scope:

NEN-EN 16859 provides guidance on methods for monitoring freshwater pearl mussel (Margaritifera margaritifera) populations and the environmental characteristics important for maintaining populations in favourable condition. The standard is based on best practice developed and used by Margaritifera experts in Europe, and describes approaches that individual countries have adopted for survey, data analysis and condition assessment. While it is recommended that the causes for pearl mussel decline should be urgently investigated, standard methods for restoring populations are beyond the scope of this document.