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European sea bass aquaculture is so recent that very little is known on the effects of the early steps of its domestication. Behavioural parameters are sensitive indicators of the domestication process since they are generally impacted as soon as the first generation. The present work compared wild-caught and domesticated sea bass juvenile swimming activity, exploration and ability to learn to discriminate between two 2-D objects associated to a simple spatial task that enabled the tested individual to visually interact with an unfamiliar congener (the reward) located behind a transparent wall at the end of one of the two arms of a maze. Ten fish from each origin were individually tested 3 times in a row during 3 days (9 trials in total). Fish were placed in a start box closed by a transparent wall located in front of two 2-D objects. Fish were filmed during 10 min after the removal of the start box wall. Different swimming variables including angular velocity, total distance travelled and velocity mean, were analyzed from videos as well as the time spent in each of 6 virtual zones including the reward zone near the congener (Cong) and the zone opposite to the reward zone (OpCong). Two learning criteria were chosen: the number of successful turns and time to reach Cong. Behavioural differences were found between domesticated and wild fish. Angular velocity was higher in wild fish while the distance travelled and the velocity mean were higher in domesticated ones. Wild and domesticated fish spent most of the time in Cong and in OpCong. No differences were seen in learning ability between wild and domesticated fish. However, our findings for learning require confirmation by further studies with larger numbers of learning sessions and experiments designed to minimise stress. This study therefore demonstrated an impact of domestication on swimming behaviour but not on spatial learning. [ABSTRACT FROM AUTHOR]

Abstract: In various experiments under self-feeding conditions, sea bass groups could be divided into three categories regarding feeder actuation: high, low and zero-triggering fish. In all cases few high-triggering fish were responsible for a high percentage of the feed delivery. A question was raised about the role played by feeding motivation in such high-triggering status acquisition. It was approached by applying a 3-week fasting period in order to induce similar negative specific growth rate (SGR) in two groups of fish of similar mean weight but with either a low or a high coefficient of variation for weight (CVw) (Tlow: CVw ∼11%, 3 tanks of 60 fish each; Thigh: CVw ∼20%, 3 tanks of 60 fish each). These groups were created to test the consistency of behavioural responses in two different contexts (i.e. two population size-distributions). During the follow-up period of 40 days, the group level feed-demand behaviour was not strongly modified by the fasting period and there were no differences between Tlow and Thigh groups. Complete growth compensation was the same in all tanks as observed at the end of the experiment. At the individual level, high-triggering fish were exactly the same individuals before and after the fasting period. Up to four high-triggering fish could be observed according to the tank and when several fish were performing high-triggering activity, their rankings were sometimes reversed after the fasting period. High-triggering fish increased their activity levels after the fasting period showing behavioural plasticity. High-triggering status could neither be explained by an initial lower SGR nor a sex effect, nor by any of the measured physiological blood parameters. Thus, individual''s triggering activity levels could be related to personality and/or metabolic traits but further research is required to confirm this assumption. [Copyright &y& Elsevier]

This study aims to test the influence of size grading on self-feeding behaviour, social structure (measured by the percentage of triggering acts per individual), growth performances, and blood physiological variables of individually passive integrated transponder (PIT)-tagged sea bass juveniles, using a computerized on-demand feeding system coupled with a PIT tag monitoring device. Three consecutive periods of 27 days each were compared: a first period (P1) before grading (6 tanks of 100 fish; 40.2 ± 8.9 g) followed by a second period (P2) after grading. The protocol applied aimed to create two groups of fish of similar mean weight but with either a low or a high coefficient of variation of weight (CVw) corresponding to an imposed difference in social disruption (Tlow: CVw ~ 10%, 3 tanks of 60 fish each with social disruption; Thigh:CVw ~20%, 3 tanks of 60 fish each, without social disruption). Tlow and Thigh groups were studied over P2, and an additional 27-day period under identical conditions (P3). The grading protocol used and/or time modified the social structure when comparing P1 and P2. Thereafter, during P2 and P3, no difference could be observed in growth performances, feed demand, or physiological variables between Tlow and Thighgroups. Feeding rhythms and social structures were similar in both groups. In conclusion, such grading practice only transiently modifies feed demand behaviour and social structure built around the self-feeder, without further improvement in individual growth performances in sea bass. [ABSTRACT FROM PUBLISHER]

