Free floating fishing nets kill marine mammals, turtles and sea birds
NOAA scientists battle ocean ‘ghostnets’ using remote sensing technology
May 4, 2005
April 29, 2005 — Thousands of miles from any human habitation, fishing nets hundreds of meters long and balls of net tens of meters across, lost or abandoned by their former owners but still an environmental hazard, foul huge swaths of the Pacific Ocean. However, the sheer mass of those so-called ghostnets floating freely in waves has come as an unpleasant surprise to NOAA scientists studying the phenomenon.
Concentrated in relatively small areas of ocean by winds and currents, ghostnets present a hazard to wildlife, entangling marine mammals, turtles and sea birds and a largely unseen form of environmental pollution.
Because the synthetic materials currently used in fishing nets decay extremely slowly, they can continue to drift for years. Many end up trapped on the coral reefs, where entanglement rates are even higher than in the open ocean and where they damage the fragile coral.
The nets not only damage the reefs, but are extremely costly and time-consuming to remove.
Sea turtle found dead in fishing net in the Bay of Antongil, Madagascar.
Sea turtles are highly threatened by ghostnets and other commercial fishing activities.
One strategy to prevent the reef damage is to develop a way to predict where in the open ocean the debris is likely to accumulate and from which clean-up is much easier.
NOAA scientists are using satellite and other technologies to predict area where current and winds combine to funnel and accumulate debris into what are called convergence zones. However, a recent field deployment to confirm that the satellites accurately predicted the existence of a possible convergence zone off Hawaii gave a first substantive look into the severity of the ghostnet problem in the open ocean.
According to James Churnside, a researcher with the NOAA Environmental Technology Laboratory in Boulder, Colo., the bottom line is that, “There is a lot more trash out there than I expected.”
Using data from several satellites, scientists from the NOAA Satellite and Information Service and the NOAA Fisheries Service tracked the Pacific convergence zone through the winter. The data they collected were combined with more recent satellite data to determine the most likely areas to find aggregations of debris.
Coral reef of the Yucatan peninsula in Mexico.
Coral reefs are damaged by ghostnets.
In late March and early April, Churnside headed a field survey of areas in the Pacific from a NOAA P-3 Orion Aircraft based in Honolulu. The survey was joint project of NOAA and Airborne Technologies, Inc. of Wasilla, Alaska.
Over three days, the plane overflew the convergence zone to allow scientists to make visual observations and to use an electronic imaging system with automated pattern recognition to determine how much and what kinds of debris had accumulated.
Churnside said that about 2,000 individual pieces of debris were seen. These included at least 100 that were identified as nets or pieces of net. A number were balls of net up to 10 meters (30 feet) across.
“One piece of driftnet that was still stretched out, and presumably still fishing, was 200-300 meters long,” Churnside said.
Although surprised by just how much material was found in the convergence zone, Churnside said that a lot of analysis will need to be done to sort out whether convergence zones are more efficient at trapping debris than predicted or whether there simply is much more material floating free and available for capture than suspected.
“Those are the two possibilities, and we don’t have data yet to pick one or the other,” he said. Meanwhile, based on the success of the Orion flights, planning is underway to develop a cost-effective removal effort. There are also plans to use unmanned aerial vehicles instead of the larger Orion to identify and track the debris in the convergence zones. A pilot project for at-sea removal could begin as early as next year.
This year, NOAA has also undertaken efforts to re-establish a centralized marine debris capability within the agency. The NOAA Office of Response and Restoration is coordinating these efforts by working with Churnside and other NOAA scientists to bring together, strengthen and increase the visibility of activities related to the prevention, reduction and mitigation of debris in the marine environment. One area of focus will be coordinating activities that identify and reduce the impacts of sea-based sources of marine debris (i.e. fishing nets and derelict gear) on endangered, threatened or protected species, and sensitive habitats in United States waters.
NOAA, an agency of the U.S. Department of Commerce, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources.
This article is a release from NOAA: Original Release
Relevant Web Sites
Peter West, NOAA Research, (301) 713-2483 ext. 181