原著論文 ORIGINAL PAPER

城北ワンド群におけるトウヨシノボリ縞鰭型の生息場所特性

石田　裕子^1)*・ 安部倉　完²⁾・ 竹門　康弘³⁾

1)京都大学大学院工学研究科　〒615-8530　京都市西京区京都大学桂
2) 京都大学大学院理学研究科　〒606-8502　京都市左京区北白川追分町
3) 京都大学防災研究所水資源環境研究センター　〒611-0011　宇治市五ケ庄

Yuko ISHIDA^1)*, Kan ABEKURA²⁾ and Yasuhiro TAKEMON³⁾: Habitat characteristics of Rhinogobius sp. OR “Shimahiregata” in Shirokita Wando.Ecol. Civil. Eng. 8(1), 1-14, 2005.

1) Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8530, Japan
2) Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
3) Water Resources Research Center, Disaster Prevention Research Institute, Kyoto University, Gokasho Uji, Kyoto-fu 611-0011, Japan

Abstract:Habitat selection and food habit of a goby fish, Rhinogobius sp. OR “Shimahiregata” were studied in relation to habitat and microhabitat structure of “Wando”, lentic water-bodies formed along river banks, in the lower reaches of Yodo River, Japan from August 2001 to June 2002. The goby fish inhabited exclusively in Wando and none of the fish were found in the main channel. The fish density was more in Wando which were far from main channel than Wando connecting with main channel through a year. The distribution pattern agreed with the microhabitat preference of the fish to muddy and litter-rich substrata which were not preferred by other Rhinogobius fish. Gut contents of the fish particularly of juveniles were more in May than in other seasons. The gut contents were composed mainly zooplankton such as Cyclopidae gen. spp. and Alona spp. and benthos such as Chironomidae and Micronecta sp., most of which were typical still water inhabitants. These results showed that Rhinogobius sp. OR adapted to the lentic water condition of Wando. However, the fish used underside of unembedded stones for spawning bed in a newly constructed Wando. The density of adult fish increased in the newly constructed Wando in the breeding season and their larvae and juveniles stayed there in the growing season. It was suggested that the goby fish requires both depositional still water habitats for feeding and erosional stony habitats for spawning. Influence of the floodgate operation on environmental conditions and goby fish populations in Yodo River was discussed.

Key words: habitat selection, multiple spatial scale, Rhinogobius sp. OR “Shimahiregata”, Wando, Yodo River

摘要

城北ワンド群に生息するトウヨシノボリ縞鰭型について，生息場所スケール（ワンド間比較）と微生息場所スケール（底質型間比較）での分布様式と摂餌生態を調査した．縞鰭型は，本川では採集されず，ワンド内でのみ生息が確認された．とくに，年間を通して小型で底質の小さい閉鎖的なワンドに多く生息していた．微生息場所スケールでは，泥や落葉が多い底質に多く生息していた．充満度（体重に対する消化管内容物湿重量の割合）は５月に高く，とくに，５月の０歳魚で高かった．消化管内容物には，止水環境に生息するケンミジンコ科やシカクミジンコ属などの動物プランクトンや，チビミズムシやユスリカ類などのベントスが多く出現した．これらの結果は，トウヨシノボリ縞鰭型の生活様式が，ワンドの止水環境に適応していることを示している．
　いっぽう，繁殖期と稚魚期には新設ワンドに多く生息しており，繁殖期の成魚は長径16〜21cmの大きな石の下面に産卵していた．したがって，トウヨシノボリ縞鰭型の生息場所には，餌場としての泥や落葉が堆積した止水域の生息場所と，産卵場としての侵食が卓越した石底のある生息場所が必要なことが示唆された．また，淀川大堰の運用が淀川の環境とヨシノボリ類の個体群に与える影響を考察した．

2004年4月2日受付，2005年1月28日受理
* e-mail: ishida@wrcs.dpri.kyoto-u.ac.jp