Conservation of small hairtail Trichiurus japonicas by using hooks with large artificial bait: effect on the trolling line fishery

Taro Hirose,Shingo Watari,Masaki Sakurai,Mitsutaku Makino,Michio Ogawa

doi:10.1007/s12562-017-1142-9

Abstract

Overfishing has reduced the stock of hairtail Trichiurus japonicus around the Bungo Channel, Japan. To determine whether using larger bait in the trolling line fishery could avoid catching small/undersize hairtail, we developed and trialled a new large artificial bait (a soft plastic bait, 6 inches long). A traditional lure with natural bait (type-1), a new lure of the new artificial bait hook without natural bait (type-2), and a new lure with natural bait (type-3) were tested in fishing operations around the Bungo Channel. Compared with type-1, type-2 and type-3 caught fewer undersized and immature female individuals. The number of fish caught, yield, and composition of commercial size grades per recruitment were calculated from field data for each lure and compared. The catch sizes (number of fish per recruitment) were smaller for type-2 and type-3 than for type-1, but yield per recruitment was higher for type-3 than for type-1. Compared with type-1, type-2 and type-3 caught more large individuals, which are more valuable. The newly developed artificial bait conserves hairtail stocks by targeting larger fish, which is economically beneficial for the hairtail trolling line fishery.

Highlights

Hairtail Trichiurus japonicas is an important commercial target species in Japan, and is found in waters from Hokkaido to the Yellow Sea, the Bo Hai Sea, and the East China Sea [1]
We developed a new large artificial bait for the hairtail trolling line fishery to protect small fish and increase the hairtail stock level
We examined the composition of commercial size grades per recruitment (GPR), because this directly affects the income of fishers

Summary

Introduction

Hairtail Trichiurus japonicas is an important commercial target species in Japan, and is found in waters from Hokkaido to the Yellow Sea, the Bo Hai Sea, and the East China Sea [1]. Hairtail yields greater than 60,000 t were recorded in the 1960s in Japan, while recent catches have fluctuated between 8000 and 20,000 t [2]. From the 1960s to the 1980s, the catch from the East China Sea markedly decreased [1], so the relative importance of the Bungo Channel in Japan as a hairtail fishing ground has increased. The yield from the Bungo Channel area (Oita and Ehime Prefectures) has accounted for 30–40% of the total hairtail catch in Japan in recent years [3]. The Bungo Channel is one of the most important trolling line fishing areas for hairtail, and fishers in Oita and Ehime Prefectures mainly target this area. The annual yield of the hairtail trolling line fishery has been

Methods

Results

Conclusion