UNDERWATER OBSERVATION OF FISH BEHAVIOR T O TROLLING LINE

In order to understand the capture process of trolling gear, the fish response towards a trolling line was observed by a towed underwater vi deo camera. Fishing tackle consisted of a main line, a depressor board , a leader line, and a lure. The underwater video camera was mounted o n the depressor board to observe and record the sequence of responses towards the lure. Fish species that could be identified, were yellowta il Seriola quinqueradiata, frigate mackerel Auxis rochei, amberjack Se riola dumerili, and mackerel Scomber japonicus. Behaviour patterns wer e classified as follows: appearance into the camera view, approach to the lure, attack on the lure, touching the lure, being hooked, and cap tured. The total number of appearances in the camera view was 1361, in which the catch was only 18 due to the low attack response frequency to the approaches. A slight difference was also observed on the propor tion of missed-hookings, which was attributed to the difference in str uggling escape behaviour between yellowtail and frigate mackerel.