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Orvis HatchWatch 2023

Mayflies have an extraordinary life-cycle. Once hatched, the winged insects emerge from the water and bring our rivers to life, skirting across the water and filling the air with action. The annual mayfly hatch is a natural phenomenon worth watching, particularly for us anglers to learn about their movements as well as their role in the wider ecology and health of our rivers.

The Green Drake Mayfly (Ephemera danica) is one of the most iconic mayflies, revered by anglers from the chalkstreams of Hampshire to the limestone lochs of Caithness. 

The species takes its common name from wings of the dun which resemble the feathers on the breast of a male Mallard duck. Its nymphs live in the gravels of lakes and rivers and take either 1 or 2 years to develop. They grow to nearly 25mm long making them one of the largest British mayfly species. The adults emerge in large numbers from the water when the Hawthorn (or Mayflower) is in bloom, typically mid April to mid May. However, adults can be found on the wing throughout the year - the earliest adult record is the 1st January!

We want to find out more about the distribution of the Green Drake Mayfly to help us understand how it is faring in light of climate change, water pollution, and other pressures on our freshwaters.

As part of our Mayfly Festival over the coming weeks, we invite you to watch the mayfly hatch closely with us as it makes its way across the UK. Visit your local rivers, watch the hatch, and capture the moment the mayflies emerge. Share your images or videos with us on Instagram, tagging #OrvisHatchWatch, or complete the form below and we will add you to our #OrvisHatchWatch map. Together, we will watch and learn. 

This brief has been provided by Craig Macadam from Buglife to support its upcoming 10-year review of river fly and mayfly numbers. Craig is Conservation Director for Buglife and National Co-ordinator of the Mayfly Recording Scheme. He has been studying mayflies for over 30 years and is particularly interested in the effects of climate change on their populations. Craig is a founder member of the Riverfly Partnership and co-chairs the IUCN Species Survival Commission Mayfly, Stonefly and Caddisfly Specialist Group.

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