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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.
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 StyleMarcell 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 StyleMarcell 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.
1. Acoustic telemetry data often contain erroneous detections, which need to be addressed before further analysis.It is important that this process is systematic, standardized and reproducible. 2. The R package actel provides a systematic conditional pipeline to filter and analyse acoustic telemetry data in a reproducible fashion, for animals moving between receiver arrays. 3. actel outputs a standardised report containing the main results and the steps taken by the user, in addition to summary information for each animal and other content such as efficiency estimations for each receiver array. 4. actel improves the reproducibility of the acoustic data filtering and analysis, and simplifies the integration of acoustic data sