Many benthic species have been recorded to occur in the water column above the tidal flats in Königshafen. They were either passively suspended from the sediment or performed active migrations. Concerning both number of species and organisms, active migrations were more important. The causes for these migrations range from (1) individual escape from a sudden threat such as predator attack, over (2) group evasion of local subpopulations to avoid environmental deterioration, to (3) habitat changing of entire populations. The temporal scales involved range from seconds to seasons, and the spatial scales from cm to km. Such changes of distribution patterns have been demonstrated in juvenile molluscs and in meiofaunal copepods and plathelminths. Since migrations may interfere with many kinds of population studies in the field, new methods and concepts need to be developed to avoid and overcome pittalls. As a precaution, the migration potential of benthic species should be taken into account in any field study including population parameters.