特集: 河川環境の保全と復元
FEATURE: Conservation and restoration of river environment
事例研究 CASE STUDY

自然共生研究センターの取り組み−河川におけるハビタットの保全と復元−

萱場祐一

独立行政法人土木研究所自然共生研究センター　〒501-6021　岐阜県羽島郡川島町笠田官有地無番地

Yuichi KAYABA: Activities in Aqua Research Restoration Center for the restoration of habitats in streams and rivers in Japan Ecol. Civil. Eng. 5(2), 257-263, 2003.

Aqua Restoration Research Center, Public Works Research Institute, Mubanchi, Kasada kanyuuchi, Kawashima, Hajima, Gifu 501-6021, Japan

Abstract:Aqua Research Restoration Center (ARRC) which was established in 1998 in Gifu Prefecture, has three Experimental Streams. Three streams have the length of approximately 800 m, and the bed slope from 1.2% to 3.33%. The Stream A is a straight channel and the Streams B and C have two meandering sections Electrical fishing surveys were conducted from July to December in 1999 in order to clarify relative variation in fish abundance among the three streams. The fish surveys resulted in the higher abundance in the Streams B and C than in the Stream A, and a relationship between habitat types and the number of individuals in the three streams were analyzed to specify the factors influencing the relative abundance of fish in the two types of streams. The habitat types were partitioned into a lotic zone and a water-edge from the lateral view of a cross section. The lotic zone was subdivided into riffles, pools, runs and glides, and the water-edge was subdivided into "vegetation" and "no-vegetation". A statistic analysis proved that several sequences of riffles and pools contributed to the relative abundance of fish in the Streams B and C to Stream A, however, the vegetation at water-edge did not function in the enhancement of fish abundance compared with the riffles and pools. These results will show that we should pay much attention to the habitat structure in the lotic zone in river works such as river restoration.

Key words: experimental streams, fish abundance, habitat, pool and riffle, vegetation

摘要

本報では自然共生研究センターにおける研究活動の取り組みを紹介し,実験河川で実施した魚類の生息とハビタットに関する研究を事例研究として報告した.ここでは,河道を横断方向に流水城と水際城に区分し流水域においては早瀬,淵,平瀬,とろの4つに,水際域においては植生の有無の2つにハビタットを分類した.これらの組み合わせによりハビタットを類型化し,実験河川内の魚類の生息量との関係を分析した.その結果,流水城に早瀬と淵が存在する場合は生息量が有意に大きかった.また,水際植生の有る場合は無い場合に比べて生息量が増加する傾向が見られたが,その増加量は早瀬と淵が存在する場合に比べて小さかった.本結果は,中流域の多自然型川づくりを考える上で流水域のハビタットが重要な保全対象であることを示唆している.

2002年5月30日受付，2002年12月16日受理
e-mail: y-kayaba@pwri.go.jp