Study on Countermeasures against Jellyfish at Coastal Power Plants

Hokkaido is located to the north of the region where large number of jellyfish are seen, there were no outstanding problems with jellyfish and we didn't conduct any surveys about countermeasures. However, recently troubles by Nomura's jellyfish (giant jellyfish) has hit the fishery almost every year along the coast of the Japan Sea, including Hokkaido, and it is suggested that the troubles will continue to be seen in the future. In Hokkaido, a troubles by moon jellyfish has recently hit the fishery and similar troubles has been seen along the Pacific coast in the Tohoku region, which has not had huge problems with jellyfish before. Considering these situations, it is expected that jellyfish could greatly damage our coastal power plants in the future. Therefore, our department is conducting surveys on countermeasures against jellyfish at our coastal power plants.

• As the result of the field survey on the influx of jellyfish at our coastal power plants, we have found that Nomura's jellyfish inflow in November to January, and moon jellyfish from spring to summer, and although there were no troubles with water intake, the nets to prevent fish from inflowing were damaged and the amount of waste from traveling screens increased on a temporary basis.
• Considering the results of the survey on the countermeasures against jellyfish, the location of the power plants, and the method of water intake, we have concluded that it is appropriate to take countermeasures at our coastal power plants as followings.

1. The power plants with water intake openings faced a quiet sea surface: study on the adoption of the method for loses jellyfish on the sea1.
2. The power plants with water intake openings faced the open sea: study on the quick waste treatment systems of inflowing jellyfish.

We will propose appropriate countermeasures against jellyfish for our coastal power plants through the study and research on the following points that are needed when we consider the adoption of the method for loses jellyfish on the sea and quick waste treatment systems of inflowing jellyfish.

1. Study on the method of viability tests for jellyfish
2. Extensive analysis on the climate and ocean conditions when jellyfish inflow.
3. Study on volume reduction treatment systems of jellyfish waste in cold regions.
4. Field survey on the appearance of moon jellyfish in Hokkaido.

Photo-1 Nomura's jellyfish flowing into our coastal power plant