Predation from birds and mammals and the significance for populations of freshwater fish (38829)

It is a well-known fact that predation can be a keyfactor for many fish populations and in some areas predation may even be the most important regulating factor for fish stocks of major recreational importance. Several species of predators were earlier persecuted, but are now protected and have experienced high population growths recently. This includes species like: cormorant, grey heron, seals and otter. Thus, the protection of these species has been a conservation success, but has also caused severe conflicts between various user-groups. To handle and mitigate these conflicts,scientific documentation is severely needed. 

During a long period, DTU Aqua has carried out a number of projects that directly or as side-results have assessed the magnitude of predation and its impact on various fish stocks. This has provided some insight in when, where and by whom the important recreational fish species are being eaten. This project gathered and synthesized this knowledge to provide an overview of the significance of predation.

Outputs:
- Synthesis and analyses of existing knowledge/results.
- Method evaluation for scanning for PIT tags in cormorant/heron colonies.
- Investigations of possible causes for the recent drastic decline in grayling (Thymallus thymallus) populations.
The project was funded by the Danish Rod and Net Fishing License Funds.
Research area: Freshwater Fisheries and Ecology