Status and Trends in European Eel (Anguilla anguilla L.) Stocks and Mismatches with Recruitment

European eel stock and silver eel escapement fishery-independent and CPUE data, comprising 39 time series and 16 intermittent datasets from NW Europe, are analysed and compared to published recruitment time series data. Inter-annual and inter-site variabilities are high and geographical differences exist but analyses indicate that stock and escapement overall have fallen relatively steadily by about 40-50% since 1960. No clear relationship is however shown with recruitment, which rose to a peak around 1980 and then fell by >90% until recent years. Historical data suggest that whilst recruitment has fluctuated widely, stocks have tended to be more stable over the long term, indicating that the European eel does not exhibit standard stock-recruit relationships. Possible reasons are discussed, including sampling factors, depensation, effects of ocean-climate change on larval survival and density-dependent survival, migrations, growth and sex determination (leading to relative increases in numbers of females and hence fecundity). The latter factors may represent adaptive strategies that help maintain stability of continental populations. Implications for monitoring, modelling and management are discussed.