Assessing crucial stress on life cycle of fish in suburban streams

To assess crucial stresses to fish survival in suburban streams, a Life Cycle Risk Assessment (LCRA) was developed and verified by comparing with field survey results. In LCRA, 8 stresses produced by human activities were taken into consideration, referring to the literature. Field survey was conducted over 2 years to identify the present existence and distributions of fishes in 3 streams, which have different pollution levels and morphologies. Field survey results demonstrated that species of fishes and their populations were different in 3 streams and varied with location. Crucial stresses frequently identified by the LCRA were depletion of dissolved oxygen (DO), disappearances of habitats (e.g. deep and shallow), disappearance of spawning area, and existence of obstructions in the streams. Furthermore, most LCRA results regarding existence or non-existence of 15 fishes at 7 different sites were fairly in good agreement with field survey results. From these results, we concluded the present LCRA would be a useful tool in assessing crucial stress as well as in predicting fish species that are able to survive in streams.