Asbjørn Vøllestad

• Haugen, Thrond Oddvar & Vøllestad, Leif Asbjørn (2018). Pike Population Size and Structure: Influence of Density-Dependent and Density-Independent Factors, In Christian Skov & Anders Nilsson (ed.),  Biology and Ecology of Pike.  CRC Press.  ISBN 9781482262902.  6.  s 123 - 163
• Nater, Chloé Rebecca; Rustadbakken, A; Ergon, Torbjørn; Langangen, Øystein; Moe, S. Jannicke; Vindenes, Yngvild; Vøllestad, Leif Asbjørn & Aas, Per (2018). Individual heterogeneity and early life conditions shape growth in a freshwater top predator. Ecology.  ISSN 0012-9658.  99, s 1011- 1017 . doi: 10.1002/ecy.2178
• Nilsson, Anna; L'Abee-Lund, Jan Henning; Vøllestad, Leif Asbjørn; Jerstad, Kurt; Larsen, Bjørn Mejdell; Røstad, Ole Wiggo; Saltveit, Svein Jakob; Skaugen, Thomas; Stenseth, Nils Christian & Walseng, Bjørn (2018). The potential influence of Atlantic salmon Salmo salar and brown trout Salmo trutta on density and breeding of the white-throated dipper Cinclus cinclus. Ecology and Evolution.  ISSN 2045-7758. . doi: 10.1002/ece3.3958 Full text in Research Archive. Show summary

  Interactions between birds and fish are often overlooked in aquatic ecosystems. We studied the influence of Atlantic salmon and brown trout on the breeding population size and reproductive output of the white-throated dipper in a Norwegian river. Acidic precipitation led to the extinction of salmon, but salmon recolonized after liming was initiated in 1991. We compared the dipper population size and reproductive output before (1978–1992) and after (1993–2014) salmon recolonization. Despite a rapid and substantial increase in juvenile salmon, the breeding dipper population size and reproductive output were not influenced by juvenile salmon, trout, or total salmonid density. This might be due to different feeding strategies in salmonids and dippers, where salmonids are mainly feeding on drift, while the dipper is a benthic feeder. The correlation between the size of the dipper population upstream and downstream of a salmonid migratory barrier was similar before and after recolonization, indicating that the downstream territories were not less attractive after the recolonization of salmon. Upstream dipper breeding success rates declined before the recolonization event and increased after, indicating improved water quality due to liming, and increasing invertebrate prey abundances and biodiversity. Surprisingly, upstream the migratory barrier, juvenile trout had a weak positive effect on the dipper population size, indicating that dippers may prey upon small trout. It is possible that wider downstream reaches might have higher abundances of alternative food, rending juvenile trout unimportant as prey. Abiotic factors such as winter temperatures and acidic precipitation with subsequent liming, potentially mediated by preyabundance, seem to play the most important role in the life history of the dipper. birds, breeding, predators, river, salmonids

• Poole, W. Russell; Diserud, Ola Håvard; Thorstad, Eva Bonsak; Durif, Caroline; Dolan, Conor; Sandlund, Odd Terje; Bergesen, Knut Aanestad; Rogan, Gerard; Kelly, Sean D. & Vøllestad, Leif Asbjørn (2018). Long-term variation in numbers and biomass of silver eels being produced in two European river systems. ICES Journal of Marine Science.  ISSN 1054-3139. . doi: 10.1093/icesjms/fsy053
• Vøllestad, Leif Asbjørn; Skurdal, Jostein & L'Abée-Lund, J. H. (2018). 10 års erfaring med nasjonale laksevassdrag - virker systemet?. Vann.  ISSN 0042-2592.  2018(1), s 102- 117
• Anastasiadou, Chryssa; Daliri, Moslem; Oikonomou, Anthi & Vøllestad, Leif Asbjørn (2017). Length weight relationships, relative weight and relative condition factor of three freshwater shrimps from Greece. International Journal of Fisheries and Aquatic Studies.  ISSN 2394-0506.  5(1), s 403- 406 Full text in Research Archive.
• Carim, Kellie; Vindenes, Yngvild; Eby, Lisa A.; Barfoot, Craig & Vøllestad, Leif Asbjørn (2017). Life history, population viability, and the potential for local adaptation in isolated trout populations. Global Ecology and Conservation.  ISSN 2351-9894.  10, s 93- 102 . doi: 10.1016/j.gecco.2017.02.001 Full text in Research Archive.
• Forseth, Torbjørn; Barlaup, Bjørn Torgeir; Finstad, Bengt; Fiske, Peder; Gjøsæter, Harald; Falkegård, Morten; Hindar, Atle; Mo, Tor Atle; Rikardsen, Audun H.; Thorstad, Eva Bonsak; Vøllestad, Leif Asbjørn & Wennevik, Vidar (2017). The major threats to Atlantic salmon in Norway. ICES Journal of Marine Science.  ISSN 1054-3139.  74(6), s 1495- 1513 . doi: 10.1093/icesjms/fsx020 Full text in Research Archive. Show summary

  Atlantic salmon (Salmo salar) is an economically and culturally important species. Norway has more than 400 watercourses with Atlantic salmon and supports a large proportion of the world’s wild Atlantic salmon. Atlantic salmon are structured into numerous genetically differentiated populations, and are therefore managed at the population level. Long-distance migrations between freshwater and ocean habitats expose Atlantic salmon to multiple threats, and a number of anthropogenic factors have contributed to the decline of Atlantic salmon during the last decades. Knowledge on the relative importance of the different anthropogenic factors is vital for prioritizing management measures. We developed a semi-quantitative 2D classification system to rank the different anthropogenic factors and used this to assess the major threats to Norwegian Atlantic salmon. Escaped farmed salmon and salmon lice from fish farms were identified as expanding population threats, with escaped farmed salmon being the largest current threat. These two factors affect populations to the extent that they may be critically endangered or lost, with a large likelihood of causing further reductions and losses in the future. The introduced parasite Gyrodactylus salaris, freshwater acidification, hydropower regulation and other habitat alterations were identified as stabilized population threats, which have contributed to populations becoming critically endangered or lost, but with a low likelihood of causing further loss. Other impacts were identified as less influential, either as stabilized or expanding factors that cause loss in terms of number of returning adults, but not to the extent that populations become threatened. Management based on population specific reference points (conservation limits) has reduced exploitation in Norway, and overexploitation was therefore no longer regarded an important impact factor. The classification system may be used as a template for ranking of anthropogenic impact factors in other countries and as a support for national and international conservation efforts. classification system, management advice, Salmo salar, threat assessment.

