United States of America

To be honest I do not know a ton about shark repellents.   Maybe the best solution is to not swim or stay out of shark infested waters if one has a fear of sharks.  There has been an increasing number of shark sightings in Malibu and surrounding areas due to warmer water temperatures.  However, I feel sharks are a key part of our ecosystem in the ocean and humans should not be interfering with their habitat.  

051611bankok1141 Skylar Peak

City of Malibu, CA

Councilmember

Response 

I do not believe shark behavior has changed, I think we are in the water more and shark numbers are recovering. We are not a prey item or we would be bitten far more frequently. We will see what this year's numbers say, but one year does not make a trend. The Media is reporting almost every incident now, so reporting is putting it out there far more than in the past. I think what has changed is perception and not really the numbers. Typical psychological bias. There may be local differences or changes like Reunion, but I am not sure even there. Of course, the discussion is pointless unless we look at species specific information as well. As you know that not all sharks behave the same way and not all incidents are created equal.

A lot of incidents in the US are fishing related and that is pretty much left out in the media. For me, those do not count as it is like saying oh look a lion on the savanna eating something someone killed or came in to investigate a slaughtered animal.

Grant W. Graves

Marine Biologist

Response

Sharks are a top predator in our marine (and estuarine) systems. The role that these species play is critical to proper ecosystem function. As humans have developed an increasing (and sometimes irrational) fear of sharks, these species have in some cases faced threats that have caused possibly irreversible damage to their populations. As many shark species are migratory, utilizing a variety of habitats over their life cycles, understanding just their basic demography and behavior is a logistic challenge for scientists. Given the gaps in knowledge related to many shark species, I am hesitant to support any type of shark "repellent" that might have direct impacts to how these species function within their habitats. Additionally, the use of acoustic transmissions (e.g. orca vocalizations) or altering the electromagnetic field of a geographic location may have consequences beyond the targeted shark species. Many marine organisms rely on acoustic and sonar information to assess their environments. The use of and sensitivity to electromagnetic fields is not limited to sharks. Marine turtles, spiny lobsters, sea slugs, and other species have been demonstrated to use magnetic field for orientation and navigation. Elasmobranch species (sharks, rays, and skates) and other marine species rely on electromagentic fields to detect their prey. Disrupting these fields could have devastating consequences to important habitats for these species. Dr. A. Peter Klimley used wet suits designed to replicate the color pattern of orca whales while conducting field work in the Pacific. I think this latter approach is far more innocuous and with less consequences for unintended species. 

Sheila V. Madrak, M.S.
Doctoral Candidate
Joint Doctoral Program in Ecology
San Diego State University/UC Davis
Department of Biology

Response

All of the expert responses bring up excellent points and I whole heartedly agree with most of it. To add my personal, non-scientific, opinion. I think most shark repellent products are a fairly crude attempt at affecting a complex animal in a complex environment.  Most devices I have seen or heard of will only work on certain species, during certain circumstances and under specific conditions. It is a simplified idea to think all species of sharks will respond to a color pattern or electric field at all times when there is other stimulation in the water. How strong a deterrent has to be largely depends on how motivated the shark is. Most of the time sharks are not even interested in humans, so keeping them out of the area is not necessary. The slightest sound, movement or sight can either attract or spook a shark, depending on what they are used to, why they are in a particular location and what they may or may not fear. How often do sharks have to fear being hunted by Orcas if they live in a place where you never see Orcas? Small amounts of electric current can attract sharks. So does sound. How can you dose it considering the density of the water? Sound travels incredibly far. Electricity disperses quickly. To use electricity or sound to protect a whole area would require such a high dose that surely it would be damaging to a lot of other ocean life in the area. Trying to tag and track ALL Great whites, tiger sharks and bull sharks is simply impossible. 

It really worries me that there seems to be this attitude that the sharks are encroaching on human's swimming areas or surf spots and that there is an increase in sharks. First of all - when seen in relation to how many people are entering the ocean, there is no increase in attacks. It has been proven that shark populations are decreasing all around the globe. Creating panic over the fact that sharks come closer due to climate change is also pointless. It is a natural reaction that predators will go where they find prey. That does not mean that there is automatically an increase in danger. We cannot expect fish to stay in their neatly designated areas that make it easy for us to keep track of them. That is not how it works. And secondly, sharks contribute to the health and balance of the ocean. Surfers and swimmers are there for recreation - what is more important?

