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Migration and quality of landlocked Atlantic salmon smolt: Implications for conservation and management
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences. (Naturresurs rinnande vatten)
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Atlantic salmon Salmo salar has a complex life cycle, including long migrations and habitat shifts for both juveniles and adults. As such, salmon populations are vulnerable to habitat degradation and fragmentation along their migratory routes. This makes management and conservation a complex task requiring knowledge of salmon ecology at different temporal and spatial scales. In this thesis I highlight the use of a holistic life-history based approach in the conservation and management of wild and hatchery-reared salmon in regulated rivers and lakes.

Small populations of wild-reproducing landlocked salmon and trout Salmo trutta exist in the regulated River Klarälven, Sweden. Since the 1930s, transportation of adult spawners upstream of eight dams has given the fish access to spawning grounds. The number of returning wild spawners became critically low in the 1960s, but stocking of hatchery smolts resulted in an increase in spawners that continues today. My data show that wild smolt may suffer high mortality due to multiple dam passages. To ensure viable populations of wild populations, future management should include both up- and downstream solutions that ensure connectivity in the system.

The recreational and commercial salmonid fishery are maintained by compensatory stockings, yielding annual catches of about 75 tons, and a river return rate of hatchery fish of about 1%. As a large portion of the stocked smolts does not survive downstream migration to the lake, there has been discussion about the quality of the stocked smolt and about stocking strategies. Based on my studies, producing hatchery smolts more closely resembling wild-born conspecifics should result in reduced loss rates. I suggest changes in the hatchery and stocking procedures to increase the survival of stocked smolts. The results of my research should be applicable to other regulated systems, particularly those with mixed stocks of wild and hatchery salmonid populations.

Abstract [en]

Atlantic salmon Salmo salar has a complex life cycle, including long migrations and habitat shifts for both juveniles and adults. As such, salmon populations are vulnerable to habitat degradation and fragmentation along their migratory routes, which make management and conservation a complex task requiring knowledge of salmon ecology at different temporal and spatial scales. In this thesis, I highlight the use of a holistic approach in the conservation and management of wild and hatchery-reared salmon in regulated rivers and lakes.

Small populations of wild-reproducing landlocked salmon and trout Salmo trutta exist in the regulated River Klarälven, Sweden. Since 1930, transportation of adult spawners upstream of eight dams has been done to give the fish access to the spawning grounds. My data indicate that a large proportion of the wild smolts are lost due to multiple dam passages, and future management should include both up- and downstream solutions, ensuring connectivity in the system. The fishery in Klarälven and Lake Vänern is maintained by compensatory stockings, yielding catches of about 75 metric tons and a river return rate of stocked fish of about 1%. I suggest changes in the hatchery and stocking procedures to increase the survival of stocked smolts.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014. , 43 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:29
Keyword [en]
acoustic telemetry, hatchery, life history, migration mortality, regulated rivers, Salmo salar, salmon, smolt, trout
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-31980ISBN: 978-91-7063-561-8 (print)OAI: oai:DiVA.org:kau-31980DiVA: diva2:714124
Public defence
2014-06-05, Erlandersalen, Universitetsgatan 2, Karlstad, 10:15 (English)
Opponent
Supervisors
Available from: 2014-05-15 Created: 2014-04-25 Last updated: 2016-08-16Bibliographically 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
3. Effects of feed quality and quantity on growth, early maturation and smolt development in hatchery-reared landlocked Atlantic salmon Salmo salar
Open this publication in new window or tab >>Effects of feed quality and quantity on growth, early maturation and smolt development in hatchery-reared landlocked Atlantic salmon Salmo salar
2014 (English)In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 85, no 4, 1192-1210 p.Article in journal (Refereed) Published
Abstract [en]

The effects of feed quality and quantity on growth, early male parr maturation and development of smolt characteristics were studied in hatchery reared landlocked Atlantic salmon Salmo salar. A 2x2 factorial design was used, with two levels of feed rations and lipid content of the feed. The fish were reared from first feeding until release in May the second year. At the end of the experiment salmon fed high rations, regardless of lipid content, grew the most, whereas salmon fed low lipid feed with low rations grew the least. In addition, fish fed low lipid feed had lower body lipid levels than fish fed high lipid feed. Fish from all treatments showed some reduction in condition factor (CF) and lipid levels during their second spring. Smolt status was evaluated using both physiological and morphological variables. These results, based on Na+, K+-ATPase (NKA) enzyme activity, saltwater tolerance challenges and visual assessments, were consistent with each other, showing that salmon from all treatments except the treatment in which fish were fed low rations with low lipid content, exhibited characteristics associated with smolting at two-years of age. Smolting was mainly affected by feed rations; fish fed higher rations experienced enhanced smolting. Sexually mature male parr from the high ration, high lipid content treatment were also subjected to saltwater challenge tests, and were found to be unable to regulate plasma sodium levels. Low feed rations noticeably reduced the proportion of sexually mature male parr, while there was no difference related to lipid content of feed. Fish fed low rations with low lipid content exhibited the highest degree of severe fin erosion.