• Halvorsen, Kim Aleksander Tallaksen; Larsen, Torkel; Sørdalen, Tonje Knutsen; Vøllestad, Leif Asbjørn; Knutsen, Halvor & Olsen, Esben Moland (2017). Impact of harvesting cleaner fish for salmonid aquaculture assessed from replicated coastal marine protected areas. Marine Biology Research.  ISSN 1745-1000.  13(4), s 359- 369 . doi: 10.1080/17451000.2016.1262042 Full text in Research Archive.
• Halvorsen, Kim Aleksander Tallaksen; Sørdalen, Tonje Knutsen; Vøllestad, Leif Asbjørn; Skiftesvik, Anne Berit; Espeland, Sigurd Heiberg & Olsen, Esben Moland (2017). Sex-and size-selective harvesting of corkwing wrasse (Symphodus melops)-a cleaner fish used in salmonid aquaculture. ICES Journal of Marine Science.  ISSN 1054-3139.  74(3), s 660- 669 . doi: 10.1093/icesjms/fsw221
• L'Abee-Lund, Jan Henning & Vøllestad, Leif Asbjørn (2017). Life-history plasticity in anadromous brown trout: a Norwegian perspective, In Javier Lobon-Cervia & Nuria Sanz (ed.),  Brown-Trout: Biology, ecology and management.  John Wiley & Sons.  ISBN 978-1-119-26831-4.  Kapittel 11.  s 251 - 265
• Sandlund, Odd Terje; Diserud, Ola Håvard; Poole, Russell; Bergesen, Knut Aanestad; Dillane, Mary; Rogan, Gerard; Durif, Caroline; Thorstad, Eva Bonsak & Vøllestad, Leif Asbjørn (2017). Timing and pattern of annual silver eel migration in two European watersheds are determined by similar cues. Ecology and Evolution.  ISSN 2045-7758.  7(15), s 5956- 5966 . doi: 10.1002/ece3.3099 Full text in Research Archive. Show summary

  Many animals perform long-distance migrations in order to maximize lifetime reproductive success. The European eel migrates several thousand kilometers between their feeding habitats in continental waters (fresh-,brackish, and sea water) and their spawning area in the Sargasso Sea. Eels residing in freshwaters usually initiate their spawning migration as silver eels during autumn, triggered by diverse environmental cues. We analyzed the time series of silver eel downstream migration in Burrishoole, Ireland (1971–2015), and Imsa, Norway (1975–2015), to examine factors regulating the silver eel migration from freshwater to the sea. The migration season (90% of the run) generally lasted from 1 August to 30 November. Environmental factors acting in the months before migration impacted timing and duration of migration, likely through influencing the internal processes preparing the fish for migration. Once the migration had started, environmental factors impacted the day-to-day variation in number of migrants, apparently stimulating migration among those eels ready for migration. Both the day-to-day variation in the number of migrants and the onset of migration were described by nearly identical models in the two rivers. Variables explaining day-to-day variation were all associated with conditions that may minimize predation risk; number of migrants was reduced under a strong moon and short nights and increased during high and increasing water levels. Presence of other migrants stimulated migration, which further indicates that silver eel migration has evolved to minimize predation risk. The onset of migration was explained mainly by water levels in August. The models for duration of the migration season were less similar between the sites. Thus, the overall migration season seems governed by the need to reach the spawning areas in a synchronized manner, while during the actual seaward migration, antipredator behavior seems of overriding importance. Anguilla anguilla, daily variation, environmental variables, freshwater migration, migration onset, silver eel

• van Leeuwen, Casper; Dalen, Kristine; Museth, Jon; Junge, Claudia & Vøllestad, Leif Asbjørn (2017). Habitat fragmentation has interactive effects on the population genetic diversity and individual behaviour of a freshwater salmonid fish. Rivers Research and Applications: an international journal devoted to river research and management.  ISSN 1535-1459.  34(1), s 60- 68 . doi: 10.1002/rra.3226 Show summary

  Sufficient genetic diversity can aid populations to persist in dynamic and fragmented environments. Understanding which mechanisms regulate genetic diversity of riverine fish can therefore advance current conservation strategies. The aim of this study was to investigate how habitat fragmentation interacted with population genetic diversity and individual behaviour of freshwater fish in large river systems. We studied a population of the long‐distance migratory, iteroparous freshwater salmonid European grayling (Thymallus thymallus) in south‐eastern Norway. Genotyping (n = 527) and radio‐tracking (n = 54) of adult fish throughout a 169‐km river section revealed three major migration barriers limiting gene flow and depleting genetic diversity upstream. Individuals from upstream areas that had dispersed downstream of barriers showed different movement behaviour than local genotypes. No natal philopatry was found in a large unfragmented river section, in contrast to strong fidelity to spawning tributaries known for individuals overwintering in lakes. We conclude that (a) upstream sub‐populations in fragmented rivers show less genetic variation, making it less likely for them to adapt to environmental changes; (b) fish with distinct genotypes in the same habitat can differ in their behaviour; (c) spawning site selection (natal philopatry) can differ between fish of the same species living in different habitats. Together this implies that habitat loss and fragmentation may differently affect individual fish of the same species if they live in different types or sections of habitat. Studying behaviour and genetic diversity of fish can unravel their complex ecology and help minimize human impact. barriers, dams and weirs, natal philopatry, radiotelemetry, spawning site fidelity, Thymallus thymallus

