まぐろ延縄漁業における混獲回避技術

Abstract

This review classiˆes and explains the bycatch mitigation measures in tuna longline ˆshery based on theirfunctional mechanism across bycatch species. In longline ˆshery bycatch mortality occurs through a commonprocess that typically follows these stages: 1) ˆshing operations overlap with the distribution of non-targetanimals; 2) non-target animals perceive the baited hook(or hooked ˆsh) as food and approach it; 3) contact withthe ˆshing gear; 4) become hooked or entangled; and 5) die. Mitigation measures block one or several stages ofthis process to reduce the bycatch and resultant mortality by avoiding the spatio-temporal overlap(time and areaclosure, and modiˆcation of gear conˆguration and operational pattern), by diminishing perception and attractionof baited hooks (night setting, oSal control, and blue-dyed bait), by interrupting the physical contact betweennon-target animals and ˆshing gear(bird-scaring line, line weighting, underwater and side setting, and deterrentmethods using aversive stimuli), by preventing hooking(hook and bait modiˆcation), and by reducing post-hook-ing mortality (safe release with rescue devices). Since there is no panacea for every occasion, combined use ofcomplementary methods that ˆt the actual situation of ˆshing operation enhances the eSectiveness of mitigation.The experience and innovation of fishermen are important in developing and improving the mitigation measures.キーワード海亀類，海鳥類，回避技術，偶発的捕獲，混獲，サメ類，食害，まぐろ延縄