Toxicological assessment of river water quality in bioassays with fish.

A series of bioassays with fish was developed in order to evaluate toxicological aspects of polluted rivers in The Netherlands. A long term exposition of trout to riverwater under standardized conditions enables the detection of pathological effects such as growth retardation, liver and kidney enlargement and changes in clinical blood parameters. Bioaccumulation of heavy metals and organochlorine compounds can also be measured. Embryo-larval tests with trout were less suitable, because of yearly variations in egg quality. In the near future, sister chromatid exchange (SCE) assays in vivo with Nothobranchius may become available for the detection of mutagenic effects. It was possible to measure trends in toxicological quality of Rhinewater with these tests. However extrapolation of results to ecosystems and tracing of the causes of changes occurring in waterquality are still problematic.