Barry Bruce on the recent shark deaths
On Saturday a diver was killed by a shark off Rottnest Island in Western Australia. The fatality was the third in Western Australia in two months – the first being at Bunker Bay, Dunsborough, in early September, and the second at Cottesloe Beach, Perth, on the 10th of October.
In terms of proximity and timing the deaths are unprecedented in Australia. The closest would be the two deaths in South Australia that occurred two days and 200 kilometres apart just prior to the Sydney Olympic in September 2000.
The attacks have prompted a new wave of collective fear in WA which, in turn, is triggering a media response. What is causing the attacks? Is it abnormal? Do we need to cull sharks? These are some of the questions that being asked. And rightfully so.
In this ABC video, filmed after the second attack at Cottesloe Beach, CSIRO shark expert, Barry Bruce, says that despite the apparent increase in shark deaths the odds of being killed are still incredibly remote. It's seven minutes long but well worth watching as he unemotionally lays many of the common myths to rest.
"Every attack seems to prompt an immediate call for a shark cull...would that bring any benefit at all?
"We know that white sharks are visitors to the waters of Perth, they come from all the southern Australian waters moving through the Perth area. It would seem highly unlikely that culling at one particular point would reduce the numbers visiting that site."
Comments
No-one seems to be able to answer the question of are great white numbers increasing and by how much?
It's all well & good to have a calm and rational, as that guy in the video does, but at what stage do they admit that there's a problem? The fishing patterns ARE changing. The quotas ARE changing. At what point do they say things are a bit out of balance and need to be corrected? They can't deny it forever.
Shark attacks are tragic. I understand that probably better than alot of others having grown up surfing in SA and seeing the impact a death has on a community. However, when we venture into the water we do so at our own risk. This has always been the case and one which (mostly) people understand. We are entering their natural territory, not the other way round. To cull an animal in its natural environment (especially one that it a threatened species) is not the answer. Education surely has to be the best medicine.
I guess what I was trying to say is that sharks aren't necessarily in their 'natural' environment anymore. We've disrupted it by changing their food stocks. We've even affected their behaviour by chumming and cage diving. Is it not possible tht these things are causing the problem?
I vaguely remember, Steve, that a study off the South African coast showed numbers increasing from 5 years ago.
One thing is for certain. We are protecting the top of the food chain, while we trawl and pillage their food source on exponential levels ... I don't believe in a cull, but what I do believe in, isn't (seemingly) possible or plausible.
We stop eating seafood, and put a thousand fisherman out of work and let the ocean regrow as it was to 25 years ago.
BTW, no disrespect to anyone affected by the recent shark attacks but is Barry Bruce the Greatest Aussie name ever or what?
Barry Bruce is a Double barrel Aussie name . And adding to the frivolity is that Bruce is the name of the lovable GW in the Nemo film ..... i wonder if he changed his name to gain respect amongst punters and otehr shark enthusiasts .
But seriously Barry and many others either know very little or don't want to come out and give an inclining of what they think , as many " experts " always like to remain that and not say something to far reaching that they cannot definitely back up with hard evidence .
So i would say that GW's are opportunistic as thieves who will give anything a go once , but as accomplished as Assassin's rarely seen or known as they clearly have one up on their two legged friends and foes .
One thing strikes me is in my recollection of alot surfers + other victims have been taken in the middle of spring . Migratory , most likely . But warming oceans , juvenile prey , and perhaps tidal anomalies , ocean currents have influence . And like many other travellers knowing when the conditions are ripe will see 'em " blow in and out of town " with a fair bit of rhythm year to year .
I'm a little past my sole travelling /surfing days , but if i was young and about to step forth on the paths i've already beaten . I'd be writin' down a no go zone calender , and only surf alone a few hrs from sunrise/sunset , and only on the best of sunny days after atleast 12 hrs of offshores . And to think of some of the sojourns to ........... and ................ alone and not even seeing people on land for days and close to a week and a half at one special spot , they were testing days in lulls . But oh the rewards .
One thing is for certain the number of dodgy spots is growing with a proliferation of seal colonies and whales migrating . Perhaps we are heading back to the day when Real Men feared the ocean , as they were the ones on the " frontier " of the day . And to go overboard was a certain death , or maybe knowledge has learnt us that the sharks were just following the trail of blood that those "wooden ships " would have left years after their first catch .
So maybe man has been training em up for longer than we think .... Like atleast 500 years longer .........
