Photo/Illutration Starfish in Ono, Gifu Prefecture, on Oct. 31 are used to defend seedlings from wild animals. (Akihito Usui)

ONO, Gifu Prefecture—A fishery cooperative and an airport operator are using a method to deal with troublemaking starfish that can keep both the sea and mountains rich and fertile in central Japan.

In death, the starfish have been effective guardians of seedlings and farmland. The stench from their rotting carcasses can repel deer, crows and other wild animals that could feed on the plants.

For several dozen years now, the Onizaki fishery cooperative association, based in Tokoname, Aichi Prefecture, has been removing starfish in May and June every year because they harm fishing grounds in Ise Bay, get caught in fishing nets and mingle with the hauls.

Fishermen use seine nets to drag up to nearly a ton of starfish a year, which they bury in the ground for disposal.

The starfish drew the attention of Central Japan International Airport Co., the Tokoname-based operator of Chubu Airport that has been working on afforestation projects in Gifu Prefecture and elsewhere.

Company officials asked the fisheries cooperative to give them the starfish.

The starfish, which are dried in the sun after removal from the sea, give off a strong, foul smell when they are half-dried or wet.

For humans, dried starfish smell slightly of the sea. But for sharper-nosed animals, the odor can act as a repellent.

In fact, starfish have been commercialized for that purpose.

Central Japan International Airport and other parties in June 2023 planted 150 seedlings on a hillside in the town of Ono in the upper reaches of the Ibigawa river.

Starfish were then cut into pieces with scissors and dangled in net bags in the area.

During the first six months of the experiment, the seedlings suffered almost no damage from wild animals, said Yukiyoshi Matsuhisa, chief director with Satoyama-kai, a local nonprofit that administered the land plot.

“Most of the trees we had planted earlier in the area ended up being eaten by deer,” Matsuhisa, 69, said. “We were pleasantly surprised, all the more because we didn’t really believe what we had been told.”

The project started in earnest after the success of the trial in Ono.

In June this year, 40 kilograms of starfish collected by the Onizaki fishery cooperative were sun-dried and taken to Ono, just over 70 kilometers away.

Matsuhisa and his colleagues installed the starfish repellent not only in the mountains where they had planted seedlings but also on persimmon, pumpkin and Welsh onion fields.

The areas have so far suffered no damage from wild beasts, he said.

Matsuhisa said he is thinking about sprinkling liquid in which starfish have been soaked, or even starfish pieces, directly on the ground to reduce the work from next year.

“I like this because the ingredients are naturally derived and eco-friendly,” he said.

Masaki Hirano, a 53-year-old counselor with the Onizaki fishery cooperative, also praised the project.

“We owe marine nutrients to mineral inflow from the mountains,” he said. “We are happy to see the starfish become useful in the mountains, and we hope to continue this into the future.” 

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