Transparent by design
How the records work
What the Environment Agency data can establish, how we organise it, and where its limits matter.
Source data
The observations come from the Environment Agency National Fish Populations Database freshwater dataset. RiverFish uses the six bulk CSV archives in the monthly release. Official site, survey, species and measurement IDs are preserved.
River identity
River names are not unique and catchment labels include tributaries. Every published river uses an explicit, human-reviewed set of NFPD parent IDs, checked against WFD waterbody IDs, site names and coordinate continuity. Ambiguous names such as Wye are never grouped by text matching.
Species names
The source contains species, life stages, varieties, hybrids and unresolved taxonomic labels. Raw records remain intact. Headline diversity counts only canonical named species; variants and life stages roll up, while hybrids and genus/family-only records are excluded from that headline.
What a survey record means
A record means the taxon was observed or caught during an EA survey. It does not show that a location is publicly fishable, that the species is easy to catch, or that it is currently abundant. A zero record in one survey does not establish absence from the river.
Methods and trends
Electric fishing, seine netting, rod and line, survey effort, site coverage and strategies vary. Raw fish counts are therefore not charted as population change. Initial metrics are limited to sites and surveys where recorded, observation dates, and recorded measurements.
Species-selective surveys
The source flags surveys designed around particular species. These remain visible as observations but are not treated as comparable community surveys. Recent-survey lists label them explicitly.
Coordinates and access
Exact British National Grid coordinates are retained internally and converted to WGS84. Public coordinates are rounded to roughly 100 metres. Every map labels points as monitoring locations; none are represented as fishing access points.
Freshness and reproducibility
The current bulk snapshot was published in August 2026. Each river page separately states its latest survey year. Every import records archive hashes, row counts, fetch time and a calculation version; derived data is rebuilt and validated before publication.