Earlier this month our President, Dr Cyril Bennett, and Senior Vice President, Will Tall, converged on a secret location close to the Wandle with one thought in mind – the re-introduction of the iconic Mayfly.

As Cyril is an expert in this field, and gained his PhD in 1996 for his work on the successful re-introduction of Mayfly on the South Wey, he took the lead on this project.

Ripe for stripping
Ripe for stripping


Cyril spent the last weeks of May snatching female Mayfly from the wind as they returned to the River Avon to lay their eggs, stripping them of their precious cargo and then incubating the fertilised eggs in tanks of tap water to maintain bio-security.  We didn’t want any Avon nasties to find their way to the Wandle.





When Cyril judged the eggs were just about ready to hatch we rushed to the river to install a fly board carrying nearly 8 million Mayfly eggs.



Each slide carries one million eggs

Each slide carries one million eggs. We did try this in 2010 with approximately 200,000 Mayfly eggs spread across a number of sites further downstream, with no real result, apart from the reported sight of an adult Mayfly in Ravensbury Park.

The cream patches are mayfly egg masses
The cream patches are mayfly egg masses
A rather modest affair

This time we have concentrated all our efforts on one site and with an 7-8 million egg surge we are feeling pretty confident that it will work – especially as Cyril has already hatched several thousand Mayfly eggs in Wandle water and they are thriving.

Wandle Mayfly Hatching Eggs










This is a very exciting project, and if it comes off it will be a landmark in the rejuvenation of the River Wandle.  We hope to find the first mayfly nymphs in our monthly Riverfly Monitoring kick samples this autumn.

Until then I ask you to keep your fingers and toes crossed.

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