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Landlocked Atlantic salmon Salmo salar L. and trout Salmo trutta L. in the regulated River Klarälven, Sweden: Implications for conservation and management
Karlstad University, Faculty of Social and Life Sciences, Department of Biology. (Naturresurs rinnande vatten)
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Conservation and management of migratory salmonids requires an understanding of their ecology at multiple scales, and a holistic view, including assessment of historical and present anthropogenic impacts. In the regulated River Klarälven, with 11 hydropower dams, populations of landlocked Atlantic salmon Salmo salar and migratory brown trout Salmo trutta have declined due to human activities. Maintaining viable populations of salmon in the River Klarälven has high priority, given there are fewer than 10 native stocks of landlocked salmon in Europe. To date, natural smolt production has been maintained by collecting and transporting spawners past eight hydroelectric plants in the river, where they are released to spawn. No functioning fish passage facilities are available that allow the fish to return to the lake. To evaluate the situation for landlocked salmon and migratory trout in Lake Vänern and the River Klarälven, an analysis of catch and river return data, based on data sets covering time periods from 15 to 200 years, was performed. In addition, the loss rates and behavior of downstream-migrating wild salmon smolts as they swam past eight power stations in the regulated River Klarälven was quantified.

For the migration study, wild salmon smolts were tagged with acoustic transmitters, and the smolts were monitored as they swam along a 180 km long river segment, including eight dams, with regulated and unregulated stretches. The loss due to HEP passages was estimated to be 76%, which contrasts with the 8% loss along unregulated control stretches. Kaplan-Meier estimations showed that only 16% of the smolts passed all eight dams. Migration speed was 83% lower along regulated stretches than along unregulated stretches, and migration speed at regulated stretches was dependent on fish size, with large fish moving slower than small fish.

The analysis of historical data showed that annual returns of wild salmon are less than 3% of what they were at the beginning of the 19th century. Returns of wild trout are even lower, with just some 30 fish caught annually. Lack of basic ecological information, as river return and fisheries catch rates, estimates of wild smolt production and survival, and releases of hatchery-reared fish, complicate an effective management of these unique populations. There is need for coordination of present and future research, monitoring, and restoration strategies. In this thesis I identify some measures to improve the status of the River Klarälven salmon and trout that should be of broad interest to resource and fishery managers.

Place, publisher, year, edition, pages
Karlstad: Karlstad University , 2011. , 26 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2011:53
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-8523ISBN: 978-91-7063-389-8 (print)OAI: oai:DiVA.org:kau-8523DiVA: diva2:447500
Presentation
2011-11-25, Erlandersalen, 11D 227, Karlstad, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-11-23 Created: 2011-10-11 Last updated: 2011-11-23Bibliographically approved
List of papers
1. Conservation of endemic landlocked salmonids in regulated rivers: a case-study from Lake Vänern, Sweden
Open this publication in new window or tab >>Conservation of endemic landlocked salmonids in regulated rivers: a case-study from Lake Vänern, Sweden
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2012 (English)In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 13, no 4, 418-433 p.Article in journal (Refereed) Published
Abstract [en]

Conservation of migratory salmonids requires understanding their ecology at multiple scales, combined with assessing anthropogenic impacts. We present a case-study from over 100 years of data for the endemic landlocked Atlantic salmon (Salmo salar, Salmonidae) and brown trout (Salmo trutta, Salmonidae) in Lake Vänern, Sweden. We use this case-study to develop life history-based research and monitoring priorities for migratory salmonids. In Vänern, small wild populations of salmon and trout remain only in the heavily regulated Rivers Klar (Klarälven) and Gullspång (Gullspångsälven), and commercial and sport fisheries are maintained by hatchery stocking. These populations represent some of the last remaining large-bodied (up to 20 kg) landlocked salmon stocks worldwide. We found that one of four stocks of wild fish has increased since 1996; the other three remain critically low. Hatchery return rates for three of four stocks appear stable at roughly 1% and annual fisheries catch is roughly 75 metric tons, with an estimated 7.5% of hatchery smolts being recruited to the fishery; this also appears relatively stable since 1990. Our analysis reveals much uncertainty in key data requirements, including both river return and fisheries catch rates, estimates of wild smolt production and survival, and hatchery breeding and genetics protocols. These uncertainties, coupled with a lack of information on their riverine and lacustrine ecology, preclude effective management of these unique populations. We conclude with a framework for a life history-based approach to research and monitoring for Vänern salmon and trout, which should be applicable for all endemic, migratory salmonid populations.

National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-8799 (URN)10.1111/j.1467-2979.2011.00437.x (DOI)000310273500004 ()
Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2017-12-08Bibliographically approved
2. Multiplicative loss of landlocked Atlantic salmon Salmo salar L. smolts during downstream migration through multiple dams
Open this publication in new window or tab >>Multiplicative loss of landlocked Atlantic salmon Salmo salar L. smolts during downstream migration through multiple dams
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2013 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 29, no 10, 1306-1317 p.Article in journal (Refereed) Published
Abstract [en]

Relatively little is known about the downstream migration of landlocked stocks of Atlantic salmon Salmo salar L. smolts, as earlier migration studies have generally focused on upstream migration. However, in watersheds with many hydroelectric plants (HEPs), multiplicative loss of downstream-migrating salmon smolts can be high, contributing to population declines or extirpations. Here we report the results from a study of wild landlocked Atlantic salmon smolts in the River Klaralven. Salmon smolts, tagged with acoustic transmitters, were released at different locations and followed as they passed 37 receivers along a 180-km-long river segment, including eight dams as well as free-flowing control stretches. We found that 16% of the smolts successfully migrated along the entire river segment. Most losses occurred during HEP passages, with 76% of the smolts being lost during these passages, which contrasts with the 8% smolt loss along unregulated control stretches. Migration speed was 83% slower along regulated stretches than along unregulated stretches. The observed lower migration speed at regulated stretches was dependent on fish size, with large fish moving slower than small fish. Discharge affected migration speed but not losses. As previously shown for anadromous populations, our study of landlocked salmon demonstrates similar negative effects of multiple passages of HEPs by downstream-migrating smolts. On the basis of this and previous migration studies, we advocate using a holistic approach in the management and conservation of migratory fish in regulated rivers, which includes safe passage for both upstream- and downstream-migrating fish. Copyright (c) 2012 John Wiley & Sons, Ltd.

Place, publisher, year, edition, pages
John Wiley & Sons, 2013
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-8801 (URN)10.1002/rra.2616 (DOI)000328420900009 ()
Available from: 2011-11-23 Created: 2011-11-23 Last updated: 2017-12-08Bibliographically approved

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