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.

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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.

Lecture: Sarah Fowler on the challenges & opportunities of shark conservation

Last week Tony and I attended a talk at the Kalk Bay Save Our Seas Shark Centre by Sarah Fowler. Sarah was introduced by Christoper Neff (back in town following the recent shark bite incident in Fish Hoek) and is one of those people who has had such a busy and productive working life that it’s almost futile to try and summarise her qualifications and experience… But she’s a co-author of the fantastic Sharks of the World field guide, founded the European Elasmobranch Society, is a founding trustee of the Shark Trust and has worked in advisory positions to government agencies as well as in an independent capacity as an environmental consultant. She is also the Vice-Chair of International Treaties at the Shark Specialist Group. There’s a better biography of her here – it’s incredibly impressive, and really comforting to know that there are individuals of this calibre involved with shark conservation internationally. Apart from Save Our Seas, our experience of shark conservationists locally has been somewhat dispiriting.

Challenges of shark conservation

Sharks are intrinsically vulnerable animals, perched as they are on the top of the food chain. They are late maturing, long-lived creatures that undergo long (9-18 months – can you imagine!) gestation periods and usually give birth to small litters of well-developed young. They thus have a low population growth rate, and a low resilience to onslaughts by fisheries. Many species of sharks return over and over to the same locations to breed, making them vulnerable to specific habitat threats. Shark populations are also slow to recover, in light of their reproductive characteristics described above.

There is a lack of management of shark fisheries – in many instances, sharks are not the target species but are often bycatch or a byproduct of what the fishery is actually trying to catch. Shark fisheries are low volume, and low value (but the trade in sharks and shark products is high value). From a management perspective, other fisheries have a higher priority to governments and in management treaties.

The IUCN Red List evaluates the global conservation status of plant and animal species. The Shark Specialist Group is responsible for preparing species assessments for elasmobranchs (sharks and rays) for the Red List. There are about 1,040 such species listed on the Red List, of which more than 17% are threatened. The most threatened species are

  • large bodied coastal species such as sawfish, hammerhead and porbeagle sharks, skates, and spiny dogfish
  • deep water benthic (bottom-dwelling) species targeted by fisheries or taken as bycatch
  • freshwater species
  • oceanic pelagics, which are an unregulated target of bycatch fisheries.

Funnily enough, the white shark is not a typical shark (nor is the whale shark). Both are actually fairly well protected, but they differ from the “average” shark in several other ways. The typical shark – if one were to average across all shark species – is small (about 1 metre long), flat (batoid), with uncertain distrubition, unknown population trends, and largely unknown life history. It is probably endemic to a particular region, making it vulnerable to habitat loss. It is utilised bycatch if not actually targeted by fisheries (in other words, if they’re caught by accident, they are used rather than thrown back into the sea). Its fisheries are unregulated and unrecognised. There is no fisheries management or biodiversity conservation attention being paid to the average shark. The species is probably on the IUCN Redlist as critically endangered, or there is insufficient data on it.

What needs to be done

Urgent conservation and management actions are required. Fisheries management (quotas and Total Allowable Catch or TAC) at a regional and national level is required. Shark finning must be banned.

Since some shark species (such as great whites and bull sharks) are highly migratory and regularly cross international borders, countries must co-operate in the conservation of such species. The Convention on Conservation of Migratory Species (CMS) is one means of cementing co-operation. The CMS Shark Memorandum of Understanding is intended to improve the conservation status of several species of sharks listed in the CMS appendices. South Africa signed this treaty in May 2011, and is one of seven African signatories out of a total of 16 countries.

Who should take action?

How we can take action?

These aren’t complicated, time-consuming or difficult things to do. Most of them require a keyboard and a word processing program, a pen and paper, or firing off an email.

  • follow codes of conduct for diving and angling
  • write to elected representatives and government ministers (and shadow ministers)
  • ask them to follow scientific advice (this is VITAL – scientists are the only ones with no financial or status-related interests in the game) for national fisheries management and biodiversity conservation measures
  • ask what your government is doing to implement international biodiversity conventions
  • get yourself photographed hanging onto a shark’s dorsal fin, while wearing a bikini

(Regarding that last point, if you’ve read my post on the proliferation of ridiculous “shark activists” and conservationists that seem to bedevil us, you’ll be well aware of my views of that sort of exploitative, self-promotional behaviour.) Sarah was extremely diplomatic when I asked her about the sheer number of organisations that claim to be saving sharks, and whether this represents an unneccesary division of labour. Perhaps better results could be achieved by one or two organisations that envelop all the others? In reply, Sarah said that there is a role for every kind of organisation, from pure scientific research groups to those who are in favour of more direct (not illegal) action. She wryly observed that some groups’ only role seems to be to make everyone else look good!

This was a fascinating talk from someone who has been actively involved in shark conservation for many years. It confirmed my long-held suspicions that shark conservation is not glamorous work, and anyone who claims that it is – or is constantly getting themselves photographed with no other outputs in evidence – is not doing what they’re claiming to be doing.

Here’s a video of Sarah Fowler discussing a similar subject (at an event covered here).

[youtube=http://www.youtube.com/watch?v=pdJdZWvzme4&w=540]

I actually don’t know too well what the status of South Africa’s shark conservation action plan is (if there is one), and will do my best to find out and report back when I do.

Lecture: George Branch on evolution

The fourth in the Save Our Seas Shark Centre in Kalk Bay’s series of talks was presented by George Branch, who (in my eyes at least) has achieved near-legendary status as a marine biologist and author. He is one of the authors of Two Oceans, the invaluable reference guide to South African sea life, and also wrote the classic reference The Living Shores of Southern Africa in the 1980’s with his wife Margo. The topic of his talk was The Myths and Magic of Evolution, a subject that interests me enormously but until a couple of years ago it was not part of my education (formal or self-taught) at all. Unfortunately, at this stage in my life, I am so ignorant on the subject that I simply cannot judge where to start learning about it.

Enter the Save Our Seas Shark Centre! Prof Branch turned out to be a wise, patient (I asked several stupid questions) and fascinating teacher – clearly he is not only passionate about his areas of specialisation, but also about communicating the subject matter to others, at both beginner and expert level. Several times in his talk he indicated that he’d changed his mind and learned new things in the past two years – which impressed me enormously. I spent a good part of my young adulthood in the presence of frighteningly dogmatic individuals, to whom an idea such as the one espoused by John Maynard Keynes when he said, “When the facts change, I change my mind – what do you do, sir?” would be anathema. Fortunately Prof Branch is not dogmatic – he is gracious, curious, and thorough.

The subject of evolution is controversial in some circles, and Prof Branch started his talk by stating that no science is any use (in fact, I wouldn’t even call it science) if you can’t test the ideas. An untestable hypothesis is doomed to remain just that – a hypothesis, or a belief. Beliefs are only good for and useful to their holder. The talk was divided into five sections –

  1. The basics of evolution
  2. Tests of evolutionary theory
  3. New advances
  4. Controversy
  5. Guidelines

We found the basics of evolution, as set out by Charles Darwin helpful:

  • more individuals are born than survive to reproduce (this is obvious – I am one of those individuals)
  • variety exists among individuals of a species (also obvious – compare my freckles to Tony’s easily-tanned skin)
  • fitter individuals are more likely to reproduce (“survival of the fittest” – a runty little shark who can’t swim fast isn’t going to find himself a sharky girlfriend – and the definition of “fitter” will vary among species)
  • if characteristics are inherited, species slowly evolve, through either adaptation/microevolution (small changes), or speciation/macroevolution (splitting off into a new species)

The first two points listed above were obvious in Darwin’s time. According to Prof Branch, today we have evidence of all four processes.

It annoys and frustrates me that a discussion of science must mention religion, but unfortunately a lot of the objections to evolutionary studies have come from the religious right. One of the common difficulties is reconciling a seemingly random process (evolution) with the idea of a creator characterised by order. With this in mind, Prof Branch (who has spiritual convictions of his own and is apparently occasionally challenged about evolution at church by those less well versed in the sciences) pointed out that evolution is not a random process. The mutations that add variety to populations are random, but the selection process is not random.

