Home testing of the SharkShield

One of the joys of having a manoeuvreable, user-friendly little boat is the opportunities that arise to participate in a variety of  interesting events. Lately, we have been doing a number of open water swims; not swimming, but providing boat support to a swimmer who is traversing a stretch of open ocean. Last year we did the Swim for Hope around Cape Point, and the Freedom Swim from Robben Island to Big Bay, and several more of the same in 2015.

We used SharkShields at the Swim for Hope events, and with the increasing number of swims that Tony has been supporting we thought it might be time to invest in a SharkShield for use in these events. The SharkShield is a portable device designed to be worn by a surfer, free diver or scuba diver. It has a long antenna which emits an electric current which is intended to repel sharks. When used for open water swimming, the SharkShield is typically attached to the side of the boat with the antenna in the water alongside, creating a radius of 3-5 metres within which the current can be felt by a shark. If you touch the end of the antenna there is a noticeable pinching sensation, so swimmers have to be careful when approaching the boat.

Tony testing some SharkShields in the pool
Tony testing some SharkShields in the pool

Proper scientific testing of the device in Australia and South Africa indicates that it is by no means foolproof, and does not work in all situations, but it seems to have a certain usefulness if your visiting white shark is in the right frame of mind. The paper reporting the results of the SharkShield tests says:

Our study assessed the behavioural effects of the electric field produced by the Shark Shield Freedom7™. The study was performed in two locations and tested two distinct approach and behavioural situations to assess whether the response to the Shark Shield™ was consistent across behaviours. The electric field did not affect the proportion of static baits consumed, but significantly decreased the number of breaches, and surface interactions on a towed seal decoy.

The authors suggest that since breaching requires significant energy outlay, sharks may be more cautious to mount a breaching attack in the presence of anything out of the ordinary (I’m paraphrasing). Even with knowledge of the device’s usefulness only in certain situations, it still provides great peace of mind to swimmers while they swim in parts of the ocean where sharks are known to be mobile, such as False Bay.

The Freedom7 unit outside its neoprene case
The Freedom7 SharkShield unit outside its neoprene case

Tony was able to examine and test several lightly- to well-used Freedom7 SharkShields to see which of them worked, and what the battery life was like. In the process he shocked himself several times, which provided great entertainment to me and caused some consternation to the cats, who were themselves strolling around alarmingly close to the antennae. The unit itself is filled with something that looks like glycerin, to keep it pressurised and protect the electronics. The red switch at right turns the device on and off, and red and green lights indicate whether it’s on, charged, and functioning. A wet hand applied to the end of the antenna also gives information on whether the device is functioning…

The shark repellent cable that was tested at Glencairn this summer is a massively scaled up version of these retail SharkShields. It is essential that development and testing of non-lethal shark mitigation devices continues, to provide an alternative to measures such as the KwaZulu Natal shark nets, and the French government’s shark fishing activities at Reunion in response to multiple shark bite incidents at the island.

Testing a shark repellent cable at Glencairn

Signage at Glencairn explaining the test
Signage at Glencairn explaining the test

Perhaps you have noticed some new signage and a little wooden hut at Glencairn beach, where an exciting test – of an electronic cable to repel great white sharks – is underway. The cable is a massively scaled up version of the Shark Shield technology with which many surfers and lifesavers will be familiar. The Shark Shield has been subjected to scientific testing, and is effective in certain circumstances.

The risers on the cable are clearly visible at low tide
The risers on the cable are clearly visible at low tide

The cable is a collaboration between the KwaZulu Natal Sharks Board (who would like an alternative to the gill nets and drum lines currently used to harvest sharks and other marine life off South Africa’s north coast), and the Institute for Maritime Technology (IMT) in Simon’s Town, a division of ARMSCOR. Shark Spotters and the City of Cape Town are assisting with the testing phase, which started in November and will continue until the end of March 2015. A permit has been obtained from the Department of Environmental Affairs.

