Photo/Illutration An ayu fry is called “hiuo” (ice fish) because of its translucency. (Provided by the Shiga prefectural government’s Fisheries Management Division)

OTSU—The January haul of “ayu” sweetfish from Lake Biwako was only 3 percent of the average and the smallest since record-taking started in 2009, the Shiga prefectural government said.

Poor spawning due to last summer’s scorching heat likely contributed to the low catch, officials said.

“This is something I have never experienced during my career of more than 40 years,” said a fisherman with the Shigacho fisheries cooperative association based in the prefectural capital of Otsu.

The ayu, a representative fish species produced in this landlocked prefecture, accounts for about half of the entire fish catch from Biwako, Japan’s largest lake.

The fishing season for ayu fry, called “hiuo” (ice fish), opens in December.

A maze of netting, called “eri,” fixed in the water has been a traditional way to catch hiuo during winter and early spring. The Shigacho fisheries cooperative association operates 12 eri, the most in the prefecture.

According to prefectural government officials, a study of 14 eri, or about half of all nets operated by fisheries cooperative associations, showed the January hiuo catch averaged 4.3 kilograms per eri.

That was only 2.9 percent of the mean catch of 149 kg per net averaged over 10 years from 2014.

The latest figure was smaller than the 6.5 kg of January 2017, when poor ayu growth due to excessive spawning caused a record-poor catch.

The officials said extreme heat lasted through September last year. As a result, the water temperature in rivers flowing into Biwako was 24 degrees during the ayu spawning season of September and October, up 2 degrees from the average.

The searing temperatures and low rainfalls also decreased the river water volume. The number of ayu eggs found between August and October last year was only about 20 percent of the average for that period.

Oddly, a fishery experiment station in January found about 20 percent as many ayu shoals this year as there are in an average year. The prefectural government is conducting a follow-up study to determine why the ayu catch has been smaller than corresponding levels.

The water level in Biwako has remained low since autumn, prompting the prefectural government to set up a drought management headquarters in January for the first time in 18 years.

Officials said there has been no confirmed causal relation between the drought and the poor catches.

“Fishermen have told us the low water level has changed water currents around the eri nets, and ayu are no longer coming their way,” Shiga Governor Taizo Mikazuki told a news conference on Feb. 20. “The hauls are extremely poor, and we are closely observing the trend.”

Prefectural officials said fisheries cooperative associations have been unable to fulfill orders placed by ayu breeders because of the poor catches, and shipments to retailers and restaurants have also been in arrears.

“It pains me when we cannot meet demand,” the Shigacho fisheries cooperative fisherman said. “Some fishermen have suspended their operations because they don’t pay. We would be very badly off if things were to remain like this.”

Related News