长江中游草鱼仔鱼的日龄和生长研究

Daily age and growth of larval grass carp from the middle reaches of the Yangtze River

采用耳石日轮鉴定了 1998年采自长江九江江段和 1999年分别采自长江石码头和纱帽江段的草鱼仔鱼的日龄 ,并依据日龄推算了仔鱼的孵化期和估计了日生长率。采自九江、石码头和纱帽江段的仔鱼的平均日龄分别为 10 .7d ,8.8～ 16 .0d和 7.0d。石码头江段仔鱼中 ,5月 16日样本的日龄稍高 (16 .0d) ,其余样本的日龄比较接近 (8.8～ 9.5d)。采自石码头江段的所有仔鱼的体长平均生长率为 0 .11mm·d-1,特定生长率为1.32 %。各批次仔鱼的体长与其日龄的相关性通常很差 ,这表明长江中游仔鱼的生长不整齐 。

Ages of grass carp (Ctenopharyngodon idellus) larvae collected from Jiujiang section of the Yangtze River in 1998, Shimatou and Shamao sections of the Yangtze River in 1999, were determined by counting the increments in otolith. Birth date and daily growth rate of body length of the larvae were estimated based on the daily age. Average age of the larvae from Jiujiang, Shimatou and Shamao sections were 10.7d, 8.8-16.0d and 7.0d, respectively. In the samples from Shimatou section, the age of larvae sampled on May 16 was older than that of the other samples. The average and specific growth rate of body length of the larvae from Shimatou section was 0.11mm .d -1 and 1.32%, respectively. The correlation between body length and age was insignificant except in few samples, which suggested that the growth rate of larvae from the middle reaches of the Yangtze River was unequal, and some individuals might have suffered from the food absence.