EXPERIMENTAL STUDIES ON THE HABITAT RESTORATION FOR THE CONSERVATIONOF THE INDIGENOUS FISHES ON THE PHRAGMITES REED BED OF LAKE BIWA, CENTRAL JAPAN

为了改善当地鲤科鱼类的繁殖栖息地，我们通过刮去表层土壤，将芦苇床陡峭的岸边改造成平缓的斜坡。从4月至5月，在实验区内发现的本地鲤科鱼的产卵卵和幼虫数量多于陡岸控制区。但是，在随后的6月至8月，当人为地保持低水位时，外来鱼类幼虫在那里占主导地位。另一方面，南菖蒲生长在水位低于表层土壤至少一次的地方，即它从土壤中出来的时期。这表明，保护本地鱼类和植物不仅需要栖息地的恢复，还需要根据其生态特征进行水位控制。

To improve the reproductive habitat of the indigenous cyprinid fishes, we modified the steep shore of thePhragmites australis reed bed into gentle slope, by scraping off the surface soil. More numerousspawned eggs and larvae of the indigenous cyprinid fishes were found in the experiment areas than incontrol of steep shore, from April to May. But, alien fish larvae dominated there in the subsequentJune to August, when the water level was kept artificially low. On the other hands, P. australis grew onthe area where water level was below the surface soil at least once, during the period it came out fromrhizome. This indicates that conservation of the indigenous fishes and plants requires not only habitatrehabilitation but also water level control based on their ecological characteristics.