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- Andersson, Magdalena, et al.
(författare)
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Assessing Movements between Freshwater and Saltwater by Brown Trout (Salmo trutta L.) Based on Otolith Microchemistry
- 2024
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Ingår i: Animals. - : MDPI. - 2076-2615. ; 14:14
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Tidskriftsartikel (refereegranskat)abstract
- By analyzing otolith microchemistry, we examined the use of freshwater and marine environments by brown trout Salmo trutta L. that spawn in the Swedish River Emån and migrate to the Baltic Sea. We estimated the time juveniles spent in freshwater and the number of times the fish returned to freshwater, presumably to spawn. Twenty-six percent of the fish migrated to sea by 1 year of age. However, 13% spent less than one year in the river. Most brown trout (48%) migrated to the sea between 1 and 2 years of age. On average, brown trout, which averaged 4.4 years in age (range 3–6 years), returned to freshwater 2.3 times, and there was an inverse relationship between time spent in freshwater after hatching and the number of visits to freshwater. Our results do not support the classical life history pattern, where brown trout spend one or more years in freshwater before migrating to the sea. Here, we found evidence that part of the population leaves freshwater during their first year. While the cause for precocial migration in the River Emån is not known, our results from this permanently flowing river do not support the idea proposed for other Baltic Sea populations, where the risk of drought has been suggested to be the cause.
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| 3. |
- Bolonina, Alona, et al.
(författare)
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Strategies for mitigating the impact of hydropower plants on the stocks of diadromous species in the Daugava River
- 2016
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Ingår i: International scientific conference "Environmental and climate technologies", CONECT 2015. - : Elsevier. ; , s. 81-88
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Konferensbidrag (refereegranskat)abstract
- The Daugava River is the largest river in Latvia. Daugava Hydro Power Plants built in 1939 - 1974 are Latvia's most important renewable resource in generation of electricity. The absence of fish passage structures excludes upstream migration of diadromous species. Compensatory stocking activities are introduced annually. The need for studying alternative or additional impact mitigation measures is based on biodiversity conservation aspects and possible changes in EU legislation. The case study of solutions for improving the Daugava River connectivity is introduced and further strategies for mitigating the impact of HPP are proposed in the paper.
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| 4. |
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| 5. |
- Calles, Olle, 1974-, et al.
(författare)
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A simple management tool for planning the restoration of river longitudinal connectivity at watershed level: priority indexes for fish passes
- 2009
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Konferensbidrag (refereegranskat)abstract
- The fragmentation of the longitudinal connectivity of rivers due to man-made obstacles causes relevant impacts upon fish migrations and therefore the reopening of fish migration routes through the construction of fish passes is a key issue which should be planned at watershed level. The competent watershed Authorities need to prioritize the interventions, addressing the often limited resources to the sites where the construction of a fish pass can have the higher benefit/cost ratio. The present study was therefore aimed at identifying a simple management tool, based on already available or easily collectable data, which could support and address decisional processes in watershed planning. The proposed priority indexes for fish passes, based on obstacle characteristics, length of the potential reopened reach and fish species distribution and migratory capabilities, were tested in 2 Italian watershed (Arno and Magra rivers) over a total river length of more than 400 km. The results (priority lists) coming from the application of such indexes can be considered a preliminary step for the definition of a restoration plan which could help the competent Authorities to address the available resources towards more detailed studies to be carried out at sites classified with the higher priority levels. This is the case of the Regional Natural Park Monte Marcello-Magra, where within a LIFE+ project (P.A.R.C. Petromyzon And River Continuity) recently funded, the first results of the priority indexes application will be analyzed in greater detail and will consequently lead to the design and construction of fish passes with a particular focus on sea lamprey (Petromyzon marinus) migration routes restoration
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| 7. |
- Calles, Olle
(författare)
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Annual report on the research activities within the fellowship program 2009
- 2010
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Rapport (refereegranskat)abstract
- The focus of the research has been on restoration of rivers longitudinal connectivity for fishmigration, as stated in the research program title. The activities have consisted of a mix ofstarting new studies* and continuing ongoing studies. All of the activities have involved acooperation between Olle Calles and Claudio Comoglio as well as several other partners.The projects are described in detail in this report and their titles are:1. Reintroducing marble trout to Dora Baltea (VdA): the impact of brown trout andhabitat modifications*2. Reintroducing marble trout to highaltitude rivers in VdA*3. The ecology and biology of a new Ligurian fish species *4. Reestablishment of longitudinal connectivity on the River Nestos, Greece*5. Introducing restoration ecology to Costa Rican rivers*6. Reestablishing connectivity on the Torrente Chiusella, Piemonte*7. Fish ladders or biocanals: on the potential of naturelike design8. Reducing silver eel mortality at turbine intakes using lowsloping racks9. The depth preference of silver eels approaching obstacles10. Testing rehabilitative measures for downstream migrating diadromous fish at ahydroelectric plant
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