The second part of the “basics” was an explanation of sexual selection, also observed by Darwin. To summarise it as far as one safely can, sexual selection occurs as one gender (I think usually the female of the species!) “likes” something in the other gender, that characteristic will be favoured (i.e. lead to more reproductive opportunities in those carrying it) EVEN if it’s a DARN NUISANCE. Just think about birds of paradise, or peacocks as an example.

There are as many as fourteen different tests or lines of evidence one can follow to test whether the predictions made by evolutionary theory are correct. Some of these are survival rates (clearly not every creature that has ever lived has survived to reproduce – if they had, the universe would be completely filled with bacteria, the population of which would be expanding outwards at the speed of light), and the evidence of the fossil record (increasing complexity diversity, and size in newer fossils, and also the existence of intermediate forms). Another line of evidence for evolution is the vestigial organs that occur in many creatures, such as the eye remnants in blind cave fish, the pelvis and femur remnants that exist in dolphins, and remnants in some microbes of the ability to photosynthesise. One can also observe “evolution in action”: speciation in plants, fast evolution of diseases such as flu and HIV, and many other examples.

I’m not going to go into the recent discoveries that Prof Branch covered, but suffice it to say there is enough material for several conferences. He also passed quickly over several new ideas that are being studied – we were running out of time!

In closing, Prof Branch discussed what many perceive as the conflicting forces of religion and science. Science provides us with facts, and through testing of ideas and experiments, it tells us what is true. Religion tells us how to employ those facts in our lives. The example of the different spheres of influence held by science and religion that he gave was of the atomic bomb – a stunning use of science, but a wholesale failure of ethics.

Two of the myths about evolution that Prof Branch dispelled at the end of his talk were particularly interesting to me. First, evolution cannot explain the origin of life. It can explain how life developed and increased in complexity, but not how it started. Second (I knew this already but it’s a stupid and oft-repeated objection to evolution by people who are too intellectually lazy to come up with anything more cogent) evolution is not “just a theory”. I encourage you to look up theory in the dictionary. When scientists talk about the “theory of relativity”, “theory of gravity”, “atomic theory” and “theory of evolution”, they are meaning it in the first sense.

In closing, I’ll list the guidelines Prof Branch gave us for handling the subject:

  • Respect the views of others
  • Recognise the different goals and limits of science and religion – they can be complementary
  • Be frank about ignorance, both personal and scientific
  • Insist on the testability of ideas and opposing ideas

I’ll leave you with a quote from Billy Graham that Prof Branch used towards the end of his talk:

I don’t think that there’s any conflict at all between science today and the Scriptures. I think that we have misinterpreted the Scriptures many times and we’ve tried to make the Scriptures say things they weren’t meant to say, I think that we have made a mistake by thinking the Bible is a scientific book. The Bible is not a book of science. The Bible is a book of Redemption, and of course I accept the Creation story. I believe that God did create the universe. I believe that God created man, and whether it came by an evolutionary process and at a certain point He took this person or being and made him a living soul or not, does not change the fact that God did create man. … whichever way God did it makes no difference as to what man is and man’s relationship to God.

Billy Graham: Personal Thoughts of a Public Man, 1997. p. 72-74

I am sorry that religious discourse has to intrude on a discussion of science. Many of those objecting to the theory of evolution on the basis of their personal beliefs are unfamiliar with the scientific method, the peer review process, and the language of science. Hopefully if, like me, your ability to comprehend this material was (or is) impaired by religious dogma and pseudo-science, you will be able to read the mainstream scientific literature that discusses the subject and gain more factual information in order to make an informed judgment on the topic.

For further reading, you can try Darwin’s Origin of Species (may be a bit dense – I haven’t read it), The Greatest Show on Earth by Richard Dawkins (be warned, he is an angry little man, but a good scientist), Guns, Germs and Steel by Jared Diamond (one of my most favourite books and authors), or The Structure of Evolutionary Theory by Stephen Jay Gould. Gould and Dawkins have both written a lot on the subject and may be a good place to start.

[Given my relative ignorance on this subject, if anything I’ve said here is inaccurate, you can be sure it was an error of transcription or comprehension on my part, and not an error of fact by Prof Branch!]

