The influence of sea temperature, salinity and oxygenation on intracellular ciliates dynamics in Slovene Mediterranean mussels (Mytilus galloprovincialis)

1280 adult Mediterranean mussels (Mytilus galloprovincialis), 960 from shellfish farms and 320 from natural beds, were monthly collected over a one-year period in the Slovene Sea, measured and weighted to calculate the condition index and microscopically examined for the presence of the intracellular ciliates of mussels. Water temperature, oxygenation and salinity were measured at each sampling. The prevalence of infection with intracellular ciliates of mussels was 22.9%: 24.4% in cultured and 18.4% in wild mussels. The highest prevalence of infection was detected in spring when the average sea temperature was 15.2 degree C, the average oxygenation 9.3mg/1 and the average salinity 29.6ppt and the lowest prevalence was found in summer with the average sea temperature 24.1 degree C, average oxygenation 7.6mg/1 and average salinity 38.1ppt. We determined that only salinity had an impact on infection with intracellular ciliates - the higher the salinity, the lower the infection. The average condition index of infected mussels seemed to be slightly higher than of the healthy ones, but the differences between infected and healthy mussels were not statistically significant.