Does catch-and-release angling alter the migratory behaviour of Atlantic salmon?

Electronic tracking studies have recently focused on the potential negative effects of catch-and-release (C&R) angling in Atlantic salmon (Salmo salar L.). Common for these studies is that the fish were tagged between C&R, and the effects of C&R can thus not be separated from the extra handling effects associated with the tagging procedure. In addition, reference groups and information on the behaviour prior to C&R is not available. In this study, 95 homing multi-sea-winter Atlantic salmon were tagged with radio transmitters in the fjord before entering the River Alta, Northern Norway, and thereafter manually tracked until the spawning period. Ten of these salmon were caught and released by anglers in the river. All ten fish survived the angling event, and nine were observed in known spawning areas during the spawning. No difference in migratory behaviour prior to or after C&R was observed between caught and released fish and a reference group. Individuals both among the C&R fish and the reference group showed downstream movements and migratory stops associated with C&R in previous studies. In spite of making studies logistically more challenging and expensive, the use of reference groups is important when assessing natural versus non-natural behaviour and to separate C&R effects from tagging effects.