The ProtectFish project aims to analyse the measures used to monitor and manage threatened fish species in European Union rivers, fill data gaps, study policy options and build dialogue among stakeholders to deliver recommendations for the conservation of these fish populations
European freshwater fish populations face interacting pressures, including habitat degradation and fragmentation, pollution, hydromorphological alteration, and rising water temperatures. The European Red List of Freshwater Fishes (1) shows that over 40% of freshwater fish species in Europe are threatened with extinction, with nearly two-thirds facing elevated conservation concern. Also, in Europe, migratory fish species have declined by an average of 81% since 1970. (2)
Understanding the role of predation
In recent years, predation pressure, notably from the great cormorant (Phalacrocorax carbo sinensis), has emerged as an additional factor impacting freshwater fish populations, leading to conflicts between biodiversity conservation objectives (e.g., bird species versus fish species conservation objectives).
Existing evidence indicates that predation by piscivorous birds can contribute to substantial mortality in vulnerable fish populations. As cormorants move across national borders, their monitoring and management require a European Union (EU)-wide coordination approach.
Early analysis by ProtectFish shows that cormorant populations have generally stabilised in countries in the Western Baltic Sea (Denmark, Northern Germany) and in some countries further east (e.g. Poland and Finland). However, other countries (e.g. Sweden and Estonia) have seen marked increases over the last decade.
Evidence indicates that predation is an important cause of the critical situation of many freshwater fish species in the EU. However, despite measures taken individually by EU Member States to regulate the pressures, success in reducing the impact of predation has been marginal at best. For a great migratory species such as the cormorant, management measures developed in close cooperation with all stakeholders, and at the EU level, may lead to better results: improve biodiversity, boost the ecosystem services rendered by freshwater ecosystems and reduce societal conflicts.
However, fragmented monitoring data and limited understanding of predator–prey interactions continue to constrain conservation assessments and management decisions. A significant challenge lies in the limited availability of harmonised monitoring data, as well as insufficient understanding of population trends and pressures affecting protected fish and bird species.
The ProtectFish approach
The EU-funded ProtectFish project was established to address some of these evidence gaps by investigating the effectiveness of different management measures intended to protect threatened freshwater fish species, with the European grayling (Thymallus thymallus) as the focal species.
ProtectFish will improve the definition of “favourable conservation status” of EU river fish, assess the factors that most affect the status of EU river fish, and test whether predation avoidance measures could help to reach the ‘Good Ecological Status’ criteria for EU rivers required by the EU’s Water Framework Directive (WFD). ProtectFish investigates predator-prey interactions while also considering the wider pressures affecting protected river fish.
The project combines field experiments, population modelling, ecological research and stakeholder engagement to develop policy and management recommendations.
The project’s main objectives are to:
Evaluate the current conservation status and the monitoring, reporting and protective measures of EU-listed river-fish species.
Update and expand the scientific knowledge of cormorant populations in the EU and assess effective, balanced, and feasible methods for their management.
Using current and new data on the status of fish and cormorant populations and their interactions, generate knowledge-based recommendations for balanced, integrative and adaptive management for a balanced river biodiversity.
The project’s final output will be management and policy recommendations to improve both the status and protection of Europe’s river biodiversity.
Emerging evidence
Through field and modelling studies in several locations throughout Europe, and on different scales, ProtectFish is testing the impacts of a range of factors like flow, temperature and predation on the status of populations, and whether it is possible to improve river fish populations by reducing the impact of cormorants.
Some key preliminary findings of the ProtectFish project (the project is ongoing and will end in May 2028):
Cormorant predation has direct and measurable impacts on fish populations, including mortality of adult fish and significant non-consumptive mortality caused by stress or injuries.
Habitat complexity measures alone are insufficient to substantially reduce predation pressure – in EU rivers – under conditions of high predator density.
Flow regime alteration, predation pressure and rising water temperatures are identified as among the strongest stressors (in that order) affecting the long-term stability of European grayling populations (the project’s target species).
An innovative method to estimate fish stocks for European grayling was developed by the project, supporting more transparent and reproducible conservation status assessments under Article 17 of the Habitats Directive.
Management effectiveness depends strongly on local ecological, administrative, and societal conditions, highlighting the need for flexible, context-specific approaches.
Growing cormorant populations and increasing evidence of their impacts on freshwater fish highlight the need for coordinated cross-border monitoring and adaptive management across Europe, for example through a European cormorant management plan.
Public interest in predator-fish conflicts is strong, as reflected in the active participation of volunteers and local stakeholders in activities conducted by ProtectFish.
These preliminary findings show that freshwater fish decline cannot be tackled through isolated measures. Cormorant predation must be considered alongside other pressures.
References
European red list of freshwater fishes – Publications Office of the EU
https://wwflpr.awsassets.panda.org/downloads/2024-living-planet-report-a-system-in-peril.pdf
