Conclusion

The current study recorded the ichthyofauna diversity and assessed the water quality of 36 lakes in Bangalore district, Karnataka. The order Cypriniformesis dominant in Bangalore lakes. The rapiddecline inichthyofauna diversity is noticed in Bangalore lakes due to water pollution, habitat degradation,overfishing,invasion of exotic species and climate change. A decline in the population of native species is evident due to the invasion of exotic species. The lakes of Bangalore are polluted due to the sustained inflow of raw sewage and partially treated wastewater. In the present study, PCA helped in understanding the vital physico-chemical parameters that caused changes in lake water quality. PCA of the water quality data evolved four PCs, explaining about 81.4 per cent of the total variance. The main factors affecting lake water quality are water temperature, TDS, EC, total hardness, calcium, magnesium, chloride, turbidity, BOD and COD. These factors correspond to ionic and organic pollution of lakes mainly due to the sustained discharge of untreated

or partially treated domestic sewage and industrial wastewater. The water quality index (WQI) for the 36 monitored lakes, revealed that about 56 per cent of lakes fell under very poor water quality category. Lakes such as Basavanapura, Mallathahalli and Sheelavanthakere are polluted and are with poor fish diversity and yield. This necessitates rejuvenation of lakes and arresting anthropogenic pollution sources to protect the aquatic life in lakes of Bangalore. A regular monitoring of lakes and its biodiversity is necessary to raise awareness among the community and conserve the fragile productive ecosystems.

Acknowledgments

We thank The ENVIS Division, The Ministry of Environment, Forests and Climate Change, Government of India and Indian Institute of Science (IISc) for the sustained support to ecological research.