Riverflies
Riverflies, along with all other native freshwater invertebrates are an important part of the freshwater ecosystem and food chain. This webpage gives details about riverflies, their declines and how you can help.
 Stuart Crofts.bmp) |
| Iron blue mayfly (Alainites muticus) © Stuart Croft |
What are Riverflies?
Riverflies include three groups of insects; mayflies (Ephemeroptera), caddisflies (Trichoptera) and stoneflies (Plecoptera). Riverflies are at the heart of freshwater ecosystems and are a vital link in the aquatic food chain as a food source for fish and birds. They live most of their lives as larvae in freshwater habitats before emerging as adults. They are good indicators of environmental quality as they are sensitive to changes in water quality. More than 280 species of mayflies, caddisflies and stoneflies are present in Britain.
Click here for a copy of Buglife’s ‘Riverflies’ leaflet to learn more.
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| A stonefly larva (Nemoura dubitans) © Mike Hammett |
Riverfly Declines
There is strong evidence that over at least the last few decades there has been a widespread decline in the numbers of riverflies in some British rivers. The declines in riverfly numbers are of concern as their populations reflect the health of our water environment. The health of our freshwater habitats is vital for the plants, animals and people dependent on them. Many factors threaten riverfly survival, for example:
- Habitat loss. As many ponds have been lost in recent years through in-filling or draining. Modification of river channels e.g.: straightening or widening can cause the loss of important bank-side and shallow in-stream habitat.
- Pollution. Water with high nutrient levels and other pollutants in run off from farmland. Excess nutrients can also lead to large algal growths, which smother vegetation and reduce water oxygen levels making unfavourable conditions for riverflies. Toxic insecticides can be present in run off from agricultural land or from industrial sites e.g. damaging acidic runoff from conifer plantations and disused mines. The impact of insecticides is demonstrated by the fact that just a teaspoon full of cypermethrin pesticides can devastate riverfly populations for kilometers of river.
- Soil erosion. From farmland can also lead to unnaturally high levels of silt in watercourses which can smother the river bed, clogging the gills of larvae and preventing plant growth.
- Abstraction. Reduced flow levels can effect riverflies as a reduction provides less habitat for riverflies and causes pollutants become more concentrated.
- Light pollution. As artificial light can cause adults to become disorientated and attract them away from the water.
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| Yellow mayfly nymph (Potamanthus luteus) © Mike Hammett |
Rare and Threatened Species
Eight riverfly species have conservation status assigned by the Government and are listed on the UK Biodiversity Action Plan (BAP):
- Mayflies - Southern iron blue, Yellow mayfly
Stonefly - Northern february red; Rare medium stonefly Caddisflies - Small grey sedge, Window winged sedge, Scarce grey sedge, Scarce brown sedge To find out more about the eight riverfly BAP species click here.
To find out how Buglife and The Riverfly Partnership are helping to conserve the eight riverfly BAP species click here.
What can you do?
- If you are a land owner or manager read our Riverfly Summary Sheets to see where you could contribute to riverfly conservation. Find them at the bottom of the Riverfly BAP species page.
- If you are part of an Angling group why don't you get your group involved with the the Riverfly Partnerships Angling Monitoring Initiative, which gives anglers the skills to go out and monitor their rivers. The monitoring groups will also be involved in the BAP species monitoring
- Get involved in managing your local river by joining a local rivers group, contact your local Wildlife Trust office or the Association of Rivers Trusts to find existing groups - if you don't have one why don't you set one up
- Stand up for your local river through the 'Our rivers' campaign
- Make a pond as part of the Million pond project ponds are an important habitat for a number of mayfly and caddisfly species, for more on making ponds see the Pond Conservation website
- Don't dispose of unwanted chemicals carelessly - chemicals washed or poured into drains often end up in rivers and other water habitats. Follow the Environment Agency’s Pollution Prevention Guidelines: general and near water.
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| Window winged sedge (Hagenella clathrata) © Matthew Wallace |
