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In this study, histological effects of water pollution to freshwater cyprinid, Alburnus mossulensis, was investigated. Water, sediment, and fish samples were taken from four stations in Karasu River (Erzurum, Turkey) between June and September in 2015-2016. In water and sediment samples, the concentrations of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, and Pb were detected. Histopathological changes in gill, liver, and kidney tissues were determined by degree of tissue change (DTC), and hepatosomatic index (HSI) was calculated. The mean concentrations of heavy metals in water and sediment samples were lower at station 4. The trend of some metal contents found in the fish was in increasing order of Zn < Cu < Cr < Pb. The observations on histopathology included cellular degeneration, congestion, dilatation, vacuolization, edema, vasodilatation, hyperplasia, hypertrophy, infiltration, melanomacrophage aggregates, glomerulopathy, fibrosis, and necrosis. It was observed that the DTC and HSI values in fish varied significantly from station to station. The results showed that the higher severity of histopathological alterations in the fish tissues was strongly correlated with agricultural and domestic activities in the area. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]