New Study Reveals the Activity Patterns of the European Catfish
MARE researchers Gil Santos, Filipe Ribeiro, Esmeralda Pereira, Alexandra Silva, Pedro Raposo de Almeida, Diogo Ribeiro and Bernardo Quintella are the authors of the article ‘Behaviour of the Apex Predator European Catfish (Silurus glanis) on a Recently Invaded Reservoir’, recently published in the scientific journal Ecology of Freshwater Fish. The study reveals important findings about the activity patterns of the European catfish in the River Tagus, enabling new approaches to effectively control its population. 
The European catfish (Silurus glanis), a large predatory species with extreme fertility, is one of the main threats to freshwater ecosystems in Portugal. In particular, in the River Tagus, its proliferation has contributed to the decline of native fish populations, which makes it urgent to understand its behaviour in order to develop more efficient control strategies.
In this context, this team of researchers from MARE has been dedicated to studying catfish behaviour, most recently with a focus on activity patterns and depth use throughout the year. Using acoustic biotelemetry, an advanced technique that allows continuous monitoring of fish movements, the researchers monitored 10 adult individuals in the Belver reservoir on the River Tagus for an entire year. This study provided important data on the activity and depths occupied by the species in different environmental conditions.
The results indicated that the European catfish remains active throughout the year, with some seasonal variations. Peak activity occurs in summer, when the fish are most active, while autumn is the period of least movement. In terms of depth, the catfish occupy shallower waters in spring and summer, with average depths of 2.6 metres and 4.8 metres respectively. In autumn and winter, the species migrates to deeper waters, with average depths of 9.8 metres and 10.8 metres, respectively.
In addition, vertical movement patterns vary significantly, both seasonally and individually. The main environmental factors influencing European catfish activity were identified as river flow, water temperature and photoperiod (the amount of light available during the day). Depth utilisation, on the other hand, is more sensitive to river flow and photoperiod.
With this new information, it will be possible to optimise control strategies for this invasive species, such as more targeted fishing actions for the periods and areas of the year when catfish are most active and vulnerable to capture. Such strategies could significantly increase the efficiency of the species' removal, helping to protect native species and the health of river ecosystems.
These findings are crucial to the management of aquatic biodiversity, providing practical information to mitigate the threat posed by the European catfish. The implementation of these strategies could facilitate the removal of the European catfish from the Tagus River and thus contribute to the preservation of native fish communities, ensuring the sustainability of the region's aquatic ecosystems.
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Photographs by LIFE PREDATOR