Effect of sudden increase in discharge in a large river on newly emerged Atlantic salmon ( Salmo salar ) and brown trout ( Salmo trutta ) fry

• Published in: Ecology of Freshwater Fish
• Main Authors: Saltveit, S. J., Bremnes, T., Lindå, O. R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1995
• Subjects: Ecology; Aquatic Science; Ecology, Evolution, Behavior and Systematics; Norway; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1111/j.1600-0633.1995.tb00029.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-0633.1995.tb00029.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0633.1995.tb00029.x

Abstract– Downstrcam displacement of salmonid fry due to flow increase, from 12–15 m 3 / s to >100 m 3 s , was documented in the river Suldalslåen, Western Norway. In May only fry of brown trout ( Sulmo trutta ) occurred in the drift, while from the beginning of June only newly emerged Atlantic salmon ( Sulmo sular ) were found. The maximum number of Atlantic salmon fry drifting during a single day was estimated to be 17 000 individual. Their density in the drift was higher during the night than during the day, and their appearance in the drift coincided with the predicted period of emergence. Total brown trout numbers in the drift were estimated to vary between 4000 and 16 000 per day. Fry displaced downstream from the lowermost part of the river were lost from the population. The total losses were estimated to be between 75 000 and 100 000 Atlantic salmon fry which represents between 5.6 and 11.1%) of juvenile mortality during the first year of life.