Juvenile rainbow trout (Oncorhynchus mykiss) in a tank. Photo: Tilo Pfalzgraff.

PhD defence about metabolic consequences of stress in fish in aquaculture

Tuesday 25 Jan 22


Tilo Pfalzgraff
PhD student
DTU Aqua


Peter Vilhelm Skov
Associate Professor
DTU Aqua
+45 35 88 32 63

On 8 February 2022, Tilo Pfalzgraff from DTU Aqua will defend his PhD thesis. It is possible to attend the defence online on Zoom.

The extraordinary growth of the aquaculture industry in recent decades has increased focus on animal welfare in fish production. While in the past, fish were believed to be less sensitive, research has shown that they are as affected by stress-related issues as birds and mammals.  

Aquaculture related issues regarding fish welfare include water quality, stocking densities, nutrition, handling, and social stress. Some of these stressors have shown to cause chronic elevation in circulating cortisol levels, the main stress biomarker of most fish. While the short-term effects of cortisol on fish metabolism are well studied, less is known about the consequences of prolonged elevated cortisol levels.

In his PhD project, Tilo Pfalzgraff has investigated how long-term elevated cortisol concentrations effect the metabolism of rainbow trout. The project includes four experimental studies under different conditions at the aquaculture research facilities at DTU Aqua, Hirtshals. In the studies fish were treated with chronic cortisol implants that released the hormone into circulation over several weeks. 

Tilo Pfalzgraff concludes that his findings emphasize the importance of fish welfare in aquaculture production. The results show that the effects of chronic cortisol elevation due to stressful rearing conditions affect production related traits such as growth rates of the fish. Ultimately, stressful rearing conditions can result in impaired water quality, as fish with high cortisol levels have a decreased ability to absorb nutrients from the feed. Impaired water quality can result in bacterial growth and will impact the aquaculture system’s carrying capacity and thus the welfare of the fish.

About the PhD defence

Tilo Pfalzgraff will defend his PhD thesis "Effects of cortisol on the nutrient utilisation and bioenergetics of rainbow trout" on Tuesday 8 February 2022, 1:00 p.m. (CET) on Zoom (please find link below).


  • Principal supervisor: Associate Professor Peter V. Skov
  • Co-supervisor: Senior Researcher Ivar Lund


  • Senior Researcher Manuel Gesto, DTU Aqua (chair)
  • Professor Gudrun De Boeck, University of Antwerp, Belgium
  • Director of Research David J. McKenzie, Centre National de la Recherche Scientifique, France

Chair at defence

  • Senior Researcher Anne Johanne Tang Dalsgaard, DTU Aqua
Learn more

A popular science summary of the thesis can be downloaded here 

A copy of the thesis is available by e-mail on request. Please contact Karin Stubgaard, stub@aqua.dtu.dk

Link to Zoom and guidelines for online attendance

It is possible to attend Tilo Pfalzgraff’s defence on Zoom using this link:

Please, enter the meeting 10 minutes prior to the defence proceedings are scheduled to start. All participants are muted per default, but we ask you to double check that your microphone is turned off at all times. 

There will be instructions regarding the proceedings in the beginning of the defence.