[Melissa Block:] From NPR News, this is ALL THINGS CONSIDERED. I'm Melissa Block.
[Michele Norris:] And I'm Michele Norris. They're known as ghost nets. Every year, fishing boats lose or abandon nets that can stretch for miles in the open ocean, and as they drift, they sweep up fish, turtles, sea birds and whales. Until recently, nobody knew how to find these nets. Now a team of American scientists says it has learned how to track their movements through the Pacific Ocean. NPR's John Nielsen reports.
[John Nielsen Reporting:] Mary Donohue, a marine biologist, used to lead a team of divers whose job it was to keep isolated coral reefs in the Hawaiian islands clear of ghost nets. She says it was an impossible job.
[Ms. Mary Donohue:] When you think of an old fishing net, you think of maybe one piece or two, but there are just hundreds of thousands of pounds of this gear, and it's on nearly every island and on nearly every coral reef.
[Nielsen:] At times, these ghost nets balled up into blobs of whitish nylon that Donohue says could weigh a ton and drift 60 feet beneath the surface of the water.
[Ms. Mary Donohue:] And what happens is they roll along the reef like a giant bulldozer. There's just this swath of broken coral and scoured bottom and animals here and there.
[Nielsen:] The divers on the ghost net team worked for the National Marine Fisheries Service. Armed with knives and rust-proof scissors, they kept an eye out for man-eating sharks and critically endangered Hawaiian monk seals, especially the ones with fishing nets wrapped around their necks like nooses.
[Ms. Mary Donohue:] Sometimes, even, there are two or three inches of skin over the piece that's entangled around the seal's neck, so it's almost like, you know, digging around in there and doing surgery to get the piece of netting off of the animal.
[Nielsen:] Donohue, who now works for the Sea Grant program at the University of Hawaii, says the ghost net problem didn't exist back when fishing nets were made of biodegradable materials like hemp. Now, however, nets are made of nylon and other substances designed to last basically forever. Nobody knows exactly how many ghost nets there are in the world's oceans or how much damage they are doing. Also, until recently, nobody even knew where they were, according to Tom Veenstra. He's the leader of a federally funded effort to find ghost nets in the North Pacific.
[Mr. Tom Veenstra:] Yeah, it's your typical needle in a haystack. People don't quite realize how large the North Pacific Ocean actually is; it's huge. And we know the nets are out there. If they're widespread, it's not even worth thinking of going out to find them. You just happen-it'd be happenstance that you would run across one.
[Nielsen:] Veenstra's team just made that haystack much smaller. First, armed with satellite readings of ocean temperatures, climate patterns, currents, winds and wave heights, they built a computer model. It predicted that in many winters these forces would push ghost nets and other debris into places called convergence zones, north of the Hawaiian islands. To see if the model was right, the team tried an unusual test. Late last winter Veenstra and a colleague named Jim Churnside went to Hawaii and boarded a research plane operated by the National Oceanographic and Atmospheric Administration. The plane bristled with specialized sensors and high-resolution cameras. But when the plane took off, the pilots didn't get their flight plan from Veenstra but from a satellite expert sitting in an office in suburban Maryland. He was using the computer model to guide the plane to where the ghost nets were supposed to be. Veenstra says he say nothing at first. And then on the horizon, he saw a lot of birds. Then one of his cameras photographed what might have been a ghost net and then another and then another.
[Mr. Tom Veenstra:] In the three flights we took, roughly 2,000 sightings that we had. We're now going through the data and we expect that number to increase.
[Nielsen:] Jim Churnside said he saw at least a hundred balled-up fishing nets in these floating landfills, along with a lot of other kinds of trash.
[Mr. Jim Churnside:] Plastic bags, plastic bottles, oil pads that they use to soak up oil from surface spills, one life ring without a body in it. And we saw one drift net that was 2 to 300 meters long that was still stretched out. You could still see the whole line of floats, so it was, you know, still presumably fairly efficiently fishing.
[Nielsen:] Veenstra says he's disturbed to discover that these ghost nets are converging on one of the more biologically rich parts of the Pacific, an area known to teem with fish, birds, turtles and whales. But he also feels vindicated because now he knows where the nets are.
[Mr. Tom Veenstra:] It's actually in an area that maybe we can go clean it up. Maybe it's economically feasible to now take a vessel or a number of vessels and send them out in this area and actually do some mitigation efforts at sea.
[Nielsen:] Meanwhile, back in Hawaii, Mary Donohue says she hopes this cleanup starts fast. The longer it takes, the closer those balled-up ghost nets will get to the Hawaiian coral reefs and to the Hawaiian monk seals that live in them. John Nielsen, NPR News, Washington.