Fish in freshwaters of the world. Because freshwater systems often act as a sink for ... fish back into the population, the local proliferation of pest fish species, and clear ...
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THE WATER RESOURCE
Human caused Impacts in freshwater fish
Institute of Limnology Dr. Raúl A. Ringuelet
Florencio Varela, Buenos Aires, Argentina
Nature organizes life in ecosystems, communities of organisms and the environment functioning together as a whole. A pond or a coral reef is good examples.
Surface waters sustain freshwater biodiversity (FB) and ecological functions (EF) while serving for human needs.
FB benefits: Fisheries, Aquaculture, Recreation, Crops, Medicines. FB importance: 25 % of Phyla are found in freshwaters. 40 % of the fish are from freshwaters.
Geographic distribution of organisms is uneven. For fish species from temperate regions it is lower than for tropical regions. Three richest areas: northern South America, central Africa and Southeast Asia (RAINFORESTS).
Threats to FB: habitat loss (agriculture, forestry, dams and urbanizations), Pollution, Introduction of exotic species and over harvesting. Main effects are responsible for modification of hydrological cycle. Erosion, flooding, siltation.
EF from different processes: i.e. Nitrogen fixation, habitats, oxygen generation, and recycling of nutrients.
Chemical criteria, Laboratory toxicity bioassays and Environmental effects monitoring.
At those sites where pollution impacts are known to exist, one may observe changes in a number of biological and chemical indicators of pollution stress. Less obvious is as the presence of a number of potentially serious impacts on fish populations. Such observations included the complete absence of a keystone fish species, complete failure to recruit young fish back into the population, the local proliferation of pest fish species, and clear signs of over fishing. Recent research has led to the hypothesis that thermal pollution, or elevations from natural temperature, could have dramatic effects on biodiversity because these changes greatly favour a number of warm water pest species.
Integrity to maintain adaptive communities with biological or functional organizations comparable to natural unpolluted waters of the area.Thank you for your attention.