1. Yangtze finless porpoise (YFP) is Critically Endangered, It relies on its biological sonar sensing system for important life activities. The rapid development of the Yangtze valley has brought busy shipping, which has resulted in increased noise.
2. Two locations on the shipping channel and non‐shipping branch were selected. Passive acoustic monitoring was used to record the biosonar signals of porpoises and underwater noise. The number of click trains, echolocation encounters, buzzes and buzz ratios were counted and the root mean square sound pressure level of noise was calculated in five diel phases.
3. A non‐parametric test was used to analyse the differences among different phases and between different locations. The aim of the study was to detect the spatial and temporal variations in the biosonar activity of YFPs and underwater noise between non‐shipping and shipping channels, and to provide scientific advice for YFP conservation.
4. Significant spatial and temporal patterns were observed both in biosonar activity and noise. Average biosonar activity, including click trains, buzzes, buzz ratio and echolocation encounters, was higher in the non‐shipping channel than in the shipping channel, whereas the noise level was higher in the shipping channel than in the non‐shipping channel.
5. In the non‐shipping channel, the buzz numbers and buzz ratios, indicators of porpoise feeding activity, were higher at night than during the day while the noise level was higher during the day than at night.
6. These findings may be associated with the noise avoidance strategies of YFPs to adapt to the busy shipping on the Yangtze River. Maintaining the non‐shipping status of some branches of the Yangtze River can provide more shelters for the YFPs. Strengthening the measures for banning navigation at night or reducing the vessel speed at night throughout the entire year would improve the YFPs’ feeding success.

中文翻译：

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长江下游无鳍海豚的生物声纳活动的时空变化及其与水下噪声的关系：其余的避难所是否是较安静的非航运分支？

1. 长江无鳍海豚（YFP）处于极度濒危状态，它依靠生物声纳传感系统进行重要的生活活动。长江流域的快速发展带来了繁忙的航运，导致噪音增加。
2. 选择了运输渠道和非运输分支上的两个位置。被动声学监测用于记录海豚和水下噪声的生物声纳信号。计算咔嗒声的数量，遇到回声的位置，嗡嗡声和嗡嗡声比率，并在五个diel阶段计算噪声的均方根声压级。
3. 使用非参数检验来分析不同阶段之间以及不同位置之间的差异。该研究的目的是检测非运输和运输渠道之间YFPs生物声纳活动的时空变化和水下噪声，并为YFP保护提供科学建议。
4. 在生物声纳活动和噪声中都观察到了显着的时空格局。非运输渠道中的平均生物声纳活动（包括点击火车，嗡嗡声，嗡嗡声比率和回声定位遭遇）高于运输渠道，而运输渠道中的噪声水平则高于非运输渠道。
5. 在非运输渠道中，夜间的嗡嗡声数量和嗡嗡声比（夜间）高于白天，而噪声水平则比夜间更高。
6. 这些发现可能与YFP的噪声避免策略相适应，以适应长江中繁忙的运输。保持长江某些支流的非运输状态可以为YFP提供更多的庇护所。整年加强夜间禁止航行或降低夜间船速的措施将提高YFP的饲喂成功率。