A group of researchers led by Craig O'Connell at the University of Massachusetts Dartmouth, have discovered that C8 barium-ferrite (BaFe12O19) permanent magnets might be the key to repelling bull sharks (Carcharhinus leucas) from shark nets.
The research - to be published in the journal Ocean & Coastal Management - measured the responses of C. leucas to bait and barriers where permanent magnets were present. They discovered that bull sharks were less likely to approach bait or to enter areas when magnets were present. These results suggest that if magnets were used along shark nets they might deter C. leucas from approaching the nets.
The research - to be published in the journal Ocean & Coastal Management - measured the responses of C. leucas to bait and barriers where permanent magnets were present. They discovered that bull sharks were less likely to approach bait or to enter areas when magnets were present. These results suggest that if magnets were used along shark nets they might deter C. leucas from approaching the nets.
Shark nets are used extensively in three regions of the world: Queensland and New South Wales in Australia, and Kwa-Zulu Natal in South Africa. The use of these shark nets is somewhat controversial; whilst they have been put in place to protect beach-goers from large sharks who may stray close to shore and pose a risk to anyone in the water, the shark nets also result in the mortality of thousands of sharks per year. Furthermore, as the nets are non-discriminatory, other marine life such as dolphins and juvenile whales can also fall victim to shark netting. Finding a guaranteed way to repel sharks away from the nets would not only ensure that sharks are protected from the nets but could even lead to the removal of the nets altogether if the sharks could be kept away from the shore.
The finding that permanent magnets can be used to deter select elasmobranchs is consistent with what we know about the biology of certain sharks; sharks have specialist sensory organs called Ampullae of Lorenzini which they use to detect bioelectric fields and are hypothesised to be capable of detecting the magnetic field of the Earth.
The researchers plan to publish similar papers focusing on the great white (Carcharodon carcharias), giant hammerhead (Sphyrna mokkaran) and the tiger shark (Galeocerdo cuvier). The inclusion of multiple shark species in this long-term study is important as there is a possibility that highly visual sharks such as C. carcharias may not be as sensitive to magnetic fields as C. leucas.