Wind and Tide, All Men Abide
I don't know any surfer who would honestly be upset, on the most basic level, if sharks were no longer an issue. Plain fact.
If sharks were not an issue, I suppose that would be nice, but at what expense. Imagine if there were no sharks and every tom , dick and harry could venture into the ocean with no fear, probably putting man at the top of the food chain in the ocean too. Look at what man has done to the land, we do enough harm to the ocean from sea level, let the masses underneath it and they will rape and pillage. Top to bottom, you say "the balance needs to be corrected".Well isn't that what mankind has been doing the last hundred years and now we are just correcting the corrections from days gone by, keep on tinkering with the balance of nature and it will eventually fall over.
I'm a surfer from the area in question, and I can tell you that it is the talk of every lineup and every carpark at the moment. For the first time in my 30 years of surfing in this part of the world people are genuinely nervous and skittish about getting into the water. There have always been sharks here, but now it's a bit more serious. There are a few theories about why but the most commonly agreed upon is that the population of whales that migrates up and down this coast has increased in number quite significantly in recent years. This means the number of sharks tailing them looking for the sick and the young has also increased. This time of the year those whales are moving past here to the south to meet the Japanese whaling fleet in Antarctica. This seems reasonable to me - there is clearly a lot more whales around than before. But there is also a lot more people in the water than there ever has been. The Perth metro beaches are so much more crowded than ever before, as are the beaches down south and it seems like factors are colliding in this respect.
cull the white pointers we dont need them. my m8 shit him self recently at parsons beach sa an 8footbrozny i paddled straight in didnt wait 4 m8 i wasnt goin 2 rescue him if he was bitten. well done 2 the lads down at semaphore jetty who caught 2 yeserday. there are way 2 many sharks and no fish
Always very safe surfing in Japan and Asia due to the popularity of shark fin soup! Shark Shields work I'm sure the authorities could set up networks of transmitters to repel sharks from city beaches. At my local last year we had a spate of sightings in the lineup of bronzies and 1 great white - that one had us nervous. I used to paddle out at the crack of dawn and sometimes just before - not any more!
Agree with zenzen. Only today I bumped into a mate who I hadn't seen for many years and the convo immediatley turned to sharks. Like zenzen says, sharks have always been a constant in the region, but things are decidely a little hairy now. Last week, I watched a wave breaking several hundred metres from shore, it looked pretty good and their would normally be some crew onto it. But not today and I sure as hell wasn't going out there on my own. But go to the "name" spots and they're packed. Probably just business as usual, or is it a case of safety in numbers??
Listening to Barry, whilst he was happy to quote his shark attack stats dating back to the 1800's, what the CSIRO probably do not and are unable to record are the ever increasing shark sightings and encounters occuring in the South West and Perth/Rotto regions.
It's abnormal.
Previous comments allude to the fact that no one wants to readily admit that Great White Shark numbers are increasing and the human interface - for whatever reason. I'm no scientist, but several decades of protection has to mean an increase in numbers. Scientists are happy to say that whale numbers have increased as have seal populations in the South West...But not Great White Shark numbers? So Great Whites don't only eat Seals, fair point, but has anybody been to False Bay or Dyer Island in South Africa...and as Barry points out, the Neptune Islands in South Oz? Sure, most probably do not hang around and move on, but they know where to go for a scrumptious, fatty, food source.
And for the record, the attacks in WA are not just a seasonal occurrence. Fatal attacks have occurred in the months of December, July, August, September, October, March....
I'm not saying that there should be a cull, I'm just saying that numbers have increased (in my opinion)and Bazza thinks that a cull will make no difference.
I'd like to hear from fishermen in the region and see what they think regarding the Great White numbers. Yep, more people = more encounters...but is there more?
Thanks to all you guys for the feedback down south WA..As some of you may recall my organisation Whitetag operates a not for profit environmental trust TAG FOR LIFe.We provide funding and logistical support to scientists researching the shark,in particular the white shark in Australian waters.We are currently co funding a research project out of Victoria on juvenile whites up an down the eastern seaboard and it appears Victoria is the point of origin for an eastern population.
