Thus, it is necessary to establish and accept a unified scheme for 

 conditioning ichthyo-toxicological investigations in order to obtain com- 

 parable data on the toxicity of the pollutants of water. It is no secret 

 that the Mont Blanc of experimental data on toxicity accumulated in the 

 world literature is of little value. The reason for this is simple: data 

 from different authors are hardly comparable because of the absence of 

 standardization in performance of the experiment and because of the lack 

 of uniform expression of the results. Today when the agenda is inter- 

 national cooperation in the field of aquatic toxicology and ichthyo-toxi- 

 cology, the absence of unified standard scheme for conducting toxicity 

 experiments and determining MPC values is especially distressing. 



Therefore, it is necessary to consider again the standard scheme of 

 ichthyo-toxicological investigations (Lukyanenko, 1967, 1968) which 

 includes acute, subchronic and chronic experiments. The acute experiment 

 is performed for preliminary evaluation of the degree of toxicity of a 

 substance using the "fish-test" method. The indicator of toxicity is the 

 death of the experimental fish. It is reasonable to conduct the experi- 

 ment at relatively high temperatures, and relatively low oxygen content, 

 taking into account the range of fluctuations in natural water body. 

 Water hardness and pH value are selected in such a manner as to show the 

 maximum toxicity of the substance tested. The least resistant fish 

 species of ichthyofauna tested should be used as the test object. In this 

 case, it is important to keep in mind the characteristic of resistance for 

 the given species at various stages of ontogenesis, selecting the least 

 resistant from them. Taking into consideration the relation of lethal 

 effect and test duration, the duration of the acute test should be limited 

 to 24 hours . 



A subacute test is carried out to show the path of the toxicant's 

 effect on fish and function development mechanisms, with the most sensi- 

 tive methods for determining the threshold concentration demonstrated in 

 the chronic test. Concentrations of the substance which possess an ex- 

 pressed toxicity effect on the organism are used. They are usually found 

 within a range of 1/2-1/10 of the lethal concentration. The test is con- 

 ducted on the least reistant species of fish. Duration of the tests is 

 from 10 days to 1 month. Since the toxicodynamics of the majority of 

 substances discharged into water bodies is unknown (applicable to fish), 

 the most complete set of indicators possible which allow us to evaluate 

 the functional condition of the organism's various systems is necessary. 

 Together with indicators integrally reflecting the organism's condition, 

 such as increase in live weight, level of feeding excitability, and 

 intensity of oxygen consumption, finer (or more delicate) physiological 

 and biochemical indicators (activity of various enzymes, hemotological 

 indicators, humoral and cell factors of inborn immunity, behavioral re- 

 actions, and electro-physiological tests, which characterize the condition 

 of various functional systems should be used. 



The chronic test - is the final stage of ichthyotoxicological research. 

 Its task is to demonstrate the threshold concentration, toxic effect zone 

 and maximum inactive concentration. It is expedient to test 3-5 concentra- 

 tions with a five-fold interval. The initial concentration and range of 



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