Among the strategies that can be used to improve fish welfare in a rearing environment, domestication and/or selective breeding was proposed to minimize fish responsiveness to husbandry practices. To verify this hypothesis on a recently domesticated species, the sea bass Dicentrarchus labrax, two experiments were realized, each using two populations differing according to their level of domestication or selection. For the first experiment, we used one population produced from wild parents (Wild; initial body mass: 106 ± 3 g), and one population from parents selected for growth for one generation (Selected 1; initial body mass: 129 ± 4 g). For the second experiment, we used one population produced from parents domesticated for two generations (Domesticated; initial body mass: 72 ± 3 g), and one produced from parents selected for growth for two generations (Selected 2; initial body mass: 89 ± 4 g). The first experiment was carried out over 112 days with 240 fish (60 fish per tank, 120 fish per population), and the second one over 84 days with 200 fish (50 fish per tank, 100 fish per population). Two variables, self-feeding behavior and growth performance, were measured over the time of the experiments. After a control period, the fish were submitted twice, at three-week intervals, to an acute stress treatment consisting of draining the tank and leaving the fish out of water for one minute. Both self-feeding behavior and growth performance were altered by the acute stress treatment. During the first post-stress period, the Domesticated and Selected (1 and 2) groups showed more pronounced post-stress exposure responses than the Wild fish: they modified their feeding rhythm, their feed intake, and their growth rate. During the second post-stress period, feeding rhythm was still affected (being more diurnal with a well defined peak), but the feed intake and growth rate results showed that the Domesticated and Wild groups seemed less affected than the Selected (1 and 2) populations, which continued to express a high post-stress response. According to these results, it can be concluded that: (1) an application of two acute stress treatments, at three-week intervals, modified fish feeding behavior and growth performance; (2) the domestication process seemed to improve fish adaptation abilities to this kind of stress; and (3) the process of selection for growth led to a final, better growth, but did not seem to improve fish acute stress tolerance. [ABSTRACT FROM PUBLISHER]

Abstract: Domestication and selection may affect fish behaviour, sometime as soon as at the first generation of domestication. However, knowledge about how both processes impact on fish spatial exploration and swimming activity still is to be improved. The objective of this experiment was (i) to evaluate spatial exploration behaviour and swimming activities of three sea bass strains having different domestication and selection levels and (ii) to analyse their responses to an acute stress. Sea bass exploration and swimming activities were studied before, during and 40min after a stimulation (standardized fall of an object). The experimental tank was divided in to four zones, and the time spent, the distance travelled in each zone and the swimming complexity were quantified for each period from video recording. Results showed that fish from all strains presented the same flight response and that stimulus exposure induced a significant decrease in exploratory behaviour and swimming activity. The present study has also demonstrated that only one generation of captivity could be sufficient to obtain fish presenting the same behavioural characteristics than fish reared since at least two generations. Moreover, this study has highlighted that selection for growth seemed to select fish characterized by a bolder personality and potentially better adapted to rearing environment. It allowed us to suggest that selection for growth may have a higher effect on fish personality than domestication only. [Copyright &y& Elsevier]

Biological variability is no longer considered as statistical noise, but rather as an adaptive benefit. This variability comes from consistent differences in behavioral and physiological responses among individuals to a changing/challenging environment, named “coping style”, “temperament” or “personality”. Many studies have described how to characterize personality traits and how to assess their consistency over time and between different contexts; however, little is known about the environmental factors shaping personality development. Because contrasting personalities are maintained with evolution, this lead to the widespread assumption that genes play a predominant role in personality. In many cases, personality traits are however also likely to be determined by individual experience, which is probably at least as important as genetics in shaping personality. The aim of this study was to assess how environmental variability (herein food predictability) impacts behavioral responses, particularly the shyness-boldness axis, one of the most widely shared animal personality trait. Here, we reared juvenile seabass (95 days old) from two divergent strains selected for feed deprivation tolerance under standard conditions for 40 days. Thereafter, we submitted them to two feeding treatments (Predictable versus Unpredictable) starting at 135 dph and lasting 60 days. Seabass reared under a predictable food supply (PFS) grew faster and were shyer than fish reared under an unpredictable food supply (UFS) ( i.e. they took more time to exit the refuge zone of a Z-maze; UFS: 132.47 ± 34.63 s; PFS: 336.79 ± 56.97 s) but their exploration tendency was similar. We also examined the behavioral responses of these fish facing a hypoxic challenge. Hypoxia tolerance results were consistent before and after the two feeding treatments. Our findings show the importance of early environmental experience as a driving force shaping boldness. In addition, we provide further evidence that predictable feeding time should be respected in studies assessing essential functions such as growth and behavior. Although personality traits are partially heritable, this study demonstrates the important influence of environmental conditions and life history on behavior. [ABSTRACT FROM AUTHOR]

Abstract: Because captivity constitutes a drastic environmental change, domestication is expected to induce a rapid genetic selection for behavioural traits. In this study, we searched for genetic differences in behaviour among brown trout juveniles from two strains differing for their domestication history, i.e. an almost pure native wild Mediterranean population (W) and an Atlantic domesticated strain (D). In order to assess pure genetic differences among strains, males from the two origins were mated with Mediterranean females to produce two experimental crosses (WW and WD). The swimming activity characteristics of individual WW and WD juveniles were compared before and after the application of a stress (light switched off suddenly, followed by a 5-min period of darkness). For each of the fish observed, mating type origin (WW or WD) was unambiguously reassigned by genotyping. Behavioural responses differed between WD and WW fish. Angular velocity and the time spent immobile were greater for WW fish both before and after the short period of darkness, indicating higher reactivity. Once the light had been turned on again, mean velocity and total distance travelled were higher in WD than in WW fish. WD fish tended to recover levels of swimming activity higher than those before the dark period. This study therefore demonstrates an impact of genetic origin and domestication on swimming activity repertoire (higher reactivity in WW fish), a behavioural trait of particular importance for individual ecological performance. Owing to the contrasted domestication history of the two strains used in the comparison, we assume that the domestication level largely contributes to the behavioural changes observed. [Copyright &y& Elsevier]