Differences in fish assemblages in protected and non-protected freshwater streams in a tropical urbanized country

The importance of protected areas on native fish assemblage in freshwater streams is not well understood. We investigated differences in fish communities and environmental factors in 38 protected and non-protected streams in Singapore. Eight hundred and twenty-eight individuals from 33 species were documented (with one new record), with natives comprising 70.5% of all species. A canonical correspondence analysis found that protected streams were defined by lower pH, temperature, and conductivity, higher cross-sectional areas and water velocity and permit requirements, which was supported by a correspondence analysis that also found more native species in protected streams. Overall abundance of fish was higher in non-protected streams but consisted of higher proportions of non-native species. Conditional inference tree analysis of abiotic and biotic factors across sites found that pH and stream velocities predicted for higher native fish species richness. As such, protected streams with their limited accessibility to the public, low pH and faster flow regimes are more likely to maintain native fish assemblages. This reiterates the importance of maintaining protected areas that help conserve freshwater fish communities, especially in Singapore and other parts of Southeast Asia where there is high rate of habitat loss, modification and development.