关键词: 长江, 江豚, 种群, 评价

Abstract: Based upon the data of ecological surveys of finless porpoise．Neophocaena phocaenoides，in the middle and lower reaches of the yangtze River and specimens collectedin recent years, the current state of the porpoise was analysed and evaluated．Mainresults are highlighted as follows: (1) The porpoise distributes in the middle andlower reaches of the yangtze River． Yichang (1 669km from the estuary) is upperrange of the distribution．The porpoise also distributed in Lakes Dongting and Poyang．The distribution patterns are clumped along the vertical direction of the river andshorewize along the horizontal direction of it． (2)The estimated population size ofthe porpoise is 2 700 individuals．Density of population is highest in winter and lowestin summer． (3)Most common groups are of 1-5 individuals， which isabout 88%in ratio．(4) It is reckoned theoretically that 539 new calves arebornevery year.Annual reproductive rate is 20%． (5)Though analysis and comparasion the changeofdensity of the populations among the river．Chinese coastal waters and Inland Sea of Japan， it is infered that partof the population seems possibly to take long distance andlarge scale movement between the river and ocean，which is related with the reproduction．

Key words: Yangtze River, finless porpoise, population, Evaluation