變色雀鯛稚魚期的日齡與成長

Abstract

本文係以耳石鑑定日齡的方法(Otolith ageing)，探討臺灣北部龜吼岩岸海域仔稚魚的變色雀鯛之日齡與成長。標本採集的時間為1990 年 5 月、 7 月以及 1991年5 月。這些標本的標準體長(SL)介於9.35 mm 到28.65 mm 之間。 在仔稚魚耳石與個體體長關係方面，扁平石(Sagitta)、星狀石(Astericus)與礫石(Lapillus)等三對耳石的長、寬與仔稚魚之標準體長之間有顯著的正相關關係。同時在耳石的長、寬與個體體長間可以導出直線關係式。 將仔稚魚以400mg/l 濃度的四環素浸泡 24小時後，蓄養11天，以進行耳石螢光標誌實驗。結果測得在耳石上新產生的輪紋數之頻度分佈中，星狀石輪紋敷介於 7 至 11 輪之間，然而分佈之型量(Mode)為 10 輪，因此，推論變色雀鯛仔稚魚的星狀石具有形成日輪(Daily ring)的現象。 根據耳石具日輪的現象，讀取9尾仔稚魚左、右耳石的輪紋數並加以相互比較，結果顯示左、右耳石輪紋數之間並無顯著差異，經利用左耳石或右耳石的輪紋數，進一步利用45尾體長介於9.35mm到25.00m間的個體來推算出變色雀鯛仔稚魚期的成長情形，結果顯示變色雀鯛仔稚魚在日齡為23日到56日之間呈直線方式成長。其直線關係式為 Lt(mm)=-0.9503+0.4850*t(day): L：標準體長; t：日齡。 另外，讀數1991年最早補充(Recruitment)入龜吼岩礁海域族群的仔稚魚耳石日輪數，結果顯示這些仔稚魚是在四月中旬所孵化出來的。

The present thesis presents results from a study of the age and growth of juvenile neon damselfish Pomacentrus coelestis, from the northern coast of Taiwan. Specimens ranging from 9.35 to 28.65 mm in standard length, were collected in summer 1990 and May 1991. Otoliths of the fish were used as age indicators. The fish size and dimensions of otoliths, namely, sagitta, astericus and lapillus, were positively related. Thus, the linear relationship between the standard length of the fish and the width or the length of each otolith are presented. An experiment was undertaken for the validation of daily ring formation in the otolith. A number of juvenile fish were reared in the laboratory and their otoliths were marked in 400 mg/l tetracycline solution for 24 hours. Thereafter these individuals were moved to the tank containing normal sea water and reared for 11 days before nine of them were sampled for otolith removal. The counts of’ the newly formed increments on the asterici of these specimens were in the range between 7 and 11. However, the mode of the data distribution is 10. This finding supports the view that the increments appeared on the astericus of P. coelestis have formed daily, Moreover, on each of another group of 9 juvenile individuals, numbers of the right otolith increments were compared with that of the left, with results showing that there are no significant difference between the paired otoliths. Overall, a linear growth curve was deduced based on the standard lengths (SL) of 45 juveniles, whose ages were in the range of 23?56 days. The equation is: Lt (mm)=-0.9503+0.4850*t(day); where Lt: standard length, t: age. Furthermore, retrospects based on the otolith increments of the first recruitment of P. coelestis in 1991, which were collected in May, have revealed that these individuals were hatched in April.