Lecture: Meaghen McCord on Bull Sharks

A couple of weeks ago Tony and I attended at talk on bull sharks (also called Zambezi sharks by South Africans) given by Meaghen McCord of the South African Shark Conservancy (SASC) based in the Old Harbour in Hermanus. We’ve heard Meaghen talk before at False Bay Underwater Club, but we were particularly keen to attend this talk (held at the Save Our Seas Shark Centre in Kalk Bay) because some exciting things have happened since Meaghen spoke at FBUC. It was the third (we missed the second one because we were in Malta) in a series of talks at the Shark Centre, concerned with sharks and man. The first speaker was Christopher Neff.

Truth and fiction about bull sharks

Bull sharks (Carcharhinus leucas) are one of the species of sharks that are tolerant of brackish and fresh water conditions. They are not the only species that doesn’t mind freshwater – other examples include the Ganges river shark (found in the Ganges in India – surprise!) and a cluster of Australian freshwater shark species all from the genus Glyphis. They are not, as is popularly believed, solitary or territorial, but have been known to form feeding and hunting aggregations. Nor do they have the highest testosterone level of any animal – an often repeated assertion that Meaghen pointed out is false. This idea was based on a 1970s-era study involving only three animals: a male bull shark, and two female sharks.

The internet abounds with misconceptions and pejorative words about bull sharks, calling them “known man eaters” and citing their enthusiasm for attacking humans. As Meaghen noted, even innocent-looking deer are known to attack humans, and the most dangerous creature on earth – measured in terms of deaths it directly causes – is the anopheles mosquito.

Bull sharks have a low value in fisheries as their flesh is full of ammonia and urea (in other words, it tastes gross!), but they are killed for the shark fin trade – particularly in developing nations such as India and Mozambique. They are also favoured by sport fishermen. Until recently there was no limit on how many could be caught by each angler, but they are now restricted to one bull shark per day. Which is still one too many, if you ask me. As a result of the fishing and the finning, the IUCN lists them as globally near threatened.

Some knowledge exists in Africa regarding bull shark distribution patterns, growth, movement and reproductive habits, but there is nothing in the way of relevant management measures for these creatures. As you’ll see shortly, it’s vital that international co-operation takes place on this species, because they cross borders with alacrity!

Bull sharks in South Africa

Prior to 2009, bull sharks had only been recorded as far south as the Sundays River. Some gut instinct, persistence, luck and hard work led Meaghen and her team to catch a bull shark in the Breede River in 2009, representing a 366 kilometre range extension for the species. What’s more, the shark they landed measured 4 metres total length (tip of snout to farthest extent of caudal fins) which was 50 centimetres longer than the largest bull shark EVER recorded anywhere in the world!

The upper reaches of the Breede River (near Swellendam)
The upper reaches of the Breede River (near Swellendam)

The shark they caught was named Nyami Nyami after the Zimbabwe river god, and was tagged and tracked for 13 days, during which time she did not leave the river at all. She went as far as 32 kilometres upriver, but spent most of her time around 11-15 kilometres up the river, eating the bait off the recreational anglers’ hooks. Her movement was mostly tidally driven, and theories for this include energy saving (important for wild animals), and the possiblity that fish are driven off the river banks by the outgoing tide, resulting in a free meal for the passing shark.

The tags in use in the Breede at the moment are acoustic tags that emit a signal that can be detected by a hydrophone. In order to track the shark, the SASC team has to follow it around with a boat, orienting the hydrophone to find the maximum signal strength to figure out which way the shark is moving. If they get too far from the shark, it’s lost.

Pumpkin

Since meeting Nyami Nyami, in January 2010 the team caught, tagged and tracked two males, both three metres long, called Pumpkin and Jeremy respectively. Jeremy was named after Jeremy Wade, the host of Discovery Channel’s River Monsters show and a so-called “extreme angler” who helped in the capture of both sharks (and was filmed during the process for his show, I assume).

