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Dr. Torbjørn Forseth
Department of Aquatic Biodiversity, The Norwegian Institute for Nature Research (NINA), 7034 Trondheim, Norway

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0 Climate Change
0 Fisheries Management
0 Life history and growth
0 Thermal adaptation
0 Environmental effects of hydropower

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Life history and growth
Climate Change
Thermal adaptation
Conservation limits
Fisheries Management

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Journal article
Published: 28 April 2021 in Water
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Fish swimming performance is strongly influenced by flow hydrodynamics, but little is known about the relation between fine-scale fish movements and hydrodynamics based on in-situ investigations. In the presented study, we validated the etho-hydraulic fish swimming direction model presented in the River Mandal from Southern Norway, using similar behavioral and hydraulic data on salmon smolts from the River Orkla in Central Norway. The re-parametrized model explained the variation of the swimming direction of fish in the Orkla system in same degree as the original model performed in the Mandal system (R2: 84% in both cases). The transferability of the model when using it from one river to predict swimming direction in the other river was lower (R2: 21% and 26%), but nevertheless relatively high given that the two localities differed in hydraulic conditions. The analyses thus provide support for the fact that the identified hydraulic parameters and their interaction affected smolt behavior in a similar way at the two sites, but that local parametrization of the base model is required. The developed etho-hydraulic models can provide important insights into fish behavior and fish migration trajectories and can be developed into prediction models important for the future development of behavioral downstream migration solutions.

ACS Style

Marcell Szabo-Meszaros; Ana Silva; Kim Bærum; Henrik Baktoft; Knut Alfredsen; Richard Hedger; Finn Økland; Karl Gjelland; Hans-Petter Fjeldstad; Olle Calles; Torbjørn Forseth. Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts. Water 2021, 13, 1230 .

AMA Style

Marcell Szabo-Meszaros, Ana Silva, Kim Bærum, Henrik Baktoft, Knut Alfredsen, Richard Hedger, Finn Økland, Karl Gjelland, Hans-Petter Fjeldstad, Olle Calles, Torbjørn Forseth. Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts. Water. 2021; 13 (9):1230.

Chicago/Turabian Style

Marcell Szabo-Meszaros; Ana Silva; Kim Bærum; Henrik Baktoft; Knut Alfredsen; Richard Hedger; Finn Økland; Karl Gjelland; Hans-Petter Fjeldstad; Olle Calles; Torbjørn Forseth. 2021. "Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts." Water 13, no. 9: 1230.

Journal article
Published: 07 September 2020 in Sustainability
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Repeat spawners constitute an important component of Atlantic salmon populations, but survival of post-spawning individuals (kelts) are often compromised by anthropogenic structures such as hydropower plants (HPPs). Potential effects of HPPs include migration delays and associated increased energy depletion, which potentially results in increased overall mortality. We combined a detailed 3D hydraulic model with high-resolution 3D tracking of tagged kelts (length 73–104 cm) to obtain estimates of kelt movement through water. These estimates were then used in an energetics model to estimate hourly energy expenditure while negotiating the HPP area. Hourly kelt energy expenditure varied between 0.8 and 10.1 kJ × h−1 and was dependent on kelt length. Degree of additional energy depletion can amount to several percent of remaining energy content (our study indicates 4–5 percentage points) potentially leading to reduced post-spawning survival. In turn, this can nullify the iteroparous breeding strategy and jeopardize long-term stability and persistence of Atlantic salmon populations inhabiting HPP rivers.

ACS Style

Henrik Baktoft; Karl Gjelland; Marcell Szabo-Meszaros; Ana Silva; Milan Riha; Finn Økland; Knut Alfredsen; Torbjørn Forseth. Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival? Sustainability 2020, 12, 7341 .

AMA Style

Henrik Baktoft, Karl Gjelland, Marcell Szabo-Meszaros, Ana Silva, Milan Riha, Finn Økland, Knut Alfredsen, Torbjørn Forseth. Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival? Sustainability. 2020; 12 (18):7341.

Chicago/Turabian Style

Henrik Baktoft; Karl Gjelland; Marcell Szabo-Meszaros; Ana Silva; Milan Riha; Finn Økland; Knut Alfredsen; Torbjørn Forseth. 2020. "Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival?" Sustainability 12, no. 18: 7341.

Perspectives and paradigms
Published: 22 December 2018 in Biological Invasions
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In 2017, Norway experienced an invasion of the Pacific salmonid pink salmon (Oncorhynchus gorbuscha) in numbers never before seen in rivers all along the coast. Significant numbers were also caught in other parts of northwestern Europe. Pink salmon has been observed in variable numbers in Norwegian waters in the summer and autumn of most years since 1960, after the first successful Russian introduction of pink salmon fry in rivers draining to the White Sea in northwest Russia in 1959. With the exception of 1960, pink salmon have been most abundant in odd years, based on the odd-year broodline of the 2-year life salmonid. Even-year fish has generally been less abundant, but in recent years, significant numbers of this broodline have also been caught. In this paper we review the available information on pink salmon in Norwegian rivers and discuss (1) to what extent the presence of this species in Norway has been driven by Russian introductions and natural reproduction in Russian, and lately in Norwegian, rivers, and (2) the likelihood of reproducing populations of pink salmon being established in more Norwegian rivers. Considering the continued propagule pressure in terms of adult pink salmon entering and spawning in Norwegian rivers, it is puzzling that self-propagating populations apparently only have been established in some rivers in the northernmost part of the country. The potential impact of pink salmon on native salmonids and river ecosystems is discussed briefly. Extensive research is required to understand the mechanisms that determine the fate of pink salmon as an alien species, and specifically the possible impact of pink salmon on native salmonids and the environment in the recipient rivers and in the ocean.

