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Aquatic Insect Sampling

Our Watershed Monitoring Specialist explains how insects can tell us how clean our rivers and streams are, and how he collects samples. Benthic macroinvertebrates (BMI) are small animals that can be seen with the naked eye and have no backbone. These animals include worms, snails, mussels, leeches, crayfish as well as the immature life stages of insects that​​ live among the stones, logs, sediments and aquatic plants on the bottom of streams, rivers and lakes. BMI can live in streams for up to three years. During this time, they are exposed to the full range of water quality conditions in the stream. By monitoring them, NVCA can evaluate stream health over time. Some species require excellent water quality to survive while others are quite tolerant of pollution. By looking at the different species at a site, we can identify whether stream health has been good, fair or poor over their lifespan. Since BMI are at the bottom of the food chain, their community responds quickly to changes in stream health conditions.​