Beekprik in de Achterhoek in tijden van droogte en lozingen

Brook lamprey in the region Achterhoek in times of drought and water pollution. Brook lamprey (Lampetra planeri) is endangered and shows a fragmented distribution in the Netherlands. In the region Achterhoek two small, isolated populations are present. The extended periods of drought in the summers of 2018 and 2019 led to a shortage of water and desiccation of part of the streams it occupies. The effect of the drought on population quality was studied by looking at densities and demographics of the larvae. It shows an overall negative effect on the brook lamprey population. Densities drop, year classes disappear and reproduction failed due to the drought. These effects were not seen in nearby, unaffected streams. Additionally, a chemical spill, detected in June 2019 let to high mortality of fishes in one of the streams. The results show that both populations in this region are very vulnerable. To restore their sustainable state, conservation measures should focus on restoration of stream morphology, removal of barriers and improving water quality.