Large numbers of jellyfish have been swarming near nine thermal power plants on Ise Bay. Chubu Electric Power Co. estimates that there are close to 24,000 tons of the sea creatures swimming around the area, twice the usual level and the second-most recorded in the past decade.
Measures are being taken to ensure the jellyfish don’t clog the power plants’ water intakes and disrupt their operations.
Chubu Electric launched a research project in 1999 to predict the number of jellyfish in Ise Bay. They discovered that most jellyfish larvae transform into polyps in three major areas: near the port of Nagoya; along the coast of the Chita Peninsula from Tokoname to Morozaki, Minamichita, in Aichi Prefecture; and along the coast of the Shima Peninsula from Matsusaka to Toba in Mie Prefecture.
Every winter, the research group collects samples of polyps and compares them with past results to predict how many larvae will develop into adult jellyfish in the following year. Last winter’s findings indicated the number this year would be 1.5 to 1.8 times higher than usual.
“We don’t know the reason why the number is so high this year, but we need to monitor the situation closely,” said Minoru Hamada, 46, an assistant project manager in Chubu Electric’s technology development department.
If jellyfish block the water intake, a power plant can’t draw enough water from the sea to cool the steam used to turn the turbine, and the plant has to reduce its electricity output.
Each plant has adopted various measures, including putting up nets, to stop the jellyfish from swimming too close, but this is only effective when dealing with small numbers. It is not enough to prevent large amounts of jellyfish from swimming in all at once.
The number of jellyfish near the thermal power plants usually peaks in July, August and September. However, this year they started gathering around the plants in May, resulting in reduced electricity output at three of the plants for a total of nine days.
They were the Hekinan plant in Hekinan, Aichi Prefecture, the Shin-Nagoya plant in Nagoya and the Kawagoe plant in Kawagoe, Mie Prefecture.
It’s a pressing problem for Chubu Electric because it has become increasingly dependent on thermal energy since its Hamaoka nuclear plant has been shut down over quake and tsunami fears.
“The effect of the jellyfish isn’t fully known yet, but it can have a serious impact on electricity output if they keep increasing, especially during this season when there is high electricity demand,” a Chubu Electric official said. “We need to monitor the jellyfish further and take actions swiftly if necessary.”
This section, appearing Saturdays, features topics and issues from the Chubu region covered by the Chunichi Shimbun. The original article was published July 27.