Photo/Illutration A diver working 6 meters below the surface off Rausu in Hokkaido uses a knife to remove a piece of “ghost gear” as it is lifted up by the anchor of a boat on Aug. 17. (Photo by Tomoyuki Yamamoto)

RAUSU, Hokkaido--A silent killer is stalking the wild beauty of the Shiretoko Peninsula, a World Natural Heritage site.

The culprit: lost or discarded fishing nets that can wreak havoc on local biodiversity for decades.

Divers have been working feverishly since June to remove the threat to marine life known as “ghost gear.”

The nets trap even seals and seabirds.

BAGS OF TANGLED TRASH

In mid-August, three divers who spent part of a day retrieving abandoned fishing gear returned to port with a 76.6-kilogram load that included discarded gillnets. Some days, the trio bags as much as 100 kg of tangled fishing equipment.

The team is led by 71-year-old Katsunori Seki, who runs a diving shop in Rausu that offers diving tours. The others are diving instructors Tomoyuki Aoyagi, 56, and Riki Niikura, 31.

Donning dry suits, they head out to sea in a boat from Matsunori Port.

As soon as it reached a spot where ghost gear was detected in a preliminary survey, Seki and Aoyagi jumped into the water from the gunwale with air tanks strapped to their backs.

Formations resembling rocks protruded from the sea floor.

A closer look revealed fishing nets and ropes of varying thickness that had become entangled to form large masses.

The divers attached the boat’s anchor to one of the lumps so Niikura, who had remained on board, could slowly winch it off the seafloor.

Because the tangled mass was covered in fine sediment, the ghost gear stirred up a cloud of mud as it rose to the surface.

Visibility rapidly decreased.

Restricted to seeing only what was within arm’s reach, Seki and Aoyagi used knives to tear at the lines to fill collection bags.

A fish with a large, flattened head and white stomach was entangled in the mess.

It was a Steller’s sculpin about 25 centimeters in length, which appeared to have died only a few days previously.

“The Steller’s sculpin is a carnivorous fish. I think it got tangled while going after a small fish to eat,” Seki said. “Poor thing.”

Other creatures he had seen fall victim to ghost gear included a wolffish, seabirds such as a Japanese cormorant and even a seal.

The diving activities are organized by town authorities under a donation program sponsored by Sapporo-based Air Water Hokkaido Inc.

Commissioned by the municipality, the divers are expected to work until February next year.

“As a town that boasts a World Natural Heritage site, environmental conservation is a major issue for us,” said Yusuke Miyake of the planning and finance section at town hall.

“We want to clean up the ocean, even if only slightly, and remove the human trash that is causing problems for the natural world,” said Seki.

According to an estimate by the World Wide Fund For Nature (WWF), ghost gear may account for around 10 percent of the world’s marine plastic waste.

In warm southern oceans, discarded nets can snare on coral reefs, inhibiting their growth and posing a threat to local marine life.

Ghost gear can also get entangled around ship propellers, disrupting their navigation.

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