Claire Corlett

Fish Food, Fish Tanks, and More

Making a better shark net | Eco Shark Barrier, Sorrento Beach Hillarys


I’m at Sorrento Beach, Hillarys. I live it not
too far from here and like many locals I’m curious about a our new shark barrier. Without it I don’t think this beach would be nearly as popular, and I
definitely wouldn’t be swimming out this far. But what I really want to know is
does this million dollar project actually protect us against sharks? Let’s
take a look. You might already be familiar with shark
nets such as the ones used at Sydney’s Bondi Beach. By their very nature, nets
catch everything that swim inside them this can be a problem for delicately
balance ecosystems where bycatch of whales dolphins and other marine
creatures can have serious negative effects.
Nets aren’t tough enough to be installed close to shore, which gives an
opening for sharks to get through this happens a little more regularly than you
might hope for. With these problems in mind Western Australian inventor Craig
Moss developed what is now the Eco Shark Barrier. Unlike a net it doesn’t try to
catch sharks instead it physically stops them getting through; just like a wall. The barrier is made of thousands of
these cross shaped pieces which we can snap together to form a grid. This means
that smaller fish and other marine creatures can pass through easily while
stopping sharks dolphins and other large species. Of course that’s only useful if
the barrier doesn’t break. The first line of defense is material selection. The
barrier is made of nylon polymer which is a material with high tensile strength as
well as good toughness. Tensile strength is what means I can pull on the barrier
without breaking while toughness is what it allows it to survive rough conditions.
The next line of defense is the modular nature of the barrier itself. This means
that if there’s a problem with one of the components you can just pop it off
and replace it. Swimming along the barrier you can notice some yellow
connectors contrasting with the regular blue these are the ones that have been
replaced since the barrier was installed. The hardest bit is actually just finding the
breaks in the first place. Because of this you often find the inventor Craig,
out on his boat, monitoring the line. The properties of nylon used in this barrier
ensure that it can perform as function well. Good rigidity ensures that it
doesn’t capture marine life while excellent toughness means that it can be
connected all the way up to the beach. The barrier needs to extend from seabed to surface. In order to stop sharks from swimming over we have these air filled floats down below we have 60 anchors and about 100 tonnes of other weights which ensure that the bottom stays on the sea floor Stopping sharks from swimming under To date there has been no bycatch from
the system but what about other effects on marine life. Swimming along the
barrier it’s easy to see that it’s turning into its own ecosystem. Sea
lettuce and Sargassum weed grow along its surface turning the net into a weird
mash of natural and synthetic. The fish also seem to enjoy it.
On the morning we filmed I spotted herring, blue box fish, tarwhine and bat
fish. Infact there is so much life here that Marine rehabilitation centres are
looking into using a similar system for marine conservation. Talking with some
regular beachgoers they did raised an issue the jellyfish and seaweed seem to
be getting caught on the swimming side of the barrier. Since the floats at the top
are designed to be removable it might be possible to lower the barrier every
month or so in order to ensure that this builds up can flow out to sea. If you’re
interested in snorkeling I’d recommend swimming along the barrier
and further out further out. Here the water is more clear and sea life much more
interesting. Massive thank you to Craig for letting
us borrow some the samples from his barrier, and to the city of Joondalup for
allowing us to film here. Of course if you want to swim anywhere that isn’t
directly behind this barrier then you’re going to need your own personal shark
deterrent. I’ve just written an article for the Pelican magazine discussing the
science behind different shark mitigation technologies. If you’re
interested go check it out. New episodes of Perth Science are landing every month,
so make sure to subscribe to the channel so as not to miss them. Until next time
this has been James Dingley from the Atomic Frontier. Keep Looking Up

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