Attraction of zebrafish, Brachydanio rerio , to alanine and its suppression by copper

Preference responses of zebrafish to 10 −3 , 10 −4 and 10 −5 M alanine (Ala) were concentration‐ dependent. Behavioural responses to copper (Cu) and Cu + Ala mixtures were also assessed. Zebrafish avoided 100 and 10 μg Cu l −1 , but not 1 μg l −1 . Mixtures of 10 −3 m Ala+ 100 μg Cu l −1 and 10 4 M Ala + 10 μg Cu 1 −1 were avoided as intensely as was Cu alone. Responses to 10 −3 M Ala + 10 or 1 μg Cu l −1 and 10 4 M Ala +1 μg Cu l −1 did not differ statistically from controls (no detectable preference or avoidance). These results demonstrate, firstly, that a concentration of a pollutant avoided by itself (10 μg Cu l −1 ) may not be avoided when encountered with an attractant chemical stimulus (Ala) and may suppress the preference for an attractant stimulus, and secondly, that a concentration of a pollutant not avoided by itself and not considered deleterious (1 μg Cu l −1 ) suppresses attraction to Ala (an important constituent of prey odours for many fishes).