A tenacious requiem shark
The Galapagos shark (Carcharhinus galapagensis) is a species of requiem shark, in the family Carcharhinidae, found worldwide. This Galapagos shark prefers clear reef environments around oceanic islands. It is a large shark that reaches 9.8 feet. They have a wide variety in their diets. Galapagos sharks are bold and have behaved aggressively towards humans and are thus regarded as dangerous.
Family: Carcharhinidae – Requiem sharks
Common Name– Ground Sharks
Common Name– Requiem Sharks
Status: IUCN Red List NEAR THREATENED
Average Size and Length: The average length of a Galapagos shark is 9.8 feet, with a possible maximum of 11 to 12 feet.
Average Weight: The maximum recorded weight of a Galapagos shark is 430 pounds.
Teeth and Jaw: The mouth usually contains 14 tooth rows (range 13–15) on either side of both jaws, plus one tooth at the symphysis. The upper teeth are stout and triangular in shape, while the lower teeth are narrower; both upper and lower teeth have serrated edges.
Head: The snout of the Galapagos shark is wide and rounded, with indistinct anterior nasal flaps. The eyes are medium and round.
Demographic, Distribution, Habitat, Environment and Range: Galapagos sharks can be found over continental and insular shelves near the coast, preferring rugged reef habitats with clear water and strong converging currents. They are also known to congregate around rocky islets and seamounts. The Galapagos shark is capable of crossing the open ocean between islands and has been reported at least 31 miles from land. Juveniles seldom venture deeper than 82 feet while adults have been reported to a depth of 590 feet.
The Galapagos shark is found mainly off tropical oceanic islands. In the Atlantic Ocean, it can be found around Bermuda, the Virgin Islands, Madeira, Ascension Island, Cape Verde, Saint Helena and São Tomé Island. In the Indian Ocean, it can be found from Walter’s Shoal off southern Madagascar. In the Pacific Ocean, it can be found around Lord Howe Island, the Marshall Islands, the Marianas Islands, the Kermadec Islands, Tupai, the Tuamotu Archipelago, the Hawaiian Islands, the Galapagos Islands, Cocos Island, the Revillagigedo Islands, Malpelo, and Clipperton Island. There are some sightings of the Galapagos shark in continental waters off eastern Australia, the Iberian Peninsula, Baja California, Guatemala, and Colombia.
Diet: The primary food of Galapagos sharks are benthic bony fishes like sea bass, eels, flatfish, flatheads, and triggerfish. They are also known to eat octopuses. They also occasionally take surface-dwelling prey such as mackerel, flying fish and squid. As they grow larger, they consume increasing numbers of elasmobranchs like rays and smaller sharks, including other Galapagos sharks. They also are known to eat crustaceans, as well as indigestible items such as leaves, coral, rocks, and even garbage.
At the Galapagos Islands, the Galapagos shark has been observed attacking Galapagos fur seals, sea lions, and marine iguanas.
Aesthetic Identification: The Galapagos shark has a slender, streamlined body and is brownish-grey with counter-shaded white belly, with a faint white stripe on the side.
The first dorsal fin is tall and moderately falcate, with the origin over the pectoral fin rear tips. It is followed by a low midline ridge running to the second dorsal fin. The second dorsal fin originates over the anal fin. The pectoral fins are large with pointed tips. The edges of the fins are darker but not prominently marked.
The Galapagos shark can be distinguished from the Dusky shark in having taller first and second dorsal fins and larger teeth, and it can be distinguished from the Grey Reef shark in having a less robust body and less pointed first dorsal fin tip. The number of precaudal vertebrae is also different. There are 58 in the Galapagos shark, 86–97 in the Dusky shark, and 110–119 in the Grey Reef shark.
Biology and Reproduction: A known parasite of the Galapagos shark is the flatworm Dermophthirius carcharhini, which attaches to the shark’s skin.
A bluefin trevally was documented and seen rubbing against the rough skin of a Galapagos shark to rid itself of parasites.
The Galapagos shark is viviparous. Females bear young once every 2–3 years. Mating takes place from January to March. The gestation period is estimated to be around one year; the spring following impregnation, females move into shallow nursery areas and give birth to 4–16 pups. The size at birth has been reported to be 2.00–2.62 feet. There have been observations of free-swimming juveniles as small as 1.87 feet long in the eastern Pacific, which suggest that birth size varies geographically. Juvenile sharks remain in shallow water to avoid predation by larger adults. Males mature at 6.9–8.2 feet long and between 6 and 8 years old, while females mature at 7.2–8.2 feet long and between 7 to 9 years old. Neither sex is thought to reproduce until 10 years of age. The lifespan of a Galapagos shark is at least 24 years.
Males are known to bite females during courtship.
Behavioral Traits, Sensing and Intelligence: The Galapagos shark displays threat gestures to warn competitors in the search for food. At some locations they form large aggregations, though these are not true schools. When confronted or cornered, the Galapagos shark may perform a threat display like that of the Grey Reef shark. The shark performs an exaggerated, rolling swimming motion while arching its back, lowering its pectoral fins, puffing out its gills, and gaping its jaw. The Galapagos shark may also swing its head from side to side, so as to keep the perceived threat within its field of vision.
Speed: It is estimated that the cruising speed of Galapagos shark is around 3.2k/hr
Galapagos Shark Future and Conservation: The Galapagos shark is caught commercially, and the meat is said to be of excellent quality. Because of its low and slow reproduction rate, it is at risk. There are several conservation efforts and sanctuaries establish to protect the Galapagos shark.
Galapagos Shark Recorded Attacks on Humans: The Galapagos shark is potentially dangerous to humans There have been at least 3 records of unprovoked attacks with at least 2 fatalities. This is a popular shark to dive with. In the past, repellent methods have been unsuccessful, and therefore it is always to exercise caution if diving near Galapagos shark. Respect their boundaries.