ACS Style

Odd Terje Sandlund; Henrik Hårdensson Berntsen; Peder Fiske; Jorma Kuusela; Rune Muladal; Eero Niemelä; Ingebrigt Uglem; Torbjørn Forseth; Tor Atle Mo; Eva B. Thorstad; Alexey E. Veselov; Knut Vollset; Alexander V. Zubchenko. Pink salmon in Norway: the reluctant invader. Biological Invasions 2018, 21, 1033 -1054.

AMA Style

Odd Terje Sandlund, Henrik Hårdensson Berntsen, Peder Fiske, Jorma Kuusela, Rune Muladal, Eero Niemelä, Ingebrigt Uglem, Torbjørn Forseth, Tor Atle Mo, Eva B. Thorstad, Alexey E. Veselov, Knut Vollset, Alexander V. Zubchenko. Pink salmon in Norway: the reluctant invader. Biological Invasions. 2018; 21 (4):1033-1054.

Chicago/Turabian Style

Odd Terje Sandlund; Henrik Hårdensson Berntsen; Peder Fiske; Jorma Kuusela; Rune Muladal; Eero Niemelä; Ingebrigt Uglem; Torbjørn Forseth; Tor Atle Mo; Eva B. Thorstad; Alexey E. Veselov; Knut Vollset; Alexander V. Zubchenko. 2018. "Pink salmon in Norway: the reluctant invader." Biological Invasions 21, no. 4: 1033-1054.

Research article
Published: 27 September 2018 in River Research and Applications
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Dams and turbines associated with hydroelectric power plants (HEP) disrupt connectivity by affecting fish movement and survival. There has been an increasing focus on measures to facilitate downstream migration at HEPs. The fish guidance efficacy (FGE) of downstream mitigation measures largely remains suboptimal and calls for development of knowledge on factors influencing FGE. In this study, we analyse 6 years of wild Atlantic salmon smolt passive integrated transponder (PIT)‐telemetry data (N = 1,498) from a neighbouring small‐ and a large‐scale HEP. Timing of the smolt migration period was significantly different between the two rivers. Thus, river‐specific smolt‐run timing is imperative for proper measures management in regulated rivers aiming at maximizing smolt‐descent survival. A generalized linear model including additive effects of relative bypass discharge and scaled river discharge on the FGE for descending smolts received highest Akaike's information criterion support in the data and explained 74.2% of the FGE variation. This model, including no river effect, predicted high FGE (up to 90%) at low river flow (≤30% of HEP maximum capacity) when 7% of the water is allocated through the bypass. Many run‐of‐the‐river HEPs have highly variable river flow during the smolt‐run period. Our model suggests that these HEPs could utilize their manoeuvre flexibility to obtain water allocation routines between bypass and turbines that optimize both FGE and hydroelectric production.

ACS Style

Tormod Haraldstad; Erik Höglund; Frode Kroglund; Thrond Oddvar Haugen; Torbjørn Forseth. Common mechanisms for guidance efficiency of descending Atlantic salmon smolts in small and large hydroelectric power plants. River Research and Applications 2018, 34, 1179 -1185.

AMA Style

Tormod Haraldstad, Erik Höglund, Frode Kroglund, Thrond Oddvar Haugen, Torbjørn Forseth. Common mechanisms for guidance efficiency of descending Atlantic salmon smolts in small and large hydroelectric power plants. River Research and Applications. 2018; 34 (9):1179-1185.

Chicago/Turabian Style

Tormod Haraldstad; Erik Höglund; Frode Kroglund; Thrond Oddvar Haugen; Torbjørn Forseth. 2018. "Common mechanisms for guidance efficiency of descending Atlantic salmon smolts in small and large hydroelectric power plants." River Research and Applications 34, no. 9: 1179-1185.

Journal article
Published: 01 August 2018 in Science of The Total Environment
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Climate change is expected to alter future temperature and discharge regimes of rivers. These regimes have a strong influence on the life history of most aquatic river species, and are key variables controlling the growth and survival of Atlantic salmon. This study explores how the future abundance of Atlantic salmon may be influenced by climate-induced changes in water temperature and discharge in a regulated river, and investigates how negative impacts in the future can be mitigated by applying different regulated discharge regimes during critical periods for salmon survival. A spatially explicit individual-based model was used to predict juvenile Atlantic salmon population abundance in a regulated river under a range of future water temperature and discharge scenarios (derived from climate data predicted by the Hadley Centre's Global Climate Model (GCM) HadAm3H and the Max Plank Institute's GCM ECHAM4), which were then compared with populations predicted under control scenarios representing past conditions. Parr abundance decreased in all future scenarios compared to the control scenarios due to reduced wetted areas (with the effect depending on climate scenario, GCM, and GCM spatial domain). To examine the potential for mitigation of climate change-induced reductions in wetted area, simulations were run with specific minimum discharge regimes. An increase in abundance of both parr and smolt occurred with an increase in the limit of minimum permitted discharge for three of the four GCM/GCM spatial domains examined. This study shows that, in regulated rivers with upstream storage capacity, negative effects of climate change on Atlantic salmon populations can potentially be mitigated by release of water from reservoirs during critical periods for juvenile salmon.

