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Title: Report on the millennium chalk streams fly trends study : a survey carried out in 2000 among 365 fly fishermen, fishery owners, club secretaries and river keepers
Author: Environment Agency South West Region
Document Type: Monograph
Questionnaire results from 365 respondents were analysed to ascertain what observed changes had occurred in fly populations in southern chalk rivers over past decades. Detailed analysis and interpretation of the data centred on ascribing 'abundance scores' to the six reporting levels of fly hatches ranging from good hatches frequently' to absent'. The results indicate that the overall abundance score in 1999 has fallen to 34 compared with the maximum score of 100 in the last decade before the War. The main part of the reduction has occurred over the last 20 years. After 1980, the abundance score fell steeply (by about three-fifths) over the next two decades to the end of the Millennium. The most precipitous fall was over the most recent period, the 10 years between 1989 and 1999, with the abundance score falling from 65 in the 1980s to 34 in 1999. It is possible to benchmark the decline in aquatic fly abundance against the declines in populations of birds and butterflies that have recently been revealed by large-scale surveys. Between 1972 and 1996, there was an average 40% population decline among the 20 species included in the Government's Farmland Bird Index. Over this period, the tree sparrow declined 76%, the skylark 75%, the corn bunting 74%, and the turtle dove 85%. Numbers of swallows specifically are believed to have declined because of steep falls in the number of available insects. Joint research by the Butterfly Conservation Charity and The Centre for Ecology and Hydrology based upon 1.6 million sightings by 10,000 volunteers shows that a third of butterfly species have suffered falls in numbers greater than 50%, and many other species have fallen by more than 20%. The high brown fritillary has declined by 77% since the 1970s, the wood white by 62%, the pearl-bordered fritillary by 60% and the marsh fritillary by 55%. Further surveys have been published giving details of declines in other animal populations, such as bumble bees, water voles and dormice. In reporting the changes in bird and butterfly abundance, the authors of these surveys and other commentators have drawn attention to the growing body of evidence linking the declines with recent agricultural intensification and changes in practice, as well as with urbanisation and loss of habitat, especially wetland habitat.
Publisher: Environment Agency
Publication Date: 2001
Publication Place: Exeter
Subject Keywords: Chalk streamsRiver fisheriesInvertebratesFlyfishingHatchingPredationEcological indicatorsData analysis
Geographic Keywords: EA South West
Extent: 21
Total file downloads: 130

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