Shark sightings in False Bay (Jan-Nov 2011)

Thinking about shark bites (and attending a meeting)

I currently work in investments, and the investment team at the company I work for pays a lot of attention to what are known as cognitive (or behavioural) biases. Many of these biases make humans poor investors; the team I work with try actively to identify these biases when we encounter them in our own thinking about investments, and to counter them. Cognitive biases are patterns of poor judgment, hard-wired in our brains, that were once useful to us – perhaps when our ancestors were running around on the African grasslands – as they enabled quick decision making with limited information. Today, however, countless generations later and faced with survival in a concrete rather than a literal jungle, we are saddled with these brain short circuits that can in fact impair our performance in certain aspects of life, particularly in circumstances where emotions and knee-jerk reactions threaten to overwhelm logic.

Tony and I attended a meeting on on Monday 24 October 2011, held at the Fish Hoek Civic Centre. It was organised by Mark Wiley, the Western Cape Parliamentary Chair of the Committee for Culture and Sport, and was open to business owners who operate in the South Peninsula area. The focus of the meeting was to determine:

  • How the increased presence of shark sightings and the incident had affected business, sport and recreational activity in the Far South area – either positively or negatively
  • How the shark phenomenon was having an impact on the community as a whole from a perception point of view
  • If there was a need for an impact assessment
  • To advise or ask the authorities, City or otherwise, to investigate options to minimise risk to the public and for them to explore options in this regard

(I quote from the minutes – let me know if you want a copy and I will email them to you.)

Attendees included several local business owners, including Dawid Mocke of the Varsity College Surf Ski School and The Paddling Centre, Andrew Brouckaert of Fish Hoek Surf Lifesaving, some local guest house owners, Paul Botha of the Kahuna Surf Academy and a few other local surfers, Kim Kruyshaar from the Scenic South website, and a small group of ocean and/or nature lovers some of whom also have business interests in the area (we count ourselves in this group) such as Steve Benjamin of Animal Ocean, freediver Hanli Prinsloo, Jean Tresfon, Morne Hardenberg of Shark Explorers, Jenny Trethowan of Baboon Matters, and of course Sarah Titley of Shark Spotters.

During the course of the meeting I observed several of the cognitive biases I mentioned above, and realised that it’s very hard to have a conversation about an emotive topic such as shark bites on humans, without a whole host of these biases cropping up. The challenge when it comes to an issue like the shark bite one, is to remain rational and to listen to the statistics – not to the fearful, reptilian part of our brains. We need to form judgments and decisions based on evidence, and not our gut. In choosing what to have for lunch, you can listen to your gut – but not here.

What follows is a selection of statements heard (and sentiments expressed) at the meeting, and the behavioural bias inherent in each. The behavioural bias definitions are from the cognitive biases wikipedia page.

There never used to be any sharks in False Bay

“My family has lived on the mountain in Fish Hoek for sixty years and until recently no one ever saw a shark.”

Anchoring – the common human tendency to rely too heavily, or “anchor,” on one trait or piece of information when making decisions or forming thoughts.

Just because you’ve never heard of Oprah Winfrey doesn’t mean she doesn’t exist.

Just because your family never saw a shark, it doesn’t mean they weren’t there. Did they watch the sea all day, every day? Does your grandmother even know what a shark looks like when seen from an elevated point, when the sun is shining?

Your family wasn’t looking specifically for sharks, and didn’t know what to look for. The Shark Spotters undergo extensive training to distinguish between dolphins, kelp, shadows, and sharks. A lot of the time it’s not as straightforward as looking down the hill and – eureka – seeing a shark!

Sharks have only recently come to live in False Bay (and probably for sinister reasons, like to eat old people swimming at Fish Hoek)

Recency effect – the tendency to weigh recent events more than earlier events

Massive population growth and increased leisure time has given many more people access to beaches and recreational activities in the ocean. Just because they’ve only recently been drawn to our attention, it doesn’t mean sharks haven’t always been here. Sharks have been living in False Bay for longer than we have been in the area, but it’s only recently that we’ve been looking out for them – and more people in the water means more human-shark interactions.

Furthermore, as Anton Louw pointed out, evidence suggests that False Bay has been getting colder – and hence cleaner, enabling sharks to be seen more easily from above. One factor pointing in this direction is the fact that kelp, which likes cold water, never used to be found north of Miller’s Point but now proliferates off Jaggers Walk in Fish Hoek, and colder water implies cleaner water.

If there were fewer sharks in the recent past, it’s possibly because:

  • White sharks were fished aggressively until fairly recently (they became a protected species in the mid-1990’s in South Africa)
  • At one point there were only 35 seals left on seal island after aggressive culling – that means no food to support a population of white sharks, which would send them elsewhere for food in winter.

