RarePlanet.org, as you know it, will retire in spring, 2014. Please visit www.rare.org for new and improved content and subscribe to the e-newsletter for continued Rare stories and updates. Thanks for your contributions. We look forward to hearing from you on Rare.org!
Solution Search Entry

Anti-Shark Nets: Is There a Solution?

Entry Image
Entry Image
Entry Image

SharkDefense Technologies

Anti-Shark Nets: Is There a Solution?

Craig OConnell

Beach nets are anti-shark devices responsible for the near collapse of resident shark populations, in addition to substantial migratory shark mortality. One hypothesized solution to reducing shark mortality in these nets is the use of permanent magnets (materials used to overstimulate the electrosensory system of an approaching shark). To date, studies have shown that permanent magnets can repel several shark species, including: great white, bull, and tiger sharks, all species whose populations have declined in areas containing beach nets. If further scientific validation is accomplished, South African and Australian governments will be encouraged to implement this magnetic technology into beach nets as a means of rejuvenating local elasmobranch populations where beach nets exist.

Read more about this entry, view all.

Biodiversity Impact

Describe how your solution creates sustainable fisheries and promotes ecosystem health.
Beach nets (or anti-shark nets) represent a fishing technique which aims to remove sharks from densely human population beach sites, as a means to reduce the potential interaction between a harmful predatory shark and an unsuspecting beachgoer. With the continued use of these nets, it is apparent that the local elasmobranch (shark, skate, and ray) fauna are suffering in alarming fashion. Although the complete removal of beach nets to help rejuvinate shark populations is not possible, the use of permanent magnets may offer an inexpensive solution to minimize the impact of these nets on local shark populations and therefore yield a healthier ecosystem through the direct restoration of food web dynamics.

Describe how your solution protects biodiversity against local threats.
Sharks play an important ecological role within their respective ecosystems. Typically, most shark species have a top-down predatory impact, which not only affects population dynamics of prey, but also impacts the spatial distribution of their prey. However, a variety of anthropogenic sources of shark mortality, such as beach nets, have greatly impacted shark populations and therefore altered the trophic balance where these nets exist. Studies illustrate that beach nets are responsible for the near elimination of resident shark populations, in addition to the mortality of many migratory sharks. Without predatory sharks within a respected ecosystem, species diversity will be directly impacted, whereas ecosystems which still contain predatory sharks (i.e. areas lacking beach nets and heavy fishing pressures) experience greater biodiversity and higher densities of individuals. With further experimentation, if permanent magnets continue to prove to be successful shark deterrents, it can be hypothesized that we will not only be restoring the health of elasmobranch populations, but will inadvertently be impacting the populations of many other species, thus completely enhancing the species richness within a given area.

How large is the surface area where your solution is being applied?
The extent of beach net use varies depending on location. In the KwaZulu-Natal Region of South Africa, a total of 23.4 km of netting is used. Additionally, in Australia (i.e. Queensland and New South Wales), approximately 10 km of netting is employed each year. Our initial objective is to examine the effects of these magnetic barriers in South Africa and depending on our success, we anticipate collaborating with the Australian government to determine their interest in implementing the technology. Additionally, although we will be adding magnetic technology to or adjacent to these nets, the impact of this technology will most likely be regional, rather than local due to the highly migratory nature of a variety of species of shark captured in the nets. Therefore a quantifiable estimate of surface area in which our solution will be applied and will impact cannot be determined.

Human Wellbeing and Livelihoods Impact

How does your solution improve human wellbeing or improve livelihoods and how many people are being impacted by your solution?
The construction and implementation of this technology will require the effort of many individuals in South Africa. Not only will the construction of such a barrier improve the local livelihood through temporary employment where these nets would be implemented, but with the implementation of these nets, an apparent trend in local marine biodiversity may be observed. It is due to this local and perhaps regional increases in ecosystem health and diversity (which will occur over minimal time scales) that local communities will benefit through the potential for increased fisheries production. Besides just the local fishing community, South Africa thrives on shark ecotourism. With the implementation of this magnetic technology, local shark populations may increase and therefore may directly influence publich interest and economic yield in ecotourism business.

Replicability

How many years has your solution been applied?
2 years

Have others reproduced your solution elsewhere?
yes

Sustainability & Resilience

How do you manage your solution?
Although we have successfully completed our experimentation on several predatory shark species (bull shark (Carcharhinus leucas) and tiger shark (Galeocerdo cuvier)), we will need to rigorously test the effects of magnets on several others. So, prior to extensively managing the development and implementation of the "magnetic beach net", we must first effectively and thoroughly test these magnets on two remaining species of interest, the great white shark (Carcharodon carcharias) and the great hammerhead shark (Sphyrna mokarran). Once complete with the experimental phase of this research, future elements regarding the technological design and experimentation of the "magnetic beach net" will be directly managed by several scientists from the company SharkDefense Technologies. With our diverse backgrounds in Elasmobranch Physiology and Behaviour, Chemistry, Physics and Experimental Design, we are fully prepared to successfully carry out the required tasks to test and implement this technology. Additionally, the South African Government has demonstrated its support for this research and will be collaborating on several aspects and implementation of this study.

Governance

Describe the management and governance aspects of your solution as they relate to your local community.
Throughout the duration of this project, SharkDefense will be selecting local South African ungraduates to help participate in each element of the research project, whether it is (1) conducting trials, (2) data analysis, and/or (3) public presentations. It is through these efforts that our company will be giving back to the local community, in an attempt to motivate and promote the involvement of local young marine biologists in conservation-oriented scientific research. In addition to directly involving the local communities, we anticipate publishing our findings in the scientific literature. These findings will aid the scientific community in further understanding the unique electrosensory system of sharks and how we can directly target this system to selectively deter sharks away from detrimental fishing gears and anti-shark nets.