Characteristics of mature male parr in the northernmost Atlantic salmon populations

The incidence, relative abundance and biological characteristics of mature male parr of Atlantic salmon Salmo salar were studied in two subarctic (69–70 N°) river systems in the northernmost part of Scandinavia. The proportion of mature males was low (0–25%) among ≥1 year‐old parr, and clearly lower than reported earlier in more southern rivers. The ages of mature males ranged from 1+ to 6 + year, the most abundant age group was 3 + year. Both age structure and size of the mature male parr varied between rivers and years. Mature male parr in the main stem were younger and also smaller than the parr of the same age in the tributaries.