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Fig. 1 The conceptual framework of the putative mechanisms driving evolution of risk‐taking behaviour and circadian system in response to size‐selective mortality. The figure showed large size‐selective mortality typical of many fisheries and specialized predators targeting larger size classes. The same conceptual framework with opposing outcomes is valid for small size‐selective mortality typical of specialized fisheries and most gape‐limited predators. In particular, large size‐selective harvesting triggers the evolution of a fast life history, which in turn can co‐evolve with an increase of both risk‐taking behaviour and early peaks of locomotor activity (small dotted arrows). However, a plausible scenario is that harvesting disrupts the correlation of life history with other behavioural traits. Therefore, a further possibility is that large‐size selective harvesting triggers the evolution of a decrease risk‐taking behaviour through a correlated selection response with size‐at‐harvest (bold arrow and first hypothesis tested here; H1). Consequently, a decrease of risk‐taking behaviour may affect the circadian system by triggering a decrease of early locomotor activity rhythms (bold arrow and second hypothesis; H2), and reducing amplitude and robustness of circadian clock gene expression (bold arrow and third hypothesis; H3). For more details, see the main text (Fish pic source: https://pixy.org/4660397/)