Behavioral assessment of individual cognitive abilities of European sea bass (Dicentrarchus labrax L.)

Abstract

[eng] The concept of individuality in fish, related to coping styles, is key to understanding how individuals respond to the arrival of novel stressful stimuli. This study investigates the cognitive abilities of European sea bass (Dicentrarchus labrax L.) using the Cylinder task test, with the aim of categorising individual differences in coping styles. Twenty-one juvenile sea bass were analysed over several experimental phases and individuals were categorised as either proactive or reactive. Results showed that 33% of individuals exhibited a proactive (P) character, characterised by active Exploration and numerous Escape episodes, while the remaining 66% exhibited a reactive (R) coping style, associated with immobility episodes and a preference for remaining in the Comfort zone. In addition, 41% of the reactive individuals were intermediate (R-i), showing both reactive and proactive tendencies, and the remainder (59%) maintained passive tendencies. Although only 29% of the seabass successfully completed any of the phases of the experiment, the wide range of behaviour observed allowed us to classify individuals into well-defined coping styles. Five percent of individuals successfully completed all phases. The results are consistent with previous studies of coping styles in fish and suggest that this test is useful for identifying individual behavioural strategies. However, as sea bass are a social species, future cognitive testing in the presence of conspecifics is recommended. The implications of these findings are relevant to aquaculture welfare, where understanding coping styles could help to optimise individual care and management practices. Future lines of research are suggested to further elucidate the role of genetics in neural plasticity and stress regulation underlying these individual behaviours.