Aquatic macroinvertebrates are the very small life stage of insects that live under water. These tiny organisms are good indicators of stream health. By collecting samples of macroinvertebrates and comparing the number and species that are found, we can get a good idea about the quality of habitat in the stream. Macroinvertebrates are a food source for fish, thus the number and species that are found indicate the habitat quality and the food source abundance.