Underwater Observation of Fish Behaviour to Trolling Line

Abstract

In order to understand the capture process of trolling gear, the fish response towards a trolling line was observed by a towed underwater video camera. Fishing tackle consisted of a main line, a depressor board, a leader line, and a lure. The underwater video camera was mounted on the depressor board to observe and record the sequence of responses towards the lure. Fish species that could be identified, were yellowtail Seriola quinqueradiata, frigate mackerel Auxis rochei, amberjack Seriola dumerili, and mackerel Scomber japonicus. Behaviour patterns were classified as follows: appearance into the camera view, approach to the lure, attack on the lure, touching the lure, being hooked, and captured. 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 proportion of missed-hookings, which was attributed to the difference in struggling escape behaviour between yellowtail and frigate mackerel. © 1995, The Japanese Society of Fisheries Science. All rights reserved.