Like you in WA,we have been experiencing more shark activity over the past few years but, rather than call for culling,we decided to help fund Barry and his CSIRO colleagues to learn more about these animals around the aussie coast.These are good men seriously underfunded,srimping and saving for every dollar that is becoming harder to find..Too be honest,I feel as ocean users we have an obligation to learn more about the environment we have chosen to recreate in.I have grown up in coastal Victoria, am a keen surfer and like you guys out west,I agree there are purely and simply more and more people using the water both under and above.Our thirst for isolation and pristine environements is taking us further and further afield,so its only logical the chances of interaction with marine predators will increase.Please keep giving us feedback on exactly what is going on down south in WA,I know for a fact having worked with Barry for many years,he is deeply committed to his topic and sharing the research findings but,he doesnt know whats going on in every pocket of the country..Its our role as everyday water users to start providing these guys with regular feedback,even a sightings register would be useful..
Our role at TAG FOR LIFE is to educate the broader public about our marine world,so how about all surfers and ocean users jumping on board and giving us ahead,surely everyone is going to benefit !!
@Whiteshark: It wouldn't be a bad idea to create / maintain a 'Shark Spotting' web site/page, so that people could post their 'encounters' or sitings with date, time, size of shark, etc., etc. You may be able to tap into a good source of otherwise unpublished / unnoted information.
If there's already such a website / url, then post here perhaps for starters.
And thanks for all the good work you - and the scientists - are doing in this area. I think most comments posted reflect that (the majority of) surfers understand they are 'trespassing' to some degree, but if we can take steps to reduce the risk through knowledge and better understanding / data then that's got to be a good thing.
Cheers, Gray.
I was surfing the next break down (beer barrels) at the same time when that girl got bitten by a white pointer in Tassie a couple of years ago. It freaked me out and I bought a shark shield and attached it to my board. I used it once got zapped about eighty times, looked at strangely by the locals and sold it to some other guy in Hobart. It cost about 600 bucks. Did feel safe though. Anyone else got one attached to their board?
Are shark shields proven to work? I've heard from people that they may actually attract sharks to the area.
Didn't someone get taken recently (maybe in S Africa) while wearing one?
It was Peter Clarkson, the fella that got taken in South Oz last Feb. He was wearing a shark shield. At least it was reported that he was and he had a testimonial on the Shark Shield website.
I'm against Shark Shields and here's why.
Sharks have sensory organs known as ampullae which pick up electrical signals.
If someone is wearing a shark shield and sending out pulses of electric current into the ocean, surely any shark in the near vicinity would be fascinated at what the foreign signal is.
This would attract the shark to the surfer, and although he may be protected from the field around him (I'll adress this in a second) all the other surfers around would be put in danger.
For this reason I would never use one, and would not be comfortable with anyone else using one. I know lots of crew from SA who feel the same and will tell someone to go in if they have one on.
Now the reports of the field being strong enough to deter the shark as it gets closer to the person has also come under question, as I heard a story recently where one was wrapped around a big bait fish and fed to a Great White no worries..
Good info Craig. I sold it and bought another board. Never saw the guy who bought it again. Would love to know how he got on with it. It was like surfing with an electric fence attached to the back of your board. It was so annoying I swapped boards with my mate and he had a go. He wiped out and got it stuck around his leg. He was zapped mercilessly.
Wonder if the sheep carriers parked of Freo at all times of the year are a contributing factor to all this.....just a thought.
Gray,your idea of a sightings log is something we have considered for sometime and dead right,perhaps Swellnet is a great point of contact.PIRSA(primary industries of south Australia)have one operating at the moment but, joe public has no idea it exists.So yes,I think it would be a useful tool to have permanently affixed here..
Re shark shields,research has been carried out at the Neptunes and it was proven shark shields have minimal to no effect,especially on a shark hell bent on getting to its target..A number of the AB divers use them here in Vic but more for piece of mind than anything else.Most come up cursing and swearing at the damn things..
Some 7 to 8 years ago I was listening to an ABC radio show on a Sunday night whilst returning from a Motercycle event. It was about 4 animals dangerous to humans. An expert in the field gave a 10 minute or so run down on the animals invloved. The first three were something like, Funnel-Web spiders, King Brown snakes and Salty Crocs. No problems there I thought. The last was of course, Great Whites. The expert was a South African doing a research project at some University about Great White attacks by interviewing survivors (derr!)about what happened etc. The only common finding that he came up with was that in about 50% of the cases the surfers admitted to the fact that they had had a piss in their wetsuits shortly (minutes) before the attack. Now, I know statistically, a 50% correlation between two events does not prove, or even assume cause and effect, but it was good enough for me!
I know it sounds like a cliche, but we're going into their territory that they've ruled over for hundreds of thousands of years. We've been surfing in their territory for about 60 years, give or take.
