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Thousands of fish likely died in MN lake because someone released their pet goldfish

It's illegal to release goldfish into the wild in Minnesota.

A bunch of fish died in a Minnesota lake last month, and now officials think the fish kill could have been caused by a pet goldfish. 

The Minnesota DNR and the University of Minnesota say koi herpesvirus was the main cause of thousands of carp dying in Lake Elysian in Waseca County in late June. 

“What this incident tells us is the virus can be introduced by human action – a goldfish or koi was likely released from a home aquarium or pond into Lake Elysian or a connecting waterway," Craig Soupir, DNR’s Waterville area fisheries supervisor, said in a statement. 

This is the first documented case of it in a wild fish population in Minnesota. The DNR says the virus can cause disease in koi and common carp, while goldfish can be carriers of it without showing signs they have the disease. 

“The virus can be present in a lake without causing a fish kill, at least not until the right conditions are present,” DNR fisheries pathology lab supervisor Ling Shen said in a statement. “KHV is highly contagious, and as we’ve seen, very capable of causing large-scale die-offs of common carp.”

The koi herpesvirus (KHV) doesn't affect humans, and it's not believed to affect other fish species. 

Releasing your pet goldfish is illegal

The DNR is reminding people that if you're sick of your pet fish, you shouldn't release it into the wild – it's actually illegal. 

Other groups have also encouraged people not to flush your pet fish down the toilet. 

Goldfish and other ornamental fish aren't native to Minnesota, so if you're looking to dispose of one of these fish you should contact the DNR or a local humane society.

The most common non-native fish released in Minnesota are goldfish, common carp-koi and the Oriental weatherloach, Minnesota Sea Grant says

To learn more about invasive species in Minnesota, click here

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