An estimated 15-meter-long sperm whale spotted near the mouth of the Yodo River in Osaka earlier this week was confirmed dead Friday, local officials said, after it had remained in the same spot for days and was not observed spouting water.
Workers from Osaka Aquarium Kaiyukan had approached the large mammal — nicknamed "Yodo-chan" on social media — by boat to check if it was breathing, while Tsutomu Tamura of the Tokyo-based Institute of Cetacean Research said that the whale's blowhole had been submerged since Wednesday.
Sightings of whales in Osaka Bay are rare, the coast guard said when it was first seen on Monday. The bay is largely enclosed by Awaji Island, which leaves two narrow passages in the north and south. The southern opening leads to the Pacific.
The cause of death has not been determined. Tamura suggested that the whale may have been "weakened for some reason and swam into the area." It did not appear to have injuries characteristic of trauma inflicted by a ship's propeller, he added.
The whale's length had been earlier estimated at around 8 meters by the coast guard.
Osaka Mayor Ichiro Matsui told reporters the city plans to have the whale's carcass removed. The city will discuss how to dispose of it with the Osaka Ports and Harbors Bureau and other organizations.
In July 2021, a whale carcass was discovered off the coast of Osaka. It was towed away and buried on land by the ports bureau.
Its skeleton was later excavated and it has been stored at the Osaka Museum of Natural History since December.