The invention relates to a method for the determination of vitellogenin as a biomarker or end point for an exogenous oestrogenic effect on fish. The problem addressed by the invention is the creation of a non-destructive method in which the laboratory animals do not have to be killed. The method also should not necessitate any additional use of laboratory animals for carrying out tests on oestrogens, anti-oestrogens, and endocrine disruptors. This problem is solved by a method for the determination of vitellogenin as biomarker for an exogenous oestrogenic effect on fish comprising the method steps of taking a skin mucus sample from a fish by swabbing, transferring the skin mucus sample to a reaction vessel, homogenising the skin mucus sample, and taking an aliquot of the skin mucus sample for vitellogenin determination by means of an ELISA method of detection.
