Fish as indicators of water quality
Post-mortem examinations of fish in water reservoirs of various types at different levels of contamination, as well as in experimental conditions, allowed us to develop a five-point scale visually observable damage: 1 point - the reaction of the fish is mostly etymological; 2 points - observed light reversible damage; 3 - injury of medium gravity; 4 points - severe damage to fish, threatening them with death, especially in the wintering period and the effects of stress factors; 5 points - there are signs of death of fish and subsequent death. On the basis of the scale of damage to fish assesses the level of contamination of the pond or its waters: 1 point - no observed pollution; 2 points - mild sub-lethal levels of contamination; 3 points -average pronounced conditional sublethal levels of contamination; 4 points - high, chronically lethal level of contamination; 5 points - acute lethal or lethal chronically high levels of pollution. Shown a direct link between pollution levels and natural reproduction of fish.