Effluent from a sewage treatment works causes changes in serum chemistry of brown trout (Salmo trutta L.)

To evaluate the impact of effluent from a sewage treatment works on fish he alth, serum chemistry variables were investigated in brown trout (Salmo tru tta L.) held in cages (active monitoring) and wild brown trout (passive mon itoring). Means of the measured serum parameters of the different treatment groups were close or within normal ranges. However, the results of the act ive monitoring demonstrated that the serum variables of reference trout hel d in tap water were clearly different from those of the river treatment gro ups. In the active monitoring, fish exposed to effluent from the sewage tre atment works had significantly different blood urea nitrogen and bilirubin values than fish kept in river water. In the passive monitoring, total prot ein, blood urea nitrogen, and alkaline phosphatase were significantly diffe rent between the two groups. Of the numerous correlations between serum che mistry parameters and histological lesions, blood urea nitrogen and alkalin e phosphatase were found to most strongly indicate gill and liver lesions, respectively. In the passive monitoring correlations between serum chemistr y variables and histopathological lesions were restricted to bilirubin and liver lesions. This indicates that the application of serum chemistry varia bles as indicators of histological lesions in case of chronic exposure is q uestionable. A multivariate discriminant analysis was used to consider rela tionships between the single serum variables concurrently. (C) 2001 Academi c Press.