Pumping stations negatively affect the distribution of critically endangered European eel (Anguilla anguilla); a landscape-scale study using environmental DNA metabarcoding

Pumping stations in wetlands pose a threat to the critically endangered European eel and other resident fish populations, according to a recent study using environmental DNA metabarcoding. The research focused on the extensive wetland known as The Fens, examining the distribution of European eel and other fish in 152 pumping station catchments over a two-and-a-half year period.

The study found that eel occurrence was low upstream of pumping stations, with only 28.3% of sampled sites showing eel presence. This low occurrence was positively associated with the catchment area, fish species richness, and natural hydrological connectivity (such as gravity drainage or flooding), and negatively associated with the distance from the tidal limit.

Interestingly, fish species richness, rather than catchment area, improved model performance and may serve as a biotic indicator of habitat quality and connectivity. Pumped catchments with manually operated upstream water transfers experienced reduced eel presence, potentially due to the direction of water flow or timing of operations. In contrast, fish species richness increased in these pumped catchments during summer, likely because the fish were displaced into unsuitable long-term habitats.

The study concluded that pumping stations negatively impact European eel distribution and fish species richness in pumped river catchments. This finding has significant implications for European eel conservation and infrastructure management, including compliance with the EC Regulation No. 1100/2007.