ACS Style

L.E. Sundt-Hansen; R.D. Hedger; O. Ugedal; O.H. Diserud; Anders Gravbrøt Finstad; J.F. Sauterleute; L. Tøfte; K. Alfredsen; Torbjørn Forseth. Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers. Science of The Total Environment 2018, 631-632, 1005 -1017.

AMA Style

L.E. Sundt-Hansen, R.D. Hedger, O. Ugedal, O.H. Diserud, Anders Gravbrøt Finstad, J.F. Sauterleute, L. Tøfte, K. Alfredsen, Torbjørn Forseth. Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers. Science of The Total Environment. 2018; 631-632 ():1005-1017.

Chicago/Turabian Style

L.E. Sundt-Hansen; R.D. Hedger; O. Ugedal; O.H. Diserud; Anders Gravbrøt Finstad; J.F. Sauterleute; L. Tøfte; K. Alfredsen; Torbjørn Forseth. 2018. "Modelling climate change effects on Atlantic salmon: Implications for mitigation in regulated rivers." Science of The Total Environment 631-632, no. : 1005-1017.

Research article
Published: 31 July 2018 in River Research and Applications
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The spawning migration of Atlantic salmon has been characterized by tracking salmon carrying electronic tags as they ascend rivers, but still little is known about how natural obstacles such as waterfalls influence migratory behaviour and how such behaviours are mediated by various biotic (e.g., fish size) and abiotic (e.g., discharge, water temperature, and barometric pressure) factors. The Norwegian river Numedalslågen is interrupted by natural waterfalls ranging in height from 2 to 6 m. We tagged 113 Atlantic salmon with radio transmitters in the estuary and used stationary radio telemetry stations to track fish. Ninety‐one salmon were recorded in Numedalslågen, 39 of which remained in the river for spawning. Large salmon moved farther and faster upriver but also delayed longer and had lower daily probability to pass the second waterfall. Delay below and passage probability at the final, largest waterfall was affected by water discharge, wherein passage occurred when discharge was declining. Barometric pressure also influenced daily probability of ascent, albeit in opposite directions for each waterfall. Importantly, we also found that salmon with surgically implanted radio transmitters moved farther upriver on average and delayed less time below one of the waterfalls than those with externally attached transmitters. Although there is variance in timing arising from individual decision‐making, we showed that natural waterfalls delay progress of Atlantic salmon on their spawning migration and that both biotic (i.e., size) and abiotic (i.e., barometric pressure and discharge) factors influenced the salmon's decisions to pass waterfalls that they encounter.

ACS Style

Robert J. Lennox; Eva B. Thorstad; Ola H. Diserud; Finn Økland; Steven J. Cooke; Ingar Aasestad; Torbjørn Forseth. Biotic and abiotic determinants of the ascent behaviour of adult Atlantic salmon transiting passable waterfalls. River Research and Applications 2018, 34, 907 -917.

AMA Style

Robert J. Lennox, Eva B. Thorstad, Ola H. Diserud, Finn Økland, Steven J. Cooke, Ingar Aasestad, Torbjørn Forseth. Biotic and abiotic determinants of the ascent behaviour of adult Atlantic salmon transiting passable waterfalls. River Research and Applications. 2018; 34 (8):907-917.

Chicago/Turabian Style

Robert J. Lennox; Eva B. Thorstad; Ola H. Diserud; Finn Økland; Steven J. Cooke; Ingar Aasestad; Torbjørn Forseth. 2018. "Biotic and abiotic determinants of the ascent behaviour of adult Atlantic salmon transiting passable waterfalls." River Research and Applications 34, no. 8: 907-917.

Article
Published: 06 April 2018 in Ecohydrology
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Studies of hydropeaking-induced stranding mortality on fish populations have been confined to analysis of empirical data and/or short-term hydraulic-habitat modelling of individual events, and are thus limited as to how they may be used to infer long-term effects in fish populations. In this study, the effects of stranding mortality on an Atlantic salmon population were simulated using an individual-based Atlantic salmon population model with the objective of determining the sensitivity of population dynamics to stranding. It was found that density-dependent mortality (an alternative source of mortality in juvenile Atlantic salmon) partially compensated for stranding mortality, acting as a negative feedback mechanism that dampened change in population abundance. Stranding caused a perturbation in population dynamics, and effects of individual stranding events persisted in time across the life-stages of the population. Effects on population abundance depended on the time of year when stranding was applied, both because of intra-annual changes in stranding mortality probability and because of intra-annual changes in the ability of density-dependent mortality to compensate for stranding mortality. We concluded that empirical measurements of stranding mortality have limited potential for inference of overall effects on the population, and a more dynamic modelling approach, incorporating system feedback, allows for a better modelling of the impact of stranding. Sensitivity analysis showed that population abundance was highly sensitive to density-dependent mortality, and we suggest that this area should be prioritised for further research when investigating the effects of hydropeaking on rivers.

