They are the land mines of the sea, killing long after being forgotten.
Abandoned or lost fishing gear, including traps, crab pots and nets, litter the ocean floor in coastal areas around the world. Many continue to attract, entrap and kill fish and other marine life in what's called "ghost fishing."
Groups, governments and companies around the world are engaged in efforts to retrieve and recycle as much of the abandoned gear as they can get their hands on. The goal is to protect the environment, prevent marine life from being killed, remove threats to navigation, and in some cases, generate energy.
Pascal van Erp, a Dutch diver who was horrified by the amount of abandoned fishing equipment he encountered, founded the Ghost Fishing Foundation to tackle the issue.
"The problem with lost gear is enormous," he said. "It is found in all seas, oceans and inland waters at all depths, along the beach and under the sand. I think the problem never can be resolved completely, but we can keep it from getting worse by showing the problem to the public and the authorities."
For as long as mankind has been fishing, it has been losing some of that gear, but the problem has become particularly acute in recent decades with rapid advances in technology and the expansion of global fishing fleets.
Industry experts and scientists estimate that commercial fishermen lose about 10 percent of their traps per year to bad weather, currents that drag them to far-flung places or boats that sever tie lines intended to keep them in place.
Recommended solutions include degradable panels on traps that will quickly break down and allow trapped marine life to escape, and fast-degrading screws on whelk pots that serve the same purpose. Numerous international agreements also prohibit the deliberate dumping of fishing equipment at sea.
Some debris is deliberately thrown overboard; in England, small vessels can run up landfill charges of 500 British pounds ($702) per year, giving them an incentive to ditch broken gear.
"Crabs get trapped in the pots and starve to death," said John Wnek, supervisor of New Jersey's Marine Academy of Technology and Environmental Science, whose students are involved in a project to collect abandoned fishing gear from New Jersey's Barnegat Bay. "They're still fishing long after they're not supposed to be. This happens everywhere there's commercial fishing."
A 2009 United Nations report estimated there are 640,000 tons of abandoned fishing nets on the ocean floor worldwide. A 2005 survey found fishing boats in Greenland lose an average of 15 nets per day, stretching nearly 2,500 feet.
A 2001 study suggested that ghost fishing kills 4 million to 10 million blue crabs each year in Louisiana alone.
A 2002 study found 260,000 traps being lost each year in the Gulf of Arabia, leading the United Arab Emirates to mandate degradable panels in the traps, a step other jurisdictions have also adopted. The following year, a study in South Korea off the coast of Incheon found 97,000 tons of discarded fishing gear, and about 1,000 tons of lost gear are recovered each year from the Sea of Japan.
The U.S. National Marine Fisheries Service estimates 12 miles of net are lost each day of the fishing season in the North Pacific, and in Queensland, Australia, about 6,000 crab pots are lost each year.
While the scope of the problem is vast, so is the range of projects to address it. One such effort, called "Fishing For Energy," has collected over 3 million pounds of discarded fishing gear nationwide. It has already plucked more than 400 crab traps from Barnegat Bay and has its sights on 600 more. It also is active in Massachusetts, Oregon, Rhode Island, New Hampshire and Florida.
Traps that are still usable are returned to local fishermen; unusable ones are either recycled or burned in one of 40 trash-to-energy incinerators run by the energy company Covanta.
The work involves volunteers taking boats onto the bay and using sonar to detect crab pots on the bay's floor. They mark the spot with buoys and slowly sail over them, trying to snag the debris with a grappling hook dragged from a heavy rope. It is funded in part by a $109,000 grant from the National Oceanic and Atmospheric Administration.
Cleanups are also underway in other countries. A September effort in Orkney, England, retrieved 60 crab pots and 25 whelk pots, along with rope and netting that a local artist used to create doormats.