The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal)

In the past three decades the European eel Anguilla anguilla experienced up to 99% decline in recruitment in some parts of its distribution range. In addition to this long-term trend, glass eel recruitment exhibits significant inter-annual variability partially explained by large-scale oceanographic processes as well as local-scale meteorological and hydrological variables. A 40-year long time series of glass eel fishery catch in the Minho estuary, Portugal, was used to assess (a) whether local recruitment followed the general pattern of decline of A. anguilla observed elsewhere, and (b) whether environmental variables may explain inter-annual fluctuations in glass eel recruitment in the Minho estuary. The analysis shows that, in contrast to the majority of coastal systems in northern Europe and the Mediterranean, CPUE of glass eel in the Minho estuary did not exhibit a marked decline between 1974-2015 and never dropped below 20% of the 10-year mean (1974-1983), taken as baseline. The difference between the recruitment trend observed in the Minho river and that reported by WGEEL for wider European geographical scales highlights the need to calculate recruitment indices with a higher geographic resolution to better support the assessment of the status of the European eel population.