Written by guest contributor - Yolanda Evans.

A small glimpse of grey amongst the vibrant green of the kelp around the temperate coastal waters could be no other than 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 than the Sharpnose. 

Unlike many other sharks in the Hexanchidae family (Cowsharks), this species prefers waters of less than 50 m in depth, sometimes being found in river estuaries where the depth is around 1m! However, Broadnoses undertake seasonal migrations during the winter to the continental shelves, following their food and any sexually mature females.

 

Broadnose Sevengills have a unique tooth shape in their lower jaws: they are shaped like combs which they use to anchor into their prey. This shark’s favourite snack is large fish (including other sharks) and crustaceans but they have also been recorded to scavenge, having been videoed eating carrion (dead/decaying bodies). There are even reports of cannibalism as the older sharks eat the younger to reduce competition. Once they’ve eaten a meal they won’t have to eat again for weeks, in fact, in a month they only consume 6% of their body weight! 

Although they are predominantly solitary sharks, they are thought to sometimes congregate in groups to hunt. This would allow them to hunt larger prey which they wouldn’t ordinarily be able to target on their own.  Stalking behind their prey, these sevengills will then rapidly burst out to chase down their prey. 

Sevengills are ovoviviparous and can give birth to 60-108 pups, an incredibly high amount. The pups remain in shallow waters until they reach a certain size to help avoid predators. 

Recent carcasses of these sevengills have been found worldwide, all with their livers missing. Who could be behind this series of surgically-precise murders other than the infamous Orca. Orca, or Killer Whales, purposefully seek out Broadnose Sevengills for their livers rich in fats, a high calorie meal 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 behind 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! 

Orcas aren’t the only mammal to purposefully hunt down these sharks as the Broadnose Sevengills 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 are 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.

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