Photo/Illutration Boat and canoe sprint events in the Tokyo Olympics will be held in Tokyo’s Koto Ward at the Sea Forest Waterway, the water channel at the center of this aerial photo taken on Feb. 1. (Tatsuya Shimada)

An event staffer at an international boat racing competition anxiously examined the long, cylindrical floats lining the roughly 2,000-meter course at the Sea Forest Waterway in the capital’s Koto Ward.

“I hope none of them are attached to the devices,” the staff member said, worriedly gazing into the water as if a monster was lurking below the surface.

The staffer was working at a May event for selecting athletes to compete in the upcoming Games, held at the same location where the rowing and canoeing events are scheduled for the Tokyo Olympics and Paralympics.

The floats, each measuring 60 centimeters in diameter, are designed to disrupt waves to create favorable racing conditions.

But during preparations for a trial event in summer 2019, just shortly after the course was completed, officials noticed that some of the new equipment at the regatta venue had mysteriously sunk underwater.

The Tokyo government conducted a survey of the area, revealing that something from the sea had become attached to the equipment: oysters.

When the shellfish grew larger in the winter, they weighed down the devices--which are necessary for holding competitions here--fully submerging them in some places.

The floats are designed to dissipate waves generated by boats and canoes, and can lower the height of waves by about 70 percent.

“The running of the race must not be influenced by natural or artificial waves,” the World Rowing rule book states. “The banks must be so designed as to absorb and not to reflect waves.”

But the banks of the Sea Forest Waterway stand straight and reflect waves. The anti-wave unit was introduced along all the routes, totaling 5.6 kilometers, to ensure fairness for the contestants racing in different courses.

After confirming that oysters had proliferated there, the Tokyo government pulled the equipment onto the shore or hired divers to remove the shellfish between December 2019 and September 2020.

They removed 14 tons of edible Japanese oysters at a cost of 140 million yen ($1.28 million).

Not everyone was shocked by the discovery that the new venue was being overrun by seafood.

“It is no wonder that Japanese oysters grow there,” said an official with the Tokyo Metropolitan Islands Area Research and Development Center for Agriculture, Forestry and Fisheries.

The area around the Sea Forest Waterway was home to many nori farms and known as fertile fishing grounds before the 1964 Tokyo Olympics.

Tokyo was the largest oyster-catching region in Japan at many points in time until the early Showa Era (1926-1989), according to records published in 1971 on the rise and fall of fisheries in inland bays in the capital.

A 2005 survey spotted a 10,000-square-meter Japanese oyster reef in Tokyo Bay near Kasai Rinkai Park in the capital’s Edogawa Ward--just 5 kilometers from the Sea Forest Waterway.

But a Tokyo government official involved in developing the Sea Forest Waterway venue described the sudden emergence of oysters thriving on the wave-absorbing equipment as an “unexpected” development.

“The same wave-dissipating system is in operation at the speedboat racing site in Heiwajima (in Tokyo’s Ota Ward) with no problems,” the official said.

“We did not consider consuming them,” the official added. “That would entail safety checks. More important is that we do not want to grow oysters but work to contain them.”

When asked about the risk of the oysters potentially hampering the Games scheduled for this summer, the metropolitan government downplayed the possibility and said Tokyo is keeping a close eye on the matter.

Young oysters, called larvae, attach themselves to floating objects during the summer, according to the Tokyo government.

Most of the anti-wave floats on the water’s surface were set up after the beginning of February, meaning there should be no more larvae on them, officials said.

But one remaining problem is that the oysters could thrive in the winter after the Olympics are over and return to haunt the racecourse in the years to come. And since Tokyo plans on making good use of its Olympic event sites after the Games are over, that has left officials digging for a solution to the sticky situation.

“It would be unacceptable if they (wave-dispersing devices) sink,” one Tokyo official said.

The metropolitan government is currently weighing whether to call in experts or electrolyze seawater to prevent the creatures from inhabiting the equipment again.