Great white sharks are in decline
Evidence suggests they’re being killed in large numbers, yet they’re supposedly protected by law. By Enrico
In fewer than eight years, white sharks in South Africa have all but disappeared from their historical hotspots in False Bay and Gansbaai on the Western Cape coast. These areas were once known as the “white shark capital of the world” and home to a flourishing eco-tourism industry. One possible explanation for this change would be a declining white shark population.
We are part of an international research team with expertise in shark ecology, genetics, fisheries and conservation, researching sharks for more than 20 years. This has included tagging sharks and monitoring their activities in the area.
We have published numerous papers on the species. These have included research on conservation plans for sharks in South Africa, white shark cage diving, and the importance of coastal reef habitats for white sharks.
Our most recent tracking data on white sharks tells a worrying story: 18 of 21 white sharks tagged since 2019 with internal 10-year transmitters in Mossel Bay by the Oceans Research Institute have disappeared. This represents the loss of nearly 90% of the tracked white sharks in under four years. They have not been detected moving to the Eastern Cape or elsewhere:
they vanished.
Furthermore, nowadays, white sharks larger than 4m in length – the big breeders – are rarely sighted. Combined with the known low genetic diversity of this population, it is an indication that the white shark population is likely not stable in South Africa.
Based on this, we urge the government to take a precautionary approach to white shark conservation. Otherwise, South Africa could go down in history not only as the first country to protect white sharks, but also the first country to knowingly lose them.
What’s known
As far back as 2011, between 500 and 1,000 individual white sharks were estimated to be left in South Africa. Today, we barely see any larger white sharks. This in itself is a sign of a population not doing well, because the fewer adult sharks there are, the greater the decline will be.
Although white sharks have been a protected species since 1991, large numbers are legally killed every year by shark nets and drumlines (anchored hooks with large baits) operated by the Kwazulu-natal Sharks Board. This is based on an outdated 70-yearold idea that sharks should be culled to reduce the chances of encounters with humans.
Between 1978 and 2018, drumlines and shark nets captured 1,317 white sharks, of which 1,108 died. So, on average, 28 white sharks were killed every single year for the past 40 years.
Three white sharks killed in
10 weeks by one vessel equates to 40 white sharks killed by an average of four vessels operating for only three weeks per month,
10 months of a year
We have estimated that even if tens of white sharks were killed per year, this would drive the white shark population into decline.
White sharks have also been affected by the demersal shark longline fishery. Boats use fishing lines fitted with thousands of hooks, which can be kilometres long. The fishery is permitted to target and kill endangered and critically endangered small sharks. But as the smaller sharks get caught on the lines, so do larger predators chasing them, including white sharks.