Thousands of dead fish found in Lake Urpalonjärvi

Thousands of fish have been found dead in Lake Urpalonjärvi in Luumäki municipality, southeastern Finland, Yle reports. The cause of the deaths is being investigated, and test results may take several weeks.

Dead fish have been found across the lake, including roach, bream and larger fish such as pike, which are generally more resilient, according to Juha Tervonen, Luumäki’s environmental protection secretary.

Residents who have lived on the lake’s shore for 60 years have told Tervonen they have never seen anything similar.

Urpalonjärvi is a shallow lake with a maximum depth of about three metres and an area of approximately 3.5 square kilometres. Its water level is currently about 15 centimetres below average.

Test results could take six weeks

Luumäki municipality has described the fish deaths as a natural disaster. It sent dead fish to the Finnish Food Authority for examination on Wednesday. Results identifying the cause of death could take up to six weeks.

Water samples were taken from the lake and its surroundings on Thursday. Tervonen said the results are expected by the end of next week.

Several possible causes

There may be several explanations for the deaths. Tervonen said the lake contains an unusually large amount of blue-green algae, at least some of which is the so-called toxic variety that produces nerve and liver toxins.

It is also possible that the lake’s pH level has fallen, for example because of heavy rainfall in recent weeks and the resulting runoff. A lack of oxygen in the water is another possible cause.

The municipality is removing dead fish from the lake together with local water-owner associations.

Luumäki’s environmental protection authorities are advising people to avoid using water from Urpalonjärvi for household or washing purposes and to avoid swimming in the lake for the time being.