Effect of habitat improvement on atlantic salmon in the regulated river suldalslågen

• Published in: Regulated Rivers: Research & Management
• Main Authors: Raastad, Jan E., Lillehammer, Albert, Lillehammer, Leif, Kaasa, Halvard, Eie, Jon A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1993
• Subjects: Atlantic salmon
• Online Access: http://dx.doi.org/10.1002/rrr.3450080113; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Frrr.3450080113; https://onlinelibrary.wiley.com/doi/pdf/10.1002/rrr.3450080113

Abstract The River Suldalslågen, which holds a population of large Atlantic salmon, has been regulated twice for hydropower production. The first regulation occurred in 1968 and the second in 1980. Present problems include the reduced density of benthic fauna, the reduced growth rate of young salmon, the low survival of 0 + fish and the increased time required for smoltification. A programme of habitat restoration includes building a rearing channel system where water flow and the substrate can be controlled. The salmon fry are stocked in the rearing channel and in an adjacent tributary stream. The effects on macrobenthos of introduced dead organic material were also studied. Improvement of physical habitat increased the density of benthic animals, and the survival of 1 + salmon was about 30%. Experiments that included adding of 115g wheat/m 2 resulted in a threefold increase in benthic fauna compared with a control area. The largest increase in numbers was in Chironomidae in August‐September, when benthic Crustacea also showed a significant increase. An increase in macrobenthos is expected to increase the growth and survival of young salmon fry.