Behaviour of gill-net and rod-captured Atlantic salmon (Salmo salar L.) during upstream migration and following radio tagging

The behaviour of radio-tagged Atlantic salmon (Salmo salar L.) was studied in the River Ohcejohka in subarctic Finland. The objective was to determine the effects of gill-net entanglement and catch and release angling on the behaviour of upstream migrating salmon. 23 grilse and one 2 sea-winter (SW) salmon were tagged with radio transmitters and some were tracked for a period of over 3 months. Gill-net caught fish exhibited extensive downstream running, presumably caused by stress from capture and tagging. Post-tagging downstream movement in rod-caught salmon was also observed, but was not as extensive. Upstream migration was delayed in all tagged fish. The results of this study suggest that gill-net capture negatively impacts the upstream migration behaviour of Atlantic salmon and that the negative effects of capture and radio tagging can well exceed those proposed in current literature. (C) 2000 Elsevier Science B.V. All rights reserved.