Aggression and growth of different populations of Atlantic salmon parr

In order to study aggression and growth of salmon parr of different populations and the possible effect of fin-clipping on these traits hatchery reared parr originating from three populations (2 Norwegian, 1 Swedish) were stocked in three aquaria with 90 unmarked fish in each. Three aquaria were stocked with a mixed group of 30 each of the populations. These fish were fin-clipped (adipose or pelvic fins) in order to enable identification of groups. Observation time was 15 min/day/aquarium, altogether 28 days of observation were made. Total experimental time was 8 weeks. Significant differences in agonistic behaviour as well as in growth (p