Seasonal downstream movements of the European eel in a Southwestern Europe river (River Ulla, NW Spain)

Abstract

The phenology of downstream movements of Anguilla anguilla is well documented in Northern countries of Europe, but poorly known in temperate areas such as the Iberian Peninsula. For the purpose of this study continuous downstream movement fluxes of eels have been recorded using a fixed trap in River Ulla (Galicia, NW Spain) during a 13-year monitoring period. Analysis of the fixed trap data suggests that silver eels move downstream mainly in autumn, with a peak in October, while yellow eels present more activity and were captured more frequently when moving downstream in summer, with a peak in June/July. The findings from the present study suggest also that the situation for this species is critical in the area, with a significant declining trend in the eel abundance in the studied period.