The influence of zinc and copper on the latency period for feeding and the food uptake in common carp, Cyprinus carpio L.

In order to know the effect of zinc and copper pollution on in fish feeding behavior, the latency period for feeding and food uptake of common carp, Cyprinus carpio L., yearlings were examined. It was shown that exposure to these metals (1 μmol/l) increased the search reaction time (the time taken to leave the starting chamber after its front wall was raised, t1), as well as latency period for feeding (t2). The significant increase of the first index was observed in 6 h. In the presence of zinc the differences from the control were considerable within the period from 30 to 54 h. In the presence of copper, these differences remained significant throughout the time of observation. The second parameter increased in the course of the experiment, too. A significant increase of t2 was noted already at 3 h in the presence of both metals. The food uptake (the quantity of eaten midge larvae Chironomus sp for 3 min of observation) of fish in this condition gradually decreased significantly in 3 h after the start of the exposure. At the end of the experiment, the food uptake decreased by 46% and 60% and feeding reaction rate increased by 93% and 114% as compared to the control in the presence of zinc and copper, respectively. These results show that fish latency period for feeding and the food uptake are useful as parameters for evaluating metal toxicity.