Variation in winter wildfowl numbers on gravel pit lakes at Great Linford, Buckinghamshire, 1974-79 and 1984-91, with particular reference to the effects of fish removal

Published source details Phillips V.E. (1992) Variation in winter wildfowl numbers on gravel pit lakes at Great Linford, Buckinghamshire, 1974-79 and 1984-91, with particular reference to the effects of fish removal. Bird Study, 39, 177-185.
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This study is summarised as evidence for the following.

	Action	Category
	Reduce inter-specific competition for food by removing or controlling competitor species Action Link

Reduce inter-specific competition for food by removing or controlling competitor species

A controlled before-and-after study in southern England between the winters of 1984/5 and 1990/1 (Phillips 1992) found that following the removal of 6.5 tonnes of coarse fish from a gravel pit lake (17 ha) in November 1987, there was a significant increase in the average populations of mute swan Cygnus olor (3.6 individuals in 1984-1987 vs. 69.3 in 1987-91), gadwall Anas strepera (1.1 vs. 19.6), shoveler A. clypeata (4.3 vs. 36.3), pochard Aythya ferina (40.0 vs. 82.2) and coot Fulica atra (2.1 vs. 203.1). There was a non-significant increase in tufted duck Aythya fuligula population, concurrent with a general increase in the area, and no change in populations of mallard Anas platyrhynchos, teal A. crecca or wigeon A. penelope. There were no corresponding changes at a control (13 ha) lake that did not have coarse fish removed. Increases were thought to be due to increases in benthic invertebrate and macrophyte abundance.