Lateralisation of rotational swimming but not fast escape response in the juvenile sterlet sturgeon, Acipenser ruthenus (Chondrostei: Acipenseridae).

For the first time, behavioural lateralisation was shown in a chondrostean fish (sterlet sturgeon Acipenser ruthenus). A significant directional bias was found in young A. ruthenus swimming along a circular swimway. This laterality manifested itself as an individual preference for a certain movement direction (either clockwise or counterclockwise) which was consistent at the retest 10 days later. On the other hand, no significant rotational bias was observed at the population level. The same sterlet individuals displayed the C-start (the first stage of escape response) elicited by sudden low-frequency sound vibrations (50 Hz). However, the experiments failed to reveal either individual or population laterality of this response: the frequencies of leftward and rightward bends in startled fish were virtually equal. These results demonstrate that the two types of laterality can be independent in fish.