Place, publisher, year, edition, pages
Oxford: Blackwell Publishing, 2014
Keyword
lipid content; Na+, K+-ATPase; osmoregulation; smolt status; smolting
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31976 (URN)10.1111/jfb.12523 (DOI)000342828400013 ()25263188 (PubMedID)
Available from: 2014-04-25 Created: 2014-04-25 Last updated: 2017-12-06Bibliographically approved
4. Effects of feeding regimes and early maturation on migratory behaviour of landlocked hatchery-reared Atlantic salmon Salmo salar smolts
Open this publication in new window or tab >>Effects of feeding regimes and early maturation on migratory behaviour of landlocked hatchery-reared Atlantic salmon Salmo salar smolts
2014 (English)In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 85, no 4, 1060-1073 p.Article in journal (Refereed) Published
Abstract [en]

The migratory behaviour of hatchery-reared landlocked Atlantic salmon Salmo salar raised under three different feeding regimes was monitored through the lower part of the River Klarälven, Sweden. The smolts were implanted with acoustic transmitters and released into the River Klarälven, 25 km upstream of the outlet in Lake Vänern. Early mature males, which had matured the previous autumn, were also tagged and released. To monitor migration of the fish, acoustic receivers were deployed along the migratory route. The proportion of S. salar that reached Lake Vänern was significantly greater for fish fed fat-reduced feed than for fish given rations with higher fat content, regardless of ration size. Fish from the early mature male group remained in the river to a greater extent than fish from the three feeding regimes. Smolt status (degree of silvering), as visually assessed, did not differ among the feeding regime groups, and moreover, fully-silvered fish, regardless of feeding regime, migrated faster and had a greater migration success than fish with less developed smolt characteristics. Also, successful migrants had a lower condition factor than unsuccessful ones. These results indicate that the migration success of hatchery-reared S. smolts released to the wild can be enhanced by relatively simple changes in feeding regimes and by matching stocking time with smolt development.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2014
Keyword
acoustic telemetry, fat-reduced feed, fisheries management, migration success, smolt status, stocking
National Category
Biological Sciences Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-34005 (URN)10.1111/jfb.12522 (DOI)000342828400005 ()25263187 (PubMedID)
Note

The article was part of J. Norrgårds thesis and was still in manuscript form when the thesis was published.

Available from: 2014-10-04 Created: 2014-10-04 Last updated: 2017-12-05Bibliographically approved
5. Predation by northern pike Esox lucius on migrating hatchery-reared salmonid smolts
Open this publication in new window or tab >>Predation by northern pike Esox lucius on migrating hatchery-reared salmonid smolts
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Supplementary stocking of hatchery-reared smolts is the main method used to mitigate and compensate for lost production of Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) populations in rivers. The survival of hatchery reared smolts in nature is generally low, and predation is one explanation for this. In the River Klarälven, Sweden, approximately 175 000 hatchery reared salmon and trout smolts are annually released into the rivr approximately 25 km upstream of Lake Vänern, to where they migrate and remain until maturity. During 2006-2010 half of the released hatchery reared smolts tagged with telemetry transmitters did not reach Lake Vänern. The loss rate of smolts was higher in river reaches with shallow vegetated areas and in reaches with deep pool areas than in the dominant habitat type, consisting of intermediate depths and sandy, uniform bottom substrates. Similarly, average CPUE of northern pike (Esox Lucius) was high in the same habitats as where smolts were lost. Gut content analyses of pike showed that they fed chiefly on European smelt (Osmerus eperlanus) in April, hatchery-reared salmonid smolts in May and European river lamprey (Lampetra fluviatilis) in June. We argue that when these different energy and lipid rich alternative prey occur at high densities during their spawning periods they are probably an easily caught energetically favorable prey. Our results indicate that there may be ecological windows of opportunity for stocking hatchery-reared smolts that could increase survival in the River Klarälven.

Keyword
ecological window; habitat-specific predation; migration; opportunistic predator; salmonid management
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31979 (URN)
Available from: 2014-04-25 Created: 2014-04-25 Last updated: 2014-05-15Bibliographically approved

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