Coral reef communities support a larger number and greater diversity of fish than any other aquatic habitat. Reef fish are specialized for a variety of feeding strategies and habitats, adaptations that permit different species to feed within the same area and on similar food supplies. Damselfish, for example, primarily feed on algae that grow on top of the coral skeletons, but parrot fish prefer the algae within the coral polyps.
Many reef fish are predators of fish or invertebrates. Even though the most impressive hunting fish are large, there are an equal number of smaller, less obvious ones. Hunters patrol the area day and night, even at dusk and dawn when fish are moving to their refuges.
A good number of reef fish are plankton eaters, including soldierfish and cardinals. Plankton feeders are not closely related to one another but share similar lifestyles. Usually they have small, streamlined bodies and forked tails, which are good at delivering bursts of speed to escape predators. They tend to feed in groups for safety.
The plant-eating reef fish include surgeonfish and damselfish, animals that use their sharp-edged teeth to clean the coral reef of algae. Alga has a tendency to grow quickly and can eventually smother and “choke” a reef to death if it is not kept in check. Grazing fish are critical to maintaining the balance of algal cover on the reef while at the same time supplying themselves with a source of energy.
Large populations and intense competition have led to the development of reef fish that fill every niche of the ecosystem. Scientists are still working to discover all of the fish that make their homes around the reef and to understand the evolutionary pressures that have resulted in these varied and colorful reef residents.