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