Eutrophication influences among others food supply, prey catchability, reproduction success, growth and mortality of fish. The first stages of eutrophication are favourable for many fish species. Proceeding eutrophication interferes so strongly with the environment that fish is brought in a vulnerable position: vegetation, which is a prerequisite for a number of species, disappears; oxygen depletion near the bottom affects fish food organisms; turbidity hampers catchability of preyfish and decomposition of dead phytoplankton or vegegation may especially at the end of the summer result in lethal oxygen contents. Hence at higher eutrophic levels the fish population surpasses the optimum and decreases again. These optima vary with the species; for the most important species the sequence from oligotrophic to hypertrophic is: 1. Coregonids and Salmondis, 2. pike, 3. roach and perch, 4. pikeperch, 5. bream. Hence the fish populations of very turbid hypertrophic waters are dominated by bream and pikeperch. This population will furthermore usually consist of smaller quantities of eel, smelt, ruffe and white bream. The total fish population in such a hypertrophic water is considerably larger than in a oligotrophic or mesotrophic lake. The vulnerability of the fish community, however, has increased too. In the hypertrophic situation the oxygen supply is the weak spot and every interfering negative influence, as for example sewage discharge, may have disastrous consequences. The many severe fish mortalities prove this to be a real dang...
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Climate change Research Articles published between Aug 08, 2022 to Aug 14, 2022
Aug 15, 2022
Articles Included: 5
Introduction: There is no consensus on the policies that should be seen as implicitly pricing carbon (see World Bank (2019a) for a discussion). The OE...Read More
Gender Equality Research Articles published between Aug 08, 2022 to Aug 14, 2022
Aug 15, 2022
Articles Included: 4
I would like to thank Anna Khakee, Federica Zardo and Ragnar Weilandt for their very useful comments as well as the participants of the workshop of 21...Read More
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