Hydroacoustics has become a requisite method to assess fish populations and allows to describe the relationships of fish with other elements of the aquatic ecosystem. This nonintrusive method is currently an integral part of the sampling procedures recommended for fish stock assessment by the Water Framework Directive and has been standardized by the European Committee for Standardization [CEN (2014) CSN EN 15910 ‐ Water quality ‐ Guidance on the estimation of fish abundance with mobile hydroacoustic methods, Category: 7577 Water quality. Biological.]. In Europe, hydroacoustic surveys are performed in freshwater using different frequencies. Consequently, there is a need to evaluate if survey results can be compared. This study aimed to carry out in situ comparisons at the 38 kHz frequency (noted f) with two other commonly used frequencies, 70 and 200 kHz. The 38 kHz frequency has seldom been compared with other frequencies in freshwater although it is widely used worldwide, especially in the Great Lakes of North America and in Sweden. In 2016, hydroacoustic data were acquired in Lakes Annecy and Bourget using methods validated in previous studies that compared the frequencies 70, 120 and 200 kHz. This study showed similar density and biomass estimations as a function of frequency, density(f) and biomass(f), between the frequencies studied for low to moderate fish densities. For higher fish densities, the results were more variable and need to be verified. Fish density(f) and biomass(f) estimations sometimes exhibit differences between frequencies, which is not fully in agreement with theoretical calculations. The aim of this study was to evaluate frequency comparisons in practise. However, if the differences on acoustic metrics, density(f) or biomass(f) between frequencies were occasionally statistically significant, the differences were small enough to be considered negligible for fish population management. These analyses led to better knowledge of the responses from fish in temperate lakes for the studied frequencies. Our findings should be considered when revising the CEN standard.

中文翻译：

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在温带湖泊水声鱼类调查的标准化协议中包括38 kHz

水声声学已经成为评估鱼类种群的必要方法，并可以描述鱼类与水生生态系统其他元素的关系。目前，这种非侵入性方法是水框架指令建议用于鱼类种群评估的采样程序的组成部分，并已由欧洲标准化委员会标准化[CEN（2014）CSN EN 15910 ‐水质‐鱼类估计指南移动水声法的丰富度，类别：7577水质。生物。]。在欧洲，水声调查是使用不同的频率在淡水中进行的。因此，有必要评估是否可以比较调查结果。这项研究旨在原位进行将38 kHz频率（记为f）与其他两个常用频率70和200 kHz进行比较。尽管在世界范围内广泛使用了38 kHz频率，但很少将其与淡水中的其他频率进行比较，尤其是在北美大湖地区和瑞典。2016年，使用之前的研究中验证的方法比较了70、120和200 kHz的频率，在安纳西湖和布尔热湖中获得了水声数据。这项研究表明，在研究中低鱼类密度的频率之间，密度和生物量估计值与频率，密度（f）和生物量（f）呈函数关系。对于更高的鱼类密度，结果变化更大，需要进行验证。鱼密度（f）和生物量（f）的估算有时会出现频率之间的差异，这与理论计算不完全一致。这项研究的目的是评估实践中的频率比较。但是，如果频率之间的声学​​指标，密度（f）或生物量（f）的差异有时具有统计学意义，则该差异足够小，可以认为对于鱼类种群管理而言可以忽略不计。这些分析使人们对所研究频率的温带湖泊鱼类的反应有了更好的了解。修订CEN标准时应考虑我们的发现。差异很小，可以忽略不计。这些分析使人们对所研究频率的温带湖泊鱼类的反应有了更好的了解。修订CEN标准时应考虑我们的发现。差异很小，可以忽略不计。这些分析使人们对所研究频率的温带湖泊鱼类的反应有了更好的了解。修订CEN标准时应考虑我们的发现。