Histopathology in fish: proposal for a protocol to assess aquatic pollution

Water pollution induces pathological changes in fish. As an indicator of ex posure to contaminants, histology represents a useful tool to assess the de gree of pollution, particularly for sub-lethal and chronic effects. However , a standardized method for the description and assessment of histological changes, mainly for use in freshwater fish, is still lacking. In this paper , the present authors propose a standardized tool for the assessment of his tological findings which can be applied to different organs. The methodolog y is based on two factors: (1) the extension of a pathological change is ra ted with a score value'; and (2) the pathological importance of this altera tion is defined as an 'importance factor'. The sum of the multiplied scare values and importance factors of all diagnosed changes results in different indices. With these indices, statistical analysis can be carried out. Asse ssment methods for the gills, liver, kidney and skin are described.