The effects of artificial shelters on aquatic organisms

In agricultural ecosystems, the ecological concern of irrigation channels and ditches has been reconsidered and materialized in channel improvement. The ecological concept has been widely accepted and applied into irrigation systems. The idea of the in-streamshelter/cover technique has been used as a new method in many countries. Recently, this eco-construction has also been installed in the irrigation system of Taiwan. In Xinhua, Tainan City, an installation of artificial shelters for southern branch of Chia Nan Irrigation Channel was completed in June 2010. In order to know the effects of artificial shelters on aquatic organisms, this study investigates aquatic organisms and environ-mental factors among different types of sampling channels (U-shaped, trapezoid-shaped, with and without artificial shelters) during the different irrigation periods from July 2010. The results indicate environmental factors are not significant differences among different types of sampling channels. The density of fish in the channel with artificial shelters is higher than without artificial shelters, and the relative abundance of native species is approximately higher than relative abundance of exotic species. The density of shrimp is the highest in the U-shaped channel (Without artificial shelters). This phenomenon perhaps results from the influence of turbidity analyzed by principal component analysis. The abundance of aquatic organisms is affected by water temperature, but this study detects that native species have more relative abundance in the channel with artificial shelters or adjacent the channel with artificial shelters at different water temperature conditions. We believe our study can provide some helpful information for the improvement of ecological engineering of Taiwan irrigation system in the future.