Unfamiliar congener used as a visual attractor in wild caught 1and domesticated sea bass (Dicentrarchus labrax) placed in a T-Maze

Abstract

The present work compared wild-caught and domesticated sea bass juveniles swimming activity, exploration and visual attraction induced by an unfamiliar congener located behind a transparent wall at the end of one arm of a T-maze. This cognitive challenge was based on the hypothesis that placed into a novel and therefore stressful environment; the fish would adopt a gregarious behaviour even though they were not familiar with the present congener. Twenty individuals of similar size from both origins were individually tested. After a 5min acclimatization period, the wall of the start-box was removed and the maze was filmed during 20 min. Different swimming variables including angular velocity (Vang), total distance travelled (Dtot), velocity mean (Vel), time spent in Immobility (Im) were analysed from videos as well as the time spent in each of 6 virtual zones including the start-box zone (Start), the zone near the congener (ZCong), the zone opposite to ZCong (OpCong) and three other zones. Vang was higher in domesticated fish and Im higher in wild fish but fish from both origins spent most of the time in ZCong showing a similar visual attraction induced by an unfamiliar congener of similar size. Nevertheless, individual variability was shown, including fish choosing to shelter in Start and fish visually attracted to the congener but located in OpCong. These results demonstrated an impact of domestication on a few swimming activity characteristics but not on gregarious behaviour. The findings are discussed with focus on ecological and aquaculture concerns and their potential interest for future cognition-based experiments on this species. © 2013 Benhaïm D, et al.