In recent, in order to secure power and water, a lot of dams have been built. For this reason, the ecosystem around the dam has been destroyed.
For example, an increase in water level caused by building the dam leads to the disappearance of the habitat of otters that inhabit at the waterside. Further, the habitat of floating-leaved plants or submerged plants that grow in shallow water has been disappeared. Furthermore, in addition to the habitat of fishes which spawn at the surface of the shallow water or the bottom of the shallow water, the habitat of aquatic insects has been also disappeared. For this reason, the habitat of birds which eat the aquatic insects and the fishes has been lost. In order to solve the problems, various floating wetland facilities have been developed.
Disadvantageously, since conventional floating wetland equipment provides the habitat for any one of the otters and the fishes, there is a problem that the conventional equipment is not suitable to allow the otters, the fishes, and the birds to inhabit together. Further, in the conventional floating wetland equipment that provides only the habitat of the fishes, since the otter which is a natural enemy of a predator such as bass or bluegill does not inhabit around the equipment, it is difficult to prevent native fishes or eggs of native fishes from being eaten by the predator. Accordingly, there is a problem that the conventional equipment does not serve as the habitat of fishes.
Moreover, in the conventional floating wetland equipment, since a frame is made of stainless steel, a large amount of polyethylene foam is required to float the frame on the water, so that a structure thereof becomes complicated.
In addition, since a second spawning ground of the conventional floating wetland equipment is filled with gravels, the conventional floating wetland equipment is not suitable for a spawning ground of fishes that prefer sands or soils.