Coast KZN

09 Sep 2020

Sardine Run helps with studying sharks to promote conservation

Jenni Bipat (South Coast Herald) Picture: Ryan Daly. A sub-adult dusky shark (Carcharhinus obscurus) is fitted with an acoustic tag alongside a vessel before being released.

During winter on the KwaZulu-Natal coast there is an influx of sharks associated with the arrival of the sardines. These include dusky sharks (Carcharhinus obscurus), blacktip sharks (Carcharhinus limbatus), spinner sharks (Carcharhinus brevipinna) and others. They make the most of winter in KZN to feed on the sardines but it’s still unclear what all these sharks do for the rest of the year.

In order to find out more about their migration and habitat, the South African Association for Marine Biological Research has been making the most of one of the best Sardine Runs on record in KZN to tag these sharks.

“In order to investigate their movements, we fit them with acoustic tags that ping a unique coded ID to underwater receivers located along our coastline from Cape Town to the Mozambique border. We are then able to follow their movements for six to eight years as they make annual migrations along our coast,” said Dr Ryan Daly.

“For some, like the endangered dusky shark, we will hopefully be able to improve their conservation by understanding more about areas that are critical for them.”

The KZN coastline remains an important nursery area for juvenile dusky sharks but not much is known about their movements as they mature, which may take up to 25 years.

“We hope that by tagging a range of juveniles and adult sharks we are able to find out more about this species and discover which areas on our coast are most important so that we can design effective conservation strategies for the species,” said Dr Daly.

As sharks are increasingly under threat from fisheries globally, South Africa remains an important shark “hotspot”.

“We need to ensure that these top predators continue to thrive and support healthy, balanced marine ecosystems.”