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3/21/21

Great Hammerhead Shark

The great hammerhead shark is the biggest of the 9 species of hammerhead sharks. There are a wide range of sizes, but the biggest can get up to 20 feet long and 900 pounds, though a more common range would be 12-15 feet. Naturally they may live up to 44 years. They live in temperate and tropical waters across the world, and during the summer often migrate towards cooler waters. Their distinguishing features include their extra tall dorsal fins, serrated triangle teeth, and ‘most hammer shaped’ head.

Great hammerhead sharks eat fish, octopi, squid, crustaceans, and their favorite - stingrays. They may also occasionally eat other sharks. Interestingly, they don’t seem to be bothered by stingray barbs. They hunt at dusk, usually by pinning prey with their hammerhead and tearing pieces off. Their wide-set eyes give them a great range of sight for spotting prey, and their special sensory organs, called ampullae, allows them to detect the electrical fields of other animals. This allows them to find stingrays and other prey buried under sand. This may also be the reason for their hammer-shaped head: it creates more area for their sensory organs to be spread out over. Hammerheads potentially could hunt humans, but they don’t and are considered harmless unless attacked. Adults have no natural predators except humans.

Great hammerheads reproduce once every two years, and have 13-42 live pups in the spring and summer. They grow relatively fast, compared to other hammerheads, and reach maturity at around 5-9 years old.

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Image Courtesy of Derek Heasley

The main reason the Great hammerhead is endangered is because of humans. They have particularly large fins, for which they are hunted to make shark fin soup. They are also hunted for meat, liver oil, hides, to be used for fishmeal, and sport. By-catch, or being caught accidentally, also threatens them. Captured hammerheads are likely to die: 90% die when caught in fisheries. Because of overfishing, great hammerheads are listed as endangered on the IUCN red list.

Great hammerheads are an important predator to their environment. Without predators like the great hammerhead, prey species may get out of control and destroy too much of whatever their prey is, eventually destroying their habitat. Usually, everything is in balance, but it is a very delicate balance.

The main thing to do is educate people who live near and off the sea. We should also work to make laws protecting hammerheads from becoming shark fin soup, and create better technology to prevent bycatch and overfishing.

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Image courtesy of Theresa Guise

Image courtesy of Craig O'Connell

Image courtesy of Jongsung Ryu

Image Courtesy of Tracey Jennings

Works Cited

Hammerhead Sharks. (2018, September 24). Retrieved October 24, 2020, from https://www.nationalgeographic.com/animals/fish/group/hammerhead-sharks/

Great Hammerhead Shark. (n.d.). Retrieved October 24, 2020, from https://oceana.org/marine-life/sharks-rays/great-hammerhead-shark

Great Hammerhead Shark. (n.d.). Retrieved October 24, 2020, from https://www.georgiaaquarium.org/animal/great-hammerhead-shark/

Cover image courtesy of Craig O'Connell