Sphyrna mokarran, or the Great Hammerhead Shark, is an endangered species within our oceans. Like many other species, these large sharks can be caught and trapped within beach nets and even fishing nets. These beach nets are used as a guard between humans and sharks, to keep as many sharks away from humans as possible. This, in theory, would reduce the amount of human-shark interaction and therefore minimize the chances of any shark attacks. Of course the sharks small enough to fit through absolutely can and will, but with the size of the Great Hammerhead, the possibilities of it fitting through the net are slim to none, and the possibilities of them getting stuck are much greater. 

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Sphyrna mokarran caught in a beach net

Since Great Hammerheads (and mostly all hammerheads) have incredible senses due to the electrical receptors (Ampullae de Lorenzini) within the “hammer” part of their head. These receptors can easily detect prey for the Great Hammerhead to eat including rays, cephalopods, other smaller sharks, and more. Great Hammerheads can even detect some magnets and magnetic fields with their ampullae too, which is really neat!

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Great Hammerhead using electroreception with Ampullae de Lorenzini

Something that scientists have actually been working on in order to reduce the amount of sharks, including the Great Hammerhead, that are getting stuck in this beach nets, is introducing large permanent magnets within the water column. In many cases (including some episodes of Shark Week!) experiments and trials have been done in order to test the theory of the magnets “scaring” off the sharks. Scientific studies do show that this in fact does work, sometimes. In most studies, Great Hammerhead sharks, as well as other sharks, react very different in the presence of a magnet than without the magnet. When their electroreceptors catch that magnetic field it seems to overwhelm them in a sense, and they swim away. The reasoning for this it seems is that these sharks are easily able to detect any changes within the magnetic field, which is really awesome!

Overall, the endangered Great Hammerhead has a wide variety of things that can kill and/or harm them and beach nets is one of them. By scientists using these permanent magnets it may significantly reduce the amount of these Great Hammerheads being caught within these nets. Although I feel it will never completely eliminate the problem, I feel like it could definitely help, which is a good thing! After all, these sharks and incredibly beautiful, and most importantly, they are very important to our ecosystem!

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Hammerhead Shark showing off those beautiful teeth!

-Selena Bianchi, Intern at Cape May Whale Watch and Research Center

Stockton University ’21

References:

https://www.echo.net.au/2018/01/hammerhead-shark-added-shark-net-toll/

https://scholar.google.com/scholar?hl=en&as_sdt=0%2C31&q=magnets+and+hammerhead+sharks&btnG=#d=gs_qabs&u=%23p%3De0uIPmSxQ9wJ

https://fineartamerica.com/featured/shark-electroreception-claus-lunau.html

https://www.naturepl.com/stock-photo-great-hammerhead-shark-sphyrna-mokarran-mouth-wide-open-feeding-in-nature-image01669373.html

https://www.int-res.com/articles/esr2015/26/n026p243.pdf