ACS Style

Richard D. Hedger; Julian Sauterleute; Line E. Sundt-Hansen; Torbjørn Forseth; Ola Ugedal; Ola H. Diserud; Tor H. Bakken. Modelling the effect of hydropeaking-induced stranding mortality on Atlantic salmon population abundance. Ecohydrology 2018, 11, e1960 .

AMA Style

Richard D. Hedger, Julian Sauterleute, Line E. Sundt-Hansen, Torbjørn Forseth, Ola Ugedal, Ola H. Diserud, Tor H. Bakken. Modelling the effect of hydropeaking-induced stranding mortality on Atlantic salmon population abundance. Ecohydrology. 2018; 11 (5):e1960.

Chicago/Turabian Style

Richard D. Hedger; Julian Sauterleute; Line E. Sundt-Hansen; Torbjørn Forseth; Ola Ugedal; Ola H. Diserud; Tor H. Bakken. 2018. "Modelling the effect of hydropeaking-induced stranding mortality on Atlantic salmon population abundance." Ecohydrology 11, no. 5: e1960.

Journal article
Published: 01 April 2018 in Ecological Engineering
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ACS Style

Marcell Szabo-Meszaros; Christy Ushanth Navaratnam; Jochen Aberle; Ana T. Silva; Torbjørn Forseth; Olle Calles; Hans-Petter Fjeldstad; Knut Alfredsen. Experimental hydraulics on fish-friendly trash-racks: an ecological approach. Ecological Engineering 2018, 113, 11 -20.

AMA Style

Marcell Szabo-Meszaros, Christy Ushanth Navaratnam, Jochen Aberle, Ana T. Silva, Torbjørn Forseth, Olle Calles, Hans-Petter Fjeldstad, Knut Alfredsen. Experimental hydraulics on fish-friendly trash-racks: an ecological approach. Ecological Engineering. 2018; 113 ():11-20.

Chicago/Turabian Style

Marcell Szabo-Meszaros; Christy Ushanth Navaratnam; Jochen Aberle; Ana T. Silva; Torbjørn Forseth; Olle Calles; Hans-Petter Fjeldstad; Knut Alfredsen. 2018. "Experimental hydraulics on fish-friendly trash-racks: an ecological approach." Ecological Engineering 113, no. : 11-20.

Journal article
Published: 01 April 2018 in Canadian Journal of Fisheries and Aquatic Sciences
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This study found empirical evidence supporting the “growth–survival” paradigm in the marine phase of Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta). The paradigm postulates that larger or faster-growing individuals are more likely to survive than smaller or slower-growing conspecifics. The study employed long-term (25 year) capture data from a trap in the River Halselva in Norway during annual migration between marine and freshwater environments. Similar results were found for both species. Growth during the sea sojourn and return rates were positively correlated, linking increased survival with growth. Specific growth rate, survival, and duration of the sea sojourn of first-time migrants were correlated, suggesting that common environmental conditions at sea influence annual fish productivity. Freshwater and sea temperatures affected migration timing, whereas annual variation in marine growth and survival did not correlate with temperatures. This suggests that other factors such as variation in energy intake were the main source of annual growth variations. Moreover, the marine growth rate of the two species may signal annual overall fjord ecosystem production, especially related to their main prey.

ACS Style

Arne Johan Jensen; Bengt Finstad; Peder Fiske; Torbjørn Forseth; Audun Håvard Rikardsen; Ola Ugedal. Relationship between marine growth and sea survival of two anadromous salmonid fish species. Canadian Journal of Fisheries and Aquatic Sciences 2018, 75, 621 -628.

AMA Style

Arne Johan Jensen, Bengt Finstad, Peder Fiske, Torbjørn Forseth, Audun Håvard Rikardsen, Ola Ugedal. Relationship between marine growth and sea survival of two anadromous salmonid fish species. Canadian Journal of Fisheries and Aquatic Sciences. 2018; 75 (4):621-628.

Chicago/Turabian Style

Arne Johan Jensen; Bengt Finstad; Peder Fiske; Torbjørn Forseth; Audun Håvard Rikardsen; Ola Ugedal. 2018. "Relationship between marine growth and sea survival of two anadromous salmonid fish species." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 4: 621-628.

Review
Published: 01 January 2018 in Marine and Freshwater Research
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This review provides a summary of knowledge on two-way fish migration of salmonids and eels past hydroelectric plants in Europe. On the basis of a summary of international literature, general designs and recommendations for best practices for fish-pass facilities are provided. The review is part of the Norwegian SafePass project, which focuses on Atlantic salmon, brown trout, grayling and European eel. According to recent international recommendations, many existing European fishways for upstream migration do not have an optimal design. This is especially evident for denil and pool-and-weir fishways in inland areas with species such as grayling and brown trout. Based on the review, we generally recommend (1) using ramps, nature-like channels and vertical-slot fishways for these species and (2) reducing water drop between the pools in pool-and-weir fishways and reducing energy dissipation compared with the design of traditional Atlantic salmon ladders. There are few well-functioning passages for downstream migration of fish in Europe and significant progress has been made in the past decade to improve technology and knowledge. Several international studies have shown that physical structures, such as fine-mesh trash racks with alternative escape routes and bypass arrangements, provide >90% passage efficiency for downstream migration, especially for brown trout and salmon, and have, in recent years, shown good results also for silver eels.

