The Social Structure And Distribution Pattern Of Chinese White Dolphins In The Eastern Seas Of Zhanjiang

This thesis contains three chapters:The first chapter:The taxonomy and distribution of the genus Sousa,the ecological study of Sousa chinensis and researches on the social organization of dolphins were briefly reviewed.The second chapter:Boat-based photo-identification surveys were conducted in the waters of Xinliao Island and Wailuo,the southern Leizhou Bay,Zhangjiang from July 2014 to June 2015.Based on the survey data between 2005 and 2014,the distribution patterns of the Chinese white dolphin population off the east coast of Zhanjiang were studied.Eighty-two boat-based photo-identification surveys were conducted in the waters of Xinliao Island and Wailuo,a total of 132 identified individuals were recorded,of which 28 were previously identified.Using software program MARK v.7.1 to estimate the number of Chinese white dolphins in the study area,results showed that the number of Chinese white dolphins in the study area was about 583(95%CI=486-760,SE=67.63),and indicated that the waters of Southern Leizhou Bay are one of the important habitat of Chinese white dolphins in Zhanjiang.Sum up the data sets from 2005 to 2015,490 boat-based surveys were conducted,resulting in a total voyage of 22584.11 km and 2310.14 survey hours.During the surveys,we found a total of 841 groups of Chinese white dolphins and 6964 dolphin sightings.From 2005 to 2015,654 distinct Chinese white dolphins were identified by photographs.Two hundred and forty-one of the cataloged dolphins were sighted in more than one occasion indicating inter-annual site fidelity of Sousa chinensis to the area off the east coast of Zhanjiang.The northernmost distribution of Chinese white dolphins in the waters of Zhanjiang is the mouth of Jianjiang River and southernmost distribution is the waters southeast of Xiayang.There are three areas with high habitat utilization,Dongli,Nanping Island and south of the Nansan Island,respectively.The third chapter:We used SOCPROG version 2.4 software to analyze the social structure.Sixty Chinese white dolphins that were identified at least 6 times were used for social structure analysis.The results showed that the Chinese white dolphins were characterized by "fission-fusion" social structure with weak and unstable associations among individuals.Average-lineage cluster analyses divided the Zhanjiang Chinese white dolphin population into 5 interrelated communities,southern A community,southern B community,southern C community,northern A community and northern B community,respectively.The southern communities was only located in the Leizhou Bay.However,the northern communities was located in Leizhou Bay and Zhanjiang Bay.Based on the results obtained by our research group,we recommend to replan the location of the Chinese White Dolphin Nature Reserve according to the home range of the communities and establish Leizhou Bay Chinese White Dolphin Provincial Nature Reserve in Zhanjiang,Upgraded to a National Nature Reserve after several years of operation.We expect the Chinese white dolphin population in Zhanjiang waters get more effective conservation.