Effects of turbidity on feeding and distribution of fish

摘要: In aquatic systems, the ability of both predator and prey to detect each other may be impaired by turbidity. This could lead significant changes in trophic interactions food web lakes. Most fish use their vision for predation location can highly influenced light level clarity water environment. Turbidity is an optical property that causes scattered absorbed particles molecules. variable lakes, due seasonal suspended sediments, algal blooms wind-driven suspension sediments especially shallow waters. There evidence human activity has increased erosion leading turbidity systems. also play a role distribution fish. act as cover small reduce risk. Diel horizontal migration common lakes considered consequence either optimal foraging behaviour or trade-off between avoidance. turbid diel patterns differ since refuge affect predator-prey interactions. Laboratory experiments were conducted with perch (Perca fluviatilis (L.)) white bream (Abramis bjorkna clarify effects on feeding. Additionally, preying different types prey, pikeperch larvae (Sander lucioperca (L.)), Daphnia pulex (Leydig), Sida crystallina (O.F. Muller), Chaoborus flavicans (Meigen) used experiments. To perch, roach (Rutilus rutilus bream, field studies A clear lake compared investigate these two over 15 year study period. The feeding efficiency was not significantly affected increasing clay up 50 NTU. suggested at levels higher than Perch are probably better using Daphnia. Increase stronger effect predating plant-attached prey. main findings this thesis show when macrophytes disappear while high present. Floatingleaved provide good clay-turbid certain too complex structure refuge. results give environments. should taken into account studying migrations LIST OF ORIGINAL PUBLICATIONS 6 CONTRIBUTION AUTHORS 7