The operation of the new Ulog hydro power plant triggered a massive fish kill in September 2025. Oxygen-depleted deep water from the reservoir killed endangered species such as the softmouth trout. These findings were formally presented today, 28 November at a conference hosted by Foundation ACT and the Zeleni Klub (Green Club) at the Parliamentary Assembly of Bosnia and Herzegovina in Sarajevo.
The tragic result of Ulog HPP releasing oxygen-depleted water: A mass fish kill on the precious Neretva
© Hrabren Kapić, Organizacija Sportskih Ribolovaca "Konjic"
Despite years of resistance, the Ulog hydropower plant went into operation in 2025. Since then, as feared, it's causing significant environmental damage.
© Bahrudin BandicOn September 12, 2025, large numbers of dead fish including the softmouth trout (Critically Endangered) and European bullhead as well as the white-clawed crayfish (Endangered), were observed along the affected stretch of the upper Neretva River, accompanied by observations of fish gasping for air, crayfish crawling onto the shore, and an intense smell of rotten eggs—clear indicators of hydrogen sulfide abundance and severe oxygen-depleted conditions.
The recently completed Ulog HPP cuts through the most valuable and previously intact river stretch of the Neretva, home to endangered species and high biodiversity, which is now directly impacted by the dam’s operations. Together with scientists and our Bosnian partners in the Blue Heart campaign, we are calling for stricter environmental regulations and an end of hydropeaking in order to save the valuable river ecosystem on the Upper Neretva.
Ulrich Eichelmann, CEO of our partner organisation Riverwatch says: “The catastrophe in September not only killed fish, it wiped out all life in that section, including water insects, molluscs etc. If the Ulog hydropower plant is allowed to keep operating illegally in a peaking regime, unleashing near-daily floods and droughts on the Neretva, the devastating damage will not only be limited to the river stretch below the plant, but the fish populations throughout the entire Neretva, all the way to Konjic, will suffer irreparable harm.”