Disputation: Svenja Christiansen

PhD candidate Svenja Christiansen at the Department of Biosciences will be defending the thesis "From acoustic scattering layers to individuals - behaviour of a mesopelagic fish at different scales" for the degree of PhD.

Profile picture of Svenja Christiansen

Svenja Christiansen. Photo: UiO.

The disputation will also be live streamed using Zoom. The host of the session will moderate the technicalities while the chair of the defence will moderate the disputation.

Ex auditorio questions: The chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking "Participants" followed by clicking "Raise hand". 

The meeting opens for participation just before 13.15 PM, and closes for new participants approximately 15 minutes after the disputation has begun.

The trial lecture is: "Influence of environmental factors on behaviour of pelagic animals".

Time and place: Dec. 15, 2021 10:15 AM, Nucleus, Bikuben, the Kristine Bonnevie building

The meeting opens for participation just before 10.15 PM, and closes for new participants approximately 15 minutes after the trial lecture has begun.

Main research findings

Enormous abundances of small fish commute each night from several hundred meters depth to forage in the productive surface waters. Such so-called mesopelagic fishes are central in the food web and their daily vertical migration likely plays an essential role in carbon and nutrient cycling. Their behaviour is so far mainly described on the community level. However, the fishes’ ecological and biogeochemical role is ultimately defined by the individuals constituting the migrating communities. Therefore, learning more about the smaller behavioural scales is essential.

Christiansen and colleagues analysed a 10-month high-resolution acoustic dataset to describe the behaviour of a vertically migrating fish (Maurolicus muelleri) at the individual level. By acoustically tracking individual M. muelleri by echosounders deployed at depth we revealed details of the three-dimensional swimming behaviour, which provided new insights into the species’ migration and nocturnal activity. The results further suggest that M. muelleri combine several anti-predation strategies and emphasize the diversity of behaviours in this single species. Moreover, knowledge of individual swimming patterns will help predicting the effects of behaviour on acoustic biomass estimates. Such knowledge is required in the crucial task of assessing the role of mesopelagic fish in the ocean.

Adjudication committee

Professor Geraint A. Tarling, British Antarctic Survey

Senior Research Scientist Anne Christine Utne Palm, Institute of Marine Research

Professor Stein Fredriksen, University of Oslo

Chair of defence

Professor Tom Andersen, University of Oslo


Professor Stein Kaartvedt, University of Oslo 

Professor Josefin Titelman, University of Oslo  

Associate Professor Øystein Ole Gahr Langangen, University of Oslo

Published Dec. 1, 2021 10:21 AM - Last modified Feb. 21, 2022 2:06 PM