Results of work have been summarized on use of some morphofunclional indices at fish health control in aquaculture. Their use helps efficiently and intravitally estimate and reject sick specimen having a low immune status. It has been revealed that the most important but labour-intensive indices are hematological ones which can be changeable at deseases of various nature and may be used at appraisal of stress-response. Indices of hemoglobin content, erythrocytes and leukocytes numbers, erythropoeitic activities, leukocytal formula as well as the absolute quantity of different leukocytes groups are informative characteristics for efficient control. The express-method of fish stress aiagnostics has been developed and worked through with application of gluco-and multisticks for estimation of 10 biochemical parameters in mucus and of glucose in blood within 2 or 3 minutes. It has bees shown that the level of a non-specific resistance and adaptive possibilifies of some specimen affect heterogeneity of indices values determined what allows to reveal the part of weakened specimen and to estimate necessity of correcting activities as well as to predict the result of the situation formed with reared fish.

The aim was to determine the effective dosages of Levofloxacin, an antibacterial drug new for aquaculture,   for the treatment of bacterial haemorrhagic septicaemia in carps and improvement of the physiological state of fish following disease and antibiotic therapy.The methods: the experiments were carried out in aquaculture on juvenile carps infected with a mixed culture of pathogens: highly pathogenic strains of Aeromonas sp., Acinetobacter calcoaceticus, and Citrobacter. Three dosages of Levofloxacin were tested: 250, 500, and 1,000 mg/kg of ichtyomass with feed for 7 days. After the antibiotic therapy, a course of feeding was carried out with SUB-PRO probiotic at a dose of 0.4 g/kg of feed   for 10 days.Scientific novelty: application of a broad-spectrum antibiotic Levofloxacin, an antibacterial drug new for aquaculture, in fish.The results: positive results were obtained with Levofloxacin, an antibiotic new for aquaculture, in the treatment of bacterial haemorrhagic septicaemia. The advantage of the drug is the inhibitory effect on a wide range of bacterial agents and the absence of negative effects on the physiological state of fish. An effective dosage  of Levofloxacin (1,000 mg/kg of ichtyomass for 7 days) was established under experimental conditions. The positive dynamics on the blood parameters of the probiotic drug “SUB-PRO” after the disease and antibiotic therapy was revealed, which provided an increase in the resistance of the fish organism.The practical significance: the findings will be crucial in the development of practical recommendations for  the treatment of bacterial haemorrhagic septicaemia of fish in aquaculture.