There are more sharks now that there have ever been before, and they are coming closer inshore

“I and all the surfers I know see sharks in the surf zone almost every day when we go surfing.”

Attentional Bias – implicit cognitive bias defined as the tendency of emotionally dominant stimuli in one’s environment to preferentially draw and hold attention.

Your buddy is more likely to share with you that he saw a shark while he was surfing than, say, a child’s kite or a peaked cap that got blown into the sea – although they are both equally likely. Sighting a shark carries far more emotional charge than almost anything else. It’s emotionally dominant, to say the least.

Chumming activities are teaching sharks to associate humans with food and drawing them inshore

Availability cascade – a self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse (or “repeat something long enough and it will become true”).

There’s no evidence for this, even though it’s a popular belief among surfers. Do some reading please. Or buy this book (and read it).

The shark population is exploding

“Just look at how many sharks have been sighted at Fish Hoek beach this spring! The population is out of control!”

Confirmation bias – the tendency to search for or interpret information in a way that confirms one’s preconceptions.

The population of an apex predator cannot explode – it simply cannot happen. Such predators are typically are slow growing, slow reproducing creatures that produce few young, with high energy requirements. The population of everything else lower in the food web – EVERYTHING – would have to explode first, before the shark population could “explode”. And then it probably wouldn’t be a population explosion – it’d be the plot of a science fiction movie.

The Shark Spotters program doesn’t work

Outcome bias – the tendency to judge a decision by its eventual outcome instead of based on the quality of the decision at the time it was made.

Cape Town’s Shark Spotters program is a world leader in approaches that combine both beach safety and conservation awareness. The spotters cannot force people to obey the flags, however, and the actions of a single selfish, irresponsible, immature individual who endangered not only his own life but that of his eventual rescuers cannot be used to tarnish the reputation of this program. This article gives a good summary of just how impressive the Shark Spotters program is.

I thought it was absolutely shameful (and an outright lie) to suggest that the Shark Spotters have somehow failed, or – as one of the attendees who has “surfed in 30 countries in the world” stated – that the spotters are poorly trained and fall asleep at their posts. Unfortunately this comment was not censured.

A rogue shark or group of sharks is responsible for biting humans and coming inshore to the beaches

Clustering illusion – the tendency to see patterns where actually none exist.

You’ve got to choose: you can’t claim that “ALL sharks are maneaters” and in the next breath claim that a single rogue shark keeps coming into Fish Hoek bay to eat swimmers. If sharks actively sought people as prey we’d see several fatalities a day – at any one time there are about 50 white sharks in False Bay, and if they each wanted a human or three for lunch (a white shark can eat four seals on the trot, no problem), I’d fancy the shark’s chances over yours.

Return Jaws to the video shop and read some proper science writing instead. The Rogue Maneater theory has long been discredited.

The business downturn in the South Peninsula is entirely due to the fear of sharks

Negativity bias – the tendency to pay more attention and give more weight to negative than positive experiences or other kinds of information.

I don’t know if you’ve noticed, but the last few years have been tough. When I fill my car with petrol and hand over R550 for a full tank, it feels as if Armageddon is nigh. As Jenny Trethowan pointed out, we’re still making our way through an economic downturn of note, and businesses everywhere have struggled. Blaming this entirely on sharks is disingenuous.

This statement also ignores the eco-tourism value of sharks. Hundreds of people joined the shark spotter on Boyes drive every day during this recent peak of sightings, scanning the bay and excitedly discussing the possiblity of seeing a shark. Do you think they all went home without having a coffee somewhere, or buying a sandwich?

The large number of sharks currently being spotted inshore is going to persist FOREVER

Disregard of regression toward the mean – the tendency to expect extreme performance to continue.

Shark sightings in False Bay (Jan-Nov 2011)
Shark sightings in False Bay (Jan-Nov 2011)

Source: Shark Spotters recent sightings

Year after year a seasonal peak of inshore sightings of white sharks is observed. Sightings typically peak in October, and then decline somewhat for the rest of the summer. During winter, the white sharks hang out at Seal Island and are hardly ever seen inshore. This same sequence occurs year after year after year. It is driven by the sharks’ search for food (they eat seal pups at the island; when the seal pups get too old, fast and wily they eat the fish that come into False Bay with the warmer water in summer), and possibly by socialising activities and the opportunity to rest in the highly oxygenated waters close to shore. There is no reason to state that THIS year the sharks are going to stay in the surf zone, set up homes there and harrass swimmers year-round.


