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Abstract(s)
The European catfish (Silurus glanis), an invasive species recently introduced to the Iberian
Peninsula, presents a significant ecological threat due to its large size, high fecundity, and strong
predatory potential. As a voracious apex predator, it can disrupt fish assemblages across the
region. While biotelemetry studies have examined its habitat use and activity patterns in nonnative areas, most focused on lentic systems using passive telemetry, leaving its lotic behaviour
understudied. Since its first record in Portugal (2014) and subsequent establishment in the Tagus
and Douro rivers, understanding its habitat use and activity patterns in these dynamic
environments has become crucial for effective management. To address this, 12 adult catfish were
tagged with radio telemetry archival tags equipped with temperature, pressure (depth), and 3Daccelerometer sensors to assess habitat use and activity patterns in a lotic stretch of the lower
Tagus River. A controlled experiment with two individuals validated acceleration-derived activity
thresholds, classifying behaviours as immobile (<0.03 g), mobile (0.03–0.78 g) or burst
movement (>0.78 g). The remaining 10 fish were actively tracked for a year. Results showed that
catfish occupied deeper habitats in winter (mean depth: 3 m) and moved to shallower areas in
spring and summer (mean depth: 1.6 m). Activity persisted year-round but was lower in winter
and autumn and higher in warmer seasons. Circadian depth use patterns remained stable, with fish
preferring shallower depths during the day and deeper habitats at night. Activity peaked at dusk
and was lowest during daylight hours. Individuals exhibited strong site fidelity, consistently
occupying small areas near riverbanks. These patterns were strongly correlated with several
environmental predictors, possibly linked to prey availability and reproduction cycles. Findings
provide valuable insights for targeted management strategies, including optimizing timing and
location of fishing efforts to improve mass removal actions aimed at controlling this invasive
species.
Description
Tese de mestrado, Ecologia e Gestão Ambiental, 2025, Universidade de Lisboa, Faculdade de Ciências
Keywords
Silurus glanis Invasões Biológicas Biotelemetria Modelos aditivos gerais Modelos Hurdle Teses de mestrado - 2025