Investigations are underway and bathing and fishing remain banned after thousands of dead fish were found floating in the Oder River between Germany and Poland. The cause of the mass die-off remains a mystery. 

German and Polish authorities search for cause of mass fish poisoning

Volunteers, police officers, firefighters and soldiers have been busy for several days on the German-Polish border, removing up to a hundred tons of dead fish from a 500-kilometre stretch of the Oder River. The cause of the “catastrophic” mass die-off has not yet been clarified, after laboratory tests found elevated salt and oxygen levels in the water, but no other toxic substances. 

“We are poking around in the dark,” Axel Vogen, Environment Minister for Brandenburg, told Tagesspiegel this week, explaining that insecticides and pesticides were being evaluated - along with 300 other substances - as possible causes of the mass poisoning. Vogel said that the salt and pH levels of the water were high enough to be toxic, and that the oxygen concentration in the water is greatly increased - although the opposite should be true, given the recent warm weather and low water level. 

Both the Polish and German governments suspect that the incident was caused by a toxic waste spillage - perhaps involving a company illegally dumping waste in the river - and Polish police have offered a 210.000-euro reward for anyone who can help find those responsible. However, the search for the exact cause has so far remained inconclusive, and not been helped by communication issues between German and Polish authorities, with Germany accusing Poland of not taking action or issuing a warning when the die-off was first noticed almost three weeks ago. 

Environmental disaster could have dire consequences for Oder ecosystem

Sascha Maier from the Association for Environment and Natural Protection Germany (BUND) told Berliner Morgenpost that not only fish were affected, but other water animals such as mussels and small vertebrates. There are concerns that the mass die-off could have dire consequences for the area’s entire ecosystem. 

Experts are worried that the as yet unidentified toxin could enter the food chain and cause havoc as it concentrates in animals who eat the fish. “We saw that other animal species such as eagles or racoons have been eating the carcasses,” Maier told Berliner Morgenpost. Karina Dörk, a city administrator in the Uckermark region, told Tagesspiegel that authorities would have to keep a close eye on how local bird, otter and racoon populations develop. 

Farmers in the area have been advised not to give the water to their sheep and cattle, while environmental ministers have decided to use floating oil barriers to stop the dead fish from floating further towards the Baltic Sea. As a precaution, the Ministry for Environment in Mecklenburg-Vorpommern called on residents to refrain from fishing or swimming in the Szczecin Lagoon. Locks have been closed to try to protect waters connected to the Oder.