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Marine Life & Conservation Blogs

Creature Feature: Great Hammerhead Shark

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In this series, the Shark Trust will be sharing amazing facts about different species of sharks and what you can do to help protect them.

We’re kicking off the new year with a classic shark – the Great Hammerhead. Known for their distinct silhouette, the Great Hammerhead is the largest species of hammerhead on the planet.    

With a distinct notch on the centre of their head, the Great Hammerhead is light grey or brown above and white below. Reaching a maximum size of around six metres, this is a big shark. There are nine species of hammerhead. Identifying them often relies on looking at head shape. The Great Hammerhead has a much straighter front edge compared to the Scalloped and Smooth Hammerheads. 

The unique hammer-shaped head (a.k.a. cephlafoil) improves their manoeuvrability. As the position of their eyes enable them to see 360°. And enhances their ability to detect electrical currents, a sixth sense that all sharks have. Sharks have lots of tiny pores covering their head and snout, called ampullae of Lorenzini. These are extremely sensitive and can detect even the faintest of electrical fields. Including those generated by the Earth’s geomagnetic field, or muscle contractions in prey. The broad flat head of a hammerhead provides a much larger surface area for these pores. Which is why they’re so good at finding prey – such as stingrays – completely buried beneath the sand. 

Great Hammerheads are nomadic and seasonally migratory. They move towards the equator during the winter and then towards the poles during the summer. Unlike other species, they are solitary and migrate up to 1,200km (750 miles) alone.

The Great Hammerhead is Critically EndangeredPopulations have declined in recent years. They are targeted and also caught as bycatch.

Although large and powerful, research has shown that Great Hammerheads are quite fragile. They are particularly vulnerable to the stress of capture. Recent research has found that individuals that are hooked have a 50% chance of dying following release. Combating the declining populations comes down to, as always, implementing scientifically informed catch limits and enforcing these. 

The species is important for dive tourism in some areas. In the video below, head of marketing for the Shark Trust – Caroline, takes in the view as a Great Hammerheads cruise by. They are a true sight to behold.

SCIENTIFIC NAME:  Sphyrna mokarran

FAMILY:  Sphyrnidae

MAXIMUM SIZE:  610cm 

DIET:  Varied. Preference for stingrays, other rays and marine catfish.

DISTRIBUTION: Worldwide, tropical seas. 

HABITAT:  Coastal-pelagic and semi-oceanic. Close inshore to well offshore. 1-300m or more.

CONSERVATION STATUS: Critically Endangered


Images from Frogfish Photography 

Distribution Map from Wikimedia Commons 


For more amazing facts about sharks and what you can do to help the Shark Trust protect them visit the Shark Trust website by clicking here.

The Shark Trust is the leading UK-based shark conservation charity. The team works globally to safeguard the future of sharks, and their close cousins, the skates and rays. Engaging with a global network of scientists, policymakers, conservation professionals, businesses and supporters, to further shark conservation. Established in 1997 to provide a voice for UK sharks, the Shark Trust has an ever-growing number of passionate supporters. And together we're creating positive change for sharks around the world. Want to join us and help protect sharks around the world? Click here! www.sharktrust.org

Marine Life & Conservation

Jeff chats to… Hannah (Mermaid) Fraser – underwater mermaid, performance artist and ocean activist (Watch Video)

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In this exclusive Zoom interview, Jeff Goodman, Scubaverse Editor-at-Large, chats to Hannah (Mermaid) Fraser – underwater mermaid, performance artist and dedicated ocean activist about her life and work and her adventure dancing with Tiger sharks.

Find out more at www.hannahmermaid.com


Rather listen to a podcast? Listen to the audio HERE on the new Scubaverse podcast channel at Anchor FM.

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Marine Life & Conservation Blogs

Creature Feature: The Spinner Shark

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In this series, the Shark Trust will be sharing amazing facts about different species of sharks and what you can do to help protect them.

This month, it’s the turn (excuse the pun) of the Spinner Shark to swim into the spotlight. This shark is famous for its aerial acrobatics. 

The Spinner Shark (Carcharhinus brevipinna) is a species of requiem shark. From the same family as the Oceanic Whitetip, Bull and Silky Sharks, amongst others. This shark is slender-bodied, with a long and narrow pointed snout.  

A highly active shark that often forms schools. The unusual name comes from the way they feed. They swim rapidly upwards through schooling fish with their mouths open. Spinning and snapping in all directions, often shooting out of the water. Sharks can spin up to three times before falling back into the water. They also take part in feeding frenzies. Many sharks will also come together to eat “trash fish” dumped off trawlers. 

Spinner Sharks are highly migratory in the Gulf of Mexico and possibly elsewhere. Moving inshore during spring and summer to feed and mate. They often head south into deeper water for winter.  

Targeted for their meat, fins, liver oil and skin. This species is likely under-reported by fisheries, due to often being misidentified with Blacktip Sharks. . Their use of coastal habitats mean they are also vulnerable to exploitation and habitat degradation. The species is listed as Vulnerable by the International Union for Conservation of Nature (IUCN).  

SCIENTIFIC NAME:  Carcharhinus brevipinna

FAMILY:  Carcharhinidae

MAXIMUM SIZE:  304cm

DIET:  Primarily fish. Occasionally stingrays and cephalopods. 

DISTRIBUTION:  Coastal-pelagic. Warm-temperate to tropical Atlantic, Indian and Indo-West Pacific Oceans and Mediterranean Sea.
 

HABITAT:  Found to 200m. Close inshore (to depths of less than 30m) – off beaches, bays and river mouths. Less common in pelagic habitats offshore.

CONSERVATION STATUS: Vulnerable 


Banner Image and in-text Image from Matthew Paulson via Flickr

Distribution Map from Wikimedia Commons 


For more amazing facts about sharks and what you can do to help the Shark Trust protect them visit the Shark Trust website by clicking here.

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