Freeze branding of juvenile salmon

Freeze branding using liquid nitrogen as a coolant was carried out on salmon parr and a sequential histopathological study was carried out for 16 weeks. The initial darkening of the brand area was due to destruction of melanophore control but the later, more diffuse, pattern was related to the invasion of the area of the stratum spongiosum and hypodermis by melanin containing cells such as are commonly found in healing teleost wounds. The traumatic damage was completely resolved well before the end of the experiment, suggesting that freeze branding is a particularly suitable short term batch marking method.