ANSWER 1

Yes. Although this field is still emerging, there is increasing evidence that climate change can differentially affect fish behavioural types within populations through two complementary mechanisms: behavioural plasticity and natural selection.
First, individuals within the same population often respond differently to environmental change, a phenomenon described through behavioural reaction norms [1]. Fish can display substantial inter-individual variation in their behavioural responses to stressors such as warming, hypoxia, acidification, or habitat degradation. For example, some individuals may strongly reduce activity or risk-taking behaviour under elevated temperatures, whereas others maintain high activity levels. This variation reflects differences in behavioural plasticity among personality types, meaning that climate-driven environmental changes can reshape behavioural expression within populations in both wild and farmed contexts.
Second, climate change may act as a selective force on personality variation. Fish populations are composed of individuals displaying a wide range of behavioural phenotypes, including bold, shy, proactive, or reactive types, and there is strong evidence that many of these traits are at least partially heritable [2]. As environmental conditions shift, certain behavioural strategies may confer higher fitness than others. For instance, under increasingly stressful or unpredictable environments, shy or more risk-averse individuals may experience higher survival, potentially leading to directional selection on personality traits over generations [3].
Therefore, yes, climate change is expected not only to modify fish behaviour through phenotypic plasticity, but also to alter the evolutionary composition of populations by selectively favouring particular personality types.
References:
1.     Dingemanse, N. J., Kazem, A. J., Réale, D., & Wright, J. (2010). Behavioural reaction norms: animal personality meets individual plasticity. Trends in ecology & evolution, 25(2), 81-89.
2.     Stirling, D. G., Réale, D., & Roff, D. A. (2002). Selection, structure and the heritability of behaviour. Journal of Evolutionary Biology, 15(2), 277-289.
3.     Biro, P. A., Beckmann, C., & Stamps, J. A. (2010). Small within-day increases in temperature affects boldness and alters personality in coral reef fish. Proceedings of the Royal Society B: Biological Sciences, 277(1678), 71-77.