Around thirty dolphins are believed to have died and dozens still remain at risk in a Tasmanian river after a rare mass stranding in the remote Western area of the island.

The dolphins are believed to have left their normal habitat of the oceans surrounding Tasmania in order to follow food upriver. This is not an uncommon occurrence, with dolphins often being seen in the rivers, but beachings on this scale are so rare to be almost unique.

It is thought that heavy storms and torrential rain caused such huge breakers in the river mouth that the dolphins became trapped, unable to return to sea.

Once trapped, the situation became worse for the dolphins as the surroundings of the river are unfamiliar to them and the species adaptions that make them so at home in the sea left them helpless in the river.

David Pemberton, a marine biologist with the Department of Primary Industries, Parks, Water and Environment, explained the problems the dolphins faced, “The water in the river is cold and dark, there is rainforest down to the edges and log jams everywhere. It’s a hard place to be an oceanic dolphin – they are used to water of a different colour and temperature.”

He also described how the dolphin’s acoustic systems, which would normally provide them with a failsafe method of navigating out of danger, would be useless due to the river’s rocky bottom and many bends.

Initial necropsies carried out on the dolphins that were found dead showed cuts which could indicate they had swum into the rocky river banks, or had hit log jams in the river.

Pemberton hopes that those remaining in the river will be able to safely return to their oceanic home, “Those who are still in the river appear to be getting on with business. It doesn’t look as if they are ramming themselves up against the banks. We hope in time they will find their way out.”