The real problem is that sharks are being wiped out and that sightings have become quite rare, except in certain locations. It is unfortunate that sometimes these locations coincide with some of the popular surf spots. Maybe choosing locations for surf competitions should consider the wildlife as much as the perfect wave. Most surfers I know are perfectly happy to be in an environment that is still wild. Extreme sports have an element of danger, so sometimes I wonder who shark repellents are made for? Is it more hype than necessity? Are we trying to sanitize the ocean so more people can enjoy it without worry? Is that what we should strive for? People are more and more removed from the natural world and feel entitled to safely use the wild places as their playground. We have managed to wipe out nearly ever "slightly" dangerous predator on land, and now this attitude is extending into the oceans. We do not need shark or bear repellents. We need to be willing to learn about our environment and enter the wild with some knowledge and acceptance that we are only one of the animals that use that space and that we need to coexist.

Stefanie Brendl

President

Shark Allies

A Snippet from Aloah Tech Writers Article-

Shark Deterrent and Detection Technology Demystified: What Works, What Doesn’t and Why.

October 26th 2015 by Purna Nemani of Aloha Tech Writers (collaborator, Stefanie Brendl of Shark Allies).

http://alohatechwriters.com/shark-deterrent-detection-technology-demystified-what-works-what-doesnt-why/

We end this article with the opinion of Hawaii Institute of Marine Biology, Shark Research Group’s Dr. Kim Holland. Holland and his team research the behavior, physiology and ecology of sharks and other fish.

“I and my students have quite a bit of experience and have done research looking at what sharks can detect, both magnetically and electrically. The short answer is they are extremely sensitive to electric fields and magnetic fields, and they’ve got very good hearing, as well. Most of the devices tend to dissuade sharks by using electric current, and that’s been tried by a number of companies over the years. We actually got some money by an oil company whose gear was being damaged by shark bites, and they wanted to know if there was some way of deterring sharks, so we did quite a lot of work trying to find some sort of electrical signature that would be aversive to sharks and turn them away, which is exactly what these other companies have tried to do with various products. And the short answer to your question is that there is no known device- either commercially available or scientifically being tested- that works to deter sharks when they are motivated to attack. It’s not there.

“We’ve casually tested a couple of the commercially-available products over the years and have had sharks swim right through it. The problem is- in order to deter a shark, reliably- you need to have a current that is not just aversive but ispainful. If we were listening to someone scrape their fingers on a chalkboard, that’s aversive, and it might be enough to get us to stop what we were doing; If they gave us an electric shock in a chair, that’s something that would be painful. So, it’s a difference between being aversive and being painful, and most of the devices that have come up over the years- because you can’t have a huge amount of electricity being used (either because you need a very large power source, or because you would shock the person wearing the system)- you need to come up with something that’s aversive, not painful, and nobody has been able to find that for sharks. So, really, the short answer to all of these questions is- and probably one of the reasons these companies are not returning your inquiries- is because none of them have really shown that they work.”

Purna Nemani  

Aloha Tech Writers

Response

The ocean attracts people to it for many reasons, one of which is that it remains one of the last readily accessible places for most people to have a true adventure in a world that has become increasingly tamed and modified for the purposes of human progress and the ‘greater good’. The intersection of human and shark in the coastal/oceanic realm is one of the things that makes life more interesting and adds a bit of mystery and unpredictability back into the lives of those who choose to spend time in, on, or under the water. This is, of course, despite the fact that there are unfortunate instances where it does not go as planned (occasional shark-attacks). Those who chose to make a living or recreate in the ocean must be aware that once they set foot in the water they are entering an environment that is home to creatures that have evolved over millions of years to be very successful and efficient at what they do, whereas we (humans) have not. This humble realization should not serve as deterrence, but rather as a reality check and a healthy dose of respect that helps people make informed decisions about where they pursue their activities and the manner in which they go about them. And, at the risk of sounding spacey, this humble realization and respect can also be used as a way to find a deeper connection with the ocean and ultimately add to the context of how we view our own place in the world and the other creatures that are riding around the sun with us.

This may come across as an unpopular or inflammatory statement to some, but perhaps the presence of sharks and the occasional shark attack can help to keep the oceans from being completely overcrowded and saturated with weekend warriors and thrill seekers out to conquer the ocean on their own terms. If the oceans are somehow made completely safe for everyone that would likely mean that an even greater percentage of our ever-growing population would end up spending time in the water, equating to more surfers crowding popular surf breaks, more scuba divers spearfishing and depleting limited fish stocks or damaging sensitive habitats, more crowded beaches, and so on.  I certainly do not want to suggest that we should not strive to make our coastal areas safe and accessible for all to enjoy, but we should be careful what we wish for.

