Habituation and conditioning in gilthead sea bream (Sparus aurata ): Effects of aversive stimuli, reward and social hierarchies

Abstract

To tailor the farming environment to a fish species, we should understand the species-specific responses to stimuli, including the degree of adaption and learning.Groups of gilthead sea bream were given a delay Pavlovian conditioning regime using a conditioning stimulus (CS) of light flashes signalling arrival of food. Controls were exposed to light flashes unrelated to feeding. Fish in both treatments showed an initial fear response of moving away from the CS combined with reduced swimming speed. In subsequent trials, the Control fish largely habituated the fleeing response but sustained to respond by reducing the swimming speed. The Conditioning fish also stopped to escape from the CS, but opposed to the Control group they gradually increased their swimming speed in response to the CS. In addition, the number of fish in the feeding/CS area increased and became similar to basal level after around 16 trials. A small and variable proportion of the fish displayed black vertical bands on their body and territorial behaviour, and a social hierarchy could interfere with the processes of habituation and conditioning. The swimming speed of the fish increased with number of dark individuals, but this was not found during the CS and the light stimulus thus seemed to overrule the effect of territorial behaviour. The persistent negative response to light flashes in the Control suggests that fish seemingly adapted to repetitive stressors are still in a state of alertness. The change in the response to light shows the potential for rewarding aversive stimuli to reduce stress. K E Y W O R D Santicipatory behaviour, classical conditioning, feeding behaviour, habituation, learning, welfare

A novel emotional and cognitive approach to welfare phenotyping in rainbow trout exposed to poor water quality

“…In the control group, the conditioned response tended to be higher than baseline level after 8 trials and it was higher in the control than in the stressed group at trial 5, showing the remarkable learning skills of the rainbow trout in a classical appetitive conditioning paradigm. The acquisition is faster than previously observed in sea bream ( Sparus aurata ), which associate a US with a CS after approximately 16 trials (Folkedal et al, 2018). The inherent stress effect of a reduced appetite, as demonstrated by a significant reduction in growth in the stressed group compared to the control group, might represent an explanation of the impaired learning in the stressed group.…”

Challenges and benefits of applying fish behaviour to improve production and welfare in industrial aquaculture

“…2010; Folkedal et al . 2018). Reward conditioning has been used to successfully reduce the stress response of Atlantic cod ( Gadus morhua ) to the moving of a dip net in the water (Nilsson et al .…”

“…Schreck et al (1995) observed an increased resistance to pathogens, reduced mortality during transport and decreased physiological response to other stressors in juvenile Chinook salmon (Oncorhynchus tshawytscha) that underwent a positive conditioning regime to associate dewatering for transport with feeding. Both Atlantic salmon and gilthead sea bream (Sparus aurata) went from being frightened by an initially aversive stimulus (flashing lights) to exhibiting anticipatory behaviour towards the same stimulus after undergoing positive conditioning and habituation (Bratland et al 2010;Folkedal et al 2018). Reward conditioning has been used to successfully reduce the stress response of Atlantic cod (Gadus morhua) to the moving of a dip net in the water (Nilsson et al 2012).…”

Water jet: a simple method for classical conditioning in fish

“…This fact makes sense since, in most aquatic environments, the complexity of surroundings is associated with the need to locate shelters, feeding areas, predators, etc., thus exemplifying the adaptive value of learning ability in these environments. In this scenario, the occurrence of classical conditioning was recently demonstrated in several studies of fish species, such as zebrafish (Danio rerio) (Manabe et al 2013;Doyle et al 2017), St. Peter's fish (Sarotherodon galilgeus) (Zion et al 2011a, b), Atlantic salmon (Salmo salar) (Bratland et al 2010), and Dourada (Sparus aurata) (Folkedal et al 2018).…”

“…In these studies, the conditioned stimulus is usually some sort of light and/or sound, which is tested in groups of fish aiming to facilitate the management of these animals (Moreira and Volpato 2004;Bratland et al 2010;Zion and Barki 2012;Folkedal et al 2018). However, when performing experiments to evaluate individual responses (e.g., understanding learning mechanisms), the effectiveness of this conditioning method may be compromised when fish located in nearby aquariums Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10211-018-0297-4) contains supplementary material, which is available to authorized users.…”