Some are intolerant of any pollution and some are quite tolerant. They are important links in the food chain, being an intermediate link between higher and lower feeding levels by providing a source of food for fish, birds, amphibians, reptiles and other macroinvertebrates. There are many types of macroinvertebrates that live along the stream bottom. Since each type has a different degree of tolerance for pollution, their presence or absence can be an indication of the health of the stream. They can be relatively easy to collect and give us a rather timely indication of the overall health of the stream.
Most aquatic insects spend the greater part of their lives as larvae.
It is this stage that is most commonly found in the stream bottom. They inhabit all types of stream habitats such as riffles, runs, and pools. To find the most diverse population, riffles would be the best place to look, as they are the most oxygen-rich. Collecting Macroinvertebrates There are several ways of collecting macroinvertebrates. You can use a sampling net or a kick net and approach a riffle from downstream, placing the net at the downstream edge and sampling from an area of about one square meter.