A note on freshwater shrimp

We’re aware there are a few conflicting ideas floating around about which species should be counted in the ‘Freshwater Shrimp’ category when submitting Riverfly survey results, so we’d like to clear things up for our monitors and co-ordinators.

In the majority of cases, the shrimp that you find in your samples will be the genus Gammarus (above). It is possible that you may encounter others. For example, in some parts of the country and at sites with low flow, Crangonyx (below) may be found. As monitors are not trained to be able to differentiate these from Gammarus, we are not expecting monitors to exclude these from their count. We have removed the subheading of ‘Gammarus’ from the next edition of the printed guide, and from Cartographer, to make this clear.

However, please do try to exclude the invasive non-native species Dikerogammarus villosus, also known as killer shrimp, and Dikerogammarus haemobaphes (below), also known as demon shrimp, from your count. From now on, training packs will contain an information sheet about demon shrimp — if you were trained before this was added, you can view it here.

If you suspect you have found one of the Dikerogammarus species, make sure you take a close-up photo if possible, so someone can verify your sighting. When you input your survey results on Cartographer, there is a ‘Notes’ box where you can mention invasive non-native species, and you can upload up to two photographs as well. Please also report them to INNS Mapper. Co-ordinators, please keep your ecology contact informed of invasive non-native species sightings.

In summary, the ‘Freshwater Shrimp’ category in Riverfly surveys isn’t just for Gammarus — count any shrimps you find, unless you recognise them to be killer shrimp or demon shrimp.

And, to prevent the spread of Dikerogammarus and other invasive non-native species, remember to follow Check, Clean, Dry procedure.

If you have any questions, please e-mail info@riverflies.org.