Yes it's tragic that people get taken, but no one is forcing people to swim in the ocean. If you don't like the risks, don't go in.
My name is Martin Grace and I am the General Manager of Shark Shield. I read the previous comment by Craig that the Shark Shield device attracks sharks. Please refer to our Frequently Asked Questions area on our website (www.sharkshield.com) which highlights why this is not true.
Sharks have a range of senses that work at various distances, with electrical sensing only working at close range. Even with our device producing a large amount of current to generate the protective field, the poor conductive qualities of sea water means that even this large electrical current/field is only rated at a 3 to 5 metre radius from the antenna.
ps. Also in regards to the other comment about getting a shock from the device. Yes it does produce a large pulsating current but if the antenna is kept underwater then if you do come into contact with the antenna it will be minimal or nothing at all. The problem is more severe if you for example you lift your leg out of the water if you find that the antenna has looped around your leg etc. Rather than the water providing the easiest current path between the two electrodes that are housed in the top and bottom of the antenna, you may become the current path between the two electrodes because one of the electrodes may now be out of the water. So as stated previously keep the antenna underwater, and for surfing preferably purchase the SURF7 model which mounts to the back of the board rather than the FREEDOM7 model that attaches to your ankle. More information about this is on the FAQ area on our website that I highlighted in my previously blog.
Either a very big white shark or killer whale was seen launching out the back of Southsides, Margaret River, about 5.30 this morning by myself and one other dude. I was in the water and the other guy was up in the carpark. It was both amazing and super heavy.
Regards Anthony (received via email).
3 to 5 metre radius from the antenna,you are joking. one ton plus of great white at full steam ,ready to take its prey,a small electrical field is not going to deter that fish.....can you confirm was peter clarkson wearing a shark shield when he was taken......your company took down his testimonial from your website hours after his fatal attack.?
Hi Victor,
Your assumptions that the field does not stop a shark is incorrect.
It's interesting to view the various websites/blogs to see people make up a variety of stories about our product with no proof behind their assumptions. I realise that this will always happen because of the type of product it is. The problem is that user can't go up to a shark to make sure it works so we will always have the doubters out there.
Please read the recent story on our website (www.sharkshield.com) in the "Latest News" area about a Shark Shield incident with a White Pointer in WA and I am sure you will change your mind. The story of the couple was also written up in WA's Sunday Times a week ago. We have not spoken to the couple or approached the newspaper to write the story so please don't go making more assumptions that somehow the whole thing was a setup.
In regards to Peter Clarkson, we will have to wait for the coroner to review the circumstances. The review will try and determine if Peter was wearing a Shark Shield, if so what model was it, was it turned on, was it charged, how long was he diving for because an old model may only last 1 to 2 hours when fully charged. So again, please don't go making assumptions about this before the facts are known.
Regards
Martin Grace
General Manager - Shark Shield
ps. What I am about to say is not inferring what will be found with Peter Clarksons review, but I should make you aware that last coroners review of a personal that was supposed to of been wearing a Shark Shield when fatally attacked by a shark found that they actually were not wearing a Shark Shield. In fact the diver had access to one in the dive boat but the dive group felt pressured not to wear it by a senior person in that group that doubted the technology. As with other reviews the coroner recommended our product be used in future.
Regards
Martin Grace
General Manager - Shark Shield
Martin you have no proof either that your product actually works other then testimonials and stories from people and the blogs that you claim are full of liars. How do these stories have more credit then the ones saying your product doesn't work?
Wheres the footage from your scientific tests? the link to your field testing recordings is not there.
Hi Rees,
Who said we have no proof. Another incorrect rumour. The Natal Sharks Board in South Africa have spent years developing and testing this technology.
Please google the scientific paper "Estimating the probability of shark attack when using an electric repellent" which was produced by "Smit & Peddemors".
Our product has also been approved by various organisations including the Australian Navy. These organisations have not taken on board the decision to use our product lightly and have investigated our product and technology.
Regards
Martin Grace
General Manager - Shark Shield
Hi Martin,
In this article in the Australian, March 2008 it claims that a shark shield was eaten by a 3.6m great white as it was activated on a float carrying boat..
(www.theaustralian.com.au/news/great-white-ate-anti-shark-device/story-e6...)
