A ‘Before and After’ Study of the Effects of Land Drainage Works on Fish Stocks in the Upper Reaches of a Lowland River

摘要

ABSTRACTFish stocks at a site in the upstream reaches of the River Soar, a lowland river in Leicestershire, showed a marked alteration following river channel works associated with a land drainage improvement scheme. The density and standing crop of all ‘large‐sized’ fish species present showed reductions of 15–100 between a 6‐month pre‐drainage period and a 3‐month post‐drainage period. The density and standing crop of the total population were reduced from means of 0.160 fish m−2and 39.0 g m−2during the pre‐drainage period to means of 0.048 fish m−2and 9.6 g m−2during the post‐drainage period, reductions of 70 and 76, respectively. It is suggested that modifications to physical features of fish habitat, particularly the elimination of in stream cover, were largely responsible for t