2020 DAERA (The Department of Agriculture, Environment and Rural Affairs) Fish Estuary-Association Scores (FEAS) dataset https://portal.medin.org.uk/portal/start.php?tpc=010_fdbff255e19248954f561d17a3eec6c8 A dataset of the degree or level of estuarine association for some 6200 fish species. The dataset comprises a fish estuary-association score (FEAS) system that numerically expresses the degree or level of estuarine association for each species. The FEAS ranges between 1.0 and 5.0 where fish species with a score close to 1.0 are regarded as freshwater species with little association or dependence on estuarine environments (freshwater straggler species) while those species with a score close to 5.0 are marine species that are typically not associated or dependent on estuaries (marine straggler species). Fish species with a FEAS close to 3.0 are dependent on estuaries for all or part of their life cycle. Estuary-use functional guild categories for each species is also provided. These consist of marine stragglers (MS), marine migrants (MM), estuarine species (ES), diadromous species (DI), freshwater migrants (FM), and freshwater stragglers (FS). Diadromous species were further sub-divided into anadromous species (DI(AN)), catadromous species (DI(CA)), and amphidromous species (DI(AM)). 20201118 20201101