中华白海豚通讯信号研究及其在人为噪音管理和探讨种群隔离程度上的应用：以北部湾和雷州湾为例

The Indo-Pacific humpback dolphins (Sousa chinensis) was listed as National Grade I Protected Animal in 1988 in China and many populations have been identified in Chinese coastal waters. However, to date there is still no direct evidence for or against a connection among these populations and dolphin conservation practice is still severely inadequate. Dolphin rely heavily on bio-sonar for navigation and communication, however, their estuary distribution preference made them most susceptible to the impact of anthropogenic noise. Information of the time and frequency parameters of whistles, the communication signals of most toothed whales and its apparent source levels and active communication space can shed some light for evaluating appropriate noise exposure levels and guiding the regulation of underwater noise pollution. Additionally, information of the apparent source levels and active communication space of whistles can also be used for defining the boundaries of separate groups in a more biologically meaningful way, and guiding the appropriate approach distance for dolphin-watching boats and research boat during focal group following. Additionally, whistle comparison have been widely used for analyzing the isolation and exchange rate among populations of the same species. In this research proposal, whistle of humpback dolphins, as well as underwater soundscape, from Beibu Gulf, including Sanniang bay and Hepu and Leizhou bay will be collected by combining regular boat based acoustic survey and passive acoustic monitoring strategy. Whistle parameters, including time and frequency parameters, apparent source levels and active communication space will be calculated and their possible geographic variation, including micro- and macro-geographic variation will be investigate by combing animal behavior, local ambient noise level and fish acoustics. Dolphin appropriate noise exposure level and isolation and exchange rate among dolphin populations will be further investigated. The above obtained information will be helpful for managing underwater anthropogenic noise pollution and conservation of local humpback dolphins.

中华白海豚是国家一级重点保护动物，在我国沿海有多个地理种群，但是不同种群之间的隔离程度尚不清楚，同时保护力度都十分欠缺。白海豚主要依赖声呐信号进行导航和交流，其河口分布习性使得她们更容易受到航运等人为噪音的干扰。海豚通讯信号（哨叫声）的物理属性能够为研究海豚的合理噪音暴露水平以及降低人为噪音对海豚的影响提供参考。同时，基于哨叫声的比对能够研究海豚不同地理种群间的隔离程度以及个体迁移规模。本研究拟在北部湾（包括三娘湾和合浦水域）和雷州湾水域，采用船基野外声学考察和被动声学监测手段，研究不同种群中华白海豚哨叫声的时频特性、声源级、海豚行为和水下声场（包括鱼类声学和噪音）在时间和空间上可能存在的差异（包括微地理、宏地理间隔以及年度间的差异），并探讨海豚的合理噪音暴露水平以及不同群体间的隔离程度和个体迁移规模。相关信息能够为涉水人工噪音管理方案的制订以及中华白海豚的保护提供帮助。

鲸类不同地理种群的通讯信号（哨叫声）的差异性可用于评估种群间的隔离状况。采用宽带录音设备，我们开展了珠江口、雷州湾和三娘湾3个不同地理种群的中华白海豚的哨叫声的差异性比对研究，并探讨了这些白海豚地理种群间的隔离程度和原因。通过分析累计2850个信噪比较高的哨叫声，并测量了声信号的17个频率和时间参数，结果发现和三娘湾水域相比，珠江口和雷州湾水域白海豚的哨叫声的组成类型相似，同时平滑型和弦型是最常用的类型。广义线性模型分析表明，不同地理种群和哨叫声类型间均存在显著的差异。三娘湾水域哨叫声的频率参数均显著高于珠江口和雷州湾水域，后两者之间无论是在信号的整体水平还是各个声音类型之间的比对均没有显著性差异。典型判别函数分析的结果同样表明，珠江口和雷州湾水域的哨叫声的差异性小于他们和三娘湾水域之间的哨叫声的差异性。不同水域的哨叫声的频率参数均呈现出随着年度的推移而增加的趋势，根据声学生态位假说，这很有可能是对当地日益增长的水体噪声污染的一种适应对策。中华白海豚关键水域的水体噪音可聚类成3组：低频频带、中频频带和高频频带。各频带的声压级受昼夜节律和潮汐节律的影响显著。中频频带的频带范围以及声压级变化的时空模式和该水域中的鱼类声信号的频带以及监测率都有较高的吻合度，表明鱼类是中频频带信号的声源。低频频带的主要贡献声源为风浪，而高频频带的主要贡献声源可能为鳞虾和海豚声呐。中华白海豚主要在噪音较低以及有鱼类发声的期间被监测到，推测白海豚具有避噪和被动窃听鱼类发声的行为。三个地理种群中华白海豚的哨叫声的差异性可能是由琼州海峡的地理屏障以及栖息地噪声环境的叠加影响导致。由于三娘湾中华白海豚种群较为独立且种群较小，我们应引起重视，并采取更多有效保护行动以防止这一小种群的灭绝，另外，我们应该重视相关水域的水体噪音污染，进而降低水体噪音对中华白海豚的影响。

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