Riverfly Monitoring
Riverflies monitoring in Chalgrove Brook – keeping an eye on the health of our brooks
CWaCS have been keeping a keen eye on the wildlife in our brook, through monthly monitoring of the invertebrate life found there.
Members of CWaCS has received training via the Riverfly Partnership, an organisation started by anglers who together with the environment agency set up the ‘Anglers Monitoring Initiative’, a simple method of monitoring the health of a stream or river by looking for 8 key invertebrate groups. Subsequent training has been carried out by the River Thame Conservation Trust, a charity that looks after the River Thame Catchment.
The invertebrate species we monitor are sensitive to changes in the water quality, therefore as the same survey is carried out each month any drop in numbers can indicate a pollution incident upstream. This information is then passed onto the Environment Agency to take action.
To catch the sample we use a method called ‘kicksampling’, stirring up the bed of the stream to dislodge any invertebrates living there, a pond net is held downstream for 3 minutes and there is also a 1 minute hand search to turn over larger rocks. The sample is then carefully examined and the number of each species counted up.
The Chalgrove Brook has proved to be one of the best performing rivers in the Thame catchment; we have had consistent results for several years. We normally find several species of Mayfly, which spend a year living in the water to emerge on the wing for 1 day in which they mate, lay eggs and die! We also find Caddis fly larvae, who build delicate cases around themselves from small stones, sand grains or shells, and plenty of Freshwater Shrimp. In recent years we have seen an increase in small fish, since the creation of the Fish Bypass at Stadhampton. Sadly, we do see a lot of invasive Crayfish.
The Chalgrove team have now grown to the point where we are monitoring not only Chalgrove, but also Stadhampton, and the main River Thame at Chiselhampton Bridge. The data we collect goes into a national database which allows the Environment Agency and NGOs to monitor the health of our waterways across the country.
