Aquatic insects are used as model organisms for assessing the health status of lenthic or lotic ecosystems. Biomonitoring using entomological indicators is one of the widely accepted tools to analyze the impacts of sewages in aquatic environment. The present study was aimed to assess the health status of a semi urban river system, Killiyar using entomological indicators. Season wise sampling of aquatic insects was done at four selected segments according to the rapid bioassessment protocol recommended by Environmental Protection Agency. The present study could identify 29 families of aquatic insects for screening the levels of pollution in Killiyar. Family Biotic Index (FBI) showed that there was a remarkable variation in water quality along the river. Hilsenhoff’s family biotic index obtained for river origin was in the range 4.40 - 5.02 indicating excellent water quality. High value of family biotic index, least occurrence of intolerant groups and dominance of tolerant taxa in the midstream and downstream segments showed that increased contamination of water by various sources. Immediate attention is needed to cease the degradation of this precious ecosystem.      Keywords: Aquatic insects, Biomonitoring, Family Biotic Index, Killiyar, Water pollution

Fishes are continuously exposed to the microorganisms present in water and in the sediment. The present study was attempted to screen the pollution indicator bacteria in the tissues of an estuarine fish Mugil cephalus from Kureepuzha Backwater, a part of Ashtamudi Lake. Total heterotrophic bacteria, total coliform bacteria, Escherichia coli and fecal streptococci were enumerated from the fish tissues using standard microbiological procedures. Comparison of bacterial count in the skin, gill and gut of Mugil cephalus revealed that highest count of indicator microbes were found in the skin followed by the gill and gut of fish from all sites except site 4. Fishes from site 4, they show bacteria predominantly in the gut. Two way Anova showed a significant difference in microbial count between sites and between tissues except Total heterotrophic bacteria and fecal streptococci between sites. Results of physico chemical parameters also supports that the anthropogenic activities accumulated in the study area, causing the disruption of hydrological quality of Lake and thus increases the load of detrimental microorganisms. Hence it is recommended that good processing of fish such as washing, scraping scales, removal of gills and gut contents and proper cooking help to reduce microbial pathogen in fish body and make it safe for consumption.