ACS Style

Hans-Petter Fjeldstad; Ulrich Pulg; Torbjørn Forseth. Safe two-way migration for salmonids and eel past hydropower structures in Europe: a review and recommendations for best-practice solutions. Marine and Freshwater Research 2018, 69, 1834 .

AMA Style

Hans-Petter Fjeldstad, Ulrich Pulg, Torbjørn Forseth. Safe two-way migration for salmonids and eel past hydropower structures in Europe: a review and recommendations for best-practice solutions. Marine and Freshwater Research. 2018; 69 (12):1834.

Chicago/Turabian Style

Hans-Petter Fjeldstad; Ulrich Pulg; Torbjørn Forseth. 2018. "Safe two-way migration for salmonids and eel past hydropower structures in Europe: a review and recommendations for best-practice solutions." Marine and Freshwater Research 69, no. 12: 1834.

Journal article
Published: 01 December 2017 in Canadian Journal of Fisheries and Aquatic Sciences
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Competition for limited resources and the resulting density-dependent processes are key factors in driving stream salmonid population dynamics. Here we test for the combined effects of density and shelter availability on the movement of juvenile Atlantic salmon (Salmo salar) in a Norwegian river. Individually marked, hatchery-reared salmon juveniles were released at 26 sites along a 2.5 km long stretch and recaptured after 12 months. The spatial variation in shelter availability and density of salmonids was quantified prior to the release. We found no effect of released fish number on the number of marked salmon moving more than 12.5–112.5 m away from their release site. However, the ratio of pre-experiment fish density per shelter was positively related to the number of movers. Thus, fish that were released at sites where the amount of shelter was low relative to the density of the pre-experiment population were more likely to move. These results support the prediction from smaller scale experimental studies that shelter availability may act to determine local carrying capacity in stream-living salmonid populations.

ACS Style

Maxim A.K. Teichert; Anders Foldvik; Sigurd Einum; Anders Gravbrøt Finstad; Torbjørn Forseth; Ola Ugedal. Interactions between local population density and limited habitat resources determine movements of juvenile Atlantic salmon. Canadian Journal of Fisheries and Aquatic Sciences 2017, 74, 2153 -2160.

AMA Style

Maxim A.K. Teichert, Anders Foldvik, Sigurd Einum, Anders Gravbrøt Finstad, Torbjørn Forseth, Ola Ugedal. Interactions between local population density and limited habitat resources determine movements of juvenile Atlantic salmon. Canadian Journal of Fisheries and Aquatic Sciences. 2017; 74 (12):2153-2160.

Chicago/Turabian Style

Maxim A.K. Teichert; Anders Foldvik; Sigurd Einum; Anders Gravbrøt Finstad; Torbjørn Forseth; Ola Ugedal. 2017. "Interactions between local population density and limited habitat resources determine movements of juvenile Atlantic salmon." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 12: 2153-2160.

Original article
Published: 28 November 2017 in Fish and Fisheries
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Much effort has been devoted to developing, constructing and refining fish passage facilities to enable target species to pass barriers on fluvial systems, and yet, fishway science, engineering and practice remain imperfect. In this review, 17 experts from different fish passage research fields (i.e., biology, ecology, physiology, ecohydraulics, engineering) and from different continents (i.e., North and South America, Europe, Africa, Australia) identified knowledge gaps and provided a roadmap for research priorities and technical developments. Once dominated by an engineering‐focused approach, fishway science today involves a wide range of disciplines from fish behaviour to socioeconomics to complex modelling of passage prioritization options in river networks. River barrier impacts on fish migration and dispersal are currently better understood than historically, but basic ecological knowledge underpinning the need for effective fish passage in many regions of the world, including in biodiversity hotspots (e.g., equatorial Africa, South‐East Asia), remains largely unknown. Designing efficient fishways, with minimal passage delay and post‐passage impacts, requires adaptive management and continued innovation. While the use of fishways in river restoration demands a transition towards fish passage at the community scale, advances in selective fishways are also needed to manage invasive fish colonization. Because of the erroneous view in some literature and communities of practice that fish passage is largely a proven technology, improved international collaboration, information sharing, method standardization and multidisciplinary training are needed. Further development of regional expertise is needed in South America, Asia and Africa where hydropower dams are currently being planned and constructed.

ACS Style

Ana T. Silva; Martyn C. Lucas; Theodore Castro-Santos; Christos Katopodis; Lee Baumgartner; Jason Thiem; Kim Aarestrup; Paulo Santos Pompeu; Gordon O'Brien; Douglas C. Braun; Nicholas J. Burnett; David Z. Zhu; Hans-Petter Fjeldstad; Torbjørn Forseth; Nallamuthu Rajaratnam; John G. Williams; Steven Cooke. The future of fish passage science, engineering, and practice. Fish and Fisheries 2017, 19, 340 -362.

AMA Style

Ana T. Silva, Martyn C. Lucas, Theodore Castro-Santos, Christos Katopodis, Lee Baumgartner, Jason Thiem, Kim Aarestrup, Paulo Santos Pompeu, Gordon O'Brien, Douglas C. Braun, Nicholas J. Burnett, David Z. Zhu, Hans-Petter Fjeldstad, Torbjørn Forseth, Nallamuthu Rajaratnam, John G. Williams, Steven Cooke. The future of fish passage science, engineering, and practice. Fish and Fisheries. 2017; 19 (2):340-362.

