A structure built to secure cooling water for the nuclear power plant in Hungary has raised concerns about the free movement of fish and the recovery of sturgeon populations.
The Danube Sturgeon Task Force (DSTF), an international platform for the conservation of Danube sturgeons, has expressed serious concern about the possible consequences of a new bottom sill in the Hungarian stretch of the Danube. In a letter dated October 2026 to the Hungarian minister responsible for the environment, the platform calls for a careful assessment of the impacts and evidence that the structure allows fish to pass freely.
According to the letter, the sill was built as an emergency measure to secure cooling water for Paks Nuclear Power Plant. Such a structure raises the level of the riverbed, and changes in the riverbed and flow velocity can hinder sturgeon movement.
The concerns focus on the sterlet (Acipenser ruthenus), a sturgeon species that is still present but rare in the Hungarian Danube. DSTF points out that these fish move considerable distances along the Middle Danube, between Gabčíkovo and the Iron Gates. Free movement upstream and downstream connects local groups and maintains genetic exchange between them. A new barrier could weaken these connections.
DSTF therefore calls for:
- Evidence that fish can pass in both directions at all water levels, with particular attention to sterlet.
- An assessment of alternative solutions, as well as removal or modification of the temporary sill to allow migration.
- Sturgeon-specific monitoring, as conventional fish monitoring methods often fail to detect their presence reliably.
- A strictly limited duration and regular review of any operating permit, supported by comprehensive monitoring of the impacts.
The platform asks for its position to be considered in the environmental impact assessment procedure, described in the letter as ongoing. It also calls for the International Commission for the Protection of the Danube River to receive the necessary information so that countries and observers can assess the potential transboundary impacts.
The issue also matters for Bulgaria as part of the Danube basin. DSTF warns that new barriers could hinder both the movement of existing populations and efforts to restore the future return of sturgeons that migrate between the sea and the river to stretches they cannot currently reach. Their conservation requires a connected river and coordinated action among the Danube countries.
Source: Danube Sturgeon Task Force (DSTF), October 2026.