ヒヌマイトトンボの生息環境の保全と復元に関する研究

抄録

The damselfly, Mortonagrion hirosei, was designated as an endangered species by the Environment Agency in 1991, because its habitat is vulnerable to the effects of land reclamation and river improvement. The low-flying insect lives in reed plains and measures about three centimeters long when fully grown. Relationships between the habitat of the damselfly, salinity, topography and vegetation were studied at 9 tidal rivers from Hinuma marsh in Ibaraki Prefecture to the Nagaitaura Bay in the Tsushima Islands. The larvae of the damselfly were collected only from the pool in a sunken place covered with dead leaves on the riverside. Salinity and the time required for the completion of the habitat of the damselfly were above 0.50‰ and about 4 years, respectively. The damselfly which lived on the riverside at Suigo ohashi bridge across the Tonegawa River was died out in 1998, because the salinity of its habitat was not enough for their life. It was supposed that the salinity of the habitat was the most important environmental element required for holding communities of the damselfly.