Chicago/Turabian Style

Ana T. Silva; Martyn C. Lucas; Theodore Castro-Santos; Christos Katopodis; Lee Baumgartner; Jason Thiem; Kim Aarestrup; Paulo Santos Pompeu; Gordon O'Brien; Douglas C. Braun; Nicholas J. Burnett; David Z. Zhu; Hans-Petter Fjeldstad; Torbjørn Forseth; Nallamuthu Rajaratnam; John G. Williams; Steven Cooke. 2017. "The future of fish passage science, engineering, and practice." Fish and Fisheries 19, no. 2: 340-362.

Journal article
Published: 01 April 2017 in La Houille Blanche
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ACS Style

Atle Harby; Torbjørn Forseth; Tor Haakon Bakken; Audun Ruud. Socio-environmental integration of hydropower facilities. La Houille Blanche 2017, 103, 5 -8.

AMA Style

Atle Harby, Torbjørn Forseth, Tor Haakon Bakken, Audun Ruud. Socio-environmental integration of hydropower facilities. La Houille Blanche. 2017; 103 (2):5-8.

Chicago/Turabian Style

Atle Harby; Torbjørn Forseth; Tor Haakon Bakken; Audun Ruud. 2017. "Socio-environmental integration of hydropower facilities." La Houille Blanche 103, no. 2: 5-8.

Journal article
Published: 03 March 2017 in ICES Journal of Marine Science
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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.

ACS Style

Torbjørn Forseth; Bjørn T. Barlaup; Bengt Finstad; Peder Fiske; Harald Gjøsæter; Morten Falkegård; Atle Hindar; Tor Atle Mo; Audun H. Rikardsen; Eva B. Thorstad; Leif Asbjørn Vøllestad; Vidar Wennevik. The major threats to Atlantic salmon in Norway. ICES Journal of Marine Science 2017, 74, 1496 -1513.

AMA Style

Torbjørn Forseth, Bjørn T. Barlaup, Bengt Finstad, Peder Fiske, Harald Gjøsæter, Morten Falkegård, Atle Hindar, Tor Atle Mo, Audun H. Rikardsen, Eva B. Thorstad, Leif Asbjørn Vøllestad, Vidar Wennevik. The major threats to Atlantic salmon in Norway. ICES Journal of Marine Science. 2017; 74 (6):1496-1513.

Chicago/Turabian Style

Torbjørn Forseth; Bjørn T. Barlaup; Bengt Finstad; Peder Fiske; Harald Gjøsæter; Morten Falkegård; Atle Hindar; Tor Atle Mo; Audun H. Rikardsen; Eva B. Thorstad; Leif Asbjørn Vøllestad; Vidar Wennevik. 2017. "The major threats to Atlantic salmon in Norway." ICES Journal of Marine Science 74, no. 6: 1496-1513.

Journal article
Published: 01 August 2014 in River Research and Applications
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The performance and movements of juvenile Atlantic salmon Salmo salar exposed to variable water discharge (simulating hydropeaking) but with a stable water-covered area were studied in six experimental stream channels, both during the winter and summer. Thirty fish were stocked into each channel, and the growth, body fat and movements of the fish were followed for about 2.5 months in each season. During the winter, no effect of hydropeaking was documented on performance or movement. In the summer, fish experiencing hydropeaking had lower body mass, lower body fat, and higher movement rates than the control fish. In general, effect sizes were small, and the rapid and frequent changes in water discharge and water level in the present study had small effects on the performance of juvenile Atlantic salmon. The cumulative long-term effect at the population level is unknown, but a reduced growth rate of 10% and a reduction in body fat of 16% in the hydropeaking experiments in the summer might to some extent translate into increased smolt age and lower overwintering survival. Copyright © 2014 John Wiley & Sons, Ltd.

ACS Style

Michael Puffer; O. K. Berg; A. Huusko; T. Vehanen; T. Forseth; S. Einum. Seasonal Effects of Hydropeaking on Growth, Energetics and Movement of Juvenile Atlantic Salmon (Salmo Salar). River Research and Applications 2014, 31, 1101 -1108.

AMA Style

Michael Puffer, O. K. Berg, A. Huusko, T. Vehanen, T. Forseth, S. Einum. Seasonal Effects of Hydropeaking on Growth, Energetics and Movement of Juvenile Atlantic Salmon (Salmo Salar). River Research and Applications. 2014; 31 (9):1101-1108.

Chicago/Turabian Style

Michael Puffer; O. K. Berg; A. Huusko; T. Vehanen; T. Forseth; S. Einum. 2014. "Seasonal Effects of Hydropeaking on Growth, Energetics and Movement of Juvenile Atlantic Salmon (Salmo Salar)." River Research and Applications 31, no. 9: 1101-1108.

