How do chalk stream fish respond to flow and habitat restoration?

At the WTT Annual Get Together earlier this year, I had the pleasure of bumping into a former MSc student of mine, Simon Whitton, who now works at Affinity Water and is collaborating with colleagues at Cranfield University, supervising PhD students of his own; a perfect opportunity for another guest blog or four! Since abstraction and chalk streams have hit the headlines repeatedly and this year especially, we should follow Mickaël's progress with interest (and that of Jess Picken too)....

Chalk streams are highly important ecosystems and are a fundamental component of the landscape in the south and east of England. They are hotspots of ecological diversity and support important fisheries for trout and dace amongst others. However, the water that feeds chalk streams originates from groundwater, which is under increasing pressure from abstraction to supply our expanding urban populations. This conflict puts chalk streams squarely in the sights of environmental regulators and water companies as they try to find the best ways to preserve the ecology and the water supply. Hence, my project is sponsored by Affinity Water, and the Environment Agency, and is a part of Cranfield University’s Industrial Partnership PhD studentship programme.

My research aims to investigate the effect of habitat restoration and flow restoration on fish communities. To do this, I am using a broad set of techniques to monitor hydromorphological change (river habitat change) and biological change with a specific focus on fish communities. My study sites are on the rivers Beane and Mimram.

To put the information gathered from my field studies into context, a set of reference sites on six chalk streams has been chosen: Misbourne, Chess, Gade, Ver, as well as elsewhere on the Mimram and Beane. Data collected previously on the fish community and habitats of these rivers is being used as a baseline against which future change will be assessed.

The ultimate aim is to provide river managers with evidence on the links between fish, river flows and physical habitat. Information on how fish (and particularly coarse species) use habitats, will help us to decide which types of features to bring back into the river (plants, riffles, etc) to encourage colonisation of sites or to sustain fish populations and ensure resilience in the future.

At the moment, we have completed a first cycle of surveys. At Singlers Marsh in Welwyn, the public was amazed to see fish being caught in the stream, from small bullhead up to a nice-sized brown trout.

We have faced some challenges along the way, such as finding one of the rivers chosen for our survey to be dry in its upper reach. Unfortunately, this situation appears to have been all too common this year, as reported elsewhere on the WTTblog (e.g. Long term abstraction and fishery collapse). While I could not say much about the fish community at the time (cows were more prevalent), I could still assess the dry reach for potential habitat features which are likely to ‘re-emerge’ as the flow returns.

From the techniques we have chosen to monitor our sites, some of the most interesting use cameras to capture images from fixed points both above and below water; this will be the focus of another blog in the near futur

Further information about this specific project and about river-related research from my colleagues at Cranfield University can be found on the following websites:

Or please contact me for more information

Mickaël Dubois (, @Mickael_bio_be)