Perch (Perca fluviatilis) suitability as a water indicator was studied in field and laboratory investigations. It was found out that hematological status of this fish species was a valuable indicator of both temporary and periodical deterioration of dissolved oxygen saturation and can be used as reliable test for water quality evaluation. The anlyzed hematological parametrs were tested for their sensitivity and reliability as indicators of water quality changes. Values of different parameters were given for perch kept under optimal and unfavourable conditions of water oxygen saturation.

The experiment was performed on marine Teleost Serranus scriba with lower concentrations of lindane then MPC (due to our valid law). The aim of this study was to find the effects of lindane to fish activities connected with nutrition. This motive is among the strongest. It includes parameters as: number of fish movements in the presence of prey or without it and the number of onslaughts to the prey during one hour. The results have shown that the increasing of lindane concentration caused considerable decreasing and even complete cessation of activity. Interest for prey and decreasing activity of predators in the presence of prey (typical for Serranus - as a fish of prey and the hunter) endures till the moment of convulsion.