长江中下游江豚种群现状评价

作者根据近年在长江中下游对江豚进行考察的资料和收集到的标本,系统分析评价了长江中下游江豚的种群现状,主要结果如下:1.长江江豚上至宜昌(距河口1669公里),下至长江口,以及洞庭湖、鄱阳湖均有分布。分布型式是沿长江纵向呈集群性分布,横向呈趋岸性分布;2.长江中下游江豚种群数量估计为2700头。其数量冬季最高,夏季最低。夏季的SPUE值仅为冬季的48.7％—58.6％;3.长江中下游江豚群体以1—5头最为常见,占88％;4.理论推算长江中下游每年新产生个体为539头,年出生率为20％;5.通过分析比较长江中下游和中国沿海以及日本Inland Sea江豚种群数量变动趋势,推测长江中下游江豚很可能进行“江—海”、“海—江”长距离大规模的迁移,这种迁移与生殖有关。

THE POPULATION OF FINLESS PORPOISE IN THE MIDDLE AND LOWER REACHES OF YANGTZE RIVER

Based upon the data of ecological surveys of finless porpoise, Neophocaena phoca-enoides, in the middle and lower reaches of the yangtze River and specimens collected in recent years, the current state of the porpoise was analysed and evaluated. Main results are highlighted as follows: ( 1 ) The porpoise distributes in the middle and lower reaches of the yangtze River. Yichang (1 669km from the estuary) is upper range of the distribution. The porpoise also distributed in Lakes Dongting and Poyang. The distribution patterns are clumped along the vertical direction of the river and shorewise along the horizontal direction of it. ( 2 ) The estimated population size of the porpoise is 2 700 individuals. Density of population is highest in winter and lowest in summer. (3) Most common groups are of 1-5 individuals, which is about 88% in ratio. ( 4 ) It is reckoned theoretically that 539 new calves are born every year. Annual reproductive rate is 20%. (5) Though analysis and comparasion the change of density of the populations among the river, Chinese coastal waters and Inland Sea of Japan, it is infered that part of the population seems possibly to take long distance and large scale movement between the river and ocean, which is related with the reproduction.