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The state of the UK’s Mayfly populations

In case you missed it, here’s Richard from Orvis Stockbridge kicking off the first of our Orvis Mayfly Festival Facebook Lives, chatting with Craig Macadam, Conservation Director for Buglife and National Co-ordinator of the Mayfly Recording Scheme.

Craig and Richard cover the unique work of Buglife, mayfly distribution, pressures and how we can all get involved to support riverfly conservation.

Here’s a short summary of the topics discussed in the Facebook Live.


Buglife is the only organisation in Europe dedicated to the conservation of all invertebrates. So, everything from millipedes to mayflies, spiders to snails. Buglife covers all those species and in the UK, there are somewhere in the region of about 40, 000 species of invertebrates.

As Conservation Director, Craig oversees all the conservation work in the charity, which includes practical conservation work like habitat management, research work, advocacy and outreach activities, as well as leading on Buglife's freshwater work.

Craig took over the Mayfly Recording Scheme in the early 2000s and collated together information on mayflies from around the UK. Buglife now has around 300,000 records of mayflies across the UK.

More recently, Craig also helped with the discovery of two new species in the UK and has also undertaken reviews of British mayflies to assess their extinction risk.

So, what is the current state of the UK’s Mayfly population and why?

Over the 35 years Craig has been monitoring Mayfly, there's been “winners and losers”. In the last status review that Buglife did in 2016, there were two species assessed as regionally extinct after being recorded in the early 20th century and haven't been recorded since. Sadly, a further five were assessed as being at risk of extinction. As a result, Buglife believes we have just over 50 species of Mayfly left in Great Britain. One in ten of those is at risk of extinction.

Craig’s personal research is on climate change, and he notes that there are species like the Upland Summer Mayfly that are getting pushed further and further upstream as water temperatures increase. The species in the south of England in the chalk streams are able to spread further up the country as well. Craig notes a specific example, the Yellow Hawk, which is now found right the way up to Aberdeenshire.

However, it is not just climate change to blame, water pollution is a big issue. Whether that’s gross pollution from sewage overflows to things like pesticides and fertilizers that are applied to crops, the health and quality of our waters can affect Mayfly populations.

Non-native pressures such as signal crayfish and Himalayan balsam also change the character of the banks of the river and the invertebrate assemblies, like the Mayfly are all impacted. Finally, over-abstraction of water and changing the flow characteristics also upset that whole balance.

However, it's not all bad news.

There are some species that are increasing in their distribution and numbers. These tend to be the species that have a quicker life cycle so they can have more generations. The species with longer life cycles are not as adaptable. They've got to wait for more generations before they can adapt and where climate change is acting too fast for these species to adapt.

The Orvis Hatch Watch

Get involved in this year’s Orvis Mayfly Festival by supporting the ‘Orvis Hatch Watch.’ We’re inviting you to watch the mayfly hatch closely: visit your local rivers, watch the hatch, and capture the moment the mayflies emerge.

Share your images or videos on social media using #OrvisHatchWatch and submit the entries to the easy form on the Orvis UK website. The data will be plotted on the hatch map of the UK, so you can see the fly life on your local river.

You’re also helping the bigger picture. The data will be sent off to the Buglife team to support its upcoming 10-year review of river fly and mayfly numbers.

Together, we can watch and learn about the health of this extraordinary life cycle.

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