My PhD project is a collaboration between the Molecular Ecology and Fisheries Genetics Laboratory and Natural Resources Wales (NRW), a Welsh Government sponsored body. The project is supported by the European Union’s European Social Fund through the Welsh Government via a Knowledge Economy Skills Scholarship (http://kess2.ac.uk/). The aim of the project is to develop an environmental DNA (eDNA) based survey method for estuarine fish to enhance the current fish surveys which NRW carries out as part of their estuarine monitoring programme. Environmental DNA is broadly defined as DNA extracted from environmental samples e.g. sediment or water, rather than directly from an organism. Previous work has shown it has the potential to provide a sensitive and non-invasive technique for surveying aquatic biodiversity. During the project I will be using metabarcoding, a method of identifying multiple species from their mitochondrial sequences, to assess the full biodiversity of fish in estuaries around Wales. The main thrust of the project is to develop and validate suitable field and laboratory methods for eDNA sample collection, processing and analysis. In addition I will determine appropriate eDNA survey designs for estuaries, which are hydrodynamically complex, and identify appropriate bioinformatics pipelines and data analysis methods. The final goal is to compare the biodiversity information obtained from eDNA, and practical considerations e.g. cost, against the currently used methods. Ultimately this will determine if eDNA can be used by NRW to inform policy, and to improve the conservation of biodiversity in Welsh estuaries.