Abstract

Visually verified in situ target strengths (TS) are the state of the science for determining the conversion from acoustic echo-integration surveys to biomass. Here, we show how these measurements can be made by high seas fisheries during normal operations using a net-attached acoustic optical system (AOS) without specialized personnel on board. In situ TS were collected from ∼45 cm standard length (SL) orange roughy (Hoplostethus atlanticus) in the southern Indian Ocean at 38 and 120 kHz. We use a multiple lines of evidence approach to demonstrate that the previous TS–SL equation developed for ∼10 cm smaller fish in Australia and New Zealand is not suitable for the larger orange roughy and instead propose new TS–SL equations. Our findings show that biomass estimates at 38 kHz will be reduced by ∼58% when using this new TS–SL compared to the existing TS–SL for smaller fish. This highlights the error of extrapolating TS–SL equations outside the measurement range. For this high sea region, the net-attached AOS represented a practical cost-effective method to obtain measurements and provide a result that could be used to inform the management of the stocks. We suggest that this method would be useful in all deep-water fisheries to monitor the TS of the fish for a range of environmental and ontogenetic conditions.

中文翻译：

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行业收集的印度洋公海橙鲷的目标强度

摘要

目视验证的原位目标强度 ( TS ) 是确定从声学回声整合调查到生物量的转换的科学状态。在这里，我们展示了公海渔业如何在正常操作期间使用附网声学光学系统 (AOS) 进行这些测量，而无需专门人员在船上。在38 kHz 和 120 kHz 频率下，从南印度洋中约 45 厘米标准长度 ( SL ) 的橙鲷 ( Hoplostethus atlanticus ) 中收集原位 TS。我们使用多行证据方法来证明之前的TS – SL为澳大利亚和新西兰约 10 厘米小鱼开发的方程不适用于较大的橙色粗糙鱼，而是提出了新的TS – SL方程。我们的研究结果表明，与现有的TS – SL相比，使用这种新的TS – SL时，38 kHz 下的生物量估计值将减少约 58% 。这突出了外推TS – SL的错误测量范围外的方程。对于这个公海区域，连接网络的 AOS 代表了一种实用的、具有成本效益的方法来获得测量值并提供可用于为种群管理提供信息的结果。我们建议这种方法可用于所有深水渔业，以监测鱼类在一系列环境和个体遗传条件下的TS。