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Featured Elasmobranch – Galapagos Shark

January 2009





Identification: A medium to large requiem shark with a relatively long rounded snout, fairly large eyes, the first dorsal fin originating over the inner margin of the pectoral fins, and a low interdorsal ridge. The upper teeth are rather large, broadly triangular, erect, and with a serrated cusp; lower teeth more slender, erect, and serrated. The dorsal surface color is brownish to gray becoming a light pale below; an inconspicuous light stripe extends anteriorly along the flanks from the pelvic region; fin tips are usually dusky colored.

Size: The maximum total length has variously been reported as between 300-370 cm.

Distribution: Galapagos sharks are circumtropical with a patchy distribution in warm temperate to tropical seas mostly around oceanic islands.

Habitat: A habitat limited species that can be very abundant in areas where it occurs. It prefers clear water over rugged coral or rocky bottoms. Although it will come to the surface it is often observed swimming in large aggregations near the bottom. A coastal pelagic species ranging from surface waters to 180 m on insular and occasionally continental shelves. Despite its tendency to stay close to the coast, it has been known to make considerable open ocean crossings (~50 km) between island habitats. Juveniles are found at shallower depths >25 m, while adults occur more offshore.

Biology: A viviparous species, with a yolk-sac placenta producing 6-16 pups per litter that range from 57-80 cm at birth. Adult females, which usually mature at 215-250 cm, are often observed with mating scars around the gills, fins and body; males mature at a slightly smaller size at between 205 and 235 cm. Galapagos sharks mature between 6-9 years with a maximum estimated age of 24 years. They commonly feed on various reef fishes (e.g. moray eels, parrotfishes, surgeonfishes, and squirrelfishes), octopuses and squid, and crustaceans. They has been known to eat other sharks, rays and cetaceans more than other smaller requiem sharks and have been documented to prey on sea lions and marine iguanas off the Galapagos Islands.

General interest: The Galapagos shark is common to abundant in its particular habitat and can be found in aggregations, but not in coordinated schools. It often swims along the bottom where it feeds, but will come to the surface to investigate disturbances such as anchored boats. It is a very inquisitive shark that is potentially dangerous and exhibits a threat display with an arched back, raised head, lowered caudal and pectoral fins while twisting and rolling. It can be aggressive and has been implicated in attacks on human. It is on the IUCN Red List as Near Threatened because of its patchy distribution, high levels of fishing pressures from tuna longline fisheries, targeted drop-line fishing and recreational/tourism based anglers and low intrinsic rebound potential. This species acclimates well in captivity and is frequently a display shark in many public aquaria.
By Kelsey James
Pacific Shark Research Center
Moss Landing Marine Laboratories
8272 Moss Landing Road, Moss Landing, CA 95039