Orientation of Goldfish (Carassius auratus) in Response to a Shallow Gradient of a Sublethal Concentration of Copper in an Open Field

Abstract

In slowly flowing water, seven naive goldfish 30-cm long changed their locomotor behavior upon entering a mass of water containing shallow gradients of copper chloride. The concentration was 11–17 μg/liter Cu++ in most of this mass, with small isolated pockets containing maximally 50 μg/liter. The amount of time spent by the fish, the average size of turn, and the variance of the size of turn increased in the "polluted" region. The orientation of the fish in this region deviated consistently in the upstream direction resulting in the increase in time spent in the area of highest concentration. Comparison of the locomotor behavior of the fish in sodium chloride of the same concentration and in laboratory water established that the changes mentioned were in response to the copper rather than the chloride ion.