低龄草鱼鳞片环纹的增长及幼轮和年轮特征的初步研究

幼草鱼鳞片环纹,以孵出后第二个月生长最快,往后生长减慢,冬季停止生长。幼鱼体长一般在47—70毫米形成幼轮。鳞片的“切割相”是区别年轮和幼轮的标志。幼鱼在饥饿时,环片不仅不增长,反而出现环片被吸收的现象。鳞片上各种副轮标记的形成与摄食条件的变化有关。计算了体长与鳞径、环纹数以及鳞径与环纹数的迴归方程,它们之间都呈直线正相关,相关显著性均在99%以上。  

A STUDY ON THE GROWTH OF THE CIRCULUS OF THE SCALE,AND FEATURE OF THE "FRY RING" AND THE FIRST ANNULUS IN GRASS CARP CTENOPHARYNGODON IDELLUS(C. & V.)

The present paper deals with the growth of scales of the subyearlings and yearlings of the grass carp, concentrating on the growth of circuli and features of the "fry ring" and the annuli. The results are as follows:(1) The fry of grass carp begins to grow out scale when it reached a size of about 20mm. According to our observation, the forming of circuli in the scale of the subyearling was quickest during the second month after hatching, by an average of 0.8 circulus per day. Later, the forming process decreased gradually and ceased during winter.(2) The "fry ring" may be observed in most individuals. It is situated at the miter border of the first closely-spaced circuli from the center of the scale. The body lengths of fish at the time of "fry ring" formation ranged 47—70mm.(3) The annulus is marked by a "check", where a group of old circuli of previous year are intersected by two or three new cireuli formed in next spring. This character enables one to distinguish the first annulus from the "fry ring".(4) Circulas indention form during periods of starvation, even the formed circulus around the periphery of scale was resorbed. Thus, the formation of "checks" seems to be related with the rearing conditions.(5) Positive correlations exist between body length and scale radius, between body length and the mean number of circuli on the scale, and between scale radius and number of circuli. Their regression equations are given in the paper.