Photo/Illutration Volunteers collect aquatic life from the drained moat at Wakayama Castle in Wakayama on Oct. 5. (Orina Sakakibara)

WAKAYAMA—A rare event to explore the underwater world of Wakayama Castle’s moat took place here on Oct. 5 as volunteers and city officials lowered the water level, revealing a hidden ecosystem.

The initiative, part of a TV program, allowed for a closer examination of the moat’s inhabitants and the castle’s underwater structures.

The project involved draining approximately 9,400 square meters of the moat, located north of the castle complex.

With the water depth reduced by about 1 meter from the usual 1.5 to 2 meters, a muddy bottom was exposed, revealing a world unseen for many years.

In a couple of hours, 120 volunteers collected more than 100 carp and 20 mullet, all at least 60 centimeters long.

Other notable finds included mitten crabs, freshwater prawns, crucian carp and invasive species such as bluegill and red-eared sliders. In total, more than a dozen species were identified.

“Carrying the meter-long fish was quite a challenge,” said Yuki Tamaki, a 37-year-old volunteer from the city.

“I was surprised by the abundance of life, with small shrimp jumping up as I walked,” Tamaki said.

Yoshitsugu Kaji, a curator at the Wakayama Prefectural Museum of Natural History, was particularly excited to discover Japanese pond turtle, a native species that has become increasingly rare in recent years.

“It’s likely that these turtles have been breeding and living in the moat for generations,” Kaji explained. “I was also surprised to find fewer invasive species than expected, and the abundance of small creatures suggests that the food chain isn’t severely disrupted. We hope to maintain the moat as a habitat for a diverse range of aquatic life.”

HISTORICAL DISCOVERIES

The drained moat also revealed a significant historical discovery: a large quantity of roof tiles believed to date to the Edo Period (1603-1867).

These tiles, likely from turrets and earthen walls that once stood atop the stone walls, had apparently fallen into the moat over time.

According to city officials, while Edo Period tiles have been found at the site before, the ones discovered this time are particularly well-preserved due to having been submerged in water, with distinct patterns still visible.

In addition, the city’s castle management team conducted an investigation of the stone walls, involving both ground visual inspections and 3-D photogrammetry using drones.

The data gathered will be essential for assessing the feasibility of a planned reconstruction project of turrets on the stone walls.

During the survey, the team also identified several carved markings on the stone walls.

Although the exact purpose of these markings remains unclear, two identical carvings of a circle with a skewer were discovered on the cornerstones of different sections of the wall.

“This was an excellent opportunity to examine the stone walls up close,” said Ryosuke Oyama, a curator from the team.

“We discovered differences in the construction methods between the upper and lower layers, which could provide clues about the construction period and any subsequent modifications,” he said.

Related News