珠江西部河口中华白海豚的分布和季节变化

2007-2008年采用船基截线法每月在珠江西部河口进行海豚调查,以评估该水域中华白海豚(Sousa chinensis)的分布、季节变化和群体组成。研究发现,珠江西部河口中华白海豚主要分布于从三灶岛南至大襟岛西侧水深10m的水域,20m等深线可能为该水域海豚离岸分布的界限,分布区在丰水期趋向河口北部浅水区,枯水期趋向离岸水域,季节性南北移动趋势与珠江东部河口相反;海豚目击率以丰水期较高,枯水期较低,本调查区与珠江东部河口伶仃洋周年各月目击率(头/100km)的相关分析结果呈显著的负相关(n=12,r=-0.65,P0.05),显示目击率的季节变化趋势也与珠江东部河口相反。据此推测,珠江东、西部河口种群之间可能存在海豚个体的交流。比较本调查区和以往珠江东部河口各调查区(包括伶仃洋及其邻近水域)的海豚目击率表明,西部河口也是珠江河口中华白海豚的重要栖息地之一。有必要进一步深入研究珠江西部河口中华白海豚种群的生物学及其与东部河口种群之间的关系,以便全面有效地保护珠江河口的中华白海豚。

Distribution and seasonal movement patterns of Chinese white dolphins in western Pearl River Estuary

A vessel-based line-transect survey was conducted monthly during 2007-2008 to assess the distribution, seasonal movement pattern, and population structure of the Chinese white dolphins () in the western Pearl River Estuary (WPRE). Most sightings of the dolphin occurred in the waters of <10m depth between south Sanzao and west Dajin Islands, and the 20m isobath may be the southern boundary of the dolphin occurrence in the WPRE. The dolphins tended to move north to the shallow waters in the wet season, whereas they swam south to the deep waters in the dry season. The seasonal north-south movement patterns in the WPRE was opposite to that in the eastern Pearl River Estuary (EPRE). Encounter rates of dolphins in the WPRE were high in the wet season but low in the dry season, and the result of correlation analysis between the parameters of individuals/100km based on month in the WPRE and Lingding Bay of EPRE showed significant negative correlation ( < 0.05), which may imply the individual exchanges between the western and eastern estuary alothough there were still no direct evidences. Comparing dolphin encounter rates recorded in this study and the studies in the EPRE (including Lingding Bay and nearby waters, Hong Kong waters) demonstrated that the WPRE waters was also one of the most important habitats of Chinese white dolphins in Pearl River Estuary. Further studies are necessary for more clearly understanding the population biology of the western population and its relatioship with that in the eastern part, in order to more effetively protect this animal in Pearl River Estuary as a whole.