Long-term fluctuations in fish recruit abundance in the western Wadden Sea in relation to variation in the marine environment

Fyke catches from the westernmost tidal inlet of the Wadden Sea were analysed for inter-annual variability in recruit numbers of several commercial and non-commercial fish species between 1972 and 1994. Year-to-year variability in recruits ranged between 0.28 and 1.13 standard deviation. Variability was relatively low for species such as turbot, plaice, and sole, which concentrate in nursery areas during their early life history. Correlations between species were generally low, although a few clusters of species tended to show similar patterns. Pollack and whiting decreased during the study period, whilst sole, flounder, herring, and lumpsucker became more abundant. Part of the observed inter-annual variability in recruits appears to be related to fluctuations in the environment, such as transport rate of larvae across the North Sea and quality of the nurseries, i.e. temperature, food availability, and predation pressure.