Jostein mosby (IMAGE) Norwegian University of Science and Technology Caption After being strongly impacted by industrial pollution, the Otra River has once again become a watercourse with salmon. But Jostein Mosby of the Otra salmon fishing association is worried about this year's salmon fry. The Otra is one of many Norwegian rivers that are exposed to water flow fluctuations as a result of how hydroelectric power plants are operated. Credit Photo: Hilde Mosby Usage Restrictions Credit must be given to the creator. Only noncommercial uses of the work are permitted. License CC BY-NC Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.