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 per iod of over 3 months. Gill-net caught fish exhibited extensive downstream r unning, 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 o f this study suggest that gill-net capture negatively impacts the upstream migration behaviour of Atlantic salmon and that the negative effects of cap ture and radio tagging can well exceed those proposed in current literature . (C) 2000 Elsevier Science B.V. All rights reserved.