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1767882 
Journal Article 
Population Density of Brown Trout (Salmo trutta) in Extremely Dilute Water Qualities in Mountain Lakes in Southwestern Norway 
Enge, E; Kroglund, F 
2011 
1 
Water, Air, and Soil Pollution
ISSN: 0049-6979
EISSN: 1573-2932 
219 
1-4 
489-499 
WOS:000291249700040 
We have examined populations of brown trout in low conductivity mountain lakes (5.0-13.7 mu S/cm and 0.14-0.41 mg/l Ca) in southwestern Norway
during the period 2000-2010. Inlets to the lakes were occasionally even more dilute (2007;
conductivity = 2.9-4.8 mu S/cm and Ca = 0.06-0.17 mg/l). The combination of pH and conductivity
was the best predictor to fish status (CPUE), indicating that availability of essential ions was
the primary restricting factor to fish populations in these extremely diluted water qualities. We
suggest that conductivity < 5 mu S/cm is detrimental to early life stages of brown trout, and
subsequently that there are lakes in these mountains having too low conductivity to support
self-reproducing trout populations. Limited significance of alkalinity, Ca, Al, and color
suggests that effects of ion deficit apparently overruled the effects of other parameters. 
Brown trout; Mountain lakes; pH; Conductivity