アイナメ仔魚の耳石日周輪形成の確認と成長率

We validated the daily formation 0f otolith increments of reared fat greenling Hexagrammos otakii larvae and examined the growth patterns of wild lavae. The mean notochord Length and otolith radius of newly hatched larvae were 8.31 mm and 273μm, respectively. Newly hatched larvae had some increments on their lapilli and a check was formed at hatching (hatch check). The relattonship between age and the number of increments formed outside the hatch chcck (NI)was linear regression (Nl=0.99Age-0.30, n=49, r^2=0.98, P<0.001) and its sloped did not differ significantly from 1 (t-test: P=0.31). The indicates that these increments formed daily Wild fat greenling larvae were collected from the surface layer of Mutsu Bay from February to April in 2003. The relationship between the the otolith radius (OR in μm) and notochord length (NL in mm) was represented by an allometric equation The mean back-calculated NL with the biological intercept method was 9.79mm at 10 days old, 10.9mm at 20 days old. 11.6mm at 30 days old, and 133 mm at 40 days old The daily growth rate was relatively high immediately after hatching (range: 0.15-0.17mm/day) and gradually decreased. These finding suggest that fat greenling larvae do not have a slow growth period just after hatching.アイナメ飼育仔魚の耳石日輪形成形成の確認と, 天然仔魚の成長様式を検討した｡ 礫石上には孵化時に明瞭な輪紋(孵化チェック)が形成された｡ 日齢(Age)と孵化チェックの外側の輪紋数(Nl)の関係は直線で示され(NI=0.99Age-0.30, n=49, r^2=0.98, P<0.001), 傾きは1とは有意に異ならなかったことから(t検定: P=0.31), これらの輪紋は日周輪と判断された｡ 陸奥湾では2003年2月から4月まで天然仔魚が表層で採集された｡ 耳石半径と脊索長の関係はアロメトリー式で表され, バイオロジカル・インターセプト法による平均逆算体長は10日齢で9.79mm, 40日齢で13.3mm と推定された｡ 成長率は孵化直後に比較的高く(範囲: 0.15-0.17mm/日), その後次第に低下したことから, アイナメでは孵化直後の低成長期はみられないものと考えられた