the test object, the exposure time plays a dominant role in determining an 

 ichthyotoxicological experiment. Depending on the specific problem before 

 an investigator and on the degree to which the substance of interest is 

 studied, the duration of an experiment must be limited to 24-96 hours 

 (acute experiment), to 10-30 days (subacute experiment), or 1-3 months 

 (chronic experiment). The duration of an experiment is determined by the 

 resolving powers of the research method used by an investigator. The 

 higher the sensitivity and resolving powers of a method, the shorter the 

 time for determining the toxicity of a substance and the MPC value. Just 

 as the physiological-biochemical methods for toxicity determinations are 

 different, the mechanisms of the effect of various toxin groups are not the 

 same (30). There is no doubt that unifying methods for estimating the de- 

 gree of toxicity of substances and determining the MPC for these substances 

 will bear fruits in the near future and facilitate the solution of the 

 basic problem of water toxicology which faces all water toxicologist--of 

 limitation biologically harmful substances discharged into water bodies--by 

 determining the MPC. The solution of this problem is possible only on the 

 basis of a synthesis of the ideas and general and sanitary toxicology 

 methods with the achievements of modern physiology and biochemistry of fish 

 and other aquatic organisms (31). 



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2. Cherkinskiy, S.N., and Krasovskiy, G.N. In: Industrial Pollution of 



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3. Lukyanenko, V.I. Toxicology of Fish. Moscow, 1967. 



4. Lukvanenko, V.I. In: Problems of Hydrobiology. Moscow, 1965, 



261-263. 



5. Lukyanenko, V.I. and Petukhova, L.A. In: Biology of Fish in the Volga 



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