4.07.2013

Sharks on the Coral Reef

Zebra sharks (Stegostoma fasciatum) have black and white stripes when they are young but lose the stripes and develop spots as adults. These solitary night hunters have very flexible bodies and can swim into tight places to search the cracks and crevices of the reef for small fish, snails, and clams and other mollusks. During the day, they rest on sandy ocean floor near the reef, lying with their mouths open and facing the currents to keep water flowing over their gills. The adults reach lengths of 10 feet (3.1 m).

Zebra sharks (Stegostoma fasciatum)
Zebra sharks (Stegostoma fasciatum)


An easily identifiable reef animal is the nurse shark (Ginglymostoma cirratum), a species that is distinguished by skin flaps on the nose and barbels on the chin. This docile, unaggressive bottom feeder rests on ledges and in caves. When feeding, a nurse sharks sucks up its food by creating a vacuum that pulls the prey into its mouth. Some of this shark’s favorite foods are mollusks and crustaceans, which it crushes with rounded teeth. Adult nurse sharks can reach lengths of 8 feet (2.4 m).

nurse shark (Ginglymostoma cirratum)
Nurse shark (Ginglymostoma cirratum)


The blacktip reef shark (Carcharhinus melanopterus) has a white flash on its side and a black tip on its tail. Active swimmers and aggressive hunters, blacktips work together to round up schools of fish into compact groups before attacking in a feeding frenzy. These sharks grow to be about 5 feet (1.5 m) long. In contrast, the whitetip reef shark (Triaenodon obesus) is very docile, spending the day lying beside other whitetips in a cave or on a ledge. These animals feed at night, moving around the reef shyly, hunting octopuses, lobsters, crabs, and small fish on the floor of the reef. The 5-foot (1.5-m) long animal can easily be identified by the white markings on the tips of their fins.

reef shark (Carcharhinus melanopterus)
Reef shark (Carcharhinus melanopterus)


A Japanese wobbegong shark (Orectolobus japonicus) may be difficult to spot on the reef. This quiet animal has splotchy skin that camouflages it against the reef’s soil and rocks. The wobbegong lies patiently on the bottom, grabbing prey that unwittingly swim too close. The shark grasps its chosen meal in daggerlike teeth, letting it squirm till exhausted. Then the wobbegong turns the prey so that it can be swallowed headfirst, a technique that keeps the victim’s fins from getting caught in the shark’s throat.

Orectolobus japonicus
Orectolobus japonicus


The reef’s smooth hammerhead shark (Sphyrna zygaena) is one of 10 species of hammerheads, all of which have flattened projections at the sides of their heads. The shark’s eyes are mounted on the outer edges of the head lobes, and their nostrils are set far apart. Hammerheads can grow to lengths of 14 feet (4.3 m), and they aggressively hunt fish and rays, although they will scavenge, too. In the summer, groups of hammerheads may migrate to cooler water.

hammerhead shark (Sphyrna zygaena)
Hammerhead shark (Sphyrna zygaena)