Ghost net busters

In 2009 remote Indigenous communities in northern Australia teamed up with CSIRO (Australia’s national science agency) to investigate the havoc being wrought by discarded fishing nets upon their ancestral homelands. The innovative research that resulted is now playing an important role in worldwide efforts to reduce and manage destructive marine debris.

The Gulf of Carpentaria, a large, shallow embayment that stretches across 3,500 kilometres of the sparsely populated coastline of northern Australia, has long been a haven for an impressive range of sea life.

But while the Gulf’s remoteness has protected it from many modern environmental scourges, it has proved no defence against fishing nets dumped or lost by fishing fleets in the region.

Approximately 12,000 so-called ‘ghost nets’ have been collected in the Gulf over the last decade and most seem to originate from non-Australian sources. These nets have a range of negative impacts including causing damage to coral reefs and seabeds, creating shipping lane hazards and introducing alien species into vulnerable ecosystems. But by far the most visible impact is the ensnaring of wildlife – crabs, sea snakes, sawfish, dugongs, sharks, crocodiles and even water buffalo. Turtles are particularly susceptible to becoming entangled. The Gulf, which has one of the highest rates of derelict nets in the world, also plays host to six of the seven marine turtle species currently extant but under global threat.

As disturbing as the senseless destruction of magnificent sea creatures is to anyone, it’s devastating to the Indigenous communities who make up the bulk of the Gulf’s residents. The sacred responsibility of being good stewards of the environment – ‘caring for country’ as it is commonly termed – is integral to the culture of Australia’s original inhabitants.

Since 2004, more than 31 Indigenous communities scattered across northern Australia have worked with GhostNets Australia – an environmental organisation formed and staffed by Indigenous Australians – to find local solutions to the problem of rogue nets. Rangers had long been keeping records on where nets were washing up and what species were being entangled in them and in 2009 GhostNets Australia approached Commonwealth Science and Industrial Research Organisation (CSIRO) for assistance in analysing the data and tackling the issue. Using the supplied data and oceanographic models, CSIRO research scientists Dr Britta Denise Hardesty and Dr Chris Wilcox set to work determining what types of nets were causing the most damage, where they were coming from and what, if anything, could be done to minimise the loss of marine life.

“In partnership with Indigenous communities, the CSIRO team was able to estimate where the nets came from based on where they landed,” says Dr Hardesty. “We then did some real world testing by putting transmitters on large drifting nets near the Gulf. We were spectacularly excited to see they followed the paths our model predicted. By determining where turtles are in the ocean, and where they wash ashore in nets, we’re able to predict spots where turtles are most likely to collide with ghost nets.”

As a result of the CSIRO’s work establishing the source and movement patterns of ghost nets, GhostNets Australia and various Australian Government agencies have developed a two-pronged approach encompassing both cure and prevention.

“These nets can be found and tracked with aerial surveillance or satellite monitoring but the issue is knowing where to look in what’s an immense expanse of ocean,” notes Dr Hardesty. “We can now provide good projections about the pinch points where derelict fishing gear is most likely to be found and we know what fisheries to target. That means steps can be taken to interdict these nets before they reach an important turtle breeding grounds.

“Attempting to clean up marine debris is a daunting proposition – there is so much of it in so many places. Perhaps the most valuable aspect of our research has been identifying where the nets are coming from so the issues causing those nets to be abandoned or lost – whether it’s overcrowded fishing grounds, no dockside facilities for the dumping of damaged gear, or a lack of financial incentives for fishers to recover lost nets – can be explored.”

The practical outcomes of the research collaboration between GhostNets Australia and the CSIRO include a detailed understanding of how overcrowding in fisheries and illegal fishing ultimately leads to gear washing up on the shores of Northern Australia. It’s also led to the facilitation of cultural exchanges between Indigenous rangers and overseas fishers so each can learn about the challenges and impacts faced by the other in maintaining a livelihood. More impressively, what began as a small, grass-roots project is now attracting international attention, in a world where an estimated 640,000 tonnes of fishing gear is lost or discarded annually.

“Obviously you can’t simply replicate what worked in the Gulf globally,” Dr Hardesty points out. “For instance, the issue in North American waters is more likely to be the loss of legal crab or lobster pots due to weather. Nonetheless, it is fair to say this world-leading work has attracted attention from scientists in the US, South America, Europe and Asia. There has, for example, been huge interest in applying the approach we developed in the Gulf to address entanglement issue of marine mammals, particularly whales and dolphins. My CSIRO collaborator, Dr Chris Wilcox, recently gave a presentation to the International Whaling Commission on the approach we’re taking to tackle marine debris issues.

“Chris and I are also involved in a working group comprising marine debris experts from around the world that’s been set up by the National Centre for Ecological Analysis and Synthesis, a research centre and international think tank based in California. My hope is that this CSIRO work will provide information and approaches that can be of use to anyone wanting to reduce the impact of marine debris.”