Figure 1

Mean number of abnormal behaviors observed per fish (upper panel) and number of eels showing abnormal behavior (lower panel) during a 10-min observation period 0 h, 3 h, 12 h, 36 h and 57 h after tagging. The fish were tagged with four different methods; the Økland method, Jellyman and Tsukamoto method, Westerberg method and Økland-Westerberg anchor implant method (n = 6 fish in each group). Abnormal behavior covers the sum of observed roll, backward swimming, tail, bite and ‘panic’ behaviors.