Journal article
Published: 08 October 2013 in Environmental Conservation
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SUMMARYWhile management according to biological reference points is well established for many commercial marine fisheries, similar systems for more leisure based fisheries for freshwater fishes are less common. This paper describes the scientific foundation for management according to conservation limits and management targets for Norwegian populations of Atlantic salmon, a highly valued and heavily exploited anadromous fish species. Based on stock recruitment relationships during the freshwater phase, the biomass of females necessary to attain the carrying capacity (yielding average maximum recruitment) has been established as conservation limits for each of the 439 Norwegian populations. Using a simulation model based on reported catch and estimates of exploitation rates, the probability and percentage attainment of the conservation limits have been assessed annually since 2008, and exploitation advice provided for 176 of the largest populations. The number of populations that attained their conservation limits increased substantially after the new management scheme was introduced, despite that the number of returning salmon remained at historical low levels. Overall the populations evaluated in 2011 were at 95% of their conservation limits compared to 91% in 2008 and 85% in 2005. The improvement could largely be attributed to reduced exploitation rates, due to new restrictions in both the marine and river fisheries. The new management scheme also improved the catch statistics and stimulated data acquisition for management. Implementation of management according to conservation limits has been a success in terms of attaining the main management goal of protecting the Atlantic salmon populations by ensuring that an increasing number of the populations likely are at their maximum reproductive capacity. Long-term increases in fisheries yield, the secondary management goal, are likely to be attained, but remain to be documented. Reference point based management of Atlantic salmon exemplifies management within the intersection of fisheries management and conservation biology, borrowing principles from both sides.

ACS Style

Torbjørn Forseth; Peder Fiske; Bjørn Barlaup; Harald Gjøsæter; Kjetil Hindar; Ola H. Diserud. Reference point based management of Norwegian Atlantic salmon populations. Environmental Conservation 2013, 40, 356 -366.

AMA Style

Torbjørn Forseth, Peder Fiske, Bjørn Barlaup, Harald Gjøsæter, Kjetil Hindar, Ola H. Diserud. Reference point based management of Norwegian Atlantic salmon populations. Environmental Conservation. 2013; 40 (4):356-366.

Chicago/Turabian Style

Torbjørn Forseth; Peder Fiske; Bjørn Barlaup; Harald Gjøsæter; Kjetil Hindar; Ola H. Diserud. 2013. "Reference point based management of Norwegian Atlantic salmon populations." Environmental Conservation 40, no. 4: 356-366.

Journal article
Published: 30 July 2013 in Population Ecology
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Theoretical considerations suggest that the relative abundance of age-specific limiting resources determines the ontogenetic timing of density dependence. Structural shelters may represent one such resource which can become increasingly scarce with increasing body size. Here we use a time series of juvenile Atlantic salmon (Salmo salar) densities and ask whether ontogenetic patterns of density-dependent losses in two separate reaches of a river can be predicted by considering their shelter abundances. The analyses were conducted using sampling site data (n = 30) as well as stream-reach averages. Loss rates from the egg to the young-of-the-year stage were density-dependent in both reaches. For the transition from the young-of-the-year to the yearling stage, when shelters are more likely to become limiting, the results were sensitive to the spatial scale of analysis. On the reach scale, among-year variation in loss rates was positively correlated with density in the reach with the lowest shelter abundance, whereas no such effect was found in the other reach. This demonstrates that the ontogenetic timing of density dependence can vary among areas within populations, and hence among populations, and that this variation can be explained by quantification of age-specific limiting factors. For analyses at the sample site scale this pattern was reversed, with stronger density dependence in the reach with highest shelter abundance. However, this result was clearly driven by immigration into low density sites, which masked the true reach-level effect. Thus, our study also exemplifies how population level regulation inferred from patch- or trap-based data that fails to account for animal movements can be biased.

ACS Style

Maxim A. K. Teichert; Sigurd Einum; Anders Gravbrøt Finstad; Ola Ugedal; Torbjørn Forseth. Ontogenetic timing of density dependence: location-specific patterns reflect distribution of a limiting resource. Population Ecology 2013, 55, 575 -583.

AMA Style

Maxim A. K. Teichert, Sigurd Einum, Anders Gravbrøt Finstad, Ola Ugedal, Torbjørn Forseth. Ontogenetic timing of density dependence: location-specific patterns reflect distribution of a limiting resource. Population Ecology. 2013; 55 (4):575-583.

Chicago/Turabian Style

Maxim A. K. Teichert; Sigurd Einum; Anders Gravbrøt Finstad; Ola Ugedal; Torbjørn Forseth. 2013. "Ontogenetic timing of density dependence: location-specific patterns reflect distribution of a limiting resource." Population Ecology 55, no. 4: 575-583.

Journal article
Published: 01 February 2013 in Canadian Journal of Fisheries and Aquatic Sciences
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We predict an increase in parr recruitment and smolt production of Atlantic salmon (Salmo salar) populations along a climate gradient from the subarctic to the Arctic in western and northern Norway in response to future climate change. Firstly, we predicted local stream temperature and discharge from downscaled data obtained from Global Climate Models. Then, we developed a spatially explicit individual-based model (IBM) parameterized for the freshwater stage, with combinations of three different postsmolt survival probabilities reflecting different marine survival regimes. The IBM was run for three locations: southern Norway (∼59°N), western Norway (∼62°N), and northern Norway (∼70°N). Increased temperatures under the future climate regimes resulted in faster parr growth, earlier smolting, and elevated smolt production in the western and northern locations, in turn leading to increased egg deposition and elevated recruitment into parr. In the southern location, density-dependent mortality of parr resulting from low summer wetted-areas reduced predicted future smolt production in comparison to the other locations. It can be inferred, therefore, that climate change may have both positive and negative effects on anadromous fish abundance within the subarctic–Arctic according to geographical region.

