The purpose of this study was to evaluate ecosystem health effect in the physiological levels, based on ethoxyresorufin-O-deethylase (EROD) and total oxyradical scavenging capacity (TOSC) assays using sentinel fish species. We collected fish samples of Zacco platypus in May 2008 from 3 sampling sites including upstream, midstream, and downstream of the Gap Stream. EROD activity was averaged 4.54 in the downstream, 2.7 fold higher than upstream and indicated that stream condition was degraded along with longitudinal gradient from up to downstream. Downstream, especially was significantly increased (p < 0.01) so that indicated various pollutants including nutrient enrichment and toxicant exposure from the point sources, wastewater treatment plant and industrial complex may impact to the stream condition. In the mean time, TOSC assays showed higher in the midstream than other sites, but the values were not significant, compared to the previous report on oxidative stress. Overall results indicated that our approaches applying two biomarkers can be effectively used for diagnosis of the physiological levels in an integrative stream health assessments and can be applied as useful pre-warning techniques as a biochemical alarm system of organic pollutions.