“Ghost nets” from unknown origins drift among the Pacific Ocean’s currents, threatening sea creatures and littering shorelines with the entangled remains of what they kill.
Lost or discarded at sea, sometimes decades ago, this fishing gear continues to wreak havoc on marine life and coral reefs in Hawaii.
Researchers are now conducting detective work to trace this harmful debris back to fisheries and manufacturers, and that requires extensive analysis on vast numbers of ghost nets.
The major concern is that derelict gear, long after it has gone adrift, keeps killing fish and other wildlife such as endangered Hawaiian monk seals, said Drew McWhirter, a graduate student at Hawaii Pacific University and one of the study’s lead researchers.
“These nets bulldoze over our reefs before they hit shore,” McWhirter said. “They leave a path of destruction, pulling coral heads out, and can cause a lot of ecological damage.”
Ghost nets foul oceans throughout the world, but the Hawaiian Islands — with the Great Pacific Garbage Patch to the east and another vortex of floating trash to the west — are an epicenter for marine waste.
Past efforts to identify the origins of these nets have proven difficult because debris comes from so many countries and nets have few, if any, identifying marks or features.
Experts believe that many nets are lost accidentally, but boats occasionally ditch them to avoid prosecution when fishing illegally. Other fishers cut away portions of damaged nets instead of returning them to shore.
The ghost net study is being supervised by Hawaii Pacific University’s Center for Marine Debris Research codirector Jennifer Lynch, a research biologist with the National Institute of Standards and Technology.
Lynch said that trying to trace nets back to their sources will be extremely challenging.
However, failure to do so could have some benefit.
“That’s going to be increased evidence for policymakers to see the importance of gear marking and potentially bring those kinds of regulations to the front,” she said.
For Lynch, the research is not trying to point fingers. Rather, she hopes that the study, which is to be presented to the fishing industry first, can help develop new ways to prevent damage to the marine environment.
“We’re doing this study in a very forensic way where we’re gathering as much evidence as we possibly can so that we can present the best, most accurate story,” Lynch said.
The crew obtains ghost nets from three sources: the main Hawaiian Islands; the fishing grounds of the Hawaii longline tuna fleet that often snags nets; and the shores of the uninhabited Northwestern Hawaiian Islands, which are part of the Papahanaumokuakea National Marine Monument.
A cleanup expedition to Papahanaumokuakea — the largest protected environment in the US and a UNESCO World Heritage Site — brought back nearly 45 tonnes of nets and other lost gear.
In a shed on the university’s campus, researchers pull apart bundles of fishing gear, noting the relationships between items. Then samples are taken to a laboratory for analysis.
“We only really need a small sample here to really understand how it’s constructed,” said Raquel Corniuk, a research technician at the university.
Researchers look at about 70 different aspects of each piece of net, including its polymer types. “Is it twisted versus braided? We are trying to look at how many strands does it have, its twine diameter, mesh stretch size,” Corniuk said.
The information is entered into a database, which helps scientists find patterns that could lead to manufacturers, and eventually individual fisheries or nations.
The researchers have spent about a year collecting data, and hope to have their findings published this year.
Among the ghost gear are fish aggregation devices (FADs), floating bundles of material that fishing vessels leave in the ocean to attract fish. The devices have receivers linked to satellites, but when they drift outside of designated fishing areas, they are usually abandoned.
West Coast Fisheries Consultants president Mike Conroy works with gillnet operators off California.
He said FADs are prohibited in US waters and that fishers do everything they can to prevent loss of nets, given that each net costs between US$150,000 and US$250,000.
Conroy acknowledged that ghost gear is nonetheless a problem.
“These types of research activities will point the finger in the right direction,” he said. “I think what you’ll see is that [US] west coast fisheries probably aren’t contributing much.”
However, the researchers have found some debris from the US among nets from Asian countries.
Much of the ghost net problem lies with less-developed nations that have few fishing regulations, and sometimes buy or manufacture low-quality nets, said Brian Fujimoto, a career fisher who works for a net manufacturer in Washington state.
“Their products tend to be weaker,” said Fujimoto, who is a sales executive for NET Systems. “If you look at the poly netting and ropes that you’re finding, they’re all very inexpensive stuff.”
Fujimoto said his company uses technology, colors and other construction techniques that are unique to their products, so they are easily identifiable.
Making that an industry standard is “only going to happen with the more industrialized nations, say for example, the US, Canada, Japan,” he said.
Daniel Pauly is a marine biologist and professor at the University of British Columbia’s Institute for the Oceans and Fisheries.
“These fish that are killed by lost gear are killed for no reason, not to mention the marine mammals and turtles, and other animals that we like,” Pauly said. “Clamping down on this loss, which is too easily accepted ... is a good thing.”
Jonathan Moore, principal assistant secretary of the Bureau of Oceans and International Environmental and Scientific Affairs at the US Department of State, said last year: “Illegal, unreported, and unregulated fishing, which is sometimes associated with ghost gear, is among the greatest threats to the sustainable use of our shared ocean resource.”
“Certainly, gear-marking guidelines and regulations should be a central pillar of all responsible fisheries management operations,” he said.
Although US and some international laws require identifying markers on some fishing gear, such as crab pots and buoys, nets do not require markings.
Officials with the US National Oceanic and Atmospheric Administration’s fisheries division declined to be interviewed for this story, but said in an e-mail that it is “unaware of any regulations that have been, or are being considered, with regard to ghost nets. We continue to work agency-wide on this international marine debris problem.”
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