人工産卵場における粒径組成とイワナの産着卵の生残について

摘要

砂防堰堤や治山堰堤が渓流に生息する水生生物の移動の障害になっていることは広く認識されるようになって きた。とりわけイワナ(Salvelinus leucomaenis)ゃャマメ(サクフマス，Oncorhynchus masou masou の河川型）等の河川上流部に生息する魚類，あるいはサクラマスといった海から河川上流部まで遡上することが生活環の中で不可欠な魚類の個体群にとって移動の障害は死活問題である。%Relationship of grain size distribution of artificial spawning grounds and survival of eggs of white-spotted charr (Salvelinus leucomaenis) was examined. Rates of very fine particles finer than 0.074 mm in three artificial spawning grounds were 0.8- 1.4％ by weight. The rates were much higher than those of stream beds in general mountain streams. It was feared that the extremely high rates of the very fine materials would prevent stream water with oxygen from reaching at laid eggs and cause low survival rate. The rate of eyed eggs was 90.0％ for the laid eggs, and the rate was higher than those of other artificial spawning channels. Therefore, the high rates of very fine particles did not damage the eggs in this case. However, the results should not be generalized but a reference for the development of the artificial spawning ground technology.