江豚的年龄鉴定、生长和生殖的研究

本文根据在长江中下游,长江口和中国东北沿海收到的68头江豚标本,对江豚年龄鉴定的方法作了摸索和研究。从年龄,生长和生殖的角度系统分析了江豚的一些种群生物学特征。江豚年龄与生长的关系在一定范围内遵循的幂函数型式。4-5龄以前,江豚的生长迅速,此后减慢。江豚首次性成熟年龄雌性4龄,雄性4.5龄。性成熟时体长雌性133cm,雄性140cm。根据16头胎儿资料,用对数分割法反推出江豚的交配期较长,并有两个可能的交配高峰,分娩的高峰为2-4月。断奶年龄约为0.5龄。粗略估算长江江豚的年生殖率为20％。长江的江豚和中国沿海的江豚在形态和种群结构上各具特点。从江豚的年龄组成看出,幼龄组(0-4龄)的比例较大,结构基本正常。  

STUDIES ON THE AGE DETERMINATION, GROWTH AND REPRODUCTION OF FINLESS PORPOISE NEOPHOCAEN A PHOC AENOIDES

Based upon 68 specimens collected from the northeast China coastal waters, the middle and lower Changjiang (Yangtze) River and its estuary, this work attempted to study age determination method for finless porpoise, Neophoc ena phocaenoides. Problems of age, growth and reproduction of the finless porpoise were analysed. The relationship between age and body length, in a certain phase, follows the model of power function. Y=axb A rapid growth of body length, in both sexes, appears at the ages younger than 4-5 years and reduces gradually later on. Males attain sexual maturity at about 4.5 years and females at 4 years, with the corresponding body length of 140cm and 133cm espectively. According ro the data of 16 fetuses,it was backdated with logarithmic cutting that mating period may be long and there are two,possible peaks of mating around the year. Parti ition peaks during February and April. Weaning age is about half a year. Rough estimate of annual reproductive rate is 20％. There are different characteristics in body shapes and population structures of the finless porpoises collected from the River and from the northeast China coastal waters. Age composition indicates that the immature group (0-4 years) constitutes a large proportion.