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Forskningsartikel2015Vetenskapligt granskad

Overwintering dormancy behaviour of the European eel (Anguilla anguilla L.) in a large lake

Westerberg, Håkan; Sjöberg, Niklas


Overwintering dormancy behaviour was studied in female silver eels in Lake Malaren in Sweden between 2008 and 2010. Depth choices and movements in relation to temperature were analysed from pressure and temperature records for 13 eels with implanted data storage tags, covering 17 overwintering periods and three intervening summer periods. Dormancy commenced in October-November as temperatures fell below 4-12 degrees C. Eels tended to remain motionless throughout the winter, with some short periods of activity signalled by small changes in depth distributions. During dormancy, the eel shows a clear avoidance of shallow areas <5m in favour of the 10-25-m-depth interval. Activity tended to resume 4-6months later in April-May as temperatures rose above 3-7 degrees C and ice cover broke, and eels spent more time at shallower depths of <5-10m. The majority of the eels were assessed as being in the silver eel stage at the time of tagging. During the autumn months, the diving behaviour, with frequent and large vertical excursions and periods at the surface, was similar to that seen in migrating eels in the Baltic and Atlantic Ocean. In spring and summer, the behaviour differed, being dominated by more gradual depth variations, implying that the eels reverted from silver eel migration behaviour to yellow eel foraging behaviour. Body weight declined during dormancy, but other studies of starvation over comparable time periods showed significantly higher average specific weight losses, implying that the Malaren silver eels must have fed between the end of dormancy and recapture.


Anguilla anguilla; hibernation; dormancy; data storage tag; annual activity cycle; starvation; growth rate

Publicerad i

Ecology of Freshwater Fish
2015, Volym: 24, nummer: 4, sidor: 532-543