The EPT index measures the proportion of freshwater organisms belonging to the taxa Ephemeroptera, Plecoptera, Trichoptera (or EPT for short). These species are considered to be highly sensitive to pollution and are a measure of good environmental conditions. Any significant declines to these species in a stream could indicate that a pollutant has entered the ecosystem. Streams are sampled in permanent locations on a 3-year rotational panel monitoring design. This data is also posted to, and available from ECCC's CABIN database.