Sustainable Lake Stewardship (DK)

Biomanipulation (removal of large quantity of planktivorous fish biomass) is an often used tool in lake restoration.

Project Background

This project is truly interdisciplinary and involves many of the Danish Universities. The overall aim is to further our knowledge about optimal sustainable lake restoration and explore the potential for recycling of the nutrient phosphorus (P). P is on one side in excess in many lakes, where it causes eutrophication and loss of biodiversity while on the other side P is becoming a scare resource globally as many P mines are running dry.

In the first phase of the project, Lake Ormstrup has been selected as the test object. We want to know where the phosphorus is stored and in which form; the history of the lake; how much sediment can be removed; can it be used as fertiliser; how do the fish respond to the interventions; and what are the socio-economical consequences of the activities. Both the environment and the animals in and around the lake will be rigorously mapped and characterized in 2020, 2021 and 2022.

A frequent tool used in lake restoration is biomanipulation - i.e. massive removals of planktivorous fish. The aim of this study is to better understand when (season and time of day) it is optimal to remove the fish usign various methods such as seining, gillnetting, electrofishing etc. In 2020 and 2021 the lake underwent such biomanipulation and over the next years researchers from the different universities will follow how the different trophic levels respond to this, and develop and test new lake restoration methods and technologies.

High-Resolution Fish Tracking

To explore fish behaviour, we use high‐resolution positional telemetry where we focus on both predatory and zooplanktivorus fish. Such detailed knowledge will allow us to better understand trophic relationships and interactions as well as further our knowledge about optimal lake restoration. As part of these efforts, we developed a (worlds first?) real-time tracking system, showing positions of the tagged fish in the lake “live”, i.e. with less than two minutes delay. Read more our Real-Time tracking or go directly to the tracking at https::/

Example of seine fishing in Lake Ormstrup
Example of seine fishing in Lake Ormstrup. Using information from the Real-Time tracking system on the whereabouts of tagged "Judas fish", a large group of planktivorous fish (roach) in the middle of the lake where targeted by the seine (green dots) and subsequently removed from the lake.

The real-time high-resolution tracking is only part of this large project involving researchers from several universities and covering many other aspects of sustainable lake restoration and stewardship. Besides the fish tracking, DTU Aqua is leading detailed monitoring of the fish population in the lake including density, feeding patterns, growth and recruitment. These efforts are led by project PI Dr. Christian Skov (DTU).

Project Partners

  • Poul Due Jensen Foundation, Denmark (coordinator)
  • DTU Aqua, National Institute of Aquatic Resources, Denmark
  • Southern University of Denmark, BioScience, Denmark
  • University of Aarhus, BioScience, Denmark
  • University of Copenhagen, Food and Resource Economics, Denmark

The project is funded by Poul Due Jensen Foundation.

Further info
For further info about the project, see the project site.

Henrik Baktoft
Henrik Baktoft
Senior Research Scientist