Despite years of clean-up efforts and new laws, scientists have found the number of abandoned ‘ghost nets’ in northern Australia’s Gulf of Carpentaria has increased and new, targeted measures should be introduced to tackle the problem.
Dr Norman Duke, a senior research scientist at JCU’s Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), took part in recent surveys of ghost nets (fishing nets that have been discarded or lost) in the Gulf.
This work, published recently in the international journal Marine Pollution Bulletin, was done in collaboration with the CSIRO, World Animal Protection, Earthwatch Australia and the Northern Territory Government.
Dr Duke said the surveys show the movement through the Gulf of ghost nets was found to exact a substantial toll on coastal and marine wildlife, ensnaring marine turtles, as well as dugong, crocodiles, sawfish, hammerhead sharks, sea snakes, and thousands of invertebrates.
“We analysed ghost net sighting information from a number of aerial surveys between 2004 and 2020 to investigate whether densities of ghost nets had changed through time or in space. We found an increase in ghost nets, despite substantial clean-up efforts, more than a decade of illegal fishing countermeasures, and a ban on the use of trawl and seine nets in Indonesia,” said Dr Duke.
He said it’s estimated more than 85 per cent of the ghost nets found along the Gulf coastline originate from outside of Australia’s Exclusive Economic Zone, most likely from the nearby Arafura Sea between the Gulf and PNG, with the majority from fishers based in Taiwan, Indonesia and Japan.
“The Gulf of Carpentaria acts as an accumulation area for ghost nets and other anthropogenic debris because of the bathymetry, geography, monsoonal seasonality and the influence of wind, waves, and currents. Given that an estimated nearly six per cent of all fishing nets are lost each year, reducing fishing gear losses is critically important for economic, environmental and social reasons, and is nowhere more important than here,” said Dr Duke.
He said the team recommended regular aerial surveys to look for nets with a focus on a reasonably small area in the northeast of the Gulf that had proven a ‘hot spot’ for attracting debris, and the intensification of clean-up efforts.
“We also recommend attaching transmitters or transponders to floating nets. This can better support safer, more cost-effective net interdiction.
“Without new actions of this type to reduce the loss of nets at sea and to remove lost nets from the Gulf, ghost net abundance will continue to increase and impact upon threatened species both in the Gulf of Carpentaria and in the global oceans. We must do better!” said Dr Duke.
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