Application of a Controlled Aquarium Experiment to Assess the Effect of Mesh Sizes and Mesh Opening Angles on the Netting Selectivity of Antarctic Krill (Euphausia superba)

Zhongqiu Wang,Fuxiang Hu,Liuxiong Xu,Hao Tang,Jian Zhang

doi:10.3390/jmse9040372

Abstract

Understanding the interactions between target species and netting is paramount for increasing the sustainability of trawling activities. The selectivity of the utilized netting depends on the sizes and opening angles of the mesh. The effects of the mesh size and mesh opening angle on the fishing selectivity of Antarctic krill (Euphausia superba) were assessed via micro-cosmos experiments. The results show that both the absolute abundance and the incidence of larger krill individuals passing through experimental panels are proportional to the utilized mesh size. Krill individuals larger than 35 mm passed through experimental panels at mesh opening angles larger than 50° for a 15 mm mesh size, 35° for a 20 mm mesh size and 20° for a 30 mm mesh size. Additionally, all L50 values increased with an increasing mesh size and an increasing mesh opening angle at the same mesh size. Furthermore, the selection range increased with an increasing mesh size and with an increasing mesh opening angle at the same mesh size. This paper provides scientific guidance for the choice of liner mesh sizes of krill trawl with the aim to improve fishing efficiency while minimizing fishing losses and potential negative ecosystem impacts from fisheries.

Highlights

Antarctic krill (Euphausia superba), hereafter abbreviated as krill, is a key species in the ecosystem of the Southern Ocean
The selection range (SR) increased with an increasing mesh size and an increasing mesh opening angle at the same size
The present study assessed the effects of the mesh size and mesh opening angle on the krill fishing selectivity via micro-cosmos experiments

Summary

Introduction

Antarctic krill (Euphausia superba), hereafter abbreviated as krill, is a key species in the ecosystem of the Southern Ocean. Krill is a food source for fish, seabirds, seals, whales and other organisms and the biomass of krill has been estimated at 100 million tons [1,2,3,4]. Krill is the main target species of trawl fisheries with recent yields of about 300,000 tons from the Southern Ocean [5,6]. Commercial krill trawls are usually low tapered constructions where liners with a small mesh size are fitted inside the trawl body and the cod end to reduce the catch being lost through the mesh [7,8]. The length and mesh size of the liner netting differ between different fishing trawlers. “Krill trawl 300” used by the trawler “Longteng” of

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