耳石Sr/Ca比による広島県沼田川水系の天然遡上アユと陸封アユの判別

Discrimination of amphidromous and landlocked ayu, Plecoglossus altivelis altivelis (Teleostei: Plecoglossidae) in the Nuta River, Hiroshima Prefecture, using the otolith Sr/Ca ratio

Yamamoto Kanako

Takayama Sho

Umino Tetsuya

Furusawa Shuichi

Shibata Yasuhiro

Nakamura Kazuo

生物圏科学 : 広島大学大学院生物圏科学研究科紀要

Journal of the Graduate School of Biosphere Science, Hiroshima University

6～8月にかけて主に沼田川中流域で採集したアユ30尾の耳石Sr/Ca比を調べ，由来判別を行った。その結果，30尾中12尾が天然遡上アユであることが判明した。また，支流の椋梨ダム湖（白竜湖）より上流の椋梨川で採集した13尾は，全ての個体で耳石Sr/Ca比の変動が認められなかったことから，これらはダム湖で再生産した陸封アユと考えられた。

Ayu, Plecoglossus altivelis altivelis, is a commercially important species of amphidromous fish. Thus it is being targeted for stock replenishment to sustain harvest numbers. Stock identification between amphidromous and hatchery fish was conducted using the otolith Sr/Ca concentration ratio on fish taken from the Nuta River in Hiroshima Prefecture, where 170,000 hatchery ayu had been previously released. Of 30 fish sampled from the middle-reaches, 12 were identified as an amphidromous form. Of the 13 fish sampled from the Mukunashi River, a branch of the Nuta River, all were identified as landlocked fish that would have completed their life cycle between the Mukunashi River and the artificial lakes formed by the Mukunashi Dam.

アユ

Sr/Ca比

沼田川

椋梨ダム湖

天然遡上アユ

陸封アユ

ayu

otolith Sr/Ca ratio

amphidromous form

landlocked form

Nuta River

Mukunashi River

Zoology [ 480 ]

jpn

広島大学大学院生物圏科学研究科

[ISSN] 1348-1371

[NCID] AA11768091

[NAID] 120005318715