All insects are invertebrates, invertebrates are animals without backbones. Whilst bacteria, algae and other water plants form the basis of the food chain in the river, invertebrates can be herbivores, so low down the food chain – such as daphnia or snails- or predators such as caddis-fly larvae, spiders, dragonflies or crayfish. Almost all invertebrate species can be food sources for vertebrates such as frogs, fish and birds
Because invertebrates form such a huge portion of the food chain, their presence and abundance or absence determines the overall composition of the river wildlife and is sensitive to the chemical composition and purity of the water. The invertebrate species that populate a clean river where dissolved nutrients, poisons and suspended particles are at a low level will be quite different from a polluted, murky stream. Also, different invertebrate species will be found in the main stream of the river from in the ponds and the brooks and ditches that feed into it. We use this to help us to understand our river when we sample the in channel invertebrates. You can get involved with this by volunteering with us.
This is so important that the Conservation Trust is carrying out invertebrate counts as part of its river water monitoring and casual observations by people who visit places on the river regularly can be very important in judging the health of the Thame. We do this by training our volunteers as riverfly surveyors, if you would also like to get involved then please get in touch here.
Riverflies refer to those invertebrates that spend some of their lifecycle in the water and some out of the water. Examples include mayflies, caddisflies and alderflies.
There are many other insects that reside on our rivers, ranging from those that live in the water, such as water scorpions, to the 1000s of species on the river banks trees surrounding the river. These insects may full depend on the river, or may just happen to be living next to it, but form an incredibly important part of our food chains and webs.