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.
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