長良川・木曽川・利根川を流下する仔アユの日齢

書誌事項

タイトル別名
  • Age and Growth of Ayu Larvae Plecoglossus altivelis Collected in the Nagara, Kiso and Tone River during the Downstream Migration.
  • ナガラガワ キソガワ トネガワ オ リュウカスル シ アユ ノ ニチレイ

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抄録

Ayu larvae, amphidromous salmononidei fish with a 1 year life span, were aged with otolith daily ring in order to reveal the ecological aspects of their downstream migration from the spawning ground.<br> The age of larvae ranged from 0 to 12d, body length from 4.6 to 8.8mm and sagittal otolith diameter from 20.5 to 48.0μm. Mean age of larvae collected in the Nagara, Kiso and Tone River was 4.5, 1.8 and 4.0d, respectively, and mean body length was 7.2, 6.8 and 6.9mm. Age, body length and otolith diameter had tendency to increase in the lower reaches of the rivers, whereas yolk volume decreased towards rivermouth.<br> Age, otolith diameter and yolk volume did not differ significantly between two samples collected up and down of a dam near the rivermouth of the Tone River, although body length was larger in the downstream, 7.4mm, than in the upperstream, 6.9mm. The fish density was about 4 times higher at the upperstream of the dam than at the downstream, suggesting that the drifting larvae were pooled in the dam.

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  • 日本水産学会誌

    日本水産学会誌 57 (11), 2013-2022, 1991

    公益社団法人 日本水産学会

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