Hauling Ghost Nets Off the Reefs of the Northwestern Hawaiian Islands, 2018

From the air: the team’s boat, and two divers surveying a large net lying on top of the reef. (Photo: NOAA Fisheries/Steven Gnam)

The Northwestern Hawaiian Islands stretch 1,200 miles northwest of the main islands, a chain of small islands and atolls, mostly uninhabited, protected as the Papahānaumokuākea Marine National Monument. They also sit in the middle of the North Pacific Gyre, whose currents carry debris from all around the Pacific onto their reefs and beaches. Much of it is lost or discarded fishing net. Every year NOAA sends a team to take it away; in 2018 it posted pictures along the way.

Getting ready

The team trained for a week in Kāneʻohe Bay on Oʻahu, handling small boats among reefs, and visited schools to teach children about marine debris, since the young are the ones who can stop the problem. Every piece of gear was labeled, inventoried and packed, because nothing can be fetched once the ship leaves. On September 19 they sailed from Pearl Harbor aboard NOAA Ship Oscar Elton Sette on the 1,200-mile, three-day passage to Pearl and Hermes Atoll. At sunset they gathered on the bow to practise holding their breath and to watch seabirds hunt the flying fish the ship flushed into the air.

Small-boat training in Kāneʻohe Bay. (Photo: NOAA Fisheries/Rhonda Suka)

A red-footed booby takes a flying fish the ship scared up. (Photo: NOAA Fisheries/Steven Gnam)

Cutting nets off the reef

Pearl and Hermes is a maze of coral whose reef area covers more than 450 square miles. Divers work in pairs: one swims the reef edge while the other searches the interior, with curious sea turtles, big reef fish and giant trevally following them. When they find a net, they cut and pull it free, which can take an hour, while the boat crew records its size and position. The biggest "monster" nets can take three boats and several trips. The nets are piled into the small boats, run back to the ship and craned aboard to be carried to Honolulu. On their first day there the four boat teams brought in 2,111 kg (4,654 lb) of net.

A metric ton of net goes up to the ship. (Photo: NOAA Fisheries/James Morioka)

The scar a net leaves: the coral underneath has died. (Photo: NOAA Fisheries/Steven Gnam)

A net smothers what it lies on. Coral needs sunlight and food from the water around it, so the coral under a net dies, leaving a scar that the team hopes new coral will one day recolonize. For the first time in these islands, NOAA scientists tried to measure that damage, photographing the reef before and after each removal ("structure from motion") and building three-dimensional models from hundreds of pictures.

High fives after another net comes off the reef. (Photo: NOAA Fisheries/Steven Gnam)

As Hurricane Walaka approached from the south, the team worked longer hours through the last calm, glassy days and cleared more than 22,000 pounds of debris in three days. When the storm's swell and wind arrived, the ship's captain and team leaders moved on a day early.

The beaches of Midway

At Midway Atoll the team went ashore, welcomed by the Fish and Wildlife Service and Chugach staff who look after the atoll, and the Sette sailed for Pearl Harbor to unload the reef nets. Far from any city, Midway's shores are strewn with plastic and nets. On Eastern Island the scientists picked it up by hand, a day of bending, then hauled it and the tangled nets onto small boats bound for Sand Island, the atoll's main island, loading the boats as full as they would go.

Collecting debris on Eastern Island, Midway Atoll. (Photo: NOAA Fisheries/Steven Gnam)

Divers tie lines on a massive tangle of net so the boat crew can haul it aboard. (Photo: NOAA Fisheries/Steven Gnam)

The work was a partnership of NOAA's Pacific Islands Fisheries Science Center and Regional Office, Marine Debris Program, National Marine Sanctuaries and Damage Assessment, Remediation and Restoration Program, with the University of Hawaiʻi's Joint Institute for Marine and Atmospheric Research, the National Fish and Wildlife Foundation, the U.S. Fish and Wildlife Service and Midway Atoll National Wildlife Refuge, the State of Hawaiʻi's Department of Land and Natural Resources and the monument.

Sources

• NOAA Fisheries, "Photo Journal: Taking Out Trash."