As part of our monitoring strategy for many projects we collect invertebrate samples. Different types of macro invertebrates are more tolerant to changes in water quality parameters than others. This allows us to determine changes in water quality. For instance if there is a pollution incident that reduces the dissolved oxygen content of the water then it is unlikely that stoneflies will be present. However what may be left behind in a reduced dissolved oxygen scenario is midge larvae which are capable of inhabiting a wide variety of habitats. Invertebrates act like a barometer of water quality.
This coupled with fish population monitoring allows us to monitor and track changes in these animal communities and potentially understand what is causing these changes are happening.