According to the environmental organization, a whale lost in the river cannot be put to sleep during the transfer.
French authorities are preparing to transfer a milk whale that swam far inland along the Seine River, a marine expert told the French news agency AFP on Tuesday.
The plan is to transfer the whale to a means of transport, which would take it to a sea basin for treatment and later release it.
Moving a four-meter and 800-kilogram whale is challenging and probably causes stress to the animal. According to the French environmental organization, a whale cannot be put to sleep because it needs to be awake in order to breathe.
The whale was spotted in the river last Wednesday and has so far swum 130 kilometers inland from the English Channel.
According to the expert, the animal is severely malnourished and may have internal ailments.
Milk whales usually move in the cold waters of the north, and although they move further south in autumn to look for food, they are rarely seen this far south.
In May, a killer whale also got lost in the Seine, which could not be led back to the open sea and had to be euthanized due to its poor condition.