The whale was freed by passers-by who jumped into the water to help it after becoming stuck in the harbour last week. It has since been swimming in the area and local people had put together a plan to help guide it back to the sea.
But it was found dead on Friday afternoon, Ivar Høst, a consultant with the Danish Nature Agency, confirmed.
The animal was found at Ørnedalsbugten, an area of the Mariager Fjord waterway that travels from Hobro to the Kattegat sea, Høst said.
The unhappy ending to the whale’s story did not come as a surprise, according to Høst.
“It was only a question of time before things ended badly for it,” he said.
Høst said he would travel to the bay to assess how to remove the aquatic mammal from the water – a potentially challenging task, given it is located a distance from the shore of the shallow-water area.
“It’s a large animal to have to move. We don’t yet know how we are going to get to it,” he said.
The nature consultant added that he hoped to be able to recover the animal so that more could be learned about the sei whale, the subspecies to which it belongs.
“We want to recover it so we can carry out an autopsy and research,” he said.
“That could help us learn about sei whales and why this individual died,” he said.