In the inquest regarding the incident Rod Hartley, who owns a business that manufacturers the shark shields said it was eaten due to a "problem with the electrode's configuration"
Further on he quotes "The surf product only can be guaranteed to work when it's stationary, not when it's surfing in the wave or paddling"
Seeing as surfers spend a lot of time paddling around, have the newest models been upgraded so that this issue has now been overcome?
If it's only going to be useful say 50% of the time, it might be worth not taking the risk of it attracting sharks and going it alone..
I totally understand its use for Ab Divers, the Army and other uses where each person has one, but when one surfer with it attached is out in a pack of 10-15 others who aren't, I certainly wouldn't want to be in the water at the same time.
martin ..mr grace, sir.such a hostile reply. why ? some proof is all we ask,video footage please......your testimonials are great,but the old camera dosent lie thing, well put your product to a real visual test,give some real proof.then all ocean sportsmen and women will buy and use your product.would it really stop a large pointer or tiger shark when in attack mode.south neptune island area ,hot summers day ,arvo glass off,perfect testing conditions,perfect filming conditions,not a big ask for real proof that shark shield works ?
If I could interject quickly...
Martin has got on here using his real name and not hidden behind a pseudonym, which, for someone in his position should be applauded. The debate has so far been great and there's a lot we can learn from it. Let's not see the tone lowered.
Stu (Swellnet Editor)
Victor and rees0, there's video of the white being deflected on the Shark Shield site here.. http://sharkshield.com/?/m/video
It's when the shark is unexcited though. Martin is there video when the shark is in attack mode?
Cheers Stu. In emails I can sometimes come across a bit blunt but I don't mean to. I hope I haven't wound anyone up.
Yes Rod Hartley was involved in Shark Shield proviously but I now oversee the company, which manufactures the product in Adelaide then sends it around the world.
Craig, I don't know the full history about the SURF7 newspaper article you made a link to because it is before my time. It is one of those articles that pops up tha creates doubt again. I would be interested to know if it is a true reflection of the events that occured. I think back in my office there is some information on the particular event. If I remember correctly a range of tests were carried out on the SURF7. Some tests were setup in such a way that it pushed the boundries of the design and it was know the test would fail. Please also note that the investigation into Jarrod's death, which the news article refered to found no fault of Shark Shield and in fact recommended the device be used in future.
I do know that all our products require the antenna, and therefore the two electrodes within the antenna, to be underwater for the device to emit the large electric current that produces the electric field in the water. I don't have any data on what I am about to say but when actually surfing on a wave when the antenna comes close to the surface or skims along the top then the electric field may possibly reduce.
Now if you are a surfer like me you would spend most of your time paddling through the break and then sitting and talking with your mates while you wait for the next set to come in. All of this time the antenna is not near the surface of the water because it doesn't float.
I would question that you would spend 50% of time time actually riding waves. If you do then you need to teach me some of your secrets. I know that I personally would be riding waves probably less than 10% of the time that I am out surfing. Anyway even if it was 50% I still would prefer to be protected.
Regards
Martin Grace
General Manager - Shark Shield
Sorry, I was taking into account the paddling and standing up to be around 50%. As you said, probably in an hour you're only standing for a few minutes but there'd be a lot more paddling.
Thanks for taking time to answer my questions.
No problems Craig. I think I might have to add something like a "Myth Busted" section to our website to answer a lot of these common rumours that float around.
Regards
Martin Grace
General Manager - Shark Shield
The interview video of the surfers is a bit dated, like a good 12+ years old. Surely testing and surfers views have altered since then?
I'm very sceptical of the Shark Shield in as much as I believe it would not be affective in shielding from a hungry aggressive pointer. Coroner's evidence in regards to Peter Clarkson's death will be inconclusive and not lay blame on the protection device. Working or not, who knows???
Cheers Craig,
I was more referring to the videos talked about in the FAQ's on the website. The testing with the baiting of the sharks and then placing the device into the water.
Quote:
These tests were completed by independent marine biologists. Click here to view footage of field testing.
Remember: This testing is conducted under the worst possible scenario. The shark is stimulated, hungry and excited. This is a situation that any responsible person will avoid at all costs.
The videos listed are obviously none of these because as you say Craig the Sharks don't seem at all agitated. If anything they seem Docile and curious and the behavior shown doesn't look out of the ordinary. Quite similar to a lot of other shark docos.
Your product seems to rely heavily on testmonials and 30 second videos some with the same footage repeated rather then cold hard facts or proof Martin. You even went as far as linking a story from another forum after saying that the forums and blogs are full of made up story's with no proof. Where is your proof that actually happened? Where is the 4 seconds of Go Pro Footage?
