Carcharhinus galapaguensis, C. falciformis, C. obscurus.
Requiem sharks: Galapagos, Silky, and Dusky sharks
Tiburón galapago, sedoso, y oscuro

Family: CARCHARHINIDAE (Requiem Sharks)

Description

Requiem sharks are one of the largest and best-known families of sharks. They are strong active swimmers that occur singly or in small to large groups. Most species are torpedo-shaped, and slender-bodied with rounded snouts. They may be gray to brown and usually have light-colored undersides. Because so many species are similar to each other, individual species are difficult to recognize. The species commonly seen in the Gulf of California and Revillagigedo islands include: the Galapagos shark Carcharhinus galapaguensis,the silky shark Carcharhinus falciformis, and the dusky shark Carcharhinus obscurus.

Depending on the species, requiem sharks range from less than a meter (less than 40 inches) to at least 7.4 m (just over 24 feet.)

Range and Habitat

Requiem sharks are largely circumtropical, although some species occur in temperate waters. Though mostly pelagic, they may be oceanic or coastal.

Natural History

Requiem sharks have sophisticated senses of vibration and electro-conductivity. Most are voracious predators and feed on other fishes, including sharks and rays; squids, octopuses, lobsters, turtles, marine mammals, sea birds, and in some cases garbage and debris.

Although shark attacks on humans are rare, about half of all reported attacks are from requiem sharks. Johnson and Nelson, described a behavior in another requiem shark (the gray reef shark) to signal distress and possible attack. Typically this may include: arching its back, holding the pectoral fins pointed downward, snapping the jaws, raising its snout (sometimes with the mouth open), and swimming with exaggerated jerky movements. In close encounters, the shark will swim in figure 8 loops. Results observed in Eniwetok...suggest that sharks are reacting defensively as if they are being threatened or their territory invaded. The brown colored Galapagos shark can be more aggressive than hammerheads, but they are very curious and move slowly to check the surroundings.

Johnson, R. H. and D. R. Nelson. 1973. Agonistic display in the Grey reef shark, Carcharhinus menisorrah, and its relationship to attacks on man. Copeia (1)76-84.