Orca/zebra patterned boards or suits: Sharks hunt for their prey using a combination of sight, smell, and electro-receptive abilities. Smell and electro-reception are used for long-distance detection and location of food resources, whereas sight is used in the approach and final moments leading up to capture and consumption of a prey item. The effectiveness of disruptive coloration or patterns applied to the underside of a surfboard or a wetsuit could potentially be affected by several things: the time of day/angle of the sun/cloudiness, underwater visibility/turbidity, and whether it is choppy or calm. For example, on a calm day with the sun overhead, the dark shape of a surfboard will be silhouetted against the contrasting lighter sea surface regardless of what pattern is underneath. And on other occasions where water clarity is an issue it is quite possible that the pattern might not be visible to a shark until it gets very close. And even then, the shark might not lock in on the uniqueness of the pattern in the moments leading up to an attack. Sharks roll their eyes back and/or protect their eyes with a nictitating membrane to protect them from damage during feeding, effectively and temporarily blinding them during the actual moment of attack. However, disruptive coloration/camouflage is used with great success by both predators and prey in the marine environment, and the idea could still hold great potential. The basic concept is that the animal employing the disruptive pattern is attempting to either blend in to its surroundings and/or to break up its outline to make it less distinct. One thing is certain, utilization of patterns such at these is much cheaper and simpler to employ than an elaborate electromagnetic field.

Tagging Great Whites: In recent years much has been learned about the movements and long-distance migrations of this and many other shark species. Numerous individual sharks have been documented as traveling hundreds to thousands of miles in a relatively short period of time. There are sharks that are sometimes considered as residents of a particular area and those that are transient that may only be associated with a specific location on a temporary basis. It is likely that during a shark’s lifecycle it may lean more heavily towards one or the other at different times depending on its age, its dependence on a particular food source, and/or its reproductive state. To place tags on enough of the population to be relevant to the purpose of protecting people in the water at any one location, or for multiple locations for that matter, would be quite an ambitious undertaking. In addition, any tag that has an electrical component to it, whether it is a GPS tracking tag or something designed to apply a deterrent stimulus, will be limited by the finite life span of its power source. Even the most advanced satellite tags used to track sharks over great distances have a limit to how long they are useful. Therefore, unless better batteries are developed, the tags would need to be replaced too frequently to be useful on a long-term basis. Furthermore, even if this hurdle were to be overcome, there could still be a problem with how the shark reacts to the deterrent stimulus. Suppose a shark has been fitted with a tag that delivers an electrical shock when it approaches a strategically placed safety beacon. Assuming the shark reacts with an immediate escape response, what guarantee is there that the shark would reverse course and head away from the beacon? In its panicked flight, it might end up swimming closer to the beacon unless the stimulus is strong enough and continuous enough for the shark to sense that things are becoming increasingly uncomfortable if it continues traveling in a certain direction. And even then, if it does decide to turn around and head in another direction, if it is still within range of the beacon it will still be receiving the shock, which could further confuse its direction of travel.

Electromagnetic Fields: Our lab has recently been involved in a project assessing the effects of EMFs on the marine community in southeast Florida. A system of cables that have been in place on the sea floor for many years was used as our experimental test range. The focus was on the reaction of reef fishes that live in the immediate vicinity of the cables to EMF fields of varying intensities. Field strengths tested were on par with those produced by existing and possible future marine hydrokinetic devices (MHKs), such as offshore wind turbines, solar farms, ocean thermal energy conversion devices, or anything else that uses submarine cables to transmit electrical power. Sharks and rays were encountered occasionally during this project, although in numbers too small to be relevant for a robust statistical analysis. However, anecdotally, our observations indicate that they were neither attracted nor repelled by the EMFs we were evaluating. However, it is entirely possible that utilization of EMFs of specifically enhanced/selected strength and/or frequency could be used as an effective shark deterrent on a small-scale basis. As Tom Garrison pointed out already (inverse square law), the strength of the field dissipates significantly as you move away from the source. I also agree with Claude Zanetti (response above), in that anything that is strong enough to deter an apex predator will likely have undesirable effects on the surrounding environment and other animals, including humans. But perhaps there is a “magic number” out there somewhere…an EMF of sufficient strength to deter the electro-sensitive sharks that is innocuous enough to be used in close proximity to human activity. The inverse square law could be quite useful here - the EMF producing cable (or cables – perhaps a curtain of multiple suspended cables hanging from buoys) could be located far enough offshore to prevent its effects from reaching the surfers in the lineup. More research is needed, but this idea has potential.       

Kirk Kilfoyle, M.S.
Research Assistant, PhD Candidate
Nova Southeastern University Oceanographic Center