Rattling the Cage
Updated: Aug 18
Ecotourism trips to cage-dive with great white sharks (Carcharodon carcharias) in the wild, have become increasingly popular in recent decades. Yet, despite their popularity, cage-diving with white sharks is still quite controversial. There are concerns about the methods used to attract the sharks and how this may alter the sharks' behaviour... So should you go cage-diving with great whites... Is it bad for the sharks?
Do the attractants cause damage to the sharks?
Cage diving operators use several different attractants to bring the sharks into close proximity to the boat, for easier viewing. Depending on the location, these can include baiting (displaying dead fish on the end of a bait line as a visual stimulus), chumming aka burleying (spreading an odour trail of liquidated fish tissues and oil into the water), acoustic attractants (playing attractive sounds through a microphone dropped into the water) and/or decoys (seal-shaped objects floated on the surface of the water to elicit aerial behaviours).
The main argument against the use of attractants is that feeding wild animals (known as "provisioning"), can actually be bad for their health in the long-term. In other species, the regular consumption of nutritiously poor food can lead to reduced body condition, lower fitness and increased parasite load. Yet, offering food without actually feeding can also cause animals to waste their time, when they could be hunting elsewhere, which can lead to poor health. No studies have yet been performed to asses whether provisioning specifically affects white sharks in these ways.
Feeding white sharks is illegal in South Africa and, both chumming and baiting at all are illegal in the USA, so you can choose to cage-dive in these sites only, if you have concerns about provisioning (Bruce, 2015).
Is shark behaviour changed due to cage-diving activities?
Another common concern is that the use of attractants could cause changes in the behaviour of the sharks. Using attractants to concentrate sharks around the boat inherently alters their behaviour, as they are forced to the surface. This is already not like their natural behaviours (Laroche, et al., 2007). However, less than five studies have actually been conducted to assess the impacts that the cage-diving industry has on the behaviour of great white sharks (Bruce, 2015).
As has been found in other species of sharks, there is no evidence that white sharks become increasingly aggressive as a result of ecotourism activities, but it has been proven that certain aspects of their movement patterns are altered. It has been found is that white sharks swim at shallower depths when chumming is occurring (Laroche, et al., 2007), causing the sharks to be spread over a wider vertical range in the water column (Huveneers, et al., 2018). White sharks also focus their activity around the chumming vessels temporarily (Bruce & Bradford, 2013) and patrol a more limited area than when chumming is not occurring (Huveneers, et al., 2013). It also seems their residency times at certain locations are longer when ecotourism is occurring (Bruce & Bradford, 2013). As such, ecotourism does have the potential to have an impact on white sharks' energy expenditures, as they are more active than normal during interactions with the boats, but more work is required to determine what impacts these behavioural changes actually have on white sharks.
On the other hand, it has also been proven that ecotourism does NOT stop white sharks from departing the area for their extended migrations, as normal (Bruce, 2015) and does NOT cause a decrease in their natural predatory activities overall (Laroche, et al., 2007). It has also been shown that many sharks ignore the attractants and go about their business as normal, and there is evidence that white sharks are not "conditioned" to associate boats with food. In fact, rather than "positive conditioning", there is evidence for "negative conditioning"; meaning that sharks learn that they are not fed at ecotourism vessels and so do not attend when the boats are present (Johnson & Kock, 2006). There is also no evidence that cage diving increases the risk of shark attacks in the region (to learn more, take a look at: Cage Diving and Shark Attack... Is There Cause for Concern?).
What are the benefits of shark-diving ecotourism?
Ecoutourism has a very real, positive impact on education and awareness in the general public, which can be very good for the conservation of white sharks.
Ecotourism companies drive interest in a commonly feared species, and can debunk myths and change the general perception of these sharks. Public interest in a species can be critical for driving their conservation; people will be more inclined to be supportive of protective initiatives and reject any plans which could cause them harm.
Whatsmore, ecotourism can drive the protection of a species directly, by encouraging local communities to value their living sharks. Ecotourism companies provide jobs, but also generate demand for business not related directly to the industry (shops, restaurants, cafes, hotels, transport companies near to the cage-diving site), which impact on the economy at a local and national scale. This can drive a switch to valuing sharks as a non-consumptive resource.
Great white sharks are now listed as 'vulnerable' on the IUCN Red list of Threatened Species, meaning conservation initiatives are needed in order to conserve the species. In my opinion, if cage-diving with these sharks can increase public empathy for their plight and drive people to care about their protection, the industry is good for the sharks, overall.
If you feel cage-diving is unethical, your opinion is absolutely valid. However, if you decide you would like to cage-dive with white sharks, please ensure you thoroughly research your company first! Make sure they are reputable, ideally with a shark expert on-board, and have the highest safety standards.
Great white shark cage-diving trips are now available in five places globally (Bruce, 2015):
The Farallon Islands, off the coast of California, USA,
Guadalupe Island in Mexico,
Stewart Island, New Zealand,
The Neptune Islands, South Australia,
at several sites along the coast of South Africa.
Bruce BD (2015). A review of cage diving impacts on white shark behaviour and recommendations for research and the industry’s management in New Zealand. Report to the Department of Conservation, New Zealand: CSIRO Marine and Atmospheric Research. Access online.
Bruce BD & Bradford RW (2012). The effects of shark cage-diving operations on the behaviour and movements of white sharks, Carcharodon carcharias, at the Neptune Islands, South Australia. Marine Biology, 160, 889-907. Access online.
Huveneers C, Rogers P, Beckmann C, Semmens J, Bruce B & Seront L (2013). The effects of cage-diving activities on the fine-scale swimming behaviour and space use of white sharks. Marine Biology, 11:160, 2863-2875. Access online.
Johnson R & Kock A (2006). South Africa’s white shark cage-diving industry- is there cause for concern? In: Nel, D.C. & Paschal, T.P. (Eds.). Finding a Balance: White Shark Conservation and Recreational Safety in the Inshore Waters of Cape Town, South Africa; Proceedings of a Specialist Workshop. WWF South Africa Report Series- 2006/Marine001. Access online.
Laroche RK, Kock AA, Dill LM & Oosthuizen WH (2007). Effects of provisioning ecotourism activity on the behaviour of white sharks Carcharodon carcharias. Marine Ecology Press Series, 338, 199-209. Access online.