| Summary: | Master's thesis in Coastal ecology (BIO501) Both Atlantic salmon (Salmo salar) and Brown trout (Salmo trutta) spawn in freshwaters, and availability to water courses of good water quality is of great importance for the Salmonidae populations. The industrial revolution introduced release of considerable amounts of sulphur and nitrogen taken up by the environments, including aquatic habitats. Through the 20thcentury, the pH levels dramatically dropped while levels of toxic aluminium rose in the freshwaters. The acidic and toxic waters strongly affected the salmon populations, and several of the stocks of south Norwegian rivers were eliminated. The trout, however, have managed the decrease in water quality better and have remained in the water courses. The awareness surrounding the polluting releases lead to strict, industrial restrictions as well as researching on different methodologies for improving the ecological conditions. Through this research it was found that adding limestone to the waters increased the pH levels, and national liming projects were established in the mid-1990s. It has been noticed improved water quality, and increased salmon stocks in the traditionally viewed salmon rivers.
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