More than 80 per cent of unprovoked fatal shark attacks in the past decade have occurred within 40 kilometres of wastewater outfalls, analysis by The New Daily reveals.
The findings come as the Senate inquiry into ‘Shark mitigation and deterrence measures’ handed down a controversial report this week calling for the phasing out of shark nets and drum line traps around Australia.
A research group based out of the University of Tasmania has mapped out the 129 ocean outfalls scattered around the coastline of Australia as part of the government-sponsored National Outfall Database (NOD) project.
When combined with data from the Australian Shark Attack File, the outfall maps show that 30 per cent of all attacks in Australia from 2010 to 2016 occurred within five kilometres of outfalls.
Experts have long cautioned that outfalls may attract sharks. Government websites, such as the NSW Department of Primary Industries-run SharkSmart information campaign, warn beach users to “avoid murky water, waters with known effluents or sewage”.
Nutrients discharged in these underwater pipes attract baitfish. Footage shows that in many cases the fish circle around the wastewater plume that spirals out from the sea floor like an underwater ‘tornado’.
Researchers believe the schools of baitfish attract sharks looking to feed.
Clean Ocean Foundation CEO John Gemmill said the threat from the sharks was dwarfed by the threat from ocean pollution. However, better treatment processes should be considered as a part of the solution to both problems.
“We should be looking at ways to decrease attacks and pollution.”
Qurratu A’yunin Rohmana, principal investigator with NOD, said the discharge from these outfalls is around 1380 gigalitres per year. One gigalitre is equal to a thousand megalitres. A megalitre is one million litres.
The CSIRO is currently conducting shark survey work on the east and west coasts with the aim of providing the first comprehensive estimate of great white shark populations in Australian waters.
Environment and Energy Minister Josh Frydenberg said the CSIRO is scheduled to report the findings of this work by the end of the year.
“The analysis of the survey information will provide the federal and state governments with important information to assist in the creation of shark management plans,” he said.
Mr Frydenberg said outfall discharge and shark incidents both often occur near populated areas and that more needs to be done to protect human life.
“Such measures might include beach nets, smart drumlines [a form of shark trap], beach patrols and personal deterrent devices.”
At shark attack hotpots in Queensland, New South Wales and Western Australia there have been increasing calls for a culling program.
But according to Jessica Meeuwig, Professor of Marine Science at the University of Western Australia, shark culling does not work.
“If you look at the data from the Queensland drumlines there is no material impact on the incident rates.”
Professor Meeuwig said drumlines have failed in Western Australia, too.
“They didn’t catch a single white shark. Instead, they caught 172 tiger shark species which have never been implicated in a shark incident in that region.”
Chairperson of the Senate inquiry, Greens senator Peter Whish-Wilson, said when he went surfing, he was personally more worried about pollutants than sharks.
“I never want to see a big white shark when I’m surfing but I know there is always a risk,” he said.
“I will go in the water when I know there are sharks in my area, I see the tagged ones on apps like ‘Dorsal’ and I know they are there. We often talk about it, but still go surfing.
“But I wouldn’t go in the water if I knew it was contaminated by sewage and other pollutants.”
– Map produced by NOD researcher Qurratu A’yunin Rohmana.