Dupaix A. auteur aut IRD Deneubourg J. L. auteur aut IRD Forget Fabien auteur aut IRD Tolotti M. T. auteur aut IRD Dagorn Laurent auteur aut IRD Capello Manuela auteur aut IRD text journalArticle eng text/pdf reformatted digital access Assessing the proximate and ultimate causes of animal behaviour is crucial for understanding the impact of human activities on wild species. However, for animals that are difficult to observe in the wild, such as pelagic fish species, identifying the causes and consequences of their behaviour can be particularly challenging. Here, we show the effectiveness of mechanistic modelling, combined with correlative approaches on empirical data, to determine the causation and consequences of behaviour. A behavioural model is developed to investigate the causal relationship between the associative behaviour of tropical tunas with floating objects and their physiological condition. Comparison with empirical data on tuna condition measured in the Western Indian Ocean suggests the rejection of the hypothesis that the physiological condition of tuna is a proximate cause of their associative behaviour. This study contributes to the assessment of the impact on tuna physiology of habitat changes induced by the massive use of floating objects introduced by tuna fishers. specialized behavioural ecology causation correlation fitness tropical tuna purse seine fisheries 040 020 034 292 2049 20250704 [12 ] 2025 0962-8452 https://www.documentation.ird.fr/hor/fdi:010094210 10.1098/rspb.2025.0704 0962-8452 [F B010094210] https://www.documentation.ird.fr/hor/fdi:010094210 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2025-07/010094210.pdf IRD - Base Horizon / Pleins textes 2025-07-15 2026-06-12 fdi:010094210 fre