The pride of an “alien fish hunter” fighting bluegill in the moat of the Imperial Palace

“Beep, beep, beep!

The strange-looking boat slowly moves through the moat of the Imperial Palace while emitting an electronic sound. The man holding the net at the front of the boat is Satoshi Kudo, 65, who is known as the “alien fish hunter. He is a former chief researcher at the Sakemasu Inland Fisheries Experiment Station of the Hokkaido Research Institute, and has 20 years of experience in the extermination of alien fish.

Mr. Kudo is piloting a secret weapon for the extermination of alien fish called an “electric shocker boat. The antenna-like electrodes attached to the tip of the boat emit an electric current of up to 1,000 volts, which electrocutes and stuns fish up to 2 meters deep, causing them to float up. This is the time of year when the bluegill population is at its peak.

At this time of the year, bluegill fry are swimming in clumps. “At this time of the year, bluegill fry swim in clumps, and when you run an electric current through them, they float to the surface. Communicating with the boatman at the helm behind the boat is important for efficiently catching non-native fish without electrocuting carp, crucian carp, and other native fish.

On this day in mid-December, we were at the Otemachi moat in the outer garden of the Imperial Palace. Due to the construction of the nearby railway station, we had not been able to do much extermination work in recent years. Perhaps because of this, most of the bluegills captured were young fish born this year, amounting to about 15,000.

Mr. Kudo, who was originally an employee of the Hokkaido Government, became in charge of non-native fish in 2000. The battle began in earnest in July 2001. In July 2001, black bass were confirmed to be living in Onuma National Park for the first time in Hokkaido. At the time, we were still in the dark about how to get rid of them. Even underwater blasting with dynamite was seriously considered (but eventually abandoned).

In July 2004, an “electric shocker boat” used in the U.S. was introduced to the area. In July 2004, an electric shocker boat, which had been used in the U.S., was introduced and Japan’s first extermination by boat was carried out in the Minamihoromachi Oyasui Park Swamp.

We were told by the agency, ‘We are going to introduce the boat, so please use it. At first, it was a test, not an extermination project. We wanted to see how efficient it was, but we were able to get rid of it.

Thanks to the work of Kudo and his team, black bass in Hokkaido were completely eradicated in 2007.

In 2006, the Ministry of the Environment’s Imperial Gardens Management Office, which had learned of the success in Hokkaido, approached Kudo and decided to exterminate black bass in the Imperial Gardens as well. By 2010, the black bass had been wiped out, and the next target was bluegill.

The bluegill is more difficult to eradicate than the black bass. Still, eradication is finally in sight. The bluegills in the moat of the Imperial Palace Outer Gardens are now being eradicated, and we believe that we will be able to eradicate them in a short while, no matter how strong their reproduction is. I can’t say how long it will take, but if the conditions, including the water environment of the moat, are right, eradication will be possible.

In recognition of his achievements, he received the Minister of the Environment’s Award for Outstanding Service to the Natural Environment on Greenery Day in 2005.

In recognition of his achievements, he received an award from the Minister of the Environment on Greenery Day in 2005. I feel that if I can be of any help, I will. I have been working in Hokkaido, so my body is designed for cold weather. Working in the winter in Tokyo is not that hard for me.”

I’ve been battling alien fish in the moat of the Imperial Palace for 15 years. …… The work of the “alien fish hunter” is likely to continue for a while yet.

From the December 31, 2021 issue of FRIDAY