The coastal cowsharks of South Africa are about to receive dedicated research that aims to shed light on their enigmatic ecology.
Guest blogger: Zofia Drapella
I am currently on my way to the shark capital of the world – South Africa’s Western Cape – to swim among some of the ocean’s largest predators. The Shark Project, the first of several socio-environmental projects that form part of Mike Horn’s Pole to Pole 360 expedition, aims to raise the profile of the human threat against sharks, and show that sharks themselves are more misunderstood than malevolent. With a group of dedicated divers from around the world, we will assist with pioneering shark research and attempt to banish the “maneater” myth.
While the great white shark gets most of the attention, the lesser known sevengill shark also prowls the South African waters. This enigmatic ocean giant is still poorly understood. In fact, so little is known about the sevengill shark, that it has been classified as Data Deficient on the IUCN Red List of Threatened Species.
Broadnose sevengills, prefer temperate shallow waters near the coast. These areas are also some the most heavily fished waters, making the sevengill a regular catch for inshore fisheries. Aside from overfishing, they face other threats resulting from living close to humans, namely the effects of pollution and habitat loss. And of course the fear of sharks has led to generations of bounty hunters needlessly seeking out these misunderstood giants to kill them for sport.
Dr Alison Kock admitted that these are some of the strangest sharks she has ever seen: ‘seven gills instead of the usual five, one dorsal fin instead of two, and a broad, almost smiling face.’
Don’t be fooled by the innocent smile. Sevengills are higher predators measuring up to 3m in length and are capable of devouring other sharks. They are not fussy eaters and prey on almost anything, including octopuses, rays, bony fishes and carrion. Just like other sharks, however, they certainly don’t have a “taste” for people. While shark bites do occasionally happen, fatal bites are far less common than fatal bee stings.
An adult sevengill may eat as little as one-tenth of its body weight each month. After a meal, a sevengill shark slowly digests its food for many hours or days, which allows them to cruise for weeks without eating again. But then, even this fierce and powerful hunter must be wary of its enemies. Potential predators of sevengills include larger sharks such as the great white, and even other members of its own species.
Being large sharks, sevengills play an important role in the structure and functioning of the ecosystems they inhabit. They help create stability in marine food webs by regulating the abundance and behaviour of their prey, a process known as “top down control”.
Tagging and monitoring these beautiful creatures gives us a window into their lives. The research we are going to assist with will help us to understand and therefore to conserve these incredible sharks. We will be using acoustic telemetry to further investigate regional demography, population connectivity, habitat use and migratory behaviour of poorly understood predators. Through this research the team hope to do their part to break down the stereotypes and banish the fear that costs the lives of so many sharks every year. Stay tuned for daily updates from the field that we will publish here.
***The shark research is being co-ordinated by Dr Kock and Dr Adam Barnett from James Cook University (Australia), with assistance from colleagues and students from the University of Cape Town; the Department of Agriculture, Forestry and Fisheries; the South African Shark Conservancy; Bayworld Centre for Research; SAIAB’s Acoustic Tracking Array Platform; the Ocean Tracking Network; and the Oceanographic Research Institute.
Funding is primarily from the Two Oceans Aquarium, with additional financial or equipment support from the University of Cape Town, University of Tasmania, Save Our Seas Foundation, Woolworths and Ocearch.***
Read more in an article published by the Save Our Seas magazine.
Zofia Drapella (@Zofia Drapella, Instagram AQUEDU) holds a first class Masters degree in Marine Biology from the University of Southampton. This October, together with the famous explorer Mike Horn and other environmentalist from around the world, she will assist Dr Alison Kock from Shark Spotters with pioneering shark research in South Africa. The Shark Project is part of the Mercedes-Benz sponsored Pole to Pole 360 expedition,
Follow the project on Facebook.