Aktivität und Verhalten wandernder Lampetra fluviatilis, Lota lota und Anguilla anguilla im Tidegebiet der Elbe

Abstract

Lamprey (Lampetra fluviatilis) have been observed in high numbers at the Geesthacht Dam during migration from the Elbe estuary to upstream spawning grounds on only 2 occasions; these were both periods preceding full moon by a few days. No correlation between the migration and hydrographical factors was observed. Statistical evaluation of the commercial swing net fishery landings of migrating lampreys in the Elbe estuary from 1955 to 1966 showed catch maxima about 4 days after full and new moon. If the maxima obtained in two different sections of the Elbe each followed from the same activity of the lamprey, lunar influence could have been initiatory. The observations on the migration of pigmented young eels (Anguilla anguilla) confirmed that temperature is the main factor causing upstream movement. The highest catches of burbot (Lota lota) during their upstream movement through the Geesthacht fishway from the estuary to spawning places were obtained when exceptionally high tides occurred. It is not certain if the catches became higher as a consequence of increasing individual activity. Opening and closing the various dam gates drastically changed the cross-sectional profile of the river bed and thereby influenced the path of upstream migration for lamprey. This influence was checked by observing the trap of an adjacent eel pass. By this means it became evident that lampreys ascend along the edge of the main current. Similar results have been obtained from earlier investigations with swing nets in the lower Elbe river. By other methods and for other fishes, much the same has been found. In contrast to this behaviour, pigmented young eels move upstream in still water areas as well as aside the main current. © 1967 Biologischen Anstalt Helgoland.