Investigations On Distribution And Population Size Of Chinese White Dolphin (Sousa Chinensis) Along The Coastal Waters Of Fujian Province, People’s Republic Of China

Chinese white dolphin (CWD, Sousa chinensis) is the only First-grade state protected marine cetacean in China, and mainly distributes along the southeast coastal waters. Fujian province is characterized with numerous harbours and estuaries, which is once one of the important distribution areas of the CWD. According to the literatures, this species could be found in Shacheng Port, Sanduao waters, Luoyuan Bay, Minjiang River Estuary, Xinghua Bay, Meizhou Bay, Quanzhou Bay, Xiamen Harbour and Dongshan Gulf, etc. While unfortunately, there is no direct studies on distribution, abundance and habitat quality of CWD along Fujian coastal waters except Xiamen in which National Nature Reserve has been established. From2010to2013, we mainly studied the history and current distribution, decline process, population size and habitat quality of CWD along the Fujian coast by using interviews with inshore fishermen, line-transect survey and photo-identification technology, and the main results and conclusions are as follows:1. From April2010to November2011, a series of questionnaires were conducted to collect information from local fishermen in Fujian province about their encounters with Sousa chinensis in wild in order to explore the historical and current distribution of CWD. Totally,239questionnaires were obtained at27fishing communities or fishing port along Fujian coast. The results indicated that CWD distributed Fujian coastal waters continuously in large population along Ningde waters, Luoyuan Bay, Minjiang River Estuary, Meizhou Bay, Quanzhou Bay, Xiamen Harbour and Dongshan Gulf in history (35-45years ago); and now, except Xiamen waters, there were still sporadic sightings of CWD in Ningde waters, Quanzhou Bay and Dongshan Gulf by fishermen.2. From August2010to February2013, we have conducted line-transect survey of CWD in Ningde waters, Quanzhou Bay, Xiamen waters and Dongshan Gulf and confirmed that there were resident CWD populations in these waters. The CWD occurred all the year around in Xiamen waters, and Xigang, Jiulongjiang River Estuary, Wuyu Island, and the area between the Tongan Hay to Dadeng Island represented the major distribution area of CWD in Xiamen. Significant seasonal changes in distribution in all Xiamen waters were found as well. In spring and winter, significant numbers of CWD occurred in Xigang and the mouth of I’ongan Hay, while in the other seasons, the sightings in Xigang decreased relatively with sightings in Jiulongjiang River Kstuary, Wuyu Island and the area between the mouth of Tongan Bay to Dadeng Island increasing, suggesting an outward movement pattern of CWD from the inside harbour to outside waters from spring and winter to summer and autumn.Furthermore, boat surveys also confirmed that there were still small resident CWD populations in Ningde waters, Quanzhou Bay and Dongshan Gulf. Five groups of CWD were sighted in Ningde waters, which mainly distributed near Changyao Island and Dongan Island. While in Quanzhou Bay and Dongshan (iulf we only found one group and two groups of CWD, respectively, which mainly distributed in Haiyu waters and Dashuang Island waters separately.3. By using photo-identification methods,39individuals with remarkable characteristics,6individuals,1individual and2individuals were identified in Xiamen, Ningde, Quanzhou Bay and Dongshan Gulf, respectively based on pigmentation and speckle patterns, nicks, wound marks and so on. In the study period, only the cumulative number of identified CWD increased in Xiamen, while the growth rate was slightly, which suggested there were limited individuals which had not been identified in this waters. Based on the photo-identification data, capture-recapture method (CRM) was used to estimate the abundance of CWD in Xiamen waters. The CRM methods generated the abundance estimates of40(95%CI=38-42). Plus the23young individuals without obvious identified characteristic, the population abundance was estimated to be61-65individuals in all the Xiamen waters. By contrast the individuals recognized in Ningde, Quanzhou Bay, Xiamen and Dongshan Gulf, we have not found the same one with each other, so there was no evidence that the CWD in these waters existed individual migration and communication.4. Additionally, threat factors were proposed based on the present studies, in which the construction of the port, heavy marine traffic, extensive aquaculture and so on had a significant impact on the CWD. At last, some practical measures were provided for the conservation and management in order to decrease the threats mentioned above.