Artificial lakes are used as a measure to reduce nitrogen load of streams. PhD Student Michael Schwinn has investigated the consequences for migrating brown trouts when a stream is disrupted by an artificial lake. On 3 April he will defend his thesis
Artificial lakes developed in catchments have become a common measure to reduce the amount of nitrogen that is transported by streams to coastal areas. This method is seen as a cost-efficient way to reduce the nitrogen load and provides recreational opportunities.
But artificial lakes pose a huge challenge to migrating brown trout. The trouts are born in freshwater and spend the first time of their lives there. Later on, many juveniles migrate to the sea, where they can utilize richer feeding resources. But when artificial lakes are etablished in streams, the juvenile brown trouts have large difficulties in finding their way through the lake and avoid predation on the way. This is documented by PhD Student Michael Schwinn, DTU Aqua in his thesis.
The study system for his investigations is the artificial lake Egå Engsø in the vicinity of Aarhus. He combines data from 2005, before the lake was established, with new data and shows that the average yearly mortality of brown trout in the lake is on a very high level of about 70 percent. Before the lake was created no mortality was observed in the stream.
Michael Schwinn’s findings suggest that there are high risks that sea trout populations cannot sustain themselves when artificial lakes are developed in connection to streams.
About the defence
Michael Schwinn will defend his PhD thesis "Effects of artificial lakes on migrating juvenile brown trout (Salmo trutta)" on Tuesday 3 April 2018, at 1 p.m., at DTU Aqua, The Canteen, Vejlsøvej 39, 8600 Silkeborg.
Supervisors
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Principal supervisor: Senior Researcher Anders Koed, DTU Aqua
- Co supervisors: Senior Researcher Kim Aarestrup and Senior Researcher Henrik Baktoft, DTU Aqua
Examiners
- Senior Researcher Niels Jepsen, DTU Aqua
- Doctor Andy Moore, Cefas, United Kingdom
- Research Scientist Eva B. Thorstad, Norwegian Institute for Nature Research, Norway
Chairperson at defence
- Associate Professor Christian Skov, DTU Aqua