Avoidance reactions of Mugil so-iny, Lateolabrax japonicus,Tilapia mossambica and Penaeus Orientalis to sewage and some of its constituents. were investigated using channeled avoidance trough. The results suggest that organism avoided markedly mixed sewage (industrial waste water and domestic sewage). Avoidance indexes of organisms to three organic pollutants were shown in table 1. The results showed that avoidance indexes of estuarine organisms to three organic pollutants were significant. However, the avoidance reaction of the fish was more sensitive than that of the crustacean.