Quick Definition
A species or assemblage used to assess the health or quality of an environment, because its presence, absence, or condition reflects environmental conditions.
📖 Full Definition
Bioindicators are organisms whose condition, behaviour, population size, or community composition reflects the ecological status of the environment they inhabit. Fish assemblages are widely used as bioindicators of freshwater ecological status (e.g., EU Water Framework Directive). Sensitive species (salmonids, mayfly larvae) indicate good water quality; tolerant species (carp, roach) indicate nutrient enrichment and reduced oxygen. The Index of Biotic Integrity (IBI) uses fish community attributes to score river health.
💡 Examples & Context
The presence of wild brown trout (Salmo trutta) in a river indicates good water quality, high oxygen, and low pollutant levels.