Pierce County monitors the health of streams by determining the types and numbers of bugs living on the stream beds. The health and population of certain bugs are a great indicator if the stream is healthy or not. These bugs have a short life span so it is easy to see, over time, how the water quality has changed by checking on these bugs. Water quality scientists call these bugs "benthic macroinvertebrates." But it's fine to just call them bugs.
Scientists find the bugs using fine-mesh nets, turning over rocks in the stream beds and letting the current carry the bugs into the nets. These samples are sent to a lab for testing.