The behaviour of native eastern rainbow fish helps monitor raw water quality.

The Sydney Catchment Authority (SCA) supplies raw water to the Prospect Water Filtration Plant via the Upper Canal. To help monitor the quality of water transported along the canal, fish bio-monitoring stations installed at Broughton Pass and Liverpool Dam provide an early warning system to detect potential toxic contamination of the water.

These fish monitoring stations are now testing water flowing to Sydney from the Cataract, Cordeaux and Nepean dams which supply a fifth of Sydney's needs.

The system uses Australian native eastern rainbow fish as living biological sensors to assess water quality, by monitoring the breathing frequency of the fish. Eight fish are kept in separate compartments and individually monitored against their normal unstressed state for statistically significant changes in their behaviour.

When a pollutant enters the water supply, the respiration rate of a fish responds rapidly. The breathing frequency signal is detected, amplified, filtered and transferred to the onsite computer, and processed in real time. When a significant number of fish respond simultaneously in an abnormal manner, an alarm is triggered.

This system supplements other testing to provide ongoing, real-time water quality monitoring.

The monitoring is authorised by the NSW Department of Primary Industries and conducted in accordance with its Animal Care and Ethics Committee.