鳙仔──幼鱼耳石日轮与生长的研究

DAILY GKOWTH INCREMNT IN OTOLITH AND GROWTH FOR FRY- YOUNG FISH OF BIGHEAD(Aristichthys nobilis)

催产获得受精卵，从胚胎发育后期到秋季鱼种出塘的孵化饲养过程中，连续取样剖出矢耳石，其制片在光镜下观察耳石形态、大小、轮纹排列及其间距变化，部分耳石在扫描电镜下观察轮纹的细微结构。用实测体长体重和日轮退算体长及计算体重比较研究了生长特性。耳石形态经历了由圆形、椭圆形、菱形到梨形的变化过程。耳石直径与全长呈线性相关，其关系式为ｙ＝－０．１９４４＋０．０３８８ｘ。孵出后第二天出现第一个日轮，之后每日形成一轮，日轮间距变化与鱼体生长及生态条件变化有关。以实测和退算数据用高次方程描绘的生长曲线基本一致，经ｔ检验，无显著差异。

The samples from embryonic development(artificially fertilized eggs)of latestage to young fish of big head were collected continuously in June- October 1992.Both sagit- tal otolith were removed from the fish and its sections were examined for size,morphology,ring formation and width of daily growth increments by light microscope,and microstucture ofotolit h was observed under scanning electron microscope. Growing character,were studiedfrom data on daily age,weigth and lengeh and back calculation based on the increments.Morphology of otolith was undergoing changes from round,oval,rhombic,to pear一shape.Otolith radius(μm)were linearly related to fish length(TL,mm),the equation was Y= -0.1944+0.0388 x.The initial daily growth increment in otolith was formed on the sec-ond day after hatching and continued on a daily schedule. The change of width of daily growthincrement was closely related to growing and developing of fsh and ecological condition. Thedata on the length(SL,mm)and weight(g. )obtained by measuromenting and back calculat-ing based on growth increments in otolith agreed with the growth curve of equation by t- test(P>0.05).