The investigation of parasite prevalence of rainbow trout (oncorhynchus mykiss) reared in Aydin/Bozdoğan province

This study was carried out to investigate the parasite prevalence on rainbow trout (Oncorhynchus mykiss) which were raised in cage in Kemer dam lake built on Akçay river and pools situated on the river. The cage and pools are situated between 37o 30' northern 28o 35' eastern longitude, in Bozdoğan/Aydın, in western Turkey. The experiment lasted between September, 2013 and August, 2014. Regularly, 12 fish from each fish farm were randomly selected within monthly intervals. Thus, a total of 348 fish that were examined in the laboratory were screened by both native Giemsa and Silver Nitrate for protozoans and metazoans. One hundred fifty three (% 44) fish were detected as positive various protozoans and metazoans at a total of 153 fishes. Taking into individual and mixed infection, the number of cases and their percent values in parenthesis in case of infection with one species as follows: 118 (% 33,9) T. fultoni, 19 (% 5,4) I. multifiliis, 5 (% 1,4) Apiosoma sp., 4 (% 1,1) Lernaea sp. Seven of the 153 fishes (% 2) were infected with mixed infection of T. fultoni + I. multifiliis and T. fultoni + Apiosoma sp. The certain number and percentage value of fishes exposed to mixed infection as follows: 5 (% 1,4) (T. fultoni + I. multifiliis), 2 (% 0,6) (T. fultoni + Apiosoma sp.). The effect of season, fish length and weight, water temperature (oC), intensity of dissolved oxygen (O2 mg/L) and pH level of water on the incidence of determined parasites were evaluated in the present study. A logistic regression analyse was accomplished in order to estimate the certain interest of these parameters which were supposed to have a role in the appearance of the infection. The analysed indicated that one unite increase in water temperature result an 1,116 fold increase in infection odd ratio (OR), while 0,842 fold decrease was observed in response to one unite increase in dissolved oxygen amount (O2 mg/L). Likewise, one unite increase in fish lenght (cm), induced 0,88 fold decrease in infection odd ratio (OR), however, 0,99 fold reduction in infection odd ratio (OR) was determined regarding to one unite increase in fish weight (g). At the end of the study; infection rate was detected as 44 %. The dominant species among the parasites was observed as T. fultoni. Especially in months when the water temperature is increase, the stock density is high and water is contaminated with feed residues and dead fish as a result of water quality degradation are thought to be effective in the increase of the prevalence of parasitic infections. Anahtar Sözcükler: Aydın, Rainbow trout (Oncorhynchus mykiss), Ichthyophthirius multifiliis, Lernaea sp., Trichodina fultoni