Fungal outbreak hits multiple salmon rivers in Agder, southern Norway; up to 90% of fish may die in Audna

Salmon in the Audna and Kvina rivers in Agder, southern Norway, are being severely hit by a fungal disease. Tore Jarleiv Lølandsmo of the Audna fishing rights holders' association told Lindesnes avis on 13 November: "Almost all the fish are dying." He said the association fears up to 90% of the fish stock in the river has been affected. Both the Norwegian Veterinary Institute (Veterinærinstituttet) and the County Governor's Office in Agder (Statsforvalteren i Agder) have been notified of the outbreak.

The Audna flows through the municipalities of Lyngdal and Lindesnes. The County Governor's Office suspects the pathogen is saprolegnia, commonly known as "fish fungus", but this cannot be confirmed until sample analysis is complete. Outbreaks have occurred in the Agder region before, including in the Mandalselva.

"Based on what we know so far, this looks like a fairly large outbreak. We have reported the situation to the national authorities," Anne Fløgstad Smeland, head of the nature conservation department at the County Governor's Office, told the newspaper.

In the Kvina, at least 15 dead salmon have so far been recovered. Samples have been sent for testing to confirm whether the wild salmon in Kvinesdal are infected with the same disease that is causing a crisis in salmon rivers in Trøndelag. "We have found several dead fish with the same symptoms as the fish in Trøndelag. As recently as Wednesday, we sent five fish to the Veterinary Institute in Bergen for testing. They arrived today, but because of the huge testing volume we have not yet received any response," Roald Aamodt of the Kvina river owners' association told Agder.

According to the Veterinary Institute, ulcerative dermal necrosis (UDN) is a serious skin disease affecting anadromous salmonids and wild trout. UDN causes skin cells to die and often forms wounds, reducing the fish's resistance to infections such as the oomycete fungus Saprolegnia and bacteria. Saprolegnia infects fish in freshwater.

iLaks has previously reported that several rivers in Trøndelag were hit by the skin disease UDN, with wounds appearing on salmon skin followed by fungal infection. The Veterinary Institute has called that outbreak an international disaster.