Study On Spatial Distribution Pattern And Social Structure Of Indo-Pacific Humpback Dolphin(Sousa Chinensis) In Jiangmen Waters,Guangdong

The Indo-Pacific humpback dolphin(Sousa chinensis)distributes in estuarine and inshore waters of Indian,the coastal waters of Southeastern China and Southeast Asia.In 1988,it was listed as China's first-class protected animal,and in 2017 it was listed as a vulnerable species by the International Union for Conservation of Nature Red List of Endangered Species.It is an important indicator species of inshore marine ecology and has highly ecological,scientific and cultural valueJiangmen waters is an important distribution area of Indo-Pacific humpback dolphin in China,and there is a provincial nature reserve.In order to find the basic situation of this population and evaluate the effectiveness of the nature reserve,the population dynamics and site fidelity,spatial distribution pattern,and social structure were studied.In 2016-2018,a total of 690 individuals were identified in the study area,with 79%of the individuals in the breeding period,and the number of individuals in the early and late breeding period was equal.The annual change of population abundance remained stable relatively,with a slight increase and no significant seasonal changes.Although frequent immigration and emigration were observed and the population showed highly mobility,nearly one-third of individuals still exhibited strong site fidelity.Overall,it was a prosperous and stable population.The Indo-Pacific humpback dolphins in Jiangmen waters distribute from the northeast of Xiachuan Island to the west of Hebao Island and Dajin Island,with a total habitat area of 676 km2.The core-use area is from the south of the power plant to Dajin Island and Hebao Island,with an area of 74 km2.Most core-use areas are not covered by nature reserve.From 2016 to 2018,the range of habitat increased slightly,and there was a tendency to extend eastward.From spring to winter,the location of the habitat moved to the northeast.The core-use area was the largest in winter,and it was far away from the power plant.There was no obvious difference between the distribution range of juvenile individuals and the distribution range of all individuals.In the category of intermediate use intensity,there were two hotspots,but individuals in each hotspot area rarely had direct communication,existing sensitive site fidelity.The Indo-Pacific humpback dolphins in Jiangmen waters presented a social model of fission-fusion.Group size here was larger than group size in many other waters.Association between individuals showed both casual acquaintances and preferred companions.Individuals who had witnessed more than 4 times were grouped into two clusters.Each cluster had its own preferences in terms of spatial distribution,and they also shared some core-use areas.According to the specific situation of the spatial distribution pattern and social structure of the Indo-Pacific humpback dolphins in Jiangmen waters,specific suggestions were made on the priority of the conservation zone adjustment,focused individuals and interregional linkage protection.