River Fish Index (RFI)

The River Fish Index (RFI) is an overall measure of the difference between the composition of the stand at a given station, observed from electric fishing sampling, and the composition of the stand expected under baseline conditions, i.e. under conditions not or very little modified by humans.
A fish stand is the result of many factors, occurring at various scales of space and time. In addition to information on the presence or absence of a particular species, the analysis of the results of the various samples makes it possible to approach the classification of the status of aquatic environments.
Fish is an integrative organism of environmental conditions, i.e. stands are able to resist when environmental conditions become less favourable, and apart from acute mortalities, large immediate changes in the stand are not necessarily observed.
On the other hand, if the aggression is serious (acute pollution for example) or if environmental conditions change permanently, the stand will change, in the first case by the sudden disappearance of certain species, in the second by the establishment of a new balance of species. Thus, the observation of fish is a means of assessing the state of the aquatic environment.