Seasonal changes in condition, hepatosomatic index and parasitism in sterlet (Acipenser ruthenus L.)

Measurements of biomarker responses in fish from contaminated sites could provide valuable data for environmental risk assessment. Biomarkers are sensitive to both environmental pollution and confounding factors that are not related to pollution (e.g., season, nutritional status, and population density). Unfortunately, data about the latter group are scarce. Therefore, juvenile sterlet (Acipenser ruthenus L.) specimens were collected on a monthly basis from the Danube River from September 2002 through August 2003 to determine if seasonal changes exist in condition, hepatosomatic index, and parasitism. Fulton condition factor (FCF range: 0.27 - 0.79), hepatosomatic index (HSI range: 1.14 - 6.67) and Skrjabinopsolus semiarmatus parasite prevalence (range: 37.9 - 85.7 ;), intensity (range: 1 - 337 parasites per fish) and the mean intensity (range 9.6 _ 89.2) in sterlet showed significant seasonal variations. This study pointed out that biomarker sampling on different locations has to be performed within the short time frame in order to avoid differences generated by confounding factors. Better understanding of the life cycle of S. semiarmatus and sensitivity of different phases to pollution is needed.