Abstract
This study was aimed at a comprehensive assessment of the parasitological state of fish species of economic importance living in the reservoirs of the West Kazakhstan region. The object of the study was carp (Cyprinus carpio), Pike (Esox lucius), Redtail (Scardinius erythrophthalmus), crucian carp (Carassius auratus gibelio) and pike perch (Sander lucioperca) from the small Bykovka reservoir, Barbastau River, Gremyachy pond and Lake Krugloe. In the course of the study, morphological and microscopic methods were used and 250-300 fish samples collected in different seasons were examined. The results obtained showed that seasonal changes in water temperature directly affect the level of parasitic infestation: in summer, the infestation was highest (74.2%), and in winter-lowest (31.6%). The dynamics of the distribution of parasitic groups revealed that Trematoda and Monogenea predominate in the Warm Period, and Cestoda and Nematoda in the cold period. The levels of infestation in different fish species varied significantly depending on their ecological location and physiological characteristics: the highest rate was recorded in Carp (72.5%), and the lowest in Pike (58.4%). The results of the study show an unstable epizootological situation for water bodies of the West Kazakhstan region and prove the risk of the spread of Parasitic Diseases of a chronic nature. These data determine the need for regular preventive and veterinary-sanitary measures in fisheries.