ACS Style

Richard D. Hedger; Line E. Sundt-Hansen; Torbjørn Forseth; Ola Ugedal; Ola H. Diserud; Ånund S. Kvambekk; Anders Gravbrøt Finstad. Predicting climate change effects on subarctic–Arctic populations of Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences 2013, 70, 159 -168.

AMA Style

Richard D. Hedger, Line E. Sundt-Hansen, Torbjørn Forseth, Ola Ugedal, Ola H. Diserud, Ånund S. Kvambekk, Anders Gravbrøt Finstad. Predicting climate change effects on subarctic–Arctic populations of Atlantic salmon (Salmo salar). Canadian Journal of Fisheries and Aquatic Sciences. 2013; 70 (2):159-168.

Chicago/Turabian Style

Richard D. Hedger; Line E. Sundt-Hansen; Torbjørn Forseth; Ola Ugedal; Ola H. Diserud; Ånund S. Kvambekk; Anders Gravbrøt Finstad. 2013. "Predicting climate change effects on subarctic–Arctic populations of Atlantic salmon (Salmo salar)." Canadian Journal of Fisheries and Aquatic Sciences 70, no. 2: 159-168.

Review article
Published: 10 November 2012 in Ecological Modelling
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In this paper, we present a spatially explicit individual-based mechanistic model for predicting the freshwater population abundance of Atlantic salmon (Salmo salar L.). The model simulates the complete life-cycle at small spatial (∼50 m) and temporal (weekly) scales. Processes such as spawning, recruitment, mortality and movements are predicted using deterministic and stochastic functions, parameterized using relationships established from the literature and empirical observations. The model was used to simulate salmon population abundance within a river in western-central Norway (River Nausta). The sensitivity of population abundance to fry and parr carrying capacities, and parr and post-smolt density-independent mortalities was analyzed. The optimally parameterized model predicted similar abundances and age compositions across the developmental stages of the population to those estimated from empirical observations within the river. The effect of carrying capacities and mortalities on abundance was strongest at the developmental stage at which they operated, but also affected the abundance of subsequent developmental stages or the progeny, suggesting negative (dampening) feedback mechanisms.

ACS Style

R.D. Hedger; L.E. Sundt-Hansen; Torbjørn Forseth; O.H. Diserud; O. Ugedal; Anders Gravbrøt Finstad. Modelling the complete life-cycle of Atlantic salmon (Salmo salar L.) using a spatially explicit individual-based approach. Ecological Modelling 2012, 248, 119 -129.

AMA Style

R.D. Hedger, L.E. Sundt-Hansen, Torbjørn Forseth, O.H. Diserud, O. Ugedal, Anders Gravbrøt Finstad. Modelling the complete life-cycle of Atlantic salmon (Salmo salar L.) using a spatially explicit individual-based approach. Ecological Modelling. 2012; 248 ():119-129.

Chicago/Turabian Style

R.D. Hedger; L.E. Sundt-Hansen; Torbjørn Forseth; O.H. Diserud; O. Ugedal; Anders Gravbrøt Finstad. 2012. "Modelling the complete life-cycle of Atlantic salmon (Salmo salar L.) using a spatially explicit individual-based approach." Ecological Modelling 248, no. : 119-129.

Journal article
Published: 01 October 2012 in Canadian Journal of Fisheries and Aquatic Sciences
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We explored the mechanisms of density-dependent growth in Arctic char ( Salvelinus alpinus ) by comparing the energetics of growth, consumption, and activity obtained under three replicated density treatments in a large-scale enclosure (90 m2 surface area) experiment. The enclosures permitted the entry of zooplankton and allowed char to feed on the bottom and at the surface of the lake. We found a negative (power) relationship between growth and density. Char consumption rate decreased linearly with increasing density. Growth efficiency was affected by fish density in a similar manner as growth rate. Finally, activity increased with fish density and was particularly high at high densities. Our findings illustrate the complexity of the relationships among consumption, activity, growth rates, and fish density and bring further evidence to the possible involvement of behavioural mechanisms in density-dependent processes, notably by modulating activity costs with density.

ACS Style

Guillaume Guénard; Daniel Boisclair; Ola Ugedal; Torbjørn Forseth; Ian A. Fleming; Bror Jonsson. The bioenergetics of density-dependent growth in Arctic char (Salvelinus alpinus). Canadian Journal of Fisheries and Aquatic Sciences 2012, 69, 1651 -1662.

AMA Style

Guillaume Guénard, Daniel Boisclair, Ola Ugedal, Torbjørn Forseth, Ian A. Fleming, Bror Jonsson. The bioenergetics of density-dependent growth in Arctic char (Salvelinus alpinus). Canadian Journal of Fisheries and Aquatic Sciences. 2012; 69 (10):1651-1662.

Chicago/Turabian Style

Guillaume Guénard; Daniel Boisclair; Ola Ugedal; Torbjørn Forseth; Ian A. Fleming; Bror Jonsson. 2012. "The bioenergetics of density-dependent growth in Arctic char (Salvelinus alpinus)." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 10: 1651-1662.