原著論文 ORIGINAL PAPER

The relationship between waterfowl assemblage and environmental properties in dam lakes in central Japan: implications for dam management practice

Yoshihisa MORI^1)*, Seiichi KAWANISHI²⁾, Navjot S. SODHI³⁾, Satoshi YAMAGISHI¹⁾

森貴久^1)*・ 川西誠一²⁾・ Navjot S. SODHI³⁾・ 山岸哲¹⁾: 近畿地方のダム湖における水鳥群集と環境要因の関係: ダム管理との関連. Ecol. Civil. Eng. 3(1), 103-112, 2000.

1) Department of Zoology, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502, Japan
2) Shin-Nippon Meteorological & Oceanographical Consultant Co. Ltd.
3) Department of Biological Sciences National University of Singapore

Abstract:Winter waterfowl assemblage structure in nine dam lakes located in Kinki district, central Japan, was analysed in relation to various lake environmental properties, such as water quality, surrounding vegetation and management practices. Most waterfowl recorded in the dam lakes (41.4-100% of the total count) were the mandarin ducks and dabbling ducks, especially mallards, whereas aquatic plant and benthos consumers, such as tufted ducks and European pochards, were few. Important factors affecting waterfowl assemblage structure (richness and diversity) were surrounding vegetation and lake water level, both of which can be controlled by dam managers. The water quality or eutrophic level had little effect on waterfowl assemblage structure. These results suggest that waterfowl assemblage structure in dam lakes is greatly affected by human management. Therefore, dam managers should carefully plan their management activities so that the appropriate environment is maintained for waterfowl assemblages in dam lakes.

Key words: dams, lake properties, management, waterfowl assemblage

摘要

1998年12月に近畿地方のダム湖9ヶ所（天ヶ瀬・高山・青蓮寺・室生・布目・一庫・猿谷・九頭竜・真名川）でボートによる水鳥の個体数調査を行ない，各ダムでの水鳥群集の構成とダム湖の特性（水質・周囲の植生・湖管理など）との関係を調べた。ダム湖の特性値は各ダム管理事務所の公表値を用いた。ダム湖の水鳥群集は大部分がマガモ・オシドリ・カルガモで占められており，ハジロ類は少なかった。水鳥群集の豊かさを示す指標値（個体数・種数・密度）に対する水質の影響はあまりみられなかった。それに対してダム湖周囲の植生と水位変動の幅は豊かさを示す指標値に影響し，周囲植生において草本面積が大きいダム湖，および水位変動幅が中程度（5-10m）のダム湖は豊かさを示す指標値が高かった。また，ボートによる湖面利用がみられるダム湖ではそうでないダム湖と比較してマガモの個体数が少なかった。ダム湖周囲の植生やダム管理者が管理可能な水位，湖面利用などが水鳥群集の構成に影響を与えるという事実は，ダム湖周辺の環境整備の観点から，今後考慮しなければならない要素である。

Received 27 September 1999; Accepted 29 March 2000
* e-mail: yosihisa@zoo.zool.kyoto-u.ac.jp