Galápagos Shark

One of the largest species in its genus, the Galapagos shark commonly reaches 3.0 m (9.8 ft) long. The maximum length has been variously recorded as 3.3 m (11 ft) to 3.7 m (12 ft). The maximum recorded weight is 195 kg (430 lb) for a 3.0 m (9.8 ft) long female (longer specimens having apparently been unweighed). This species has a slender, streamlined body typical of the requiem sharks. The snout is wide and rounded, with indistinct anterior nasal flaps. The eyes are round and of medium size. The mouth usually contains 14 tooth rows (range 13–15) on either side of both jaws, plus one tooth at the symphysis (where the jaw halves meet). The upper teeth are stout and triangular in shape, while the lower teeth are narrower; both upper and lower teeth have serrated edges.

The Galapagos shark is found mainly off tropical oceanic islands. In the Atlantic Ocean, it occurs around Bermuda, the Virgin Islands, Madeira, Cape Verde, Ascension Island, Saint Helena and São Tomé Island. In the Indian Ocean, it is known from Walter's Shoal off southern Madagascar. In the Pacific Ocean, it occurs around Lord Howe Island, the Marianas Islands, the Marshall Islands, the Kermadec Islands, Tupai, the Tuamotu Archipelago, the Juan Fernández Islands, the Hawaiian Islands, the Galapagos Islands, Cocos Island, the Revillagigedo Islands, Clipperton Island, and Malpelo. There are a few reports of this species in continental waters off the Iberian Peninsula, Baja California, Guatemala, Colombia, and eastern Australia.

The primary food of Galapagos sharks is benthic bony fishes (including eels, sea bass, flatfish, flatheads, and triggerfish) and octopuses. They also occasionally take surface-dwelling prey such as mackerel, flyingfish and squid. As the sharks grow larger, they consume increasing numbers of elasmobranchs (rays and smaller sharks, including of their own species) and crustaceans, as well as indigestible items such as leaves, coral, rocks, and garbage. At the Galapagos Islands, this species has been observed attacking Galapagos fur seals (Arctophoca galapagoensis) and sea lions (Zalophus wollebaeki), and marine iguanas (Amblyrhynchus cristatus).

The Galapagos shark is often the most abundant shark in shallow island waters. In their original description of this species, Snodgrass and Heller noted that their schooner had taken "several hundred" adult Galapagos sharks and that "thousands" more could be seen in the water. At the isolated Saint Peter and Paul Rocks along the Mid-Atlantic Ridge, the resident Galapagos sharks have been described as "one of the densest shark populations of the Atlantic Ocean". At some locations they form large aggregations, though these are not true schools.

Inquisitive and persistent. However, several live-aboard boats take divers to Wolf and Darwin, the northernmost Galapagos islands, every week specifically to dive in open water with these sharks where they and the scalloped hammerheads accumulate in numbers, and only a few incidents have been reported. They are known to approach close to swimmers, showing interest in swim fins or hands, and are drawn in large numbers by fishing activities. Fitzroy (1839) observed off St. Paul's Rocks that "as soon as a fish was caught, a rush of voracious sharks was made at him, notwithstanding blows of oars and boat hooks, the ravenous monsters could not be deterred from seizing and taking away more than half the fish that were hooked". Limbaugh (1963) reported that at Clipperton Island "at first, the small sharks circled at a distance, but gradually they approached and became more aggressive ...