Having listed the statements above, I realise that there was a disturbing mindset among many of the meeting participants, who seemed opposed to scientific thinking and statistical or evidence-based reasoning. Instead they attached great importance to anecdotes, personal experience (only valuable to the individual unless recorded and shared in an objective manner that recognises shortcomings of perception, memory and understanding) and uninformed generalisations. This kind of thinking is also prevalent in media reports of shark bites, and almost all the conversations I have had with friends and family on the subject (and let me quickly add, I have also been prone to it!).

Unfortunately, as humans we actually can’t help thinking in those ways. We have to actively work against the part of our brain that wants to leap to conclusions based on stories told around the bar or in the elevator, and give it some hard facts to chew on instead. These three cognitive biases capture some of the attitudes I am talking about:

  • Bias blind spot – the tendency to see oneself as less biased than other people.
  • Confirmation bias – the tendency to search for or interpret information in a way that confirms one’s preconceptions.
  • Base rate neglect or Base rate fallacy – the tendency to base judgments on specifics, ignoring general statistical information.

Contrary to my initial expectations the meeting was conducted in a civilised manner, and despite the flawed thinking on display, for the most part the attendees agreed (or claimed to agree) that a solution to the issue of perceived increased risk owing to shark attacks in False Bay must make sense both from a conservation point of view (not killing sharks) and from a human safety perspective. (As an aside, a topic that was skipped over was the possible role of trek net fishermen in attracting sharks to the beaches… A bit of a political hot potato, methinks!)

Tony has experienced a slight dip in business as a result of the recent shark bite incident at Fish Hoek. Experienced divers aren’t generally fussed, but new and prospective diving students are frequently nervous about sharks and ask a lot of questions. I think that no matter how much income Tony lost, however, he’d be very hard pressed to suggest that killing some of the fauna of False Bay was a valid solution to the problem.

However, at least two of the participants at the meeting – both gentlemen of a certain age who claimed vast knowledge about the world’s oceans and Fish Hoek in particular – clearly favour shark nets, culling, hunting down and shooting the “rogue” sharks who persist in coming into the bay or a similar solution. To say so, however, would have been unpopular once it became clear which direction the consensus was moving.

Some of those with a purely financial interest in the public perceiving Fish Hoek beach and False Bay waters as safe also would have jumped at the idea of a solution that removed sharks from the waters around Fish Hoek – whether that involved killing them or not. Fortunately thinking like this is no longer socially acceptable as it smacks of arrogance about humans’ role on earth, and ignorance about the functioning of ecosystems. Fear of saying something socially unacceptable is a tenuous reason to hold back on expressing a favourable opinion towards a shark cull – it by no means signals or causes a change of mind on the subject – but fortunately it was sufficient of a restraint for the meeting participants to reach an agreement that was in favour of the sharks’ continued existence in False Bay, hopefully in harmony with ours.

I was relieved when the meeting concluded with Mr Wiley stating that the evening’s contributions were sufficient to request the Cape Town Sub-Council in Fish Hoek to allocate funds for a research project to making False Bay, specifically Fish Hoek coastline safer for beach users. I believe that this will take the form of a safe swimming area, but we’ll have to wait (hopefully not too long) and see.

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Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

13 thoughts on “Thinking about shark bites (and attending a meeting)”

  1. Great article. As a paddler (and a writer) I’ve been involved with this story for the last couple of years – and can attest to many conversations that I’ve had with folks who are utterly convinced by the rogue-shark, population explosion, kill the sharks arguments – and who simply don’t believe the evidence.

    Still, there seems to be a happy groundswell of support for more studied approaches to the issue. Long may it continue.

  2. Thanks for a great article. It’s great to hear not only about these types of meetings that have taken place to have someone actually give us the feedback. We’re obviously not always exposed to the activity on the coast and it’s always good to be kept in the loop.

  3. wow, what an informative and well written article. Thanks guys. Im going to share it… as Ive has so many conversations with people who think along the lines described in the biases above. Thanks for giving me good answers to present in future 😉

  4. Great approach. I was unfortunately out of the country at the time of the meeting.
    However we can not get away from the following;
    – Seal clubbing ceased in 1989. Seals have increased from app. 32k to 85k.
    – GW have become protected since 1991.
    – GW’s have 2 to 10 pups per annum per “couple” every 2 to 3 years. Say one pup per couple per year average. Check this theoretical growth over 20 years considering a life of 35 years and start breeding at 15 years.
    – Shark sightings have doubled (for Fish Hoek) over the past 5 years (Ocober figures). That means a 4 times or 400% growth (at least) over the 20 years.

    I think the biggest problem is the authorities themselves that keep on passing the buck between various departments. Nothing has happened since they came to the same decision in 2006 at the “FINDING A BALANCE” held in 2006. Is it a case of prefer not to spend the money or just can’t get going?

    Hong Kong type netting rather than the Gill netting used by KZN, taking up 6 to 7% of the Bay, will provide an immediate foolproof solution considering the spilling type waves (Fish Hoek) versus plunging waves (KZN) and the associated energy dissipation.

