- Also called:
- gray reef whaler
- Related Topics:
- shark
Galapagos shark
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What is a Galapagos shark?
The Galapagos shark (Carcharhinus galapagensis) is a type of requiem shark found in warm, clear waters, especially around reefs and oceanic islands, and gets its name from the Galapagos Islands, where it was first identified.
These sharks have a brown to grayish-brown dorsal surface and a lighter underside. They consume fishes, mollusks, and crustaceans, and are also known to eat marine reptiles, sea lions, seals, and trash. While they have few natural predators, young Galapagos sharks are vulnerable to cannibalism, and most mortality is due to human activities.
The Galapagos shark is currently listed as near threatened and has been protected from fishing in American Atlantic waters since 1999.
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Where can Galapagos sharks be found?
The Galapagos shark (Carcharhinus galapagensis) is a circumtropical species that lives in warm, clear waters, often near reef systems or oceanic islands, and over continental shelf areas. While Galapagos sharks are located worldwide, they are most common in tropical regions. They seem to like shallower water but have been found at depths of nearly 280 metres (919 feet). Studies have shown that Galapagos sharks can make steep dives reaching 680 metres (2,230 feet). They are often present in large numbers where they are found, sometimes accounting for 90–95 percent of the sharks in certain locations.
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What does a Galapagos shark look like?
The Galapagos shark is a ridgeback shark, named after the Galápagos Islands where it was first discovered. They are often found in warm, clear waters near reef systems or oceanic islands.
These sharks have a distinct appearance, with a prominent ridge between their dorsal fins. Their dorsal side is typically brown to grayish-brown, while their underside is lighter. They have a wide, rounded snout and longer, pointed pectoral fins. Growing to lengths of 3.0–3.5 meters (9.8–11.5 feet), the Galapagos shark is among the larger carcharhinid sharks.
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What do Galapagos sharks eat?
Galapagos sharks are not picky eaters; they consume a wide array of marine life. Their diet includes crustaceans, mollusks, and various fishes. They have also been known to prey on marine reptiles, sea lions, and seals. Additionally, the contents of their stomachs have revealed that they consume cephalopod mollusks like squid and octopus, and sometimes even smaller sharks. Around the Galapagos Islands, the sharks have been found to eat marine mammals such as sea lions and marine reptiles like iguanas.
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How do Galapagos sharks behave in their environment?
Galapagos sharks, a circumtropical species, favor warm, clear waters near reef systems or oceanic islands. They consume a variety of prey, including crustaceans, mollusks, fishes, marine reptiles, sea lions, seals, and even trash. They have been observed in feeding frenzies.
Though Galapagos sharks have few natural predators, younger sharks risk cannibalism from adults. The International Shark Attack File lists one fatal attack attributed to a Galapagos shark, so caution is advised when swimming with them, especially during fishing or spearfishing activities that might provoke them.
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Why are Galapagos sharks important to their ecosystem?
Galapagos sharks play a vital role in their ecosystem as apex predators. They consume various marine life, including crustaceans, mollusks, fishes, marine reptiles, sea lions, and seals, which helps maintain balance in the marine food web.
Shark finning and commercial fishing have caused a decline in shark populations worldwide. Since many shark species function as apex predators in marine ecosystems, they heavily influence the overall health of their habitats, so it has become important to monitor global shark populations and whether shark conservation measures are working.
The Galapagos Marine Reserve is one of the most important marine protected areas for sharks.
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Galapagos shark, (Carcharhinus galapagensis), shark species belonging to the family Carcharhinidae. Galapagos sharks are considered to be a circumtropical species with strong preferences for warm, clear waters near reef systems or oceanic islands and generally over continental shelf areas. Although Galapagos sharks are found worldwide, they are most commonly concentrated in tropical regions of the world’s oceans. The species was first described from specimens captured near the Galapagos Islands, from which it derives its name.
