Rivers are home to a whole range of creatures, from water beetles to otters, and everything between. You might not notice it but our rivers are teeming with life, with a whole underwater insect world lying just below the water’s surface.
River insects, also known as riverflies or invertebrates, are a vital part of our rivers. These tiny insects are the basis of the river food chain. They provide food for other creatures such as fish, amphibians, birds, and some mammals, who wouldn’t exist without the food source these insects provide. River insects also help to regulate water quality by breaking down organic matter which enters our rivers.
Interestingly river insects can also be used as a quick and accurate way of assessing water quality and river health. River insects are very sensitive to pollution, with some species being even more sensitive than others. By taking kick samples and counting how many of each species are present we can see how healthy our rivers are. If the samples are taken regularly then the results can be used to track river health over time. Then, if there are sudden dips in insect numbers, we can often trace this back to a pollution incident somewhere on the river and use our knowledge to prevent further pollution incidents.
The three main groups that we look out for are mayflies, caddisflies, and stoneflies, but there are thousands of species of river insects in our catchment, with 51 different mayfly species alone! Their small size and subtle differences mean they are very hard to identify, but here at the Trust we are lucky enough to have a few river insect experts.