Larviculture of Penaeus Monodon in a Recirculation System with Adding Nitrifier and A Semi-Static System

Abstract

In order to clarify the suitability of various characters for age-determination,thebony tissues such as scales,otoliths and vertebrae were used for comparison to determine the most reliable character for this purpose.Because the rings on the otolith are not visible,though grounded by grindstone,and the variability of otolith length increases significantly with the growth of fish,theuse of otolith for aging is abandened.On the other hand,the rings on the scale andvertebra are both clearly visible,and the number of rings increase with body length.The rings on scale or vertebra are similar in position,thus both of them are recognizedas suitable characters for aging.Since a much high frequency of regenerated scalesare found,we therefore choose the vertebra(16th vertebra)for age-determination.Although the readability of vertebra varies somewhat with fork length,the correspondingrings show regularity in position.The ring radius and the number of ringsincrease with fork length and are considered to be formed with the growth of fish,therefore,the vertebra is thought to be the most effective aging structure.本研究之目的在於比較鱗片、耳石及脊椎骨三者中何者為最適當之年齡形質，並探討適當年齡形質上出現之輪紋是否有規則性，以判斷其是否為有效之年齡形質。耳石雖經研磨，但仍無法觀測其輪紋，且耳石徑隨體長之增加變異增大。鱗片與脊椎骨上之輪紋均可觀測，且隨魚體成長而形成。各部位鱗片或各節脊椎骨上之輪紋數相同，且具相似之位置。惟鱗片中再生鱗之比例相當高，故脊椎骨為適當之年齡形質。又第16節之椎長變異最小，故以其為判讀輪紋之基準。脊椎骨上輪紋之位置具有規則性存在，而且輪紋會随著魚體的成長而形成，所以脊椎骨為一有效之年齡形質。