INDIVIDUAL RECOGNITION OF JUVENILE SALMONIDS USING MELANOPHORE PATTERNS

This article describes two small scale experiments designed to test wh ether variation in melanophore patterns could be used to identify indi vidual juvenile salmonids that are too small for conventional marking methods. Three independent observers were able to identify 30 individu al 0+ Atlantic salmon (Salmo salar) parr from photographs taken over a n 8-week period with 100% accuracy, on the basis of patterns of melano phores in the region of the eye and jaw. Counts of the number of melan ophores in two particularly variable regions of the head of 14 newly-e merged brown trout (Salmo trutta) from photographs of the same individ uals taken on different occasions were strongly correlated. Eighty-fou r per cent of the fry were correctly identified on the basis of spot n umber alone, without any reference to their patterns. Thus a combinati on of the number and position of head melanophores can be used for rec ognition of relatively large samples of very young salmonids. Problems with, and potential applications of this method are discussed.