White Shark Threats and Ocras
Great White Shark Threats -In recent years declines in Great White Sharks have been documented. Recent claims that Great White Sharks have disappeared from South Africa due to Orca Whales are inaccurate for two reasons: 1) Great white sharks have only disappeared in the False Bay region and whilst declines in numbers have been documented elsewhere, Gansbaai and Mossel Bay still have regular sightings, and 2) Orca whales cannot be held accountable for the disappearance of Great White Sharks in False Bay, or accountable for the decline in numbers documented throughout South Africa.
What do we know?
In False Bay, there is no evidence to date that Orca whales have predated on Great White Sharks in the area. There have been several recorded predations of Orca Whales on Sevengill sharks, but none have been documented on Great White Sharks. The predations on Great White Sharks by Orca Whales were documented in the Gansbaai area several times throughout 2017. The two Orca Whales who had a taste for sharks were given the name ‘Port’ and ‘Starboard’ due to their flopped over fins. As a result of these predations, Great White Sharks disappeared from the area for varying periods of time throughout the year. However, since 2017 Port and Starboard have rarely been spotted, and there has been no evidence of further predations after that year. Yet, the numbers of white sharks in the area has declined and continues to decline. Whilst many want to blame this on the Orcas Whales, this is in fact a decline that has been documented since 2012. Dr Sara Andreotti from the University of Stellenbosch released figures indicating a population estimate of 353 to 522 individuals, based on data from 2009-2012. Dr Andreotti released these results in 2016 and expressed concerns about the species’ extinction risk. As other scientists questioned her results, it has unfortunately meant that the last few years have been wasted in terms of making a concerted effort and drastic changes to save the few individuals that do remain.
Many of those scientists now agree that the number of Great white sharks could be at a critically low level in South Africa and that we need to do something before it is too late. Blaming the orca whales for this decline is only hiding what the real issues are. The decline in Great White sharks is actually unsurprisingly due to anthropogenic activities. Although the Great White Shark is protected in South Africa and has been since 1991, the population has not increased, it has in fact decreased. This is because whilst the species is protected, it’s environment and it’s food is not.
Great White Shark Threats
Beach nets and drum-lines have shown to be a huge problem in South Africa, with a number of Great White Sharks being caught in the beach nets over the years. One article reports that up to 1000 Great White Sharks were caught on the Kwazulu Natal beach nets between 1997 and 2007. Another article states more recent figures of an average of 30 Great White sharks per year. If we consider that in 2012 we perhaps only had a maximum of 522 individuals left, even 30 a year is a huge amount.
Commercial shark long-lining is also thought to be a significant threat to the Great White shark population. With fish populations declining, it seems that the fishing industry has been targeting sharks more and more. Long-lining permits given out by South African’s Department of Forestry and Fisheries, allows these long-liners to specifically target sharks. Along with a decline in Great White Sharks, declines in other species have also been observed. The number of Smoothound and Soupfin sharks in the Gansbaai area has decreased as observed by catch rates, and these species are thought to be of vital importance in terms of Great White shark prey. Furthermore, it is also likely that Great White Sharks will be caught as by-catch by these long-liners. An anonymous observer on one long-lining boat stated that two Great White sharks were unfortunately caught as by-catch on one trip.
Environmental change and pollution will also have an impact on Great White sharks. Being coastal predators they often roam inshore and will thus be affected by both habitat destruction and pollution.
These are the issues that are impacting our Great White sharks. Whilst Orca Whales can evidently impact the presence of these sharks as seen in Gansbaai in 2017, they cannot be held accountable for the decline in numbers. The decline has actually been documented since 2012 – before the Orca Whales started to predate on the sharks.
Great White Sharks in Gansbaai
Since 2017 when the Orca predations occurred, Great White sharks have returned to the Gansbaai region. Due to declining numbers, there are times throughout the year when Great White sharks are not present in the bay, but other times of the year there are still great sightings. The last two occasions the Great white sharks left the area was not a result of Orca Whales. It is actually natural for individuals to move in and out of the area, as there is no resident population of Great white sharks in Gansbaai.