Conditions for effective biomanipulation; conclusions derived from whole-lake experiments in Europe |
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Authors: | Benndorf Jürgen |
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Institution: | (1) Department of Water Sciences, Laboratory of Hydrobiology, Dresden University of Technology, Mommsenstr. 13, DDR-8027 Dresden |
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Abstract: | Since indirect effects, feedback mechanisms and time lag play an important role in top-down manipulated food webs, conclusions
regarding the reliability of biomanipulation as a management tool should be derived only from whole-lake studies, the results
of which were followed for at least three to five years. There are only a few experiments and applications of that type from
which the following conclusions can be drawn: (1) Food web manipulation should be combined with resource limitation measures
(nutrients or light) if a ‘biomanipulation-efficiency threshold of the phosphorus loading’ is exceeded. (2) The critical biomass
of undesirable fish shows a very wide range of variation (20–1000 kg ha−1) and depends on several factors, like species and age of fish, total food assemblage, refugia etc. (3) The maximum possible
stability of food web manipulation is probably achieved at a biomass of undesirable fish a little below the critical biomass
rather than by extermination of these fish. (4) High piscivore diversity increases stability and reliability of food web manipulations.
(5) Various techniques of food web manipulation should be combined, except poisoning the entire fish community. |
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Keywords: | food web manipulation whole-lake experiment long-term response phosphorus loading fish water quality management |
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