Broadnose sevengill shark (Rock shark)

Notorynchus cepedianus

It is the most common shark in Tristan waters! And now protected within the MPZ since its global population is declining.

Broadnose sevengill shark © Rob Mrowicki
Broadnose sevengill shark © Rob Mrowicki

Rock shark is distinct from other sharks because it has only one dorsal fin and seven pairs of gill slits. Its known locally as rock shark because of its round and grey head. It has a wide mouth and small eyes. When encountered under water it looks like it is smiling.

It is found in most cool temperate - cold water areas, close inshore, except in North Atlantic Ocean. In Tristan waters rock sharks are commonly seen close to shore among the kelp forests around Nightingale and Inaccessible. Although this shark has a global distribution, rock sharks at Tristan are probably an isolated population as they are not known for long travelling trips. Unfortunately the global population is in decline after many shark fisheries depleted their populations.

They mate between autumn/ winter and females reproduce every other year. After 12 months gestation, pups are born in shallow areas at about 40 - 53cm long and doubling their size within their first six months.

While diving we encounter them cruising near the ocean floor, but they can be fast swimmers and quick hunters of seals, dolphins and other smaller sharks.

IUCN/ Conservation Status — Vulnerable globally

Length —  Up to 300cm

Weight – More than 100 kg

Life span — Between 30–50 years

Reproduction — Mating occurs between autumn-winter

Sightings around Tristan islands – Close to shore in the kelp forest

Marine life on Tristan

The waters surrounding the Tristan islands are home to a diverse range of fish and invertebrates, including the commercially valuable crayfish.