Riverfly Monitoring at Winnall Moors

River Itchen at Winnall Moors Nature Reserve © HIWWT

Learn about the monthly riverfly surveys conducted by us at Winnall Moors!

England has 85% of the world’s chalkstreams, many of which are found in Hampshire. The Hampshire and Isle of Wight Wildlife Trust are already involved in protecting, preserving and learning about these special systems. Click here to learn more about our projects with Southern Chalkstreams and Watercress and Winterbournes.

Trainee Ecologist Kate Gwynn conducting a riverfly survey at Trust site: Winnall Moors

Trainee Ecologist Kate Gwynn assisting with a Riverfly sruvey at Winnall Moors.

Trainee Ecologist Kate Gwynn has been able to do their bit for Hampshire’s chalkstreams by getting involved with the Anglers’ Riverfly Monitoring Initiative (ARMI) at Winnall Moors. The ARMI is established throughout the UK and allows severe changes in water quality to be detected using monthly freshwater invertebrate surveys.

What happens on a survey?

The surveys involve a 3 minute kick sample and 1 minute hand search taken in the same location at Winnall Moors every month. These samples are sorted on site and the numbers of 8 target groups of invertebrates are counted. Once recorded, everything is put back in the river where it was found.

What happens to this information?

The data collected from this survey is used to calculate a score based on invertebrate numbers. This score will vary seasonally as populations naturally fluctuate. However, in the event of a pollution incident, invertebrate numbers will drop below the ‘trigger level’ assigned to the river and this is reported to the appropriate environmental body.

Why is it important to monitor rivers?

Riverflies are at the heart of freshwater ecosystems. They spend most of their lives in water as larvae and as adults stay near the water to breed. This makes riverflies an essential part of aquatic food webs. If the riverflies are not doing well, this could impact on other species which rely on them as a food source.

The initiative is important for all rivers in the UK. It helps protect the water quality, deepen the understanding of riverfly populations and highlight important habitats for conservation.

Ephemera danica Mottisfont BR

Ephemera danica is a type of mayfly, also known as an upwing fly. Mayfly's are one of the groups recorded in the Riverfly surveys.  © Ben Rushbrook

We always encounter lots of other freshwater species on these surveys, including fish such as the Bullhead and Sticklebacks, as well as, damselflies and dragonflies. 

If you see us at Winnall Moors, please come over and see what we have found and talk to us about riverflies!

Bullhead fry

Bullhead fry found during a riverfly survey at Winnall Moors © Kate Gwynn

After any survey or contact with water we always follow the check, clean, disinfect and dry method. This makes sure all of our kit is clean and more importantly helps prevent the spread of invasive species and disease.