Abundance analyses of mega‐epibenthic species on the Dogger Bank (North Sea): Diurnal rhythms and short‐term effects caused by repeated trawling, observed at a permanent station

Abstract

Within our long term monitoring programme at the Dogger Bank (North Sea), a permanent station at the north-eastern tail end of the Dogger Bank was sampled yearly with a 2m beam trawl since the year 1994. The sampling procedure was repeated every 3h within a timeframe of 48h. All species above a size of 1cm were recorded quantitatively. The analysis of the dataset, consisting of thirteen sampling years, revealed rhythmic abundance fluctuations of one crustacean and two fish species, depending on the time of day. In order to check the accuracy of the results obtained, we further analysed the dataset for short-term effects of continuous trawling at the same track on the abundance of individual species. No direct effect on the abundance of particular species was detected, but the analysis revealed a periodic fluctuation of the mean number of individuals and the mean catch volume.