Behavioral and morphopathological responses of Sliver Carp (Hypophthalmichthys molitrix) to acute toxicity of copper and zinc

Fishes are simple and reliable indicators for assessing of heavy metals in waters. This study investigate acute toxicity of Cu (NO3)2 and Zn (NO3)2 in Hypophthalmichthys molitrix. A total of 270 farmed silver carps with mean weight of 52.6±8.1gr and 17.2±2cm, including 135 for each metal were bought and located adjacent to 0, 5 and 10mg/L for 96 hours. Behaviorally, jumping and circling activities, collecting on water surface at early times, inverse swimming and collecting in the bed of aquarium signs were observed that increased with increase of concentration. Morphologically, damages such as color change, swelling of gills, blood clotting in gill, swelling and darkness of bile sac were observed in fishes related to Cu2+. About zinc, white spot, inflammation and discoloration to reddish of skin, sinking and red spot under the eyes and loss scales were observed. In died fishes, pathological signs such as hyperemia, swelling and hemorrhage in gill, hemorrhage in gut, dropsy and bile darkness were observed. LC50-24h of it was measured 2.539mg/L, while LC50-96h of zinc nitrate was measured 4mg/L. Therefore, copper nitrate was more toxic than zinc nitrate and mortality of fish can be related to their adverse affects on gill, kidney and liver