The species composition and indices of the myxosporeans infecting fish from the different nature conservation Black Sea regions were considered on the base of the original investigations and literature data. Myxosporean inhabiting the Red Book fish hosts were investigated. The myxosporean species potentially pathogenic for the fish health were identified and epizootological situation was estimated.
In the present study, we investigated the comparative infection levels, ecology and host-parasite interrelationship of a nematode Hysterothylacium aduncum (Rudolphi, 1802) in whiting, Merlangius merlangus (L., 1758) in southern (Sinop) and northern (Balaklava Bay) coasts of the Black Sea for the first time. Fish were collected throughout a period from May 2011 to March 2014 from local fishermen. A total of 690 fish specimens near Sinop and 423 fish near Balaklava Bay were examined for parasites. Hysterothylacium aduncum was the only nematode species identified in the digestive tract of the Black Sea whiting Merlangius merlangus. Prevalence of infection, mean intensity and mean abundance values were determined according to season, length classes and sex of fish at both localities. These infection indices were always higher in Sinop samples than those of Balaklava Bay samples.
Complex influence of infection by myxosporeans Myxidium gadi Georgevitsch, 1916; Ceratomyxa merlangi Zaika, 1966 and nematode Hysterothylacium aduncum (Rudolphi, 1802) on the morphophysiological and biochemical parameters of the Black sea whiting Merlangius merlangus euxinus (Nordmann, 1840) were studied. Significant decrease of spleenosomatic index and increase of hepatosomatic index in fish with average and high intensity of infection were found. The dependence of hepatic antioxidant enzyme activities on intensity of infection was observed. Increase of superoxidismutase, catalase, glutation-S-transferase activities in fish with average and high intensity of infection and decrease of peroxidase activity in specimens with average intensity of infection were shown.