During our most recent Citizen Science Practical training, our participants extracted a water sample, as part of the miniSASS river health monitoring process, with the aim of understanding the health of that particular river. The results lead to a very interesting discovery. The sample contained Rat-tailed maggots, small aquatic organisms found to be living in the river. Rat-tailed maggots are the larvae of the Hoverfly and due to their very unique design they are unfortunately a very good indicator of poor river health.

These organisms can survive in poorly oxygenated water thanks to their tail which acts as a respiratory tube. Also known as a telescopic breathing tube, the Rat-tailed maggots snorkel type tail allows the larva to breathe air while underwater.

What does a rat-tailed maggot signify when it comes to river health? High pollution levels, largely from sewer contamination, and the subsequent reduction in dissolved oxygen in the water are an ideal environment to the well adapted Rat-tailed maggot, one of the very few aquatic organisms that can survive in such high levels of oxygen-deprived water. As such, the presence of these unique organisms give us an unfortunate yet clear indication of the state of river we are assessing.

Next time you are doing a clean-up or any other river health related activities in your local area, look for this interesting organism and share your findings with us!

If you would like more information on our Citizen Science Practical training or would like to acquire the testing kits for your water project, please send us an email at This email address is being protected from spambots. You need JavaScript enabled to view it.