Appreciate the information Martin and others.
To you Martin - do you know of anyone who has been attacked by a shark while wearing a Shark Shield? (By that I mean a working, charged device). Has it happened?
I reckon that the only way to work out whether it is a goer is if Martin straps one to his leg and jumps in a big pool of great whites in an agitated and excited state. He should have a Go Pro strapped to his bonce. I reckon sales will either then escalate or de-escalate according to whether Martin has his head still attached to his body at the end of the frenzy. If this is the case I will buy one again. Go on Martin make that sales pitch.
There are plenty of opportunities for the Shark Shield to be tested on a daily basis at Neptune Island. Depending on which tour operator you choose you can either go with the berley or non-berley route (the soothing sounds of AC/DC get the sharks circling the boat).
However, Neptune's is more like an safe haven for the Great White these days as they are being fed on a daily basis and do not act in an aggressive manner so tests can be flawed.
As for the videos on the Shark Shield website, I beleive the consumer is only being shown what Shark Shield want them to see. None of those videos show an aggressive shark.
May I suggest that Shark Shield extend their next testing program further up the West Coast of SA where the sharks aren't being fed on a daily basis or have been humanised as such. The attacks which have occured in those areas, particularly the two-in-two-days where both fiercely aggressive attacks and not exactly "love bites".
ryder, how about we get jeff smucker views on this,he would certainly be the man to point to the best testing area,with his knowledge of local waters and sharks. jeff if you are out there give us some knowledge. love to know if you or jessiah or other tow in surfers use the shield, west coast or other places in the world....do you think using a shield would deter a white pointer in attack mode?
Jeff dont use any shield I know that.He has a theory based around time in water, the less time floating around the better.When him and josiah are on song I doubt they are in the water more than 30 seconds.Those suckers can smell you miles away and can take an hour or two to reach you thats the risk of long sessions in the water down there.I have paddled with Jeff on occasions but he dont like doing it.He knows whats swimming around down there.
cheers,
Schmucker is like Chuck Norris, only tougher. Sharks dont fuck with him.
To be honest Victor, I imagine it wouldn't be in the best interest of Shark Shield to be putting their device for surfers and divers in those remote waters. It would fail miserably in my opinion.
As I said, the info and videos on their website are so outdated and out of tune with reality of a real life shark attack that conducting any tests in the Neptunes with humanised Great Whites is just toying the results in favour of their product.
None of the guys who regularly surf the coast that I know of use a shark shield. Lopez pretty much summed it up best. The amount of time these guys actually spend floating in the water would be like 5% of their entire session. Yet, the sessions without ski's are still taken at own risk, like any surf session. Ski's which were once frowned upon along the West Coast are now considered a saviour. Everyone is happier in the water knowing that a ski is only an ear-shot away.
Paul buckland was wearing a shark shield when he was killed by a great white in smoky bay scolloping. The deckhand was shocked trying to pull paul in after the shark had attacked him. i know these people personally
One of my close friends used a shark shield for early morning solo surfs on the West coast of SA and actually had an interesting encounter.
One morning a shark (he estimated it do be a medium size Bronzie) came at him, dorsal fin above the surface. It got to with 3-4 metres and veered off at near a right angle. He said it then came up at him again from his side, at which point he paddled towards it (in an attempt to make it think he was the predator - interesting reasoning) and again it got to with in 3-4 metre range and veered off sharply.
Now it may not stop a 20 Ft monster, but in that situation it seemed to work.
Also in regards to Craig's worry about it attracting sharks: I was under the impression electricity conducts relatively poorly in water (compared to say, a metal) and as such the distance an electric field travels reduces exponentially - Hence why when lightning strikes water people nearby (again, a relative term) don't get sizzled.
PS: I actually invested in a surfing Surf shark shield out of curiosity and found that, regardless of claims, the drag really did inhibit my paddling and wave riding speed. Shark shield makers queried my setup of the device, which was found to be correct. I think perhaps it would be less noticeable on larger boards.
I didn't use it for more than a dozen sessions and now it sits in my cupboard.
Regarding the electric shocks, they aren't nearly as bad as people claim. A nuisance, yes, but not really that bad - and even kind of fun, though not ideal when wrapped around your head.
Roubydouby, contrary to your thoughts on sea water not being that conductive, it is actually a pretty good conductor of electricity compared to drinking or pure water due to the extra ions present.
