Evaluation of fluorescent pigment marking of brown trout (Salmo trutta L.) and Atlantic salmon (Salmo salar L.)

Fish farm and field trials have been conducted into the longevity and reliability of fluorescent pigment spray marking on brown trout Salmo trutta and Atlantic salmon (S. salar ). These have shown that the technique produces high quality marks for a minimum of 20 months for brown trout and 7 months for Atlantic salmon. In addition a minimum size of 6.8 cm for the successful marking of brown trout fry has been established. High mortalities were found when the technique was used on fish which were subject to stress. Causes of stress are discussed and mortality rates of < 1% have now been achieved.