The Tokyo Metropolitan Government has installed oil fences in the Izu island chain to protect fishing ports from a possible deluge of drifting pumice stone ejected from an underwater volcano months ago.

Small amounts of floating stones have already been seen in the chain of islands, which falls under the jurisdiction of the metropolitan government and extends south of the capital.

However, the Japan Agency for Marine and Terrestrial Science and Technology (JAMSTEC), based in Yokosuka, Kanagawa Prefecture, predicted that a large amount of pumice would reach the Izu island chain this week.

The fences were installed at the ports of Kozushima Island and Mikurajima Island on November 18.

Designed to contain oil spills, fences are used as barriers to prevent pumice from entering harbor mooring areas and impacting fishing operations.

The fence on Kozushima Island is about 60 meters long while that on Mikurajima Island is 40 meters.

The metropolitan government will consider whether other islands will require similar protections depending on the movement of the pumice stone.

According to JAMSTEC’s analysis, the stones will remain around the Izu island chain until they leave the sea at the end of the month.

Since November 9, small amounts of pumice have been confirmed in ports or off seven islands in the chain, including Kozushima and Mikurajima, according to the Tokyo Metropolitan Government.

The stones are around 1 to 10 centimeters in size and have so far had no reported impact on vessel operations.

In Okinawa Prefecture, huge amounts of pumice from the volcanic eruption clogged ports, fouled coasts and forced fishermen to stay ashore.

The Japan Meteorological Agency reported that the eruption of the submarine volcano Fukutoku-Okanoba, located 1,300 kilometers south of central Tokyo, continued from August 13 to 15.

No eruptions have occurred since, but the agency is closely monitoring volcanic activity in the Ogasawara island chain where Fukutoku-Okanoba is located.

“It is likely that the volcano is still very active under the seabed,” said a JMA officer responsible for the observations.

Mikurajima Island has only one port, so the oil barrier will be moved there when fishing vessels need to enter the mooring area.

The oil fence on the west side of Kozushima Island will not impact fishing vessel operations at this time. The island has two harbors, and in the fall and winter, fishermen use the Miura fishing port on the east side.

Problems could arise if the flow of pumice stone prompts additional damage prevention measures.

“If they put up an oil fence at Miura fishing port, we will have to suspend fishing,” said Yoshiki Maeda, general manager of the Kozushima Fishing Cooperative Federation.

Kazutaka Hamakawa, 43, a fisherman from Kozushima Island, said he went out to sea fishing in the early morning of November 18 and when he returned around noon he saw pumice floating near from the port of the island.

“We can avoid the pumice stone during the day, but it is invisible at night,” he said. “We’re afraid our ships will break into a piece of pumice stone, but we’ll see how it goes and keep fishing. You can’t change the way things are.

His colleagues were forced to end their fishing operations early that day because a filter that allows seawater to flow into their vessel to cool its engine became clogged with pebbles.

Normally around 10 fishing boats leave the port of Mikurajima Island per day if the sea is not rough.

“We will have to stop fishing for now if the pumice stone hits (our port),” said an official from the Mikurajima Fishing Cooperatives Federation.

The official said the situation is unfortunate as the season approaches when the price of yellowfin increases.

“We are so nervous,” the official said.

(This article was written by Yoshitaka Unezawa, Hidemasa Yoshizawa, Yasukazu Akada and Yumi Nakayama)