    I think it is important that we get a firm commitment and timelines from the local and provincial authorities.

    Let us do something for a change rather then talking talking talking…..
    Rudi Coetzee

    1. This looks like a credible source of information on the GW:

      Nothing I’ve read shows that the GW shark population is expanding – but rather that at best the population might be plateauing.

      Don’t forget that while the GW is protected in South African waters, they are very wide ranging animals, having been tracked migrating from South Africa up the east coast – and even across to Australia. And anywhere offshore, they are acutely vulnerable to our friends from the Far East who are slaughtering all shark species for their fins. So inferring that because a GW shark may be able to have 2-10 pups every two years and therefore the population is expanding, is erroneous.

      I have to question too the assertion that shark sightings have doubled since 2006. I think the reason for this might be found in the way shark spotting is carried out and the way the sightings are recorded (ie I doubt that this is a rigorous scientifically based set of observations).

      I know that there have been rigorous investigations into the viability of netting all or part of Fish Hoek and that it has been shown to be impractical and potentially ecologically disastrous.

      In the meantime, action HAS been taken in the form of research, of increased spotting/alerting capabilities and experiments with electronic devices. It is completely wrong to imply that nothing has been done.

    2. Hi Rudi
      thanks for your comments. You might also want to consider seal clubbing….something that shouldnt ever have started, could in fact have been the cause of a huge imbalance in nature, secondly when it is claimed there are more shark sightings than five years ago, nobody was counting then. GW dont pup as often as you think and the mortality rate is very high.
      The best ”shark scientist” we have is Allison but she does not have the funds to tag every shark in False bay…..find the funding and every shark in the world would get a tag but noboby really wants to put their money where their mouth is. If tourism is down in the south could the long drawn out roadworks not be a contributing factor. Close a highway in Joburg and the city comes to its knees…in Capetown we just blame the sharks. It seems hard to believe all the tourist drawn to Cape town are coming just to swim in Fishoek. I would feel comfortable saying less than 5% of the tourist even walk on the beach there.
      Spend a few hours at the save our Seas foundation, talk to the shark people and see just how difficult it is to get science, research and facts to compete with hyped up media and ill informed guess work from people that dont even use the ocean or have any concept of the complex balance of nature. There is so little funding for any form of research and that is where the problem lies.

  5. Hi All
    No intention to club anything – except maybe the authorities.
    I urge you all to read “Finding a Balance” on the Shark Spotters website.
    Just for interests sake, I got my figures from the Shark Spotters with regards to sightings. I am sure that we are not going to suggest that they did a bad job in Fish Hoek during the early phases of their existance before the City of Cape Town subsidy came in?
    What I have listed about the GWs and the seals are facts not assumptions. We can all perform guess work or decide what we use as a base of our theories. That unfortunately does not deliver foolproof solutions.
    The first time I saw a shark underwater was in 1966 at Smitswinkelbay. I also have dived at every spot along the coastline over the past 50 years (without a Sharkshield7).
    We are not trying to tell any GWs or Seals to go away. We are looking for secure swimming/surfing areas and we have the solutions – but the authorities need to go ahead and implement them. (Pity we can’t transport Monwabisi to Fish Hoek or at least the concept of the tidal pool and the breakwaters – combined with Hong Kong netting).
    Our issue is more with the authorities and politicians that arrange these workshops/meetings and then fades away – until it happens again. We can’t just sit back and wait for them to action. They need to provide us with action timelines.
    With regards to marine scientists. As I was a technical researcher for 40 years of my life, I must state that they do have a problem with regards to funding. Unfortunately this turns them into lobbyists (who pays my salary?) rather than scientists. Presently they can’t tell us more than we know – unless they have real stats on population increases. I have done enough research now to realise this. Maybe in another 20 years? At least we have KZN Sharks Board with good stats.
    Tourism stats one can obtain from various websites or Department of Tourism. I have interviewed many tourists stopping at the Galley for lunch – also have a good idea why they do not want to swim anymore. But maybe it is just another elusion and not scientific facts?
    In the meantime enjoy the diving – one of the best sports in the world!

  6. Just for Rob.
    I am aware of all that you stated above. I have been aware of the non-contact barrier from the word go when WITS was still involved with the KZN Sharks Board. However, I see nothing in the Cape or more specific Muizenberg and Fish Hoek Bay.
    Fish Hoek Bay according to those that are involved in the HK type netting is the ideal beach with a shallow beach, spilling type waves with long energy disappation patterns, etc. We would not know what it does to the beach if we do not try them out. Maybe the Oceanographic Department of the CSIR located in Stellenbosch (if the still exist) should get involved to model this before implementation.

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