Conservation of landlocked Atlantic salmon in a regulated river : Behaviour of migratory spawners and juveniles

• Main Author: Hagelin, Anna
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013) 2019
• Subjects: Atlantic salmon; conservation; migration; spawning; hydropower; competition; juveniles; brown trout; hatchery reared; fallback; delay; Biological Sciences; Biologiska vetenskaper; Lost River; Norway
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-71333

Hydropower dams represent one of the major threats to river ecosystems today. The dams block migratory routes in many rivers, which is problematic for migratory fish species. Trap-and-transport may be an alternative to fish passage solutions, as a strategy to compensate for lost river connectivity. Stocking of hatchery fish is another mitigating measure often used to compensate for reduced yields in fisheries, but also as supportive breeders in declining populations. In this thesis, I report the results from radio-telemetry studies where the behavior of migrating Atlantic salmon spawners has been investigated in a regulated river. I also studied the function and success of using hatchery fish as supportive breeders and if there are any effects of migratory timing on migratory success. Further, I evaluated upstream passage performance by Atlantic salmon and brown trout at fishways in rivers Klarälven, Sweden and Gudbrandslågen, Norway. The goal was to determine if prior fishway experience had an effect on passage success. I identified three problems associated with the current river management, namely the high incidence of fallbacks among the early migrating salmon, the negative effects of high river flow and prior experience on fishway efficacy and that the use of hatchery-reared fish as supportive breeders have little, if any, positive effect on reproduction. Finally, I examined the competitive interactions that may occur when reintroducing Atlantic salmon to areas with native grayling and brown trout. I found no evidence of Atlantic salmon affecting grayling or brown trout. Instead, Atlantic salmon were dominated by the other two species, which indicates that reintroduction of salmon may not be successful, especially if habitat diversity is constrained. Conservation and management of migratory salmonids requires an understanding of their ecology and life-histories. In the regulated river Klarälven, populations of landlocked Atlantic salmon and migratory brown trout have declined due to river exploitation. The ...