梭鱼仔鱼耳石日轮形成及自然种群日龄的鉴定

DAILY GROWTH INCREMENTS IN OTOLITHS OF MULLET LARVAE, MUGIL SO-IUY BASILEWSKY AND DETER-MINATION FROM FIELD-COLLECTED ONES

梭鱼实验种群样本,系于1987年5月,从山东大沽河口搜集的亲鱼经人工授精后孵出的仔鱼在实验室培育取得;自然种群样本,于同年同地区采集。对于实验种群耳石生长轮形成的周期性进行了研究。结果表明,实验种群培育天数(D)与耳石生长轮数(N)之间的关系以回归式N=D-1.89表达之;根据实验种群耳石轮纹形成的周期性规律,鉴定了自然种群的日龄,表明二者具相似的周期性规律;协方差分析表明,梭鱼早期阶段的生长,自然种群比实验种群快。

The present paper deals with formation of increments in otoliths of laboratory-reared Mu-gil so-iuy larvae and daily ring determination of field-collected larvae from the Dagu River Mouth, Shandong Province in 1987. Results show:The daily deposition of growth increments in otoliths was verified by examining larvae after the fifth day of hatching in the laboratory. Relationship between chronological age and the number of daily growth increments is expressed by the regression equation: N = D-1.89, Where N is the number of increments and D the number of days after hatching.The width of the mean increament was 0.28-0.60 μm in 5-15 d around the nuclear margin and increased to 1.60-2.08 jxm in 40-50 d. Growth increments observed in field-collected larvae were the same as those of the reared ones. The age determination method was applicable to the growth study of larvae. Covariance analysis showed the body growth of field-coi-lected larvae was more rapid than those of the laboratory-reared ones.