Franziska Bockelmann, PhD student at DTU Aqua presented her work under the ProtectFish project at the Freshwater Symposium in Vingsted (Denmark) 5-6 February 2025. The symposium, attended by over 250 participants, focused on biodiversity.
Mrs. Bockelmann’s 20-minute presentation highlighted key findings and advancements in freshwater biodiversity research under our ProtectFish project.
Annual symposium to highlight freshwater research
The Freshwater Symposium is organized every two years by the Copenhagen University, the Aarhus University, the University of Southern Denmark, and DTU (Technical University of Denmark). It targets researchers, water managers and private consultancies (water engineers).
This year’s edition marks the 9th symposium in the series, welcoming over 250 paying participants.
The purpose of the symposium – focussing on biodiversity – is to provide an opportunity for researchers and managers of fresh waters to:
- meet,
- exchange knowledge,
- and discuss how to ensure a diverse and rich aquatic environment.
It aims further highlighting freshwater research among Danish key stakeholders.
Challenges for river fish in Europe
During her presentation, PhD student Bockelmann underlined that in Europe, one of the most threatened animal groups is the river-fish. It has been estimated that more than 70% of migratory river fish species are lost from EU rivers. Almost all river-fish are in a negative trend according to IUCN, she added. A subject upon which ProtectFish has communicated before, see this article.
This negative trend did however not concern Denmark but quite the contrary. Fish populations have recovered due to many dam removals and river restorations, and especially migratory fish have thrived in the Danish rivers. This picture changed when cormorants started to forage in inland waters after 2010, Bockelmann argued.
Now, the country has a situation where fish populations in most rivers are significantly diminished. Some have even species reached an unsustainable stock level. This is the case for the grayling (Thymallus thymallus) that was very abundant before 2010 but now struggles to renew its populations.
Change is possible through scientific and collaborative initiatives such as ProtectFish
The HORIZON Europe project ProtectFish focuses on the threatened river fish, with grayling as central species. The grayling is a species listed in the EU Habitats Directive and is as such protected by EU law.
As part of ProtectFish and the national Projekt Stalling, DTU researchers try investigating how river fish can be protected from predation.
In the upstart of the project, five long (4–12 km) river stretches were monitored using electro-fishing [NB: Fish don’t get hurt by our expert’s electrofishing techniques. This is an inoffensive method when carried out by trained people to put them to sleep for measuring and tagging them]. The results showed standing fish biomasses of 5-20 kg/ha, much lower than the “normal” levels of 100 – 300 kg/ha.
“Should this “new normal” lack of fish abundance be accepted or are there management measures that may improve river fish populations?” Bockelmann asked the audience.
Bockelmann’s presentation was well received, prompting questions about the project, her work for DTU Aqua, and ProtectFish’s key developments.
Media contact for any further information – Aliénor: protectfish@alienor.eu
More information: Ferskvandssymposium den 5. – 6. februar 2025 | VINGSTED aktivt hotel & konferencecenter
ProtectFish presented at freshwater symposium – Denmark