Pumpkin was caught again in March 2011, and fitted with a pop-up archival tag (PAT). It was shortly after doing this that Meaghen came to talk at FBUC, and she shared how the tag had been programmed to pop off Pumpkin’s body after 99 days. It records light intensity, depth, temperature, and a range of other measurements, and when it pops to the surface it announces its location (barring any malfunction) to a passing satellite.

Beach on Ilha de Magaruque, one of the Bazaruto islands
Beach on Ilha de Magaruque, one of the Bazaruto islands

Pumpkin’s tag came off after only 53 days, and surfaced somewhere near the Bazaruto Archipelago off Mozambique. The shark had travelled over 2000 kilometres in just under two months – completely rubbishing the commonly-held view that these are sluggish, lazy animals. A reward is offered for the return of the tag itself (just in case you’re heading to Mozambique any time soon) – certain data can only be retrieved with the device in hand.

SASC

SASC’s objective is “promoting understanding of and participation in the management of bull sharks in Southern Africa.” They recieve funding from Save Our Seas, and support from the Department of Agriculture, Forestry and Fisheries (DAFF). Their experience with Pumpkin has led to what Meaghen called “three burning questions” that they’d like to answer:

  1. What is the role of bull sharks in the Breede River?
  2. How do they influence community structure in estuarine systems?
  3. How can this information be used to co-manage estuaries and apex predators?

The bull shark project aims are to determine the genetic structure of the Breede river bull sharks, and determine whether they are a distinct genetic group. They also aim to determine abundance and population structure of these sharks (how many males, females, what ages they are, etc.) and to find out how they utilise their habitat.

A question that I’d love to see answered (and which they plan to) is whether the Breede river is a pupping ground for Zambezi sharks! The St Lucia estuary is the only known pupping area for these sharks in South Africa, but it’s been closed to the sea for the last decade.

The Breede river is also impacted by physical activities and chemical substances brought there by humans, and it’s important to determine how these affect the sharks, their distribution and movement in the river.

Future plans

SASC plans to collect fisheries and eco-tourism data, conservation status, current management strategies, distribution and abundance data for contribution to an online “bull shark atlas” which will facilitate international co-operation and education as regards this species. They’d also like to find out whether these sharks exhibit philopatry (return to their own birthplaces, and possibly breed there too).

An acoustic array is planned, comprising a set of permanently fixed receivers in the river that will record the movements of tagged animals. SASC hopes to tag prey fish such as dusky kob and spotted grunter, as well as sharks. An exciting development in this regard is the Ocean Tracking Network, an international initiative that will be by led locally by the South African Institute for Aquatic Biodiversity. The OTN will comprise a large number of underwater receivers or listening stations that can all read and record data from compatible tags. In this way a fish tagged in South Africa can be tracked all over the world, if it swims near any of the OTN receivers.

The Breede river system is massively impacted by human activity in various ways, and SASC would like to define the role of apex predators in this sort of environment. There are also plans to study niche partitioning (such as concentration on specific food sources by each species in the face of competition) with other large apex predators. Great whites, bronze whalers, ragged tooth sharks and hound sharks are also found around the river mouth.

Bull sharks and people

Unsurprisingly, some of the Breede river residents and holiday home owners have reacted very negatively to the discovery of sharks on their doorstep. The fact that these sharks were there long before the people were, and that no incidents of any kind have been reported, as well as the presence of several other shark species just outside the river mouth (as I mention above), makes this reaction a bit ridiculous. The presence of these sharks also indicates that the Breede river is a healthy ecosystem, which should inspire pride in those who live near it. Meaghen said that SASC receives co-operation and enthusiastic support from many of the locals too – particularly those who have been in the area for a long time. Personally, I’d be thrilled if a shark lived in my front garden!

I particularly liked the thoughts expressed by one of the other members of the audience, who apparently has a boat and house at the Breede river and has offered to help Meaghen with the project. He expressed concern that “Rambo types” will come to try and catch the sharks or prove something about themselves, but he also said that the bull sharks “deserve to be there”, and they don’t come and harrass him in his bed, so he sees no reason to disturb them in their home.

For pictures of bull sharks, check out the SASC website or use the Google – I don’t have any taken by either me or Tony and I hate poaching other people’s pictures! They are very beautiful creatures, with sharply delineated, squared-off faces.