Marine Life & Conservation Blogs
Creature Feature: Broadnose Sevengill Shark
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.
Written by guest contributor – Yolanda Evans.
A small glimpse of grey amongst the the vibrant green of the kelp around the temperate coastal waters could be no other then the incredible Broadnose Sevengill shark! Hinted by their common name, these sharks have seven pairs of gill slits – unlike the typical five. These sharks can reach up to 3 metres long and are commonly misidentified as the other species of sevengill the Sharpnose Sevengill. The Broadnose is distinguished by small black and white freckles on their fins and underside and a much larger head then the Sharpnose.
Unlike many other sharks in the Hexanidae family (Cowsharks), this species prefers waters of less then 50 m in depth; sometimes being found in river estuaries where the depth is around 1m! However, Brodnose’s make seasonal migration during the winter to the continental shelves, following their food and sexually mature females.
Broadnose Sevengill’s have a unique tooth shape in their lower jaws: they are shaped like combs which they use to anchor into their prey. This sharks favourite snacks large fish (including other sharks) and crustaceans but they have been videoed eating carrion (dead/decaying bodies), making them scavengers. There are even reports of cannibalism as the older sharks eat the younger to reduce competition. Once they’ve eaten a meal they wont have to eat again for weeks, in fact, in a month they only consume 6% of their body weight!
Predominantly being a solitary shark, they do sometimes congregate in groups to hunt. They mainly do this to get to bigger prey which could be too much work for a single shark. Stalking behind their prey, these sevengill’s will then rapidly burst out to chase down their prey.
Sevengill’ are ovoviviparous and can give birth to 60-180 pups, an incredibly high amount. The pups remain in the shallow waters until they reach a certain size to help avoid predators.
Recent carcasses of these sevengill’s have been found worldwide, all with their livers missing. Who could be behind this series of surgically-precise murders other then the infamous Orca. Orca, or Killer Whales,purposefully seek out Broadnose Sevengill sharks for their livers rich in fats, making a high calorie snack for these mammals. The Orca turn the shark over on their backs, putting them in a state of tonic immobility, and then using their sharp conical teeth they precisely remove the liver leaving the rest of the shark as it doesn’t have the same nutritional value. However, a few videos have emerged of these Orcas then playing with their food, pushing the dead sharks body up and down with their snouts!
Orca’s aren’t the only mammal to purposefully hunt down these sharks as the Broadnose Sevengill’s are also targeted by humans for their meat, skin for leather, and their oil, however, their main threat is being caught as by-catch during industrial fishing. The IUCN lists them as Data Deficient, however, it is expected that they are Near Threatened.
SCIENTIFIC NAME: Notorynchus cepedianus
FAMILY: Hexanchidae
MAXIMUM SIZE: Up to 3.3 meters (10.8 feet) in length
DIET: Feeds on a variety of prey including fish, squid, crustaceans, and even other sharks
DISTRIBUTION: Broadnose Sevengill Sharks have a cosmopolitan distribution, found in coastal and offshore waters in temperate and tropical regions worldwide.
HABITAT: Found in a variety of habitats, including estuaries, bays, and shallow reefs, as well as deeper waters of up to 150 meters (492 feet) in depth.
CONSERVATION STATUS:
While there is little data on population trends, this species is known to be caught as bycatch in some commercial and recreational fisheries, and there is also concern over the impact of habitat loss and degradation on their populations.
For more great shark information and conservation visit the Shark Trust Website
Banner image – Aaron Scheiner | Wikimedia Commons
In-text Image – derekkeats | Wikimedia Commons
In-text Image – Coco | Wikimedia Commons
Project SIARC has been nominated alongside 16 other projects from across the UK to be named National Lottery Project of the Year.
The marine environment in Wales is teeming with life; beneath the often-murky waters are little understood species of shark, skate and ray (elasmobranchs) of conservation importance.
Project SIARC is catalysing links between fishers, researchers, communities and government to collaborate and safeguard elasmobranchs and support a green recovery in Wales.
“We are so grateful for this nomination – it’s thanks to all of our wonderful communities, partners and volunteers working with us to help safeguard and celebrate sharks, skates and rays in Wales”, commented Project SIARC Technical Specialist and regular Scubaverse contributor Jake Davies.
