Predicting spawning bed erosion and longevity : a case study in tributaries to river Vindelälven, northern Sweden
Timber floating operations in Scandinavia during the 19th and 20th centuries has contributed to severe negative impacts on riverine ecosystems. Increase in water velocity and lack of stream bed heterogeneity as a result of stream channelization lead to increased bed load transport. Since availabilit...
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| Formato: | H2 |
| Lenguaje: | Inglés sueco |
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SLU/Dept. of Wildlife, Fish and Environmental Studies
2013
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| _version_ | 1855570872984666112 |
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| author | Tylstedt, Viktor |
| author_browse | Tylstedt, Viktor |
| author_facet | Tylstedt, Viktor |
| author_sort | Tylstedt, Viktor |
| collection | Epsilon Archive for Student Projects |
| description | Timber floating operations in Scandinavia during the 19th and 20th centuries has contributed to severe negative impacts on riverine ecosystems. Increase in water velocity and lack of stream bed heterogeneity as a result of stream channelization lead to increased bed load transport. Since availability and recruitment of new suitable spawning substrate in Scandinavian watercourses is sparse, spawning habitats for salmonids has become a scarce commodity. Lately, increasingly more attention has been given to the recreation and improvement of brown trout (Salmo trutta) spawning habitats in restoration projects. While much of the research on spawning habitat has been focused on evaluation of the influence that the constructed spawning grounds have on fish populations, few studies have been conducted to evaluate the persistence of these constructions over time.
I evaluate erosion of constructed spawning beds as an effect of sediment transport attributable to water discharge. Two easily applicable sediment transport prediction models are applied to spawning beds in restored tributaries to river Vindelälven. I evaluate these as a method to determine suitable locations for construction of spawning beds. I also evaluate erosion of constructed spawning beds attributable to spawning activities by female brown trout by deploying PIT-tag marked pebbles over spawning beds in tributaries to River Vindelälven and use received data to develop a model describing the erosion process.
Analyses of erosion attributed to water flow suggest that both models tested in the study needs refinement to be reliable for prediction of erosion in the water systems investigated in this study. The results highlight the complexity of near-bed shear stress and water velocity.
The evaluation of spawning bed erosion attributed to spawning activity suggests that there is a spatial heterogeneity in erosion probabilities over a spawning bed. Erosion differed in magnitude between central-, downstream- and upstream sections, though no difference in movement between pebbles deployed along the edges of the bed compared to pebbles deployed in the middle of the stream could be proven. A longevity model, based only on the bed erosion caused by female digging activity, suggests that a spawning bed have a lifespan in the range of 13 to 35 years, depending on gravel depth.
The prediction tools developed in this study can offer guidance for fisheries managers and significantly improve and facilitate restoration efforts, provided the user of the models understand their limitations. I give suggestions for improved data collection approaches and bring forth alternative methodologies. |
| format | H2 |
| id | RepoSLU5607 |
| institution | Swedish University of Agricultural Sciences |
| language | Inglés swe |
| publishDate | 2013 |
| publishDateSort | 2013 |
| publisher | SLU/Dept. of Wildlife, Fish and Environmental Studies |
| publisherStr | SLU/Dept. of Wildlife, Fish and Environmental Studies |
| record_format | eprints |
| spelling | RepoSLU56072013-05-24T13:29:27Z Predicting spawning bed erosion and longevity : a case study in tributaries to river Vindelälven, northern Sweden Erosion och livslängd på lekbottnar : en fallstudie i biflöden till Vindelälven, norra Sverige Tylstedt, Viktor Salmo trutta stream restoration longevity erosion spawning bed Vindelälven Timber floating operations in Scandinavia during the 19th and 20th centuries has contributed to severe negative impacts on riverine ecosystems. Increase in water velocity and lack of stream bed heterogeneity as a result of stream channelization lead to increased bed load transport. Since availability and recruitment of new suitable spawning substrate in Scandinavian watercourses is sparse, spawning habitats for salmonids has become a scarce commodity. Lately, increasingly more attention has been given to the recreation and improvement of brown trout (Salmo trutta) spawning habitats in restoration projects. While much of the research on spawning habitat has been focused on evaluation of the influence that the constructed spawning grounds have on fish populations, few studies have been conducted to evaluate the persistence of these constructions over time. I evaluate erosion of constructed spawning beds as an effect of sediment transport attributable to water discharge. Two easily applicable sediment transport prediction models are applied to spawning beds in restored tributaries to river Vindelälven. I evaluate these as a method to determine suitable locations for construction of spawning beds. I also evaluate erosion of constructed spawning beds attributable to spawning activities by female brown trout by deploying PIT-tag marked pebbles over spawning beds in tributaries to River Vindelälven and use received data to develop a model describing the erosion process. Analyses of erosion attributed to water flow suggest that both models tested in the study needs refinement to be reliable for prediction of erosion in the water systems investigated in this study. The results highlight the complexity of near-bed shear stress and water velocity. The evaluation of spawning bed erosion attributed to spawning activity suggests that there is a spatial heterogeneity in erosion probabilities over a spawning bed. Erosion differed in magnitude between central-, downstream- and upstream sections, though no difference in movement between pebbles deployed along the edges of the bed compared to pebbles deployed in the middle of the stream could be proven. A longevity model, based only on the bed erosion caused by female digging activity, suggests that a spawning bed have a lifespan in the range of 13 to 35 years, depending on gravel depth. The prediction tools developed in this study can offer guidance for fisheries managers and significantly improve and facilitate restoration efforts, provided the user of the models understand their limitations. I give suggestions for improved data collection approaches and bring forth alternative methodologies. Timmerflottningsverksamheten under 1800- och 1900-talet förde med sig förödande konsekvenser för ekosystem i rinnande vatten i scandinavien. Rensning av block och stenar resulterade i ökade vattenhastigheter och en omfattande sedimenttransport. Då tillgång och rekrytering av grus i lämplig storlek för fisklek i scandinaviska vattendrag är låg, har lekområden för laxfiskar blivit en bristvara. Under senare år har allt mer uppmärksamhet riktats mot återuppbyggnad och förbättring av lekområden för öring (Salmo trutta) inom restaureringproject i Sverige. Medan stor del av forskning kring lekområden har haft fokus på hur restaurerade lekbottnar påverkar fiskpopulationer, få studier har utvärderat hållbarheten av dessa konstruktioner över tid. Här utvärderar jag erosion av konstruerade lekbottnar som en effekt av sedimenttransport som kan tillskrivas vattenflöde. Två lättillämpliga prediktionsmodeller för sedimenttransport är applicerade på lekbottnar i restaurerade biflöden till Vindelälven. Jag utvärderar dessa som en metod att för bestämma lämpliga lokaler att konstruera lekbottnar på. Jag utvärderar även erosion av konstruerade lekbottnar som en effekt av sedimenttransport som med kan tillskrivas lekaktivitet av öringhonor, genom att placera ut lekgrus försedda med PIT-märkning över lekbottnar i biflöden till Vindelälven och använder erhållen data för att utveckla en modell som beskriver erosionsprocessen. Analyser av erosion som kan tillskrivas vattenflöden tyder på att modellerna behöver justeringar för att prediktera erosion i vattensystem utvärderade i den här studien på ett tillförlitligt sätt. Resultat i den här delstudien belyser komplexiteten av vattenflöden och skjuvspänning på botten av rinnande vattendrag. Utvärdering av erosion på lekbottnar som kan tillskrivas lekande öring tyder på att det finns en rumslig heterogenitet i sannolikheten för erosion över en lekbotten. Storleksorningen på erosion skillde mellan centrala- uppströms- och nedströms delar av lekbottnar, men det kunde inte påvisas någon kanteffekt. En livslängdsmodell baserad enbart på bädderosion som följd av öringhonors lekaktivitet visar att en lekbotten har en livslängd på mellan 13 och 35 år, beroende på initiellt djup på lekgruset minsta medeldjup på lekgrus i de centrala delarna av lekbottnen som en öring behöver för att kunna leka. Genom att använda och tillämpa mina prediktionsverktyg med försiktighet och genom att förstå deras begränsningar kan de ge vägledning för fiskeriförvaltare och därmed underlätta och förbättra restaureringsåtgärder. Jag ger förslag på förbättringar i metodik för datainsamling och för fram alternative metoder för datainsamling. SLU/Dept. of Wildlife, Fish and Environmental Studies 2013 H2 eng swe https://stud.epsilon.slu.se/5607/ |
| spellingShingle | Salmo trutta stream restoration longevity erosion spawning bed Vindelälven Tylstedt, Viktor Predicting spawning bed erosion and longevity : a case study in tributaries to river Vindelälven, northern Sweden |
| title | Predicting spawning bed erosion and longevity
: a case study in tributaries to river Vindelälven, northern Sweden |
| title_full | Predicting spawning bed erosion and longevity
: a case study in tributaries to river Vindelälven, northern Sweden |
| title_fullStr | Predicting spawning bed erosion and longevity
: a case study in tributaries to river Vindelälven, northern Sweden |
| title_full_unstemmed | Predicting spawning bed erosion and longevity
: a case study in tributaries to river Vindelälven, northern Sweden |
| title_short | Predicting spawning bed erosion and longevity
: a case study in tributaries to river Vindelälven, northern Sweden |
| title_sort | predicting spawning bed erosion and longevity
: a case study in tributaries to river vindelälven, northern sweden |
| topic | Salmo trutta stream restoration longevity erosion spawning bed Vindelälven |