Whilst BART are out and about river dipping we often see freshwater shrimp (Gammarus) with these bright orange spots in their bodies – a sign of a spiny headed worm parasite. The Environment Agency are now asking for anyone who finds these shrimp with parasitic spots, either whilst Riverfly monitoring or playing about in streams, to send them in to the details below.  This is an exciting project and we are looking forward to seeing the results! Thank you in advance for your help.


A project is underway to establish the distribution of a fish parasite that uses the freshwater shrimp Gammarus pulex as an intermediate host. The parasite we are interested in is a spiny-headed worm called Pomphorynchus. It causes the shrimp Gammarus pulex to develop either single or multiple orange spots in the body, like those in the picture above. These spots increase the chances of the shrimp being eaten by a fish, completing the life cycle of the parasite.

If you find any shrimps like these during your river surveys, please let us know. If possible, put a small number of shrimps into a small container with some wet tissue and send them to us at the address below. Please include the name of the river and either a grid reference or the name of the nearest town. Should you require any containers sending to you, please let us know.

We are hoping to obtain samples of shrimps from as many rivers as we can throughout England and Wales and even a single shrimp can help provide some very useful information. Many thanks!


Please send samples to: Hannah Bradley

Environment Agency, National Fisheries Laboratory

Bromholme Lane



PE28 4NE


If you have any queries or would like more information about this project, please contact: hannah.bradley@environment-agency.gov.uk.