The Beibuwan Gulf represents a crucial distribution area of Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises [Neophocaena phocaenoides) in China. However, the systematic research on the distribution pattern and its tempo-spatial variation of these two species in this waters is still deficient, and it is still unclear whether they are o-verlapped with each other. In 2003 -2004 and 2011 -2012 surveys, we conducted boat-based surveys twice at Shatian, Beibu Gulf with 4 876. 8 km survey route in total, and collected the spatial distribution data of both species. Only humpback dolphins were sighted in 2003 -2004, whereas both species were sighted in 2011 -2012. Compared with the result of April and May 2003 - 2004, the encounter rate of humpback dolphins in April-May, 2011 was significantly higher (0. 152 vs 0. 028 individuals/km survey line). The Minimum convex polygon ( MCP) , 95% Fixed kerne ( FK) home range and 50% FK core range of Indo-Pacific humpback dolphins were 162. 6 km2, 271. 35 km2 and 56. 78km2, respectively. From 2003 -2004 to 2011 -2012, the 50% FK core range enlarged and moved eastward. The MCP, 95% FK home range and 50% FK core range of finless porpoises were 97. 21 km2, 318. 72 km2 and 38. 18km2 respectively. The finless porpoise is mainly distributed in the periphery of the distribution area of Indo-Pacific humpback dolphins, and a small part of distribution area of both species is overlapped. Based on the analysis of some possible factors, it was suggested that finless porpoises possibly migrate inshore-toward seasonally, whereas Indo-Pacific humpback dolphins have preference to the estuary area, which might have led to the different distribution pattern of both species.%北部湾是中华白海豚和江豚的重要分布区,但是对该水域两物种的分布格局及时空变化的研究却比较少,也不清楚这两个物种分布区是否有重叠.2003～2004年与2011 ～2012年期间,我们在北部湾沙田水域进行了船只调查,总计航程4 876.8 km,收集了两个物种空间分布的数据.结果表明,2003 ～ 2004年仅发现中华白海豚,2011 ～2012年则同时发现了中华白海豚和江豚.与2003 ～ 2004年4～5月相比,中华白海豚在2011年4～5月份的遇见率明显增加(0.152vs0.028头次/km).中华白海豚的MCP、95％ FK家域和50％ FK核心域面积分别为162.6 km2、271.35 km2和56.78 km2,2011 ～2012年50％ FK核心家域有所扩大且东移.江豚的MCP、95％ FK家域和50％ FK核心域面积分别为97.21 km2、318.72 km2和38.18 km2.江豚主要分布于中华白海豚的外围远岸水域,同时两个物种的分布区有小部分重叠.基于多种因素的分析,我们推测,江豚可能存在季节性迁移以及中华白海豚对河口区有明显的偏好,可能是造成它们分布格局不同的原因.
展开▼
