Passive acoustic monitoring (PAM) involves recording the sounds of animals and environments for research and conservation. PAM is used in a range of contexts across terrestrial, marine and freshwater environments. However, financial constraints limit applications within aquatic environments; these costs include the high cost of submersible acoustic recorders. We quantify this financial constraint using a systematic literature review of all ecoacoustic studies published in 2020, demonstrating that commercially available autonomous underwater recording units are, on average, five times more expensive than their terrestrial equivalents. This pattern is more extreme at the low end of the price range; the cheapest available aquatic autonomous units are over 40 times more expensive than their terrestrial counterparts. Following this, we test a prototype low-cost, low-specification aquatic recorder called the ‘HydroMoth’: this device is a modified version of a widely used terrestrial recorder (AudioMoth), altered to include a waterproof case and customisable gain settings suitable for a range of aquatic applications. We test the performance of the HydroMoth in both aquaria and field conditions, recording artificial and natural sounds, and comparing outputs with identical recordings taken with commercially available hydrophones. Although the signal-to-noise ratio and the recording quality of HydroMoths are lower than commercially available hydrophones, the recordings with HydroMoths still allow for the identification of different fish and marine mammal species, as well as the calculation of ecoacoustic indices for ecosystem monitoring. Finally, we outline the potential applications of low-cost, low-specification underwater sound recorders for bioacoustic studies, discuss their likely limitations, and present important considerations of which users should be aware. Several performance limitations and a lack of professional technical support mean that low-cost devices cannot meet the requirements of all PAM applications. Despite these limitations, however, HydroMoth facilitates underwater recording at a fraction of the price of existing hydrophones, creating exciting potential for diverse involvement in aquatic bioacoustics worldwide.

中文翻译：

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HydroMoth：测试用于水生环境的低成本录音机原型

被动声学监测 (PAM) 涉及记录动物和环境的声音以进行研究和保护。PAM 用于陆地、海洋和淡水环境的各种环境中。然而，财政限制限制了在水生环境中的应用；这些成本包括潜水录音机的高成本。我们使用对 2020 年发表的所有生态声学研究的系统文献回顾来量化这种财务限制，表明市售的自主水下记录装置平均比陆地同类产品贵五倍。这种模式在价格范围的低端更为极端；最便宜的水上自主装置比陆地同类装置贵 40 多倍。按照此，我们测试了一款低成本、低规格的水生录音机原型，称为“HydroMoth”：该设备是广泛使用的陆地录音机 (AudioMoth) 的改进版本，经过修改后包括防水外壳和可定制的增益设置，适用于各种水生应用。我们在水族箱和野外条件下测试 HydroMoth 的性能，记录人工和自然声音，并将输出与使用市售水听器拍摄的相同录音进行比较。尽管 HydroMoths 的信噪比和录音质量低于市售的水听器，但 HydroMoths 的录音仍然允许识别不同的鱼类和海洋哺乳动物物种，以及计算生态系统监测的生态声学指数。最后，我们概述了低成本、低规格水下录音机在生物声学研究中的潜在应用，讨论了它们可能存在的局限性，并提出了用户应该注意的重要考虑因素。一些性能限制和缺乏专业技术支持意味着低成本设备无法满足所有 PAM 应用的要求。然而，尽管有这些限制，HydroMoth 以现有水听器价格的一小部分促进了水下录音，为全球水生生物声学的多元化参与创造了令人兴奋的潜力。一些性能限制和缺乏专业技术支持意味着低成本设备无法满足所有 PAM 应用的要求。然而，尽管有这些限制，HydroMoth 以现有水听器价格的一小部分促进了水下录音，为全球水生生物声学的多元化参与创造了令人兴奋的潜力。一些性能限制和缺乏专业技术支持意味着低成本设备无法满足所有 PAM 应用的要求。然而，尽管有这些限制，HydroMoth 以现有水听器价格的一小部分促进了水下录音，为全球水生生物声学的多元化参与创造了令人兴奋的潜力。