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Effects of feed quality and quantity on growth, early maturation and smolt development in hatchery-reared landlocked Atlantic salmon Salmo salar.
Karlstad University, Faculty of Social and Life Sciences, Department of Biology. (Naturresurs rinnande vatten)
Karlstad University, Faculty of Social and Life Sciences, Department of Biology. (Naturresurs rinnande vatten)
Karlstad University, Faculty of Social and Life Sciences, Department of Biology. (Naturresurs rinnande vatten)
Department of Organism Biology, Comparative Physiology, Uppsala University.
(English)Manuscript (preprint) (Other academic)
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.

Keyword [en]
lipid content; Na+, K+-ATPase; osmoregulation; smolt status; smolting
National Category
Ecology
Research subject
Biology
Identifiers
URN: urn:nbn:se:kau:diva-31976OAI: oai:DiVA.org:kau-31976DiVA: diva2:714116
Available from: 2014-04-25 Created: 2014-04-25 Last updated: 2014-05-15Bibliographically approved
In thesis
1. Migration and quality of landlocked Atlantic salmon smolt: Implications for conservation and management
Open this publication in new window or tab >>Migration and quality of landlocked Atlantic salmon smolt: Implications for conservation and management
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
acoustic telemetry, hatchery, life history, migration mortality, regulated rivers, Salmo salar, salmon, smolt, trout
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-31980 (URN)978-91-7063-561-8 (ISBN)
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

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