• Villar, Jaime Otero; L'Abee-Lund, Jan Henning & Vøllestad, Leif Asbjørn (2017). Temporal and spatial variation in recreational catches of anadromous brown trout, Salmo trutta, in Norwegian rivers. Hydrobiologia.  ISSN 0018-8158.  797(1), s 199- 213 . doi: 10.1007/s10750-017-3176-5
• Vøllestad, Leif Asbjørn (2017). Understanding brown trout population genetic structure: A northern-European perspective, In Javier Lobon-Cervia & Nuria Sanz (ed.),  Brown-Trout: Biology, ecology and management.  John Wiley & Sons.  ISBN 978-1-119-26831-4.  Kapittel 5.  s 127 - 144 Show summary

  Freshwater fishes live in complex environments, and are commonly structured into completely or partly reproductively isolated populations. This population structure is influenced by the local geography, the geological history of the landscape and present-day human-mediated changes in the aquatic landscape as well as long-distance translocations of fish. Historic contingency is particularly important in temperate Northern Europe due to glacial cycles followed by isostatic rebound of landmasses and changes in sea levels. Thus, present distribution and diversity is the result of post-glacial immigration from various glacial refugia and a number of human activities (translocations, stocking activity, changing of waterways). On top of these processes, various biological characteristics such as dispersal propensity, site fidelity and breeding systems impact on local-scale distribution. In this chapter I evaluate data extracted from 75 publications on the genetic diversity and population differentiation of brown trout Salmo trutta in Northern Europe. In total, I extracted and evaluated 389 estimates of allelic richness, 461 estimates of observed heterozygosity, 506 estimates of expected heterozygosity, 104 estimates of effective population size (Ne), and 1112 estimates of pairwise population differentiation (FST). I briefly discuss factors impacting on population structure and diversity.

• Bærum, Kim Magnus; Vøllestad, Leif Asbjørn; Kiffney, Peter; Remy, Alice Melisande Jacynthe & Haugen, Thrond Oddvar (2016). Population-level variation in juvenile brown trout growth from different climatic regions of Norway to an experimental thermal gradient. Environmental Biology of Fishes.  ISSN 0378-1909.  99, s 1009- 1018 . doi: 10.1007/s10641-016-0533-6 Show summary

  Climate-change scenarios predict increasing temperatures and more precipitation at high latitudes. Ectothermic species are highly affected by these environmental variables and due to few dispersal opportunities many populations will need to adapt to these environmental changes. Understanding if, where, and how such adaptation processes occur is important for our understanding of the possible impacts of a changing climate. Individual growth, a key life-history trait influencing population-level parameters is directly affected by temperature especially in ectotherms. Thermal adaptations that optimize growth are therefore expected in such organisms. However, knowledge about how ectothermic animals modify growth rate in the face of climate change is poor at best for many species especially at the local population level. Here, we present a common-garden experiment exploring variations in growth reaction norms for three populations of Salmo trutta (a temperate freshwater fish) over three discrete temperatures. The populations originated from different climatic regions of Norway that vary in temperature and precipitation. Thermal growth reaction norms varied among populations, however we found no convincing evidence for either local thermal adaptations or countergradient adaptations. Rather, the population variation tended to correlate with a variable indicating east vs west climate region, that is strongly associated with a gradient in precipitation in Norway. This results suggests precipitation levels with corresponding flow regimes to have a stronger selection potential for early juvenile growth compared to temperature in these systems. Keywords Climate change . Temperature . Precipitation . Adaptation . Fish . Salmonids

• Edeline, Eric; Groth, Andreas; Cazelles, Bernard; Claessen, David; Winfield, Ian J.; Ohlberger, Jan Philipp; Vøllestad, Leif Asbjørn; Stenseth, Nils Christian & Ghil, Michael (2016). Pathogens trigger top-down climate forcing on ecosystem dynamics. Oecologia.  ISSN 0029-8549.  181, s 519- 532 . doi: 10.1007/s00442-016-3575-8
• Halvorsen, Kim Aleksander Tallaksen; Sørdalen, Tonje Knutsen; Durif, Caroline; Knutsen, Halvor; Olsen, Esben Moland; Skiftesvik, Anne Berit; Rustand, Torborg Emmerhoff; Bjelland, Reidun Marie & Vøllestad, Leif Asbjørn (2016). Male biased sexual size dimorphism in the nest building corkwing wrasse (Symphodus melops): implications for a size regulated fishery. ICES Journal of Marine Science.  ISSN 1054-3139.  73(10), s 2586- 2594 . doi: 10.1093/icesjms/fsw135
• Hansson, Truls Hveem; Fischer, Barbara; Mazzarella, Anna; Voje, Kjetil L. & Vøllestad, Leif Asbjørn (2016). Lateral plate number in low-plated threespine stickleback: a study of plasticity and heritability. Ecology and Evolution.  ISSN 2045-7758.  6(10), s 3154- 3160 . doi: 10.1002/ece3.2020 Full text in Research Archive.
• Lennox, Robert J.; Falkegård, Morten; Vøllestad, Leif Asbjørn; Cooke, Steven J. & Thorstad, Eva Bonsak (2016). Influence of harvest restrictions on angler release behaviour and size selection in a recreational fishery. Journal of Environmental Management.  ISSN 0301-4797.  176, s 139- 148 . doi: 10.1016/j.jenvman.2016.03.031
• Mäkinen, Hannu; Papakostas, Spiros; Vøllestad, Leif Asbjørn; Leder, Erica H & Primmer, Craig R (2016). Plastic and evolutionary gene expression responses are correlated in European grayling (Thymallus thymallus) subpopulations adapted to different thermal environments. Journal of Heredity.  ISSN 0022-1503.  107(1), s 82- 89 . doi: 10.1093/jhered/esv069
• Mazzarella, Anna; Boessenkool, Sanne; Østbye, Kjartan; Vøllestad, Leif Asbjørn & Trucchi, Emiliano (2016). Genomic signatures of the plateless phenotype in the threespine stickleback. Ecology and Evolution.  ISSN 2045-7758.  6(10), s 3161- 3173 . doi: 10.1002/ece3.2072 Full text in Research Archive.
• Pettersen, Ruben Alexander; Østbye, Kjartan; Holmen, Johannes; Vøllestad, Leif Asbjørn & Mo, Tor Atle (2016). Gyrodactylus spp. diversity in native and introduced minnow (Phoxinus phoxinus) populations: no support for "the enemy release" hypothesis. Parasites & Vectors.  ISSN 1756-3305.  9(51) . doi: 10.1186/s13071-016-1306-y
• Tsiamis, Konstantinos; Gervasini, Eugenio; D'Amico, Fabio; Deriu, Ivan; Katsanevakis, Stelios; Crocetta, Fabio; Zenetos, Argyro; Arianoutsou, Margarita; Backeljau, Thierry; Bariche, Michel; Bazos, Ioannis; Bertaccini, Assunta; Brundu, Giuseppe; Carrete, Martina; Çinar, Melih Ertan; Curto, Giovanna; Faasse, Marco; Justine, Jean-Lou; Király, Gergely; Langer, Martin R.; Levitt, Ya'arit; Panov, Vadim E.; Piraino, Stefano; Rabitsch, Wolfgang; Roques, Alain; Scalera, Riccardo; Shenkar, Noa; Sîrbu, Ioan; Tricarico, Elena; Vannini, Andrea; Vøllestad, Leif Asbjørn; Zikos, Andreas & Cardoso, Ana Cristina (2016). The EASIN Editorial Board: Quality assurance, exchange and sharing of alien species information in Europe. Management of Biological Invasions.  ISSN 1989-8649.  7(4), s 321- 328 . doi: 10.3391/mbi.2016.7.4.02
• van Leeuwen, Casper; Museth, Jon; Sandlund, Odd Terje; Qvenild, Tore & Vøllestad, Leif Asbjørn (2016). Mismatch between fishway operation and timing of fish movements: A risk for cascading effects in partial migration systems. Ecology and Evolution.  ISSN 2045-7758.  6(8), s 2414- 2425 . doi: 10.1002/ece3.1937 Full text in Research Archive. Show summary

