Shark of the month: Galapagos shark

The Galapagos shark (Carcharhinus galapagensis) is one of the larger species of requiem sharks with an average lenght of 3.5 meters. The appearance of the Galapagos shark is quite similar to reef sharks and dusky sharks which makes it difficult to spot the differences and to identify the Galapagos shark. Galapagos sharks can be found worldwide in small isolated spots surrounding oceanic islands. The largest concentration of Galapagos sharks can be found around the Galapagos Islands, where this species of sharks is abundant.

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Picture by: Tomas Kotouc

Anatomy and appearance

The Galapagos Shark can grow an average of approximately 3.5 meters and they weigh about 190 kg. Coloration is brownish grey above and white below with faint white stripes on the sides. An identifying feature of the Galapagos Shark is its slender, streamlined body. They have a large first dorsal fin, which is falcate with a rounded tip. The dorsal fin originates over the rear tips of the pectoral fins, which are also large with pointed tips. It has a wide and rounded snout and the upper and lower jaws contain 14 rows of serrated teeth on either side, plus one tooth at the symphysis. Upper teeth are broad and triangular, whereas lower teeth are narrow.

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Habitat

Galapagos sharks are found over shelves near the coast in warm and temperate waters. They prefer rugged reef habitats with converging currents and are known for grouping together around rocky islets with clear water. Adults have been reported at depths of 180m, whereas juveniles only venture to depths of 25 meters. Although it is a coastal pelagic species, Galapagos sharks have been known to cross the ocean with sightings 50 kilometers from land.

Diet

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Picture by: Tomas Kotouc


Galapagos sharks are often encountered in large groups. They are active, apex predators who feed mainly on bottom-feeding bony fish and occasionally eat cephalopods. Larger Galapagos sharks
have a much more varied diet, consuming other sharks, marine iguanas, sea lions, and occasionally seabirds.

Population

Reproduction is ovoviviparous, with females giving birth to 4 to 16 pups every two to three years. Mating takes place from
January to March with a gestation period of one year. The size of pups at birth is about 60 to 80cm. Juveniles tend to remain in shallow water to avoid predation by other adult Galapagos Sharks. Males mature at 2.1 to 2.5 meters (6 to 8 years), with females maturing at 2.2 to 2.5m (7 to 9 years). Neither sex is thought to reproduce until 10 years of age. The lifespan of the Galapagos shark is at least 24 years.

Conservation

The International Union for Conservation of Nature (IUCN) has declared the Galapagos Shark as near threatened. The reason is its low reproductive rate limiting its ability to withstand population depletion. The Galapagos Shark is fished across many parts of its range, and its fragmented distribution has resulted in the species being extirpated in some areas. The populations surrounding the Galapagos Islands and Kermadec Islands are protected within marine reserves.

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Picture by: Tomas Kotouc

Relationship to humans

Galapagos sharks are bold and active predators. There are situations known where these sharks have behaved aggressively towards humans. Therefore Galapagos sharks are considered potentially dangerous.

 

Originally written by Ian Murphy and edited by Isabelle Walter

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