A large number of carp have died at Valens Lake Conservation Area over the weekend. The cause of the die off, based on the symptoms observed on the fish by HCA ecologists, is thought to be Koi herpes virus (KHV), which only affects carp, koi, and goldfish. Carp are a non-native species in Valens Lake.
HCA staff are working with the Ministry of Natural Resources and Forestry (MNRF), the agency fish die offs are reported to, to confirm the presence of KHV at Valens Lake. The virus can only be confirmed through laboratory tests.
KHV was first found in 1999 in the United States and is thought to have been introduced in Ontario waters through the hobby fish trade. The virus has caused similar carp die offs in Lakes Scugog, Rice, Pigeon and Simcoe and Otonabee River. KHV spreads quickly from fish to fish through close contact. The virus only survives in water for short periods of time (4-24 hours). Outbreaks of the virus in the wild are almost impossible to prevent or treat.
It is thought that KHV entered Valens Lake through improper introduction of infected fish or water. MNRF regulations state that you cannot release live bait or dump the contents of a bait bucket, including the water, into Ontario lakes, rivers, streams or within 30 metres of any waterbody. Carp species are not permitted for use as bait fish in Ontario.
The virus is not a risk to human health. It does not affect humans, and carp infected with KHV are safe to eat and handle. MNRF does advise that you should never consume fish that appear to be sick, dying or already dead, or allow pets to come into contact with them.
HCA staff are working to remove the affected fish from the lake.