River pollution from a large trout farm in Norway |
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| Authors: | A Bergheim AR Selmer-Olsen |
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| Institution: | 1. Directorate for Wildlife and Freshwater Fish, 1432 Ås-NLH Norway;2. Chemical Research Laboratory, Agricultural University of Norway, 1432 Ås-NLH Norway |
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| Abstract: | The pollution loading from Øxna Bruk, a trout farm with an annual fish production of 200–250 tons, and the influence on the water quality of River Figgjo, a mediumsized watercourse, was studied. The feed used was dry pellets. The loadings were estimated to be 0.3–0.8 g N/kg fish.24h; 0.05 g P/kg fish.24h; and 1.6–4.6 g O/kg fish.24 h as BOD7 (biochemical oxygen demand, 7 days). As a result of the fish farming activities, moderate chemical alterations were registered in the river downstream of the farm at low river flow: decreased oxygen concentration (÷ 1 mg/l) and increased concentrations of total-N (+ 0.2 mg N/l), NH3 + NH4+ (+ 0.1 mg N/l), total-P (+ 0.03 mg P/l) and ortho-P (+ 0.02 mg P/l). Compared with the receiving water, BOD7 increased maximally 1 mg O/l downstream of the farm. The salmonid stocks in the river were not affected by the effluents from the trout farm. |
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