ARSF project GB08/18: Assessing the distribution and abundance of a keystone riparian macrophyte - impacts of swan grazing and consequences for salmonid conservation. Led by: Dr. Richard Stilman, Centre for Conservation Ecology and Environmental Change, School of Conservation Sciences Bournemouth University, Talbot Campus, Fern Barrow, Poole, Dorset, BH125BB. Location: River Frome, Somerset, UK.

Submerged macrophytes can prove difficult to monitor using digital imaging. Water Crowfoot Ranunculus pseudofluitans is a keystone macrophyte in chalk streams, forming a fundamental structural component, supporting high invertebrate densities, thereby enhancing productivity to the benefit of fish populations. R. pseudofluitans grow in relatively shallow, clear water, with most biomass on or near the water surface, increasing the chances of detection using remote sensing. Several abiotic and biotic factors (e.g. shading by bankside vegetation and grazing by mute swans Cygnus olor) control R. pseudofluitans distribution. Understanding the importance of R. pseudofluitans as a major factor influencing aquatic biodiversity and as preferred habitat for fish has been pivotal in the conservation of salmonids. This project used remote sensing, existing long term datasets and new field work to map the distribution and abundance of R. pseudofluitans in a chalk stream, assess the impact of swan grazing and predict the distribution of R. pseudofluitans as salmonid habitat in order to advise river management. This was the first attempt to use remote sensing in modelling key river habitat for aquatic biodiversity of lowland rivers.