The cable is 100 metres long, and is situated at the northern end of Glencairn beach. Cape Town is an ideal location to test things like this, because Shark Spotters has ten years of shark spotting data that will give a baseline measure for “normal” white shark activity without the cable. When something new (the cable) is introduced into the environment, changes in behaviour relative to the baseline data can be ascribed to its presence. Fish Hoek was originally mooted as an ideal beach to run the test, but the trek net fishermen were concerned for their fishing opportunities and so the test was moved to Glencairn.

The cable is off the end of Glencairn beach
The cable is off the end of Glencairn beach

The cable emits a low frequency electrical pulse that – it is hoped – will repel sharks. The electrical output of the cable poses no threat to swimmers or surfers, but for obvious reasons people are requested to keep clear of it for the duration of the experiment. The cable has electrodes on either side of it, supported by vertical risers that are marked by small orange buoys (so the cable runs down the middle of the rows of buoys in the pictures). At high tide the buoys are below the surface, but Tony took the boat past at low tide and photographed them sticking out of the water.

Shark Spotters will be monitoring the cable from the mountain above Glencairn, and a video feed will also be used to closely analyse the movements of any sharks that approach the cable. The risers on the cable (marked by the orange buoys in the photographs on this page) are semi-rigid, designed to minimise the risk of entanglement of any marine life. As it is the end of whale season in False Bay, there is not much risk of a whale visiting this location. Despite that, a boat and crew are on constant standby should an entanglement situation arise.

There is a full report on the testing phase, with an artist’s impression of the cable underwater, on the Sharks Board website, including a list of frequently asked questions (which should set your mind at ease). There’s also a great post at Round About South that includes pictures of the study area, and of the cable from the KZNSB document.

It’s important to note that this is an experiment, and no additional protection from white sharks is offered or guaranteed while the cable is in the water.

Newsletter: Sweets on the boat!

Hi divers

Weekend diving

Sunday: Boat dives at 9.00 to Atlantis Reef (5-27 metres) and 12.00 to Tivoli Pinnacles (10-22 metres)

Conditions report

Both the Atlantic and False Bay have been great during the week. We had 8 metre visibility on an Atlantic charter on Wednesday, and today’s offshore winds have flattened False Bay nicely, and cleaned the water significantly. The water temperature on both sides of the peninsula is similar, 10-12 degrees, and the visibility is around 8 metres. I feel that if the water temperature is a single digit the viz needs to be double that, but we don’t always get what we want! False Bay will be the best option this weekend so we will plan to launch on Sunday, at 9.30 for Atlantis and for Tivoli Pinnacles at 12.00.

Sweets on the boat!
Sweets on the boat!

For the diary

December is starting on Monday and the season gets really busy, really fast. We are going to focus on Open Water, Advanced and Nitrox courses this December. We will add a Nitrox course free to the first 5 people that sign up for an Advanced course during December. We are also able to run the Research Diver, Drift diver and Equipment Specialist courses during December and January. To see the range of courses available take a look here.

Please diarise our open house on Saturday afternoon, 13 December. Proper invitations to follow.

For interest

On Sunday while out on the boat we passed by the prototype shark repellent cable at the end of Glencairn beach. This is a non-lethal approach to keeping humans and sharks separate, and is in the testing phase. You can see how the cable is lying with electrodes on each side of the centre cable, the electrodes marked by orange buoys on risers that stick out at low tide. There’s a description of the cable here, and we’ll have some more photos on the blog next Wednesday.

The risers on the cable are clearly visible at low tide
The risers on the cable are clearly visible at low tide

This is a great project with a potentially significant impact on the relationship between humans and sharks in South Africa. The cable was developed at the behest of the KZN Sharks Board, and is being tested in co-operation with Shark Spotters and the City of Cape Town.

For the history books

Last Friday the wreck of the Clan Stuart turned 100. She ran aground in False Bay on 21 November 1914. We had a little commemoration of our Clan Stuart dives on the blog.


Tony Lindeque
076 817 1099

Diving is addictive!

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Social media and conservation: a real life cautionary tale

Shark Spotters shared this very interesting video about social media and the role it can play in conservation efforts. It’s just under ten minutes long and the warning about language and disturbing imagery is serious, so use discretion, but I’d recommend you watch it carefully if, like most of the planet, you’re a social media addict.


I watched the video, and shared it on our facebook page, had dinner, and went to sleep.

The following morning while reading the news (or what I consider to be news), I was confronted by a real, disturbing example of how a social media campaign – one which its participants fervently believed was saving sharks left, right and centre – has actually damaged a conservation effort and possibly led to more of what the activists were trying to prevent.

The campaign was in response to the shark mitigation efforts of the government of Western Australia (#noWASharkCull is the protesters’ hashtag). These mitigation efforts involved baited drumlines to catch sharks near beaches. Target species are bull sharks, tiger sharks and white sharks. Sharks over three metres long that are found still alive on the drumlines are removed from the hooks, shot, and disposed of at sea. It’s unscientific (didn’t work in Hawaii), indiscriminate, and very expensive.

Unfortunately those who disagreed with the WA government’s measures to reduce shark bites took it too far, with vicious personal attacks, death threats – mostly issued via social media – and vandalism being the order of the day. There is also the small fact – ignored by the protesters – that the WA government’s plans are nothing revolutionary, with drumlines in use in Queensland for decades, so their protests are 50 years too late.

Perth Now reports that

The 14-week trial generated “offensive and contained personal attacks on members of the Government and staff involved with the program” on Twitter and Facebook.

Supporters said they had “no choice but to stay quiet due to the level of abuse and vilification received”, describing the level of personal attack and social media postings as “unacceptable”.

“The Government is now more acutely aware of the level of abuse that was directed towards supporters of the program and the reasons for so many staying silent,” the Government responded in the PER.

Partly because of this postulated “silent majority” who approve of the shark cull but are too afraid to express their support because of the behaviour of the anti-cull protesters, the WA government plans to continue it for another three years, with the belief that it has a mandate to do so from this (real or imaginary) silent group of supporters. Good job everyone!

Want to make a real difference? Support Our Sharks, an Australian science based conservation organisation, has excellent resources on how to make a submission against the cull. Be calm, be rational, be science-based. Be quick, because the deadline for submissions is 7 July. And maybe stay off facebook…

Thanks to Martin Graf and DaShark for putting this in my news feed.

All about the shark exclusion net at Fish Hoek beach

Over-under view of the exclusion net at Fish Hoek
Over-under view of the exclusion net at Fish Hoek

The trial of the shark exclusion net at Fish Hoek beach has come to an end, and since we’re still seeing and hearing from people who don’t know anything about the net, or how it works, I thought we’d provide a full guide to the net, using all the blog posts we’ve published since the trial was announced. It’s a combination of a conservation initiative and a human safety initiative, and has achieved both goals beautifully.

Finally, you can read about the end of the trial and the possible future of the net here, or here.

Meanwhile, the Fish Hoek business community has had its best year in recent memory, thanks at least in part to the exclusion net, which has given bathers a sense of security about visiting Fish Hoek beach again. As small business owners in the deep south, we’re grateful for the efforts of Shark Spotters and the City of Cape Town to make the local beaches safe, and also to make them feel safe.

Just to be absolutely clear, the organisations involved in the implementation of the shark exclusion net at Fish Hoek are the City of Cape Town and Shark Spotters. It was “monitored” by the thousands of swimmers who enjoyed using it!

Newsletter? What newsletter?

Dive briefing on the beach at Sodwana
Dive briefing on the beach at Sodwana

We’ve been in Sodwana this week, and Tony and I are sticking around in that part of the world for another couple of days, so there’s no newsletter today. In case you really, really need something to read, here are a few highlights from the blog this past year or so:

Bookshelf: Demon Fish

Demon Fish – Juliet Eilperin

Demon Fish
Demon Fish

Reading this so close to Thomas Peschak’s book Sharks and People made for an interesting juxtaposition of two books that are both concerned with similar subjects. Peschak makes his interest in the relationship between humans and sharks explicit in the title of his book, and goes on to explore it in a primarily visual manner.

Juliet Eilperin is an environmental reporter for the Washington Post, and despite the singular focus of its title, her concern in Demon Fish seems to be similar to Peschak’s: sharks and people. I’m not sure if this is because, as an outsider to the world of shark research, shark diving, and shark conservation she had couldn’t but focus on the human element of sharks’ existence, or whether it was a deliberate tactic.

Whatever the reason for the book’s focus, this is actually a very good introductory volume to give to someone who doesn’t know much about sharks, and who may not understand the conservation concerns surrounding them. This is not a scientific volume, and may disappoint shark fanatics who purchase it expecting to be enlightened on shark biology. Eilperin provides some facts about a few of the better known (read: more charismatic) species of shark, but the bulk of the book comprises interviews with shark scientists (such as Neil Hammerschlag, Alison Kock, Sarah Fowler, and Barbara Block), fishermen, activists (including seriously legitimate ones like Sonja Fordham), and Asian players in the shark fin trade.

Eilperin dives with sharks in the Bahamas, eats shark fin soup, and travels the world putting together a picture of sharks’ role in local economies – the lucrative fin trade, whale shark tourism in Belize, cage diving in Gansbaai, South Africa – and in human culture. After visiting a shark caller in Papua New Guinea, she traces the history of the 1916 shark attacks along the North Atlantic coast of the USA that did so much to shape our modern perception of sharks, and interviews Jaws author Peter Benchley’s wife (he is deceased). An analysis of efforts to mitigate human shark interactions, lead her to Cape Town’s Shark Spotters program, the Shark Shield device (formerly Shark POD) and the indiscriminate shark mitigation program of the KZN Sharks Board. The acknowledgements at the end of the book read like a who’s who of shark researchers and conservationists (including the venerable Eugenie Clark). Ms Eilperin’s research was thorough!

The book seems to have been reprinted as Sharks: Travels Through a Hidden World in the United Kingdom. I prefer this title, as Demon Fish seems a little bit exploitative and sensational, particularly given the fairly benign nature of the book’s contents. There is a detailed and fascinating review of Demon Fish at the London Review of Books, an interview with Eilperin here, and a very short interview with her here.

Buy the book here if you’re in South Africa, and here if you’re not. If you want to read it on your Kindle, go here.

Bookshelf: Sharks and People

Sharks and People – Thomas P. Peschak

Sharks and People
Sharks and People

Thomas Peschak has written and photographed several wonderful books – Currents of Contrast, Lost World, South Africa’s Great White SharkWild Seas Secret Shores of Africa – and will hopefully produce many more. He is a trained marine biologist, but explains eloquently in the introduction to this book how he left science to devote himself full time to photographing the natural (mostly marine) environment, and man’s interaction with it, in the belief that he could make an important contribution to conservation efforts in this way. Unlike some of the other “conservationists” who we’ve encountered paddling in South African seas, Peschak’s assessment of the impact of his work is accurate, and as a rule he does not include himself in the images, which puts him way ahead of the pack (in my book, at least).

Like all of Peschak’s books, the photographs in Sharks and People are breathtaking. They are accompanied by succinct, scientifically up to date information encompassing the various aspects of our relationship with sharks. In the acknowledgements section at the end of the book he lists the various scientists and others who assisted with fact checking the book, as well as citing various studies and papers that provided the scientific information that he discusses.

Peschak does not attempt to whitewash the complexity of our relationship with sharks, and some of his photographs are disturbing and difficult to look at. He also details the impact of the shark nets in KwaZulu Natal – uncomfortable reading, but essential not to ignore or to simplify. This  book is not a breathless injunction to save sharks based on feelings and appreciation of sharks’ beauty. Aesthetic appreciation is certainly there, but so is a clear eyed assessment of the dangers posed to one another by humans and sharks, and the role played by sharks in marine ecosystems.

The photograph on the cover of the book is this one, and Peschak explains its origins (some of that information appears here). On the back cover, you can see this photograph, which is not a composite or manufactured image, but was taken during the testing of a shark shield product in KwaZulu Natal.

You can read an extract from the book here, and also check out some of the shark photographs that appear in the volume.

You can get a copy of the book here if you’re in South Africa, otherwise here or here.

What does the Fish Hoek shark exclusion net look like?

Early in December last year, Tony escorted some members of the media on a dive/snorkel in the shark exclusion net at Fish Hoek beach. To remind you, this net is a highly visible barrier in the ocean, designed to keep sharks and humans apart, and both species alive. It was specifically designed not to catch anything, unlike the gill nets that are deployed by the Sharks Board off the KwaZulu Natal coast. This is what the net looks like from underwater:


This is what it looks like on the surface. The day was quite grey and dreary when we dived it, but the yellow buoys along the top of the net are highly visible. At the end of the day the net is retrieved, and if the weather and sea conditions permit, it is deployed again in the morning.


When the net was deployed for the first time (a trial run – it’s been tweaked and improved since then), I took some photos (part i, part ii).

Exploring: The shark exclusion net at Fish Hoek beach

The net, with a hand for scale
The net, with a hand for scale

One Tuesday in early December, Tony escorted some members of the media – Murray Williams of the Cape Argus, and Bruce Hong of Cape Talk radio, on a dive along the inside of the shark exclusion net at Fish Hoek beach. It was just before the start of the school holidays, and since the net has been trialled multiple times by now and is working well, it’s a good time to raise awareness of the additional beach safety and – importantly – peace of mind that the net offers. I tagged along as photographer.

Over-under view of the exclusion net at Fish Hoek
Over-under view of the exclusion net at Fish Hoek

The net at Fish Hoek beach is a world first. It has a fine mesh that is highly visible underwater, and is designed not to catch anything – unlike the shark gill nets in KwaZulu Natal. The net is put out in the morning and retrieved at the end of the day, but only when sea conditions allow it. The south easterly wind can bring huge quantities of kelp into Fish Hoek bay which would foul the net, so when there is a strong south easter the net cannot be deployed.

If you’re a water person, please educate yourself on how the net works, and its intention, and share it with your friends. Even now, nine months after the trial started, I hear uninformed comments from people who have not bothered to do any reading about the net, and assume it’s the same kind of net as the ones in Durban. It’s not. The whole idea is that nothing – no sharks, no humans, no klipfish – gets hurt. Shark Spotters and the City of Cape Town have been very clear on this from the start. I had a bit of a rant about this late last year.

Murray dives down to check out the exclusion net
Murray dives down to check out the exclusion net

I digress. We went to the beach, got suited up, and went to check out the net. It was spring low tide, so at its southernmost end we were in about 2 metres of water. The net is high enough that when the tide comes in and the yellow floats rise with the water level, it simply unfurls further downwards, making an unbroken curtain. The lower portion of the net rests on the sand, with two parallel weighted lines to ensure that it lies flat. You can see that in the photo above Murray is gripping one of these leaded lines, and that there is a fairly large amount of net waiting on the sand for higher tides.

Murray and Monwa discuss the net
Murray and Monwa discuss the net

We stuck close to the net, and didn’t see much marine life on the sandy bottom. I spotted a large sand shark (when I say I “spotted” him, I mean that I almost landed on top of him). We were mutually surprised, and he zipped away into the bay, sliding neatly under the bottom of the net. I also saw a box jelly cruising along the net. Given my recent history with box jellies, I kept clear! The sea floor in the area where the net is deployed is level, sandy and free from rocks. There’s more life on the catwalk side, where beautiful rock pools wait to be snorkelled.

We were accompanied by Monwabisi Sikweyiya, who is the Field Manager of Shark Spotters. He is a hero and I always feel a bit star-struck when I see him (although he has no idea why – he probably just thinks there’s something wrong with me). He swims along the net regularly – someone does each time it is deployed, actually – to make sure that it’s released properly and hanging straight down.

After the dive
After the dive

Swimming inside the net is completely voluntary. When a shark is seen in Fish Hoek bay the Shark Spotter still sounds the siren and the flag is raised to clear the water. The Shark Spotters team are still waiting to see how a shark will respond to the net when it swims close enough to be aware of it. So far none of the local sharks have come close to the net, as the summer season when sharks move inshore has only just started. Tony was half hoping that we’d be swimming along inside the net, look out through the mesh – and blammo!  – see a great white shark. But we had no such luck, if that is the right word.

You can read the article that Murray Williams from the Argus wrote after the dive, here.

Dive date: 3 December 2013

Air temperature: 22 degrees

Water temperature:  17 degrees

Maximum depth: 2.3 metres

Visibility: 4 metres

Dive duration:  25 minutes