北部湾沙田水域中华白海豚和江豚的同域分布格局及时空变化

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(0.152 vs 0. 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。

The sympatric distribution pattern and tempo-spatial variation of Indo-Pacific humpback dolphins and finless porpoises at Shatian,Beibuwan Gulf

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 overlapped 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.