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 body plan

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.

Parrotfish beak

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.

Herbivores

Herbivorous fishes are those that feed mainly or entirely on plant material.

Parrotfishes are the largest and most colorful of coral reef herbivores. They are named for their brilliant hues and beak-like mouths. Parrotfishes are believed to play a key role in maintaining coral reef health through their feeding activities.

Surgeonfishes and the closely related rabbitfishes (see below) are the mid-size models of herbivorous coral fishes. The name “surgeonfish” stems from the retractable scalpel-like spines at the base of each side of the tail, used as defensive weapons.

Rabbitfishes are named for their blunt, elongated snouts. These herbivores are closely allied with the surgeonfishes, and are common members of reef fish assemblages throughout the Indo-Pacific region from Hawaii to the Red Sea.

Dameslfishes: Unlike the wide-ranging parrotfishes, surgeonfishes, and rabbitfishes, small herbivorous damselfishes are more sedentary, territorial “farmers” that maintain and vigorously guard small patches of algae on the reef.

Planktivores

Planktivorous coral reef fishes are those that prey upon small animal plankton (zooplankton).

Open Water Plankton Feeders: The daytime open-water plankton feeding “fraternity” of coral reef fish consists of a hodgepodge of species of diverse heritage, including damselfishes, wrasses, snappers, sea basses, and surgeonfishes.

Benthic Planktivores: A diverse group of small daytime plankton feeders – such as the jawfish – avoid the dangers of open-water hunting by remaining close to the safety of the reef or other nearby benthic habitats while capturing their tiny prey.

Nocturnal Planktivores: As darkness falls, the “day shift” of planktivores seeks shelter within the reef and are replaced by a “night shift” of species adapted to low light conditions. These night hunters include cardinalfishes, squirrelfishes and soldierfishes.

Benthic Carnivores

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.

Butterflyfishes are among the most ubiquitous and colorful of daytime reef benthivores. Their forcep-like mouths armed wih fine comblike teeth serve them well in browsing on exposed coral polyp tentacles and other tiny reef invertebrates.

Triggerfishes (pictured left) – and their close relatives the filefishes, trunkfishes, and puffers – have evolved to become masterful benthic carnivores, often feeding far from the shelter of the reef. This of course requires strong defenses like stout spines.

Many grunts and snappers shelter on the reef by day and venture out only at night to feed in open sand and seagrass habitats. On Caribbean reefs, some species migrate nightly to foraging areas 1/4 mile or more away from their “home” reef.

Some other common daylight benthic carnivores that hunt and feed on or near the reef include the blennies (Blenniidae), gobies (Gobiidae), wrasses (Labridae), and goatfishes (Mullidae).

Piscivores

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).

Pursuing Predators are those that rely on sheer speed to run down prey in open water. These fishes have streamlined bodies, and are capable of extremely fast attack speeds. Examples include the jacks (Carangidae, pictured left), mackerels, and many sharks.

Stalking Predators utilize stealth to approach their prey before striking. Common coral reef fish employing this strategy include barracudas, needlefishes, and trumpetfishes. All have slender, elongated bodies that present a minimal head-on profile to prey.

Ambush Predators rely on disguise and stillness to hunt. They wait motionless for unsuspecting victims to stray into striking range. Common ambush piscivores include frogfishes, lizardfishes (pictured left), flatfishes, groupers, and scorpionfishes.

Coral Reef Food Web ►

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