2 research outputs found

    PROPOSALS FOR METHODS TO IMPROVE THE ENVIRONMENT OF THE AMAGASAKI CANAL, FOCUSING ON TROPHIC LEVEL OF Tridentiger obscurus

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    本研究では,チチブの栄養段階に着目して,尼崎運河の環境改善の方法について調査研究を行った.その結果,チチブは付着藻類を起点とする底生系の食物連鎖の上位にあり,またチチブを食する大型魚類の存在も示唆された.そこで,環境改善策として,積極的にチチブを保全し,運河内に過剰にある栄養塩をより多くの生物に利用されるようにすることを考えることができた.実際にチチブの保全のためのすみかを作成し,現地実験をした結果,適当なすみかの創出には,空隙がコウロエンカワヒバリガイによって閉塞されないような工夫が必要であることがわかった.This study focused on fish species to investigate methods for improving the environment of the Amagasaki Canal. Analysis of the food web revealed that a benthic fish species Tridentiger obscurus has an important role in transferring energy from primary producers to organisms at higher trophic levels. The result suggest that protection of the bottom dwelling T. obscurus is effective for improving the environment of the canal by making excessive nutrients ingestible for other organisms. When artificial shelters for T. obscurus was set in the canal, a large amount of mussel Xenostrobus securi attached to the shelter. The result insists that further improvements are needed to prevent clogging by the shells and make shelters available for T. obscurus

    FIELD EXPERIMENT TO CREATE AN ARTIFICIAL FISH REEF FOR Tridentiger obscurus IN THE AMAGASAKI CANAL

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    過栄養化した尼崎運河の環境を改善するために,付着藻類から上位の生物にまで及ぶ食物網の経路を創出することを考えた.本研究では,まずその端緒の検討として,底生魚のハゼ科チチブの保全を目的にした魚礁の構造と設置方法を把握することを目的に現地実験を行った.3種類の生息場をつくり,酸素不足が生じない水面付近の上層,中層,下層の3つの水深に沈設した. その結果,水底を選好するチチブであったが,夏期にはチチブは上層に移動,蝟集し,7月には下層の構造物にはチチブは確認できなくなった.ただし,夏期でも下層のDOは忌避行動をするようなレベルではなく,DOの他にも水温などが複合的に作用していることが示唆された.また構造物に独立した空隙を設けるとチチブの種内攻撃機会は減少し,小型のチチブも共に生息可能となることが推察された.To improve the environment of the Amagasaki Canal, a method for moving nutrients out of the system using a food web pathway derived from attached algae to fishes was investigated and field experiments were conducted. It was found that Tridentiger obscurus with bottom-dwelling properties gather in structures with some gap spaces installed near the water's surface. During the summer when water quality deteriorated, T. obscurus used the structures as a refuge. Such a structure would also reduce intraspecific competitions and allow for smaller T. obscurus to coinhabit around the shelter with the larger fish occupying the interstices of the structures. The stomach contents of T. obscurus suggested that they were feeding on attached algae and the shrimp in the structures. In addition, the T. obscurus were laying their eggs in the gap space of the structure
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