近自然水路工法におけるトミヨの生息 Effect of an eco-friendly rehabilitation of a channel on Pungitius sinensis
The Gente rier, 3km in length and with a 5.1m-wide botton, is a drainage channel for the farming area on wither side of it. For rehabilitaiton of tis weeds-rampant soil riverbed, an eco-friendly construction design wa adopted for the dual benefit of facilitating waterweeds control and minimizing damage to aquatic life. Specifically, in constructions sectionally implemented over several consecutive years, 80% of its soil bottom was lined alternately with flat blocks and cobble-filled blocks. This study was aimed at tracking how aquatic life fared after the rehabilitaiton of the channel. Firstly, we conducted a three-year survey of the inhabitant fish species pungitius sinensis, locally calle Tomiyo, with observation codrats installed alongside the right revetment for the 3-to 7-year-old target rehabilitated areas in an 800m-kong middle reach of the channel. The survey showed that the density of Tomiyo inhabitation of the waterweeds was 0.30 fish/m_2 in April and 1.16 fish/m_2 in September. Another survey revealed that in the five-year-old rehabilitated area the waterweeds community had virtually regained both its pre-rehabilitation climax with the Sparfanium japoicum, locally called Nagaemikuri, as the predominant plant species and its pre-rehabilitation composition ratios and coverage rates. From these results we might conclude that several years after the application of this new semi-natural technology to its bottom-lining the channel had regained a natural water environment that allowed the restoration of the aquatic plants and animals.
富山県立大学紀要 15, 105-110, 2005-03-31