectoral and pelvic fins. These are situated and oriented on the body in a way that facilitates sharp turns and sudden stops.
Coral Reef Fish Color Patterns
Coral reef fishes are perhaps best known for their bold, striking color patterns, which differ greatly from the typical monotonic "silvery" sheen we usually associate with fishes in general.
Granted, some of these patterns might seem outlandishly "showy" when viewed in artificial (e.g., aquarium) settings.
Nonetheless these color patterns - garish as they are - serve any number of functional roles in the lives of these animals, including concealment, mate recognition, and warning.
Mouths And Teeth" Feeding Apparatus
Coral reefs offer a vast array of different types of possible fish prey items. As might be expected then, there are varieties of coral reef fish species well adapted to make use of each of these ready food resources.
For example, the herbivorous parrotfishes (photo, right) have evolved large, beak-like mouths perfectly adapted to scrape microalgae from the surfaces of coral colonies.
In contrast, the equally herbivorous surgeonfishes have small mouths armed with numerous small teeth adapted for cutting and eating macro-algae.
Many carnivorous reef fishes like the pomadasyids (grunts) and lutjanids (snapper) possess generalized mouths that enable them to take all sorts of small to medium-sized prey such as small fishes and invertebrate animals.
Diversity of Coral Reef Fishes
We arranged some of the major families of coral reef fishes by feeding strategy, with four major groups recognized: herbivores, planktivores, benthic carnivores, and piscivores.
These categories are not mutually exclusive. For example, many so-called "herbivores" sometimes feed on small animals, while some "piscivores" may also occasionally take larger invertebrates. Some species may feed as planktivores while young but switch to a piscivorous lifestyle as adults.
Herbivorous fishes are those that feed mainly or entirely on plant material.
Planktivorous coral reef fishes are those that prey upon small animal plankton (zooplankton).
The term "benthic carnivores" (also sometimes referred to as benthivores) is used here to describe fishes that prey on a variety of animals living on or near the sea floor.
Some other common daylight benthic carnivores that hunt and feed on or near the reef include the blennies (Blennidae), gobies (Gobiedae), wrasses (Labridae), and goatfishes (Mullidae).
Piscivorous coral reef fish are those that prey mainly or entirely upon other fishes. There are three different basic hunting strategies employed by such predators (see below).