WHY ARE THERE SO MANY SHARKS HANGING AROUND BALLINA?
The ecological makeup of the Cape Byron area in Northern NSW makes it an extremely fertile breeding ground for marine animals. That is why it is not uncommon to see some form of marine life when you enter a beach in those areas, whether it be dolphins, whales, turtles, seals or sharks. Let’s explain…
Located just next to Light House Beach (the location of a recent attack) has recently become much dirtier, receiving a grade of D+. This is forcing a variety of fish and marine animals out towards the river mouth. Bull Sharks, often responsible for attacks, are also known to enjoy dirty, murky rivers and are known to breed and feed in rivers. Rainfall also ‘flushes‘ a various animal species that have crept up the river or spawned there over winter to be forced back down the river and out the mouth, including sharks, and their food sources. It is possible that a combination of increased prey coming out of the river and murky water conditions, are encouraging a number of Bull Sharks to feed and breed in the area.
Currents and land formation
The Byron Bay Cape creates a “diabolical junction of currents” that intersects with The Richmond and Clarence Rivers to the south, and the Brunswick and Tweed Rivers to the north. At this location, cold currents travelling up the coast on the south winds meet with sub-tropical warm currents coming down the coast, creating an extremely fertile marine ecosystem.
The East Australian Current (AEC) comes closes to Australian coastline at Byron Bay, at around 5-6km off the shore. According to the ABC, “Many marine organisms use the current as a conveyor belt, spending their larval and adult lives in vastly different parts of the ocean because of the rotating motion of the current… It warms up coastal waters, brings fish stocks down from the north, and sweeps coastal effluent away from cities, leaving warm, clean seawater in its place.” It is possible that a number of sharks are being drawn to these conditions to breed and live, but also to feed on the increased number of prey who are also doing this.
The Continental Shelf
As the most easterly point of Australia, Cape Byron is very close to the continental shelf. Sharks tend to pass closer to the coast of northern NSW as the shelf narrows, forcing them to come in close to the cliffs and beaches. In comparison, sharks are more likely to bi-pass the Gold Coast as the shelf is much further out.
THE NETS ‘WORK’ IN QLD, SO WHY WOULDN’T THEY WORK IN NSW?
As mentioned above, the ecological make up of QLD is quite different to that of Northern NSW. QLD does not have the same combination of currents, water temperatures, river mouths and proximity to the Continental Shelf. Its beaches are long and open, and not as fertile with marine life as the areas near Ballina and Byron.
Aside from damage to other animals, based on statistical evidence, the effectiveness of nets and drum lines in Queensland is extremely questionable.
The below spreadsheet maps out the shark attacks that have taken place at beaches in the Gold Coast from 1905 – 2012. As can be seen, in 1962 shark management strategies were implemented on the Gold Coast, which includes nets and drum lines. Between 1962 and 2012, there were 16 shark attacks, 11 of which occurred at beaches with nets and drum lines. That is almost 69%.
How effective can nets and drumlines be, if the number of shark attacks post 1962 were both higher, and occurred more frequently at the beaches where they are installed?
WHAT CAN WE DO INSTEAD OF NETS? Check out our alternatives page.
Feature Image: Byron-Bay.com