A fungus is attacking West River fish, and climate change could make it worse

Trout and salmon in P.E.I.'s West River are dying from fungal infections, and the Central Queens Branch of the P.E.I. Wildlife Federation wants to raise awareness of the issue.

The fungus is called saprolegnia, and it can be found in fresh water all over the Island. But it seems to be more of a problem in West River than in nearby waterways.

"Sometimes over 50 per cent of the fish can be covered in this cotton or white patch. It kind of spreads all over the fish eventually and ends up killing it," said Jordan Condon of the Central Queens Branch of the P.E.I. Wildlife Federation.

The fish also behave oddly. They swim closer to the surface and are less cautious, making them easier prey if they are not killed outright by the fungus itself.

Water temperature a factor

It tends to affect older fish, which is a problem because these are the brood stock, essential for keeping the population going.

Sonja Saksida, a research scientist and aquatic health specialist at the Atlantic Veterinary College, said saprolegnia has always been common in P.E.I. rivers, but she said the warm fall weather may be making it more deadly.

"Fall was really quite warm," said Saksida.

"We all loved this fall, but it meant that the water temperatures were warmer than normal."

The average temperature this September and October was 2 C above normal in both months. 

Trout and salmon are drawn into shallower streams to spawn by the shortening days of autumn, but they need the water to be a certain minimum temperature to spawn successfully.

"These fish were coming in to spawn, the light cues were suggesting that they need to be in the rivers to spawn," said Saksida.

"But the water temperature wasn't allowing them to spawn. So they were there for a longer period of time."

Extended periods of time in the streams could be increasing their exposure to the fungus, she said, making it more likely they will be infected.

With climate change bringing more warm fall weather, saprolegnia could become a more common problem on P.E.I., said Saksida.