You can support Project SIARC by voting for them online here and by commenting the hashtag #NLASIARC on the pinned post over on National Lottery Good Causes page.
For more information about Project SIARC, visit https://www.projectsiarc.com/.
The Kingdom of the Netherlands will ask for increased protection for the Caribbean reef shark during next month’s Conference of Parties for the Cartagena Convention (COPs) on Aruba. Caribbean reef sharks play a critical role in maintaining a healthy reef ecosystem and building resilience within the oceans. This increased protection is critical for ensuring a sustainable future for this iconic species.
The Caribbean Sea is renowned for its crystal-clear waters, vibrant coral reefs, and a dazzling array of marine life. Among the charismatic inhabitants of this underwater paradise is the Caribbean Reef Shark (Carcharhinus perezii), a species that plays a crucial role in maintaining the health of coral reef ecosystems. In the Dutch Caribbean, these apex predators face mounting threats, but there is hope on the horizon. At the upcoming Conference of Parties for the Cartagena Convention (COPs), the Kingdom of the Netherlands will seek increased protection for these magnificent creatures by listing this species on Annex III of the SPAW Protocol. Annex III includes plant and animal species which require additional protection to ensure this species is able to adequately recover their populations in the Wider Caribbean Region.
Importance
Caribbean reef sharks thrive in warm, tropical waters of the Caribbean region, with a distribution range that stretches from Florida to Brazil. This species is one of the most encountered reef shark species throughout the whole Caribbean Sea. Growing up to 3m (9.8ft) in length, this shark is one of the largest apex predators in the reef ecosystem and is at the top of the marine food web, having only a few natural predators.
In addition to being of great economic value, as shark diving is a major draw for divers from around the world, this species is also critical for maintaining balance within the reef ecosystem. Their presence helps regulate the population of smaller prey species, which in turn, prevents overgrazing on seagrass beds and coral reefs and eliminates sick or weak fish from the population. This balance is essential for maintaining the health and diversity of the entire coral reef.
Threats
Despite their ecological and economic significance, Caribbean reef sharks in the Caribbean face numerous threats that have led to a population reduction estimated to be between 50–79% over the past 29 years. In the (Dutch) Caribbean this is mainly caused by:
Habitat Degradation: The degradation of coral reefs and seagrass beds due to climate change, pollution, and coastal development has a direct impact on the availability of prey for these sharks. Loss of habitat reduces their ability to find food and shelter.
Overfishing: Overfishing poses one of the most immediate threats to Caribbean reef sharks. They are often caught incidentally in commercial fisheries, where fishermen are targeting other species, or intentionally, where they are sought after for their fins, used in shark fin soup.
A Call for Increased Protection
There are different organizations and individuals working to protect sharks and their habitats in the Dutch Caribbean. A significant milestone was the establishment of protected areas such as the Yarari Marine Mammal and Shark Sanctuary between Bonaire, Saba and St. Eustatius. Another milestone was in 2019 when the Dutch government adopted an International Shark Strategy. The strategy sets out which protective and management actions for sharks and rays are to be taken by the government in all seas and oceans where the Netherlands has influence (including the Dutch Caribbean). Additional efforts are still needed to create more marine protected areas, enhance enforcement, reduce pollution in the ocean, and promote sustainable fishing practices. These species know no (political) boundaries and their protection requires broadscale conservation efforts within the Dutch Caribbean and beyond.
Conclusion
The Caribbean reef shark is a species of paramount importance to the (Dutch) Caribbean’s coral reefs. With the extra protection being requested during the next COPS meeting in Aruba, there is hope that this species will have a healthy future. By recognizing their ecological significance and the challenges they face, we can work together to ensure a brighter future for the Caribbean Reef Shark in the Dutch Caribbean and beyond.
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DCNA
The Dutch Caribbean Nature Alliance (DCNA) supports science communication and outreach in the Dutch Caribbean region by making nature-related scientific information more widely available through amongst others the Dutch Caribbean Biodiversity Database, DCNA’s news platform BioNews and the press. This article contains the results from several scientific studies but the studies themselves are not DCNA studies. No rights can be derived from the content. DCNA is not liable for the content and the in(direct) impacts resulting from publishing this article.
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Photo + photo credit: Jim Abernethy-all rights reserved
For more information, please contact: research@DCNAnature.org
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