Animal welfare has been defined as the balance between positive and negative experiences or affective states. Despite the growing evidence of complex cognitive abilities and the expression of affective states such as pain and fear, very little is known about ability to experience memory based affective states in non-mammalian animal models. The goal of this study was to validate conditioned place preference/avoidance (CPP/CPA) tests as a method to assess the affective valence of environmental stimuli in teleost fishes. Physiological and behavioural indicators of affective state were used to characterise the response to a priori appetitive and aversive stimuli in CPP/CPA tests in gilthead sea bream (Sparus aurata). Fish were tested individually in a CPP/CPA tank divided into two halves, with one half uniformly white and one half marked by dotted wall patterns. During an initial habituation phase fish were placed in a central alley for 10min and afterwards allowed to swim freely throughout the whole tank during 20min in order to determine their initial preferred and non-preferred side (IPS/INPS). During the training phase, fish were presented either with a single aversive stimulus in the IPS (chasing with a dip net) or with a repeated appetitive stimulus (release of pellets) in the INPS. The test phase consisted of the same procedure as the habituation phase. The behaviour of each individual was video-recorded and analysed with video-tracking software. Fish submitted to appetitive stimulus increased significantly the time spent and the distance moved in the stimulation side, while fish exposed to aversive stimulus decreased significantly the time spent in the stimulation side, increased the distance moved in the non-stimulation side and showed an increase in cortisol level. Therefore, the use of behavioural (individual swimming activity) and physiological (plasma cortisol concentration) indicators of affective state during the CPP/CPA test allowed to validate the use of this test as a way to assess the affective valence attributed by fish to different environmental stimuli. Finally, this study also shows that fish are able to retain memories of events with positive/negative valence which are retrieved by environmental cues.
|Publication Title||Applied Animal Behaviour Science|
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