Natural history
The Galapagos shark is a ridgeback shark with a prominent ridge on the dorsal surface between the first and second dorsal fins. Its dorsal surface is brown to grayish brown, and its underside is lighter. This coloration is similar to that of the dusky shark (C. obscurus), a shark with which it is often confused, though the dorsal fins of the Galapagos shark are somewhat larger. The pectoral fins of the Galapagos shark are longer and more pointed, and it has a very wide and rounded snout.
The Galapagos shark is not as thoroughly studied as many other species and comparatively little is known of its life history patterns. Animals have been captured with total body lengths of 3.0–3.5 metres (9.8–11.5 feet), making it one of the largest carcharhinid sharks. Sexual maturity may be reached for males at a length of 170–236 cm (67–93 inches) and for females at a length of 235 cm (93 inches), though some estimates suggest maturity is reached at larger sizes. Little is known of their growth rates, though there is speculation that Galapagos sharks reach sexual maturity at ages of approximately ten years. Life spans have been estimated to be 20–25 years though, absent accurate studies of age and growth, these estimates are speculative.
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Habitat
Galapagos sharks seem to prefer shallower water but have been taken from depths as great as nearly 280 metres (919 feet). Satellite studies from French Frigate Shoals in the Hawaiian Islands have further shown that Galapagos sharks are capable of making bounce dives (that is, steep dives followed by rapid ascents) that reach 680 metres (2,230 feet). In shallow waters, they seem to prefer regions with strong currents though no explanation has been given for this particular preference.
That Galapagos sharks have also been taken from deeper waters suggests that they may venture into open ocean realms, perhaps as part of a movement or migratory behavior. Where they are found, they are generally present in large numbers. Some studies suggest that they account for up to 90–95 percent of the sharks present in some locations.
Predators and prey
Galapagos sharks consume crustaceans, mollusks, and fishes, but they have been known to eat or attack marine reptiles, sea lions, seals, and trash. Studies of stomach contents of Galapagos sharks reveal that fish constitute a significant percentage of the food they consume. Cephalopod mollusks such as squid and octopus are also present in large numbers, and small sharks may also be consumed. Around the Galapagos Islands, remains of marine mammals such as sea lions and marine reptiles such as iguanas have also been discovered to be prey items.
Galapagos sharks have few natural enemies. Although young sharks may succumb to cannibalism by adults, most of the mortality in the species is attributable to human activites. Galapagos sharks are actively hunted by local fishermen, who believe the species is aggressive and thus dangerous to humans. They may also die as bycatch from commercial fishing operations.
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The Galapagos shark is a viviparous (or live-bearing) species that nourishes its young through a placental attachment to the mother during embryonic development. Young are born at a length between 60 and 80 cm (23.6 and 31.5 inches). Litter sizes average eight to nine pups, but they can range from six to 16 pups. The gestation period is thought to be approximately one year and females may be reproductively active at two to three year intervals.
Relationship with humans
Galapagos sharks and other members of the family Carcharhinidae are commonly referred to as “requiem” sharks, the group of sharks often considered to be responsible for most attacks on humans. The potentially large sizes of Galapagos sharks and their tendency to be present in large numbers warrants special attention by divers and swimmers. They have been observed in feeding frenzies, and divers have reported witnessing threat behaviors including arching of the back, pointing of the pectoral fins, and shaking and quivering motions. Similar behaviors have been observed in other species as a territorial defense or a prelude to an attack. The International Shark Attack File lists one fatal attack in the Virgin Islands attributed to a Galapagos shark. Caution is recommended when swimming with this species, especially when fishing or spearfishing may excite and provoke the animals.
Conservation status
The Galapagos shark is listed by the International Union for the Conservation of Nature (IUCN) as “near threatened.” Very little is known of its natural rates of population replenishment and global movement patterns. It is the target of some commercial fisheries and is taken by long-lining (a commercial fishing practice that employs a long fishing line baited with numerous hooks). The species is also harvested for its fins or hunted by local fishermen who view its excitable and fearless nature as a threat to swimmers. In areas where it is found in high abundance, a directed fishery effort could conceivably reduce population numbers to a point where recovery would be challenged. The species is also found within several marine protected areas, including within a large “no-take” section of the Galapagos Marine Reserve, where fishing and other extractive activities are prohibited.