Abstract
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.
Highlights
Most cultured fish have been domesticated since the beginning of the twentieth century [1] and the world aquaculture production of fish relies only on a few species that have been selected mostly upon economic and technical criteria [2]
This process is so recent that most cultured fishes might rather be considered as exploited captives and only a few of them would be on the threshold of becoming domesticated [3]
Antipredator behaviour has been shown to be very sensitive to artificial rearing [4,5,6,7,8,9,11] and swimming or schoaling performance to be poorer in domestic stocks [12,13]
Summary
Most cultured fish have been domesticated since the beginning of the twentieth century [1] and the world aquaculture production of fish relies only on a few species that have been selected mostly upon economic and technical criteria [2]. Consistent differences between wild and domesticated fish have been reviewed, the main effects being an increased growth, reproductive disturbances and alterations of behavioural traits [4,5,6,7,8,9,10,11] Among the latter, antipredator behaviour has been shown to be very sensitive to artificial rearing [4,5,6,7,8,9,11] and swimming or schoaling performance to be poorer in domestic stocks [12,13]. It is known that domestication influences brain size, since hatchery-reared domesticated rainbow trout (Oncorhynchus mykiss) have smaller brains than do wild-caught fish of the same size [16] and even first generation lab-reared guppies (Poecilia reticulata) can have smaller brains than wild counterparts [17]
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