Quick Definition
The freshwater juvenile stage of a salmonid, characterised by dark vertical "parr marks" (blotches) on the flanks and adapted for territorial stream life.
📖 Full Definition
Parr are juvenile salmonids living in freshwater streams, between the alevin and smolt stages. They are characterised by cryptic dark vertical bars or oval blotches ("parr marks") on their flanks which provide camouflage among stream-bottom substrate. Parr are territorial, staking feeding stations in the stream current and defending them against rivals. They feed on aquatic and terrestrial invertebrates. Depending on species and environmental conditions, the parr stage lasts 1–5 years before smoltification triggers ocean migration.