Determination of bar spacing of bycatch reduction devices (BRDs) should consider species composition and morphometric characteristics (particularly width) of target species krill and bycatch. This study conducted a scientific investigation of the finfish bycatch in the Antarctic krill (Euphausia superba) trawl fishery by the fishing vessel SHEN LAN in the waters surrounding the South Orkney Islands from December 24, 2022, to February 20, 2023. The results show that scientific observers sampled 676 individuals of finfish bycatch. Of these, 665 were identified to species (17 species from 8 families), while the remaining 11 specimen were juveniles of the Nototheniidae family that could not be identified to the species level. IRI (index of relative importance) calculations showed three dominant (IRI value greater than 1,000) finfish bycatch species (Champsocephalus gunnari, Pseudochaenichthys georgianus, and C. aceratus from the Channichthyidae family) and four important (IRI value between 1,000 and 100) finfish bycatch species (Electrona carlsbergi and Gymnoscopelus nicholsi from the Myctophidae family, Gobionotothen gibberifrons from the Nototheniidae family, and Notolepis coatsi from the Paralepididae family). Our study provides morphometric data (particularly body width) that is crucial to model the potential for bycatch reduction by use of bycatch reduction devices (BRDs) and to determine the appropriate candidate bar spacings for BRD sea trials. Predictions suggest that a 10 mm (the maximum body width of krill) bar spacing releases a significant amount of dominant and important bycatch species (93.94% of C. gunnari, 53.99% of P. georgianus, 76.25% of C. aceratus, and 100% of G. gibberifrons). Reduced fishing pressure would reduce the risks to dominant and important bycatch species to make the krill fishery sustainable. We recommend that future BRD sea trials should initially test a 10 mm bar spacing. If marked loss of krill is observed, wider spacings (e.g. 15 mm) must be tested.

中文翻译：

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2022/23渔季南奥克尼群岛海域磷虾渔业兼捕南极磷虾和有鳍鱼类的形态特征


确定兼捕减少装置（BRD）的条间距应考虑目标物种磷虾和兼捕物的物种组成和形态特征（特别是宽度）。本研究对2022年12月24日至2023年2月20日“深兰”号渔船在南奥克尼群岛周边海域南极磷虾拖网渔业中兼捕的有鳍鱼类进行了科学调查。结果表明：科学观察员对兼捕的 676 条有鳍鱼类进行了采样。其中，665 种已被鉴定为物种（8 科 17 种），而其余 11 种标本为无法鉴定到物种水平的 Nototheniidae 科幼体。 IRI（相对重要性指数）计算显示，三种主要（IRI 值大于 1,000）有鳍鱼类兼捕物种（Champsocephalus Gunnari、Pseudochaenichthys georgianus 和 C. aceratus 来自鳅科）和四种重要（IRI 值在 1,000 至 100 之间）有鳍鱼类兼捕种（来自 Myctophidae 科的 Electrona carlsbergi 和 Gymnoscopylus nicholsi、来自 Nototheniidae 科的 Gobionotothen gibberifrons 和来自 Paralepididae 科的 Notolepiscoatsi）。我们的研究提供了形态测量数据（特别是体宽），这对于模拟使用兼捕减少装置（BRD）减少兼捕的潜力以及确定 BRD 海上试验的适当候选杆间距至关重要。预测表明，10 毫米（磷虾最大体宽）的栅栏间距会释放出大量的优势和重要副渔获物物种（93.94% 的 C.gunnari、53.99% 的 P. georgianus、76.25% 的 C. aceratus 和 100%）。 % G. gibberifrons)。 捕捞压力的减少将降低主要和重要兼捕物种的风险，从而使磷虾渔业可持续发展。我们建议未来的 BRD 海上试验应首先测试 10 毫米的杆间距。如果观察到磷虾明显损失，则必须测试更宽的间距（例如 15 毫米）。