鸭绿江香鱼耳石日轮与生长的研究

ON DAILY-GROWTH INCREMENT OF OTOLITH AND GROWTH OF AYU FISH FROM YALUJIANG RIVER

１９９２年对鸭绿江香鱼耳石日轮与生长进行了研究。人工受精卵胚胎发育后期和前仔鱼期连续剖察表明，受精后约９６小时胚体听囊内出现一对矢耳石，孵出后第２天耳石上出现第一个日轮，之后每天形成一轮。在光镜和扫描电镜下测定了幼、成鱼矢耳石的形态、直径、日轮数及其间距变化。耳石短径（ｖ， μｍ）与鱼体长（ｘ， ｍｍ）呈线性关系， ７５尾幼、成鱼的关系式为ｙ＝３．２８ｘ＋２４８．３０。以耳石日轮数推算其产卵孵化期与实地调查结果一致。耳石日轮数（Ｄ）可用孵化后日数（Ｎ）减１表示。日轮间距有规律性变化，与鱼体生长发育和生态条件密切有关。依据日龄和相关体长体重资料进行了香鱼生长特性研究，用生长方程描绘的生长速度曲线和生长拐点（位于２８３日龄）等均较客观地反映了其生长特点。

The samples of juveniles and adults of ayu fish (Plecoglossus altivelis)in Yalujiang River were collected in June through September 1992. After biological measurements of the samples, the sagittal otoliths were removed from the fish and sections were made to examine their sizes, morphology, number and widths of daily growth increments by light and scanning electron microscopes. The sagittal radius Y (um) of the otolith was linearly related to the fish length x (SL, mm), and the equation of 75 individuals was Y = 248. 3 + 3. 28X, r = 0. 917. The mode number of daily growth increments of otolith of 39 adults ranged from 330 to 351. Calculation of hatching date from daily growth increments, suggested a hatching season from mid-September to late Octomber, which agrees well with the Practical condition. Changes of width of daily growth increments are closely related to the growth and development of the fish and environmental conditions. The growth character of ayu was studied on the basis of daily growth increment and relative data of body length and body weight. The maximum mean width of each ten increments of otolith and the maximum increase in body length were calculated on the basis of widths of daily growth increments of otolith occured at the 230th and the 240th day of growth of the fish respectively. The length-weight relation was represented by the equation w=aLb, and the result was W= 9. 1809 ×10-6L3.1358. The von Bertalanffy growth equation Wt=f (t) who [1 -e-k(t-t0)]3 was used to determine the relation between age (in day) and fish weight (g.), when W∞ =275 (g.), K=4.9083 ×10-3,;then the final: According to von Bertalaffy growth-speed equation: The turn-point tr = 283 (age, in days) was obtained by equation: In addition, microscopic observation were performed on the growth of the otolith during the embryonic development of artificially fertilized eggs and the formation of first daily growth increment on otolith of larvae. The first daily ring was formed 2 days after hatching.