Zinc Avoidance by Fathead Minnows (Pimephales promelas): Computerized Tracking and Greater Ecological Relevance

Male fathead minnows (Pimephales promelas) avoided 0.284 mg∙L−1 of zinc when given a choice of clean and dosed sides of a featureless openfield tank, as frequently used in avoidance/preference experiments. More than six times as much zinc (1.83 mg∙L−1) was required to cause avoidance when males were allowed to establish a territory under a shelter on the side of the experimental chamber which was later dosed. Activity increased during zinc dosing when a shelter was present but did not change in no-shelter tests. Control period activity was positively related to strength of avoidance response. By incorporating relevant motivational factors, behaviour observed in avoidance experiments should be more predictive to nature. A new computerized tracking system automatically recorded movements of the fish, calculated various measures of locomotor response and filed results in preparation for statistical analysis.