How do silver eels migrate back to the ocean?


 (c) Björn Illing

Development of a hyperbaric flow channel to parameterize the effects of contaminants and diseases on the reproductive capacity of the European Eel

Which factors affect swimming performance, energy consumption and maturation of the European eel during its spawning migration to the Sargasso Sea? Scientists would like to answer this question, but investigations on free-living animals are not possible - their way of life is too complex. A pressure-controlled swimming flume, including a respirometer, will change that: it enables the experimental determination of various abiotic and biotic factors on migrating eels and a quantification of potential hazards.

Background and Objective

The European eel (Anguilla anguilla) exhibits a fascinating life-cycle comprising various continental and oceanic phases. Juvenile yellow and adult silver eels live in freshwater, i.e. rivers and estuaries, which they inhabit for several years until silver eels leave that have collected sufficient lipid reserves and underwent morphological adaptations necessary for a life at sea. The once in a life time spawning migration leads about 6000 km to the Sargasso Sea, where reproduction occurs and the hatched larvae start their way back to the European coasts. The spawning migration is also considered a critical phase in the eel’s life with a mobilization of energy reserves and maturation of reproductive organs during its course. In this phase, contaminants and parasites likely exhibit their strongest effect on the organism. The development of a novel hyperbaric flow channel shall give the opportunity to examine the effects of temperature, pressure, salinity, contaminants and parasites on swimming capacity, energy expenditures and gonadal maturation of various eel life stages under controlled conditions. A quantification of these effects helps us better understand the causes threatening the European eel.

"Wie wandern Blankaale zurück ins Meer?" ist ein Teilprojekt von AutoMAt, dem Verbundprojekt "Anpassung und Weiterentwicklung von innovativen, nicht-invasiven Monitoringsystemen und Auswerteverfahren für die Fischereiforschung".


Design and construction of the hyperbaric swimming flume is conducted in close cooperation with Kunststoff-Spranger GmbH, a German aquaculture engineering company. The swimming flume’s concept is oriented to so far published work and includes amongst others sensory systems for temperature and oxygen measurements. However, it is advanced by including novel hyperbaric technology that enables a simulation of different water depths.


The conceptual design and the construction of the hyperbaric swimming tunnels, including the development of control software, could be successfully completed within the project period. Parallel to some test runs, research proposals for concrete projects and experiments have already been submitted for funding.


Involved Thünen-Partners

Involved external Thünen-Partners

Funding Body

  • Federal Ministry of Food und Agriculture (BMEL)
    (national, öffentlich)


7.2013 - 12.2015

More Information

Projekt type:
Project funding number: 313-06.01-28-1-28-1-91.007-12
Funding program: Innovationsförderung
Project status: finished