Behavioural coping mechanisms and population resilience in fish inhabiting intermittent rivers

• Applicant: Dr. Jakob Gismann
• Subject Area: Sensory and Behavioural Biology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 580208860

Rivers and streams that dry for part of the year – known as intermittent rivers and ephemeral streams (IRES) – make up a large proportion of rivers globally and are becoming increasingly common as droughts intensify under climate change. In Mediterranean climates, intermittent environments already dominate freshwater systems and host a large proportion of endemic, yet often threatened fish communities. When rivers are drying, habitats fragment into isolated pools. In these, heat, predation, and hypoxia pose severe challenges for survival. Nevertheless, many fishes persist in these dynamic environments, suggesting that they have developed effective coping mechanisms, which we are only beginning to understand. The aim of this project is to uncover how individuals‘ behaviour enables fish populations to cope with the challenges of reoccurring droughts and to persist in intermittent rivers. Behavioural changes are typically animals first response to changing environments and allow for fast adjustments to the novel environmental circumstances. In drying rivers, movements into remaining refuges present an important behavioural coping mechanism allowing individuals to survive the drought. Once flow resumes, movement is crucial for fragmented populations to reconnect, thereby shaping gene flow. Yet, we lack a clear understanding of both the mechanistic details of behavioural coping, and the role of individual behavioural differences in shaping population persistence in intermittent rivers. Studying Mediterranean barbels (B. meridionalis) in north-eastern Spain, this project integrates high-resolution population monitoring, controlled behavioural experiments, and population genomic analyses. This multifaceted approach, spanning small to large spatial and temporal scales, allows to link individual behaviour with population-level processes. Behavioural experiments, performed in the laboratory and in the field, will provide mechanistic insights into how fish overcome the challenges associated with drought, while genomic analyses will help understand the extent to which gene flow is maintained across an intermittent river. By spanning research fields from aquatic ecology to behavioural ecology, and population genetics, this interdisciplinary study will advance our understanding of behaviour as a coping mechanism in intermittent environments – crucial knowledge for understanding the consequences of changing flow regimes, as more and more rivers worldwide are expected to experience periods of drought.

• DFG Programme: WBP Fellowship
• International Connection: Spain
• Participating Institution: Consejo Superior de Investigaciones Científicas ; Centro de Estudios Avanzados de Blanes ; - CEAB.CSIC -
• Host: Dr. Jolle Jolles