  Habitat fragmentation is a growing problem worldwide. Particularly in river systems, numerous dams and weirs hamper the movement of a wide variety of species. With the aim to preserve connectivity for fish, many barriers in river systems are equipped with fishways (also called fish passages or fish ladders). However, few fishways provide full connectivity. Here we hypothesized that restricted seasonal opening times of fishways can importantly reduce their effectiveness by interfering with the timing of fish migration, for both spring- and autumn-spawning species. We empirically tested our hypothesis, and discuss the possible eco-evolutionary consequences of affected migration timing. We analyzed movements of two salmonid fishes, spring-spawning European grayling (Thymallus thymallus) and autumn-spawning brown trout (Salmo trutta), in Norway’s two largest river systems. We compared their timing of upstream passage through four fishways collected over 28 years with the timing of fish movements in unfragmented river sections as monitored by radiotelemetry. Confirming our hypothesis, late opening of fishways delayed the migration of European grayling in spring, and early closure of fishways blocked migration for brown trout on their way to spawning locations during late autumn. We show in a theoretical framework how restricted opening times of fishways can induce shifts from migratory to resident behavior in potamodromous partial migration systems, and propose that this can induce density-dependent effects among fish accumulating in lower regions of rivers. Hence, fragmentation may not only directly affect the migratory individuals in the population, but may also have effects that cascade downstream and alter circumstances for resident fish. Fishway functionality is inadequate if there is a mismatch between natural fish movements and fishway opening times in the same river system, with ecological and possibly evolutionary consequences for fish populations. Brown trout (Salmo trutta), eco-evolutionary consequences, European grayling (Thymallus thymallus), fish passage functionality, life history strategy, salmonids.

• Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J. & Vøllestad, Leif Asbjørn (2016). Fitness consequences of early life conditions and maternal size effects in a freshwater top predator. Journal of Animal Ecology.  ISSN 0021-8790.  85(3), s 692- 704 . doi: 10.1111/1365-2656.12489
• Wiig, Elisabeth; Reseland, Janne Elin; Østbye, Kjartan; Haugen, Håvard Jostein & Vøllestad, Leif Asbjørn (2016). Variation in Lateral Plate Quality in Threespine Stickleback from Fresh, Brackish and Marine Water: A Micro-Computed Tomography Study. PLoS ONE.  ISSN 1932-6203.  11(10) . doi: 10.1371/journal.pone.0164578
• Østbye, Kjartan; Harrod, Chris; Gregersen, Finn; Klepaker, Tom Olav; Schulz, Michael; Schluter, Dolph & Vøllestad, Leif Asbjørn (2016). The temporal window of ecological adaptation in postglacial lakes: a comparison of head morphology, trophic position and habitat use in Norwegian threespine stickleback populations. BMC Evolutionary Biology.  ISSN 1471-2148.  16(102), s 1- 16 . doi: 10.1186/s12862-016-0676-2
• Haddeland, Peter Jørgen Tønnessen; Junge, Claudia; Serbezov, Dimitar & Vøllestad, Leif Asbjørn (2015). Genetic Parentage Analysis Confirms a Polygynandrous Breeding System in the European Grayling (Thymallus thymallus). PLoS ONE.  ISSN 1932-6203.  10(3) . doi: 10.1371/journal.pone.0122032 Full text in Research Archive.
• Pettersen, Ruben Alexander; Mo, Tor Atle; Hansen, Haakon & Vøllestad, Leif Asbjørn (2015). Genetic population structure of Gyrodactylus thymalli (Monogenea) in a large Norwegian river system. Parasitology.  ISSN 0031-1820.  142(14), s 1693- 1702 . doi: 10.1017/S003118201500133X
• Bass, Arthur; Haugen, Thrond Oddvar & Vøllestad, Leif Asbjørn (2014). Distribution and movement of European grayling in a subarctic lake revealed by acoustic telemetry. Ecology of Freshwater Fish.  ISSN 0906-6691.  23(2), s 149- 160 . doi: 10.1111/eff.12056
• Fleming, Mitchell; Hansen, Tom Johnny; Skulstad, Ole Fredrik; Glover, Kevin; Morton, Hugh Craig; Vøllestad, Leif Asbjørn & Fjelldal, Per Gunnar (2014). Hybrid salmonids: Ploidy effect on skeletal meristic characteristics and sea lice infection susceptibility. Journal of Applied Ichthyology.  ISSN 0175-8659.  30(4), s 746- 752 . doi: 10.1111/jai.12530
• Junge, Claudia; Museth, Jon; Hindar, Kjetil; Kraabøl, Morten & Vøllestad, Leif Asbjørn (2014). Assessing the consequences of habitat fragmentation for two migratory salmonid fishes. Aquatic conservation.  ISSN 1052-7613.  24(3), s 297- 311 . doi: 10.1002/aqc.2391 Show summary

