On the actual recruitment of European eel (Anguilla anguilla) in the River Ems, Germany

Data from the historical River Ems glass eel fisheries in the 20th Century have been used for the ICES recruitment series. Commercial catches ceased from 1980 and dropped to zero; thus, eel recruitment data are since lacking. The present study assessed the actual eel recruitment to the River Ems with regard to the local tidal conditions. Standardised measurements were performed on relative glass eel occurrence at the tidal weir from 2014 and quantitative sampling at the next weir upstream from 2013. Eel migration at the tidal weir was dominated by glass eels and increased 2-3 month earlier than at the upstream weir, where migration was dominated by pigmented eels. In 2016, glass eels were marked at the tidal weir and pigmented elvers were sampled at the upstream weir. The 2016 eel recruitment was estimated at about 1% of the mean historical recruitment. Eel recruitment at the two weirs was not directly linked. Many eels seem not to pass the upstream weir. Further investigations are needed to reveal whether the results represent a regular pattern. In the long run, the perpetuation of the recruitment series is also foreseen.