Also there's some info about the sensitivity of the Ampullae here http://www.elasmo-research.org/education/white_shark/electroreception.htm and here http://elasmodiver.com/shark_senses.htm Which show that the White shark can sense "electric fields at least as minuscule as 125 microvolts (millionths of a volt)."
They compare this to detecting a current 1000 miles away or so but I think this is a bit of a stretch :o
Craig - I didn't compare it to drinking water, I compared it to metal.
But that aside, that first link is very interesting! I'd love to know the detectable range of the Shark Shield and its rate of decomposition.
Maybe a question for Martin Grace?
I'm still sceptical about Great Whites detecting the EM field at distance, especially amidst the background noise of the Earth.
I am aware EM fields have different signatures depending on the voltage and Amps of their source - I wonder how these are interpreted.
Can a shark distinguish between the signature of a living animal and that of say a geological occurrence?
That aside, until we have more answers maybe you are wise not to want Shield wearing surfers in your vicinity. hmmm
Sharks have a wide spectrum of senses to use to find and hunt food.
It seems the electro-reception of the ampullae of lorenzini are more for close range "work" so there may be some merit to the shark shield concepts.
Also interesting to hear about the bloke who approached the shark and it veered off.
My fisho mate swears sharks are mostly an ambush predator and disturbing those circles of enquiry (when the shark may be using those ampullae to detect vibrations of fear, illness etc etc ) will disrupt the attack pattern.
Ie acting aggressively towards a shark showing signs of attack may prevent the attack.
Anyone got any experience of that?
We took my mother-in-law to Seaworld and when she pressed her nose up to the glass at Shark Island the sharks would veer off at 90 deg. and swim away rapidly.
Anecdotal at best but she has the same affect on humans too.
Hi Dylan,
I have just read the coroners findings on Paul Bucklands fatal shark attack and you are correct in saying that he was wearing a functioning Shark Shield but with no disrespect to him and his family it also found it was not being used correctly. The unit he used has two seperate electrodes which you are supposed to connect to your tank and fin. This distance between the electrodes creates a good size electric field. It found that Paul had one electrod attached to a float so when he saw the shark and moved to the surface of the water, both electrodes where in very close proximity to each other therefore creating only a small protective field.
Regards
Martin Grace
General Manager - Shark Shield
Sounds better than a shark shield Zenagain. Pop 'er in the post, COD to Pt Lincoln. 2 problems solved.
In regards to the different shark senses and ranges feel free to google information on this topic. For example go to http://www.shark.ch/Information/Senses/index.html
Regards
Martin Grace
General Manager - Shark Shield
Just tuned in to this discussion and have some experience that may shed light, as well as basic questions. The 2 important questions for me are: does it work, and does it create a danger for other surfers? The climate change debate involves many amateurs like myself cherry-picking bits of scientific information to support positions that contradict each other. In that case I feel most confident siding with the consensus of acknowledged experts in the relevant field. Is there a clear consensus by relevant scientists that the electrical field generated by the shark shield degrades a very short distance in seawater and so could not possibly be sensed by a shark more than say 50 metres away? I thought there was. I would seriously like to reassure guys on the west coast of SA that it defies the laws of physics for it to attract sharks, especially when I am using one. I also thought that years of field testing by baiting excited sharks had shown that when the shark shield is switched on they immediately clear off. Or is that just wishful thinking? I can say from experience that the unit on my 7'2" fish only gives me a shock when I get rolled and the electrode gets wrapped around the deck. That's usually a simple matter of rolling the board the other way, and it happens rarely. I don't notice it when paddling, duck-diving or riding a wave. The unit designed for divers really does interfere with surfing and I would not use that, or any unit that hangs off your leg. It does give me great peace of mind, especially when by myself in a sharky spot. I would like to know if the science is as clear as I thought it was.
That ABC interview was very informative.
I learned three things:
1) Shark attacks are very rare
2) But very traumatic
3) And almost impossible to predict
Knowledge is power
Rest In Peace those taken recently out West. Commiserations to family and friends of those who passed also - its not just a terrible way to go, but also leaves a shocking and traumatic memory, for those present/or not, that lingers.
Re: Culling. We share the ocean with these beasts - we owe it to them to find out more about them (we know next to nothing about sharks) before taking our fears/anger out on them. We have no idea of the numbers/behavior of many shark species, large or small.
French