  1. Man-made barriers such as dams affect the movement of aquatic species, reducing gene flow and genetic variability. Such encroachments may also lead to selective changes in life history and behaviour. Hydropower construction worldwide has fragmented many previously continuous fish habitats, leading to loss of populations and production. It is therefore important to assess potential impacts on habitats before such developments begin. 2. Here, the potential ecological and evolutionary consequences of planned hydropower development on two migratory salmonid fishes – brown trout (Salmo trutta) and European grayling (Thymallus thymallus) – were assessed, combining telemetry with population genetics. Almost 200 fish were radio-tagged and tracked weekly between March and November. Using microsatellite markers, the genetic population structure was assessed and the number of migrants among different river sections identified for both species. 3. Overall, both species displayed extensive within- and between-river movement, with larger home ranges in grayling than in trout. Regular movements between distinct spawning, feeding and wintering areas were common. These vital habitats were often located within areas of planned hydropower development. 4. Both species exhibited significant population genetic structuring within the study area, with waterfalls acting as impassable barriers to upstream gene flow for grayling. The structuring was more developed for trout than for grayling. However, downstream gene flow was common, resulting in a highly admixed trout population below a waterfall. 5. The large-scale movement patterns and extensive connectivity of the system indicate that habitat fragmentation and changes in water flow will adversely affect both species, but most strongly the trout. The reduction in water flow over large and productive stretches of the river might select for less migratory genotypes in both species. The loss of particular genotypes may reduce the biocomplexity of the system and overall population resilience. river; catchment; conservation evaluation; genetics; fish; hydropower

• Ohlberger, Jan; Thackeray, Stephen J.; Winfield, Ian J.; Maberly, Stephen C. & Vøllestad, Leif Asbjørn (2014). When phenology matters: Age-size truncation alters population response to trophic mismatch. Proceedings of the Royal Society of London. Biological Sciences.  ISSN 0962-8452.  281(1793) . doi: 10.1098/rspb.2014.0938
• Olsen, Esben Moland; Serbezov, Dimitar & Vøllestad, Leif Asbjørn (2014). Probabilistic maturation reaction norms assessed from mark-recaptures of wild fish in their natural habitat. Ecology and Evolution.  ISSN 2045-7758.  4(9), s 1601- 1610 . doi: 10.1002/ece3.1044 Full text in Research Archive.
• Otero, Jaime; L'Abee-Lund, Jan Henning; Castro-Santos, Ted; Leonardsson, Kjell; Storvik, Geir Olve; Jonsson, Bror; Dempson, J. Brian; Russell, Ian C.; Jensen, Arne Johan; Baglinière, Jean-Luc; Dionne, Mélanie; Armstrong, John D.; Romakkaniemi, Atso; Letcher, Benjamin H.; Kocik, John F.; Erkinaro, Jaakko; Poole, Russell; Rogan, Ger; Lundqvist, Hans; MacLean, Julian C.; Jokikokko, Erkki; Arnekleiv, Jo Vegar; Kennedy, Richard J.; Niemelä, Eero; Caballero, Pablo; Music, Paul A.; Antonsson, Thorolfur; Gudjonsson, Sigurdur; Veselov, Alexey E.; Lamberg, Anders; Groom, Steve; Taylor, Benjamin H.; Taberner, Malcolm; Dillane, Mary; Arnason, Fridthjofur; Horton, Gregg; Hvidsten, Nils Arne; Jonsson, Ingi Runar; Jonsson, Nina; McKelvey, Simon; Næsje, Tor; Skaala, Øystein; Smith, Gordon W.; Sægrov, Harald; Stenseth, Nils Christian & Vøllestad, Leif Asbjørn (2014). Basin-scale phenology and effects of climate variability on global timing of initial seaward migration of Atlantic salmon (Salmo salar). Global Change Biology.  ISSN 1354-1013.  20(1), s 61- 75 . doi: 10.1111/gcb.12363 Show summary

  Migrations between different habitats are key events in the lives of many organisms. Such movements involve annually recurring travel over long distances usually triggered by seasonal changes in the environment. Often, the migration is associated with travel to or from reproduction areas to regions of growth. Young anadromous Atlantic salmon (Salmo salar) emigrate from freshwater nursery areas during spring and early summer to feed and grow in the North Atlantic Ocean. The transition from the freshwater (‘parr’) stage to the migratory stage where they descend streams and enter salt water (‘smolt’) is characterized by morphological, physiological and behavioural changes where the timing of this parr-smolt transition is cued by photoperiod and water temperature. Environmental conditions in the freshwater habitat control the downstream migration and contribute to within- and among-river variation in migratory timing. Moreover, the timing of the freshwater emigration has likely evolved to meet environmental conditions in the ocean as these affect growth and survival of the post-smolts. Using generalized additive mixed-effects modelling, we analysed spatio-temporal variations in the dates of downstream smolt migration in 67 rivers throughout the North Atlantic during the last five decades and found that migrations were earlier in populations in the east than the west. After accounting for this spatial effect, the initiation of the downstream migration among rivers was positively associated with freshwater temperatures, up to about 10 ºC and levelling off at higher values, and with sea-surface temperatures. Earlier migration occurred when river discharge levels were low but increasing. On average, the initiation of the smolt seaward migration has occurred 2.5 days earlier per decade throughout the basin of the North Atlantic. This shift in phenology matches changes in air, river, and ocean temperatures, suggesting that Atlantic salmon emigration is responding to the current global climate changes. Atlantic salmon, smolt emigration, freshwater conditions, sea surface temperature, phenology, North Atlantic

• Papakostas, Spiros; Vøllestad, Leif Asbjørn; Bruneaux, Matthieu; Aykanat, Tutku; Vanoverbeke, Joost; Ning, Mei; Primmer, Craig R. & Leder, Erica H. (2014). Gene pleiotropy constrains gene expression changes in fish adapted to different thermal conditions. Nature Communications.  ISSN 2041-1723.  5 . doi: 10.1038/ncomms5071 Full text in Research Archive.
• Parra, Irene; Nicola, Graciela G.; Vøllestad, Leif Asbjørn; Elvira, Benigno & Almeida, Ana (2014). Latitude and altitude differentially shape life history trajectories between the sexes in non-anadromous brown trout. Evolutionary Ecology.  ISSN 0269-7653.  28(4), s 707- 720 . doi: 10.1007/s10682-014-9702-2
• Skog, Anna; Vøllestad, Leif Asbjørn; Stenseth, Nils Christian; Kasumyan, Alexander & Jakobsen, Kjetill Sigurd (2014). Circumpolar phylogeography of the northern pike (Esox lucius) and its relationship to the Amur pike (E. reichertii). Frontiers in Zoology.  ISSN 1742-9994.  11(67) . doi: 10.1186/s12983-014-0067-8 Full text in Research Archive.
• Taugbøl, Annette; Arntsen, Tina; Østbye, Kjartan & Vøllestad, Leif Asbjørn (2014). Small Changes in Gene Expression of Targeted Osmoregulatory Genes When Exposing Marine and Freshwater Threespine Stickleback (Gasterosteus aculeatus) to Abrupt Salinity Transfers. PLoS ONE.  ISSN 1932-6203.  9(9), s 1- 9 . doi: 10.1371/journal.pone.0106894 Full text in Research Archive.
• Taugbøl, Annette; Junge, Claudia; Quinn, Thomas P.; Herland, Anders & Vøllestad, Leif Asbjørn (2014). Genetic and morphometric divergence in threespine stickleback in the Chignik catchment, Alaska. Ecology and Evolution.  ISSN 2045-7758.  4(2), s 144- 156 . doi: 10.1002/ece3.918 Full text in Research Archive.
• Vindenes, Yngvild; Edeline, Eric; Ohlberger, Jan; Langangen, Øystein; Winfield, Ian J.; Stenseth, Nils Christian & Vøllestad, Leif Asbjørn (2014). Effects of climate change on trait-based dynamics of a top predator in freshwater ecosystems. American Naturalist.  ISSN 0003-0147.  183(2), s 243- 256 . doi: 10.1086/674610 Full text in Research Archive.
• Vøllestad, Leif Asbjørn; Skurdal, Jostein & L'abee-Lund, Jan Henning (2014). Evaluation of a new management scheme for Norwegian Atlantic salmon Salmo salar. Fisheries Management and Ecology.  ISSN 0969-997X.  21(2), s 133- 139 . doi: 10.1111/fme.12057 Show summary

  Atlantic salmon, Salmo salar L., stocks are decreasing worldwide, and major efforts are underway to conserve populations that are threatened. In a recent effort to conserve the Norwegian salmon, the Norwegian government implemented in 2007 a scheme called National Atlantic Salmon Watercourses and Fjords (NASW), where 52 rivers were given special protection. Here, the scheme is described and it is evaluated if and to what extent the scheme has led to changes in management practice. After the implementation of the NASW scheme, fewer plans for development (e.g. hydropower plants, water abstraction, flood and erosion control) at the within-river level were accepted for NASW-rivers than for rivers not in the scheme. However, at the same time, there was a tendency for fewer plans overall being sanctioned in all types of rivers probably due to overall changes in management practices not related to the NASW scheme. In total, these changes could lead to increased protection of Norwegian Atlantic salmon populations. conservation, dams, encroachments, hydropower, water abstraction

• Budy, Phaedra; Thiede, Gary P; Lobon-Cervia, Javier; Fernandez, G.; McHugh, Peter; McIntosh, A; Vøllestad, Leif Asbjørn; Becares, Eloy & Jellyman, Phillip (2013). Limitation and facilitation of one of the world's most invasive fish: an intercontinental comparison. Ecology.  ISSN 0012-9658.  94(2), s 356- 367 . doi: 10.1890/12-0628.1
• Bærum, Kim Magnus; Haugen, Thrond Oddvar; Kiffney, Peter; Olsen, Esben Moland & Vøllestad, Leif Asbjørn (2013). Interacting effects of temperature and density on individual growth performance in a wild population of brown trout. Freshwater Biology.  ISSN 0046-5070.  58(7), s 1329- 1339 . doi: 10.1111/fwb.12130
• Durif, Caroline; Browman, Howard; Phillips, John B.; Skiftesvik, Anne Berit; Vøllestad, Leif Asbjørn & Stockhausen, Hagen (2013). Magnetic Compass Orientation in the European Eel. PLoS ONE.  ISSN 1932-6203.  8(3) . doi: 10.1371/journal.pone.0059212 Full text in Research Archive.
• Pettersen, Ruben Alexander; Hytterød, Sigurd; Vøllestad, Leif Asbjørn & Mo, Tor Atle (2013). Osmoregulatory disturbances in Atlantic salmon, Salmo salar L., caused by the monogenean Gyrodactylus salaris. Journal of Fish Diseases.  ISSN 0140-7775.  36, s 67- 70 . doi: 10.1111/j.1365-2761.2012.01441.x
• Voje, Kjetil Lysne; Mazzarella, Anna Virginia Black; Hansen, Thomas F; Østbye, Kjartan; Klepaker, Tom Olav; Bass, Arthur; Herland, Anders; Bærum, Kim Magnus; Gregersen, Finn & Vøllestad, Leif Asbjørn (2013). Adaptation and constraint in a stickleback radiation. Journal of Evolutionary Biology.  ISSN 1010-061X.  26(11), s 2396- 2414 . doi: 10.1111/jeb.12240

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• Avset, Liv Mildrid Melkild; Moe, S. Jannicke; Vøllestad, Leif Asbjørn & Rustadbakken, Atle (2018, 21. mars). Norges største ørret blir stadig mindre. [Internett].  forskning.no.
• Hindar, Kjetil; Mo, Tor Atle; Eken, Morten; Hagen, Anders Gjørwad; Hytterød, Sigurd; Sandodden, Roar; Vøllestad, Leif Asbjørn & Aamodt, Knut Ola (2018). Kan Gyrodactylus salaris utryddes fra Drammensregionen? Sluttrapport fra arbeidsgruppen for Drammensregionen. NINA rapport. 1456. Show summary

  Lakseparasitten Gyrodactylus salaris er en av de alvorligste truslene mot villaksen i Norge. Bekjempelse av parasitten har derfor høy prioritet. Målet er å bli kvitt parasitten der dette er mulig, samtidig som risikoen for smittespredning til nye elver og regioner reduseres. Kjemisk behandling i kombinasjon med fiskesperrer, har de seneste årene dannet grunnlaget for bekjempelsesarbeidet, som har ført til færre infiserte vassdrag og redusert spredningsrisiko. I handlingsplanen mot G. salaris 2014-2016, utarbeidet av Miljødirektoratet og Mattilsynet, heter det at det er utarbeidet planer for utryddelse av G. salaris fra alle infiserte vassdrag med unntak av de tre smittede vassdragene i Drammensregionen. Der var forslaget å foreta nødvendige utredninger og undersøkelser med hensyn på muligheten for å utrydde parasitten. En arbeidsgruppe ble oppnevnt av Miljødirektoratet i 2015 og denne rapporten redegjør for arbeidsgruppens vurderinger. Arbeidsgruppen fikk som mandat å gå gjennom alle tilgjengelige alternativer og muligheter for å utrydde parasitten fra Drammensregionen, beskrive hvilke strategier og metoder som kan benyttes, vurdere sannsynligheten for å lykkes med bekjempelse av G. salaris i smitteregionen og beregne kostnadene ved de ulike strategiene/metodene. I 2017 presiserte Miljødirektoratet at arbeidsgruppen i tillegg til å vurdere rotenonmetoden og aluminiumsmetoden, som er de to metodene som har vært brukt mot G. salaris, også skulle foreta en vurdering av klormetoden som ennå er på forsøksstadiet. Arbeidsgruppen har vurdert Drammensfjorden med sitt ferskvannslag og forekomst av infiserte laksunger langt fra nærmeste elvemunning som den største utfordringen med tanke på å utrydde G. salaris fra regionen. En annen stor utfordring er det artsrike fiskesamfunnet i regionen med ferskvannsfiskearter med til dels dårlig kjent biologi som må bevares under bekjempelse av parasitten. De andre utfordringene som er identifisert i regionen, mener arbeidsgruppen kan løses gjennom en detaljplanlegging tilsvarende de som har gått forut for tidligere aksjoner mot G. salaris. På denne bakgrunn mener arbeidsgruppen at det er sannsynlig at G. salaris kan utryddes fra Drammensregionen med kjent metodikk, men at det forut for en kjemisk behandling må skje en kunnskapsinnhenting som gir trygghet for at de store utfordringene som arbeidsgruppen har identifisert, kan håndteres på en sikker måte. Blant viktige strategier og tiltak som forvaltningen bør vurdere, fremhever arbeidsgruppen flere gjentatte behandlinger enn det som hittil har vært vanlig, utprøving av ny metodikk som kan redusere forekomsten av parasitten, tiltak som reduserer behandlingsområdet, og tiltak som reduserer antallet laksunger i området som skal behandles. NØKKELORD : Drammensregionen (Buskerud og Vestfold), Drammenselva, Lierelva, Sandeelva, Drammensfjorden, Gyrodactylus salaris, laks, Salmo salar, utryddelse, kjemisk behandling

• Vøllestad, Leif Asbjørn (2018). Hva er det med laksen?.
• Vøllestad, Leif Asbjørn (2018). Hva er det med laksen?.
• Sandve, Simen Rød; Hvidsten, Torgeir Rhoden; Lien, Sigbjørn; Rori, Rohlfs; Jakobsen, Kjetill Sigurd; Nome, Torfinn; Varadharajan, Srinidhi; Nederbragt, Alexander Johan & Vøllestad, Leif Asbjørn (2017). Evolution after whole genome duplication - insights from the salmonids.
• Vøllestad, Leif Asbjørn (2017). Havboka. Biolog.  ISSN 0801-0722.  35(3-4), s 14- 15
• Vøllestad, Leif Asbjørn (2017). Hva er det med laksen?.
• Vøllestad, Leif Asbjørn (2017). Population differentiation and life history diversification: rapid and small scale?.
• Vøllestad, Leif Asbjørn (2017). Understanding contemporary evolution in grayling Thymallus thymallus. A long-term study.
• Bærum, Kim Magnus; Vøllestad, Leif Asbjørn; Kiffney, Peter; Remy, Alice & Haugen, Thrond Oddvar (2016). Erratum to: Population-level variation in juvenile brown trout growth from different climatic regions of Norway to an experimental thermal gradient (Environ Biol Fish, 10.1007/s10641-016-0533-6). Environmental Biology of Fishes.  ISSN 0378-1909.  99(12), s 1019 . doi: 10.1007/s10641-016-0553-2
• Dalen, Kristine; Vøllestad, Leif Asbjørn & van Leuween, Casper (2016). Effect of fragmentation and lack of precise homing on population structure in European grayling (Thymallus thymallus) within a large Norwegian river system..
• Høydalsvik, Maria N. & Vøllestad, Leif Asbjørn (2016). Population dynamics in lobster: Effects of marina protected areas.
• Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J. & Vøllestad, Leif Asbjørn (2016). The relative impacts of early life conditions and maternal size effects in determining average fitness and population growth of pike.
• Vøllestad, Leif Asbjørn (2016). Dyreriket - en zoologisk reise. Biolog.  ISSN 0801-0722.  34(2), s 46- 47
• Vøllestad, Leif Asbjørn (2016). Dødelighet i kystsonen og i havet. Hvor blir laksen av..
• Vøllestad, Leif Asbjørn (2016). Fiskeanatomi.. Biolog.  ISSN 0801-0722.  34(3), s 37- 37
• Vøllestad, Leif Asbjørn (2016). Is it possible to give highly effective lectures?.
• Vøllestad, Leif Asbjørn (2016). Population differentiation and life history diversification: rapid and small scale?.
• Vøllestad, Leif Asbjørn (2016). Understanding contemporary evolution in grayling Thymallus thymallus.
• Vøllestad, Leif Asbjørn (2016). Økologiske konsekvenser av kultivering?.
• Boessenkool, Sanne; Star, Bastiaan; Trucchi, Emiliano; Merilä, Juha & Vøllestad, Leif Asbjørn (2015). Whole genome analyses of threespine stickleback populations from the Mediterranean to Northern Europe.
• Fuchs, Daniela & Vøllestad, Leif Asbjørn (2015). Personality traits in fish – the consistency of behavior in sea trout (Salmo trutta) of Southern Norway.
• Høydalsvik, Maria N. & Vøllestad, Leif Asbjørn (2015). Population dynamics in lobster: Effects of marine protected areas.
• Juliussen, Elisabeth H. & Vøllestad, Leif Asbjørn (2015). Adaption to temperature in Atlantic cod (Gadus morhua) on a micro-geographic scale.
• Mazzarella, Anna; Boessenkool, Sanne; Østbye, Kjartan; Vøllestad, Leif Asbjørn & Trucchi, Emiliano (2015). Genomic signatures of the plateless phenotype in the Threespine Stickleback..
• Mellerud, Ida Kristin & Vøllestad, Leif Asbjørn (2015). Connectivity of Atlantic cod at the Norwegian Skagerrak coast.
• Taugbøl, Annette; Arntsen, Tina; Østbye, Kjartan & Vøllestad, Leif Asbjørn (2015). Small changes in gene expression of targeted osmoregulatory genes when exposing marine and freshwater Threespine Stickleback (Gasterosteus aculeatus) to abrupt salinity transfers..
• Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J. & Vøllestad, Leif Asbjørn (2015). Fitness consequences of early life conditions and maternal size effects in pike (Esox lucius).
• Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J. & Vøllestad, Leif Asbjørn (2015). Relative fitness consequences of early life conditions and maternal length in Windermere pike.
• Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J. & Vøllestad, Leif Asbjørn (2015). Relative fitness importance of a size-mediated maternal effect – an integral projection model approach.
• Vøllestad, Leif Asbjørn (2015). Effects of environmental variation on the population structure of grayling Thymallus thymallus.
• Hansson, Truls Hveem; Vøllestad, Leif Asbjørn & Mazzarella, Anna (2014). Salinity-induced phenotypic plasticity in lateral bony plate number of the threespine stickleback (Gasterosteus aculeatus).
• Hansson, Truls Hveem; Vøllestad, Leif Asbjørn; Mazzarella, Anna Virginia Black; Taugbøl, Annette; Voje, Kjetil L. & Fischer, Barbara (2014). Phenotypic Plasticity in threespined stickleback (G. aculeatus).
• Mellerud, Ida Kristin; Vøllestad, Leif Asbjørn & Knutsen, Halvor (2014). Connectivity among populations of Atlantic cod (Gadus morhua) at the Norwegian Skagerrak cod.
• Vøllestad, Leif Asbjørn (2014). Atlantic salmon Salmo salar. Analysis of the Norwegian catch statistics.
• Vøllestad, Leif Asbjørn (2014). Climate effects on fish migration: eel and salmon as examples.
• Vøllestad, Leif Asbjørn (2014). Contemporary evolution in grayling Thymallus thymallus.
• Vøllestad, Leif Asbjørn (2014). Hva er det med laksen?.
• Vøllestad, Leif Asbjørn (2014). Norske ferskvannsfisk – utbredelse, biologi og utfordringer.
• Vøllestad, Leif Asbjørn (2014). Population differentiation and diversification: rapid and small scale?.
• Wiig, Elisabeth; Vøllestad, Leif Asbjørn & Østbye, Kjartan (2014). Variation in armour of the three-spine stickleback.
• Hanssen, Benjamin & Vøllestad, Leif Asbjørn (2013). The life history of corkwing wrasse: effects of harvesting.
• Hansson, Truls H & Vøllestad, Leif Asbjørn (2013). Phenotypic Plasticity in threespined stickleback (G. aculeatus).
• Hesthagen, Trygve H. & Vøllestad, Leif Asbjørn (2013). Jørgen Vasshaug – lektoren som satte Østfolds fiskevann på kartet. pH-status : forum for sur nedbør og kalking.  ISSN 0808-4882.  (1), s 3- 5
• Mazzarella, Anna Virginia Black; Østbye, Kjartan & Vøllestad, Leif Asbjørn (2013). Looking for genomic signatures of platelessness in the threespine stickleback (Gasterosteus aculeatus).
• Mazzarella, Anna Virginia Black; Østbye, Kjartan & Vøllestad, Leif Asbjørn (2013). Looking for genomic signatures of platelessness in the threespine stickleback (Gasterosteus aculeatus).
• Vindenes, Yngvild; Edeline, Eric; Ohlberger, Jan; Langangen, Øystein; Winfield, Ian J.; Stenseth, Nils Christian & Vøllestad, Leif Asbjørn (2013). Effects of climate warming on trait-based dynamics in a freshwater top predator.
• Vindenes, Yngvild; Edeline, Eric; Ohlberger, Jan; Langangen, Øystein; Winfield, Ian J.; Stenseth, Nils Christian & Vøllestad, Leif Asbjørn (2013). Trait-based dynamics of a top predator in freshwaters and effects of climate change.
• Vøllestad, Leif Asbjørn (2013). Akvakultur og sjømatproduksjon.Relevant forskning ved Institutt for biovitenskap - UiO.
• Vøllestad, Leif Asbjørn (2013). Blir våre laksebestander overbeskattet?.
• Vøllestad, Leif Asbjørn (2013). Harren i Lesja: oppsummering av 20 år med forskning.
• Vøllestad, Leif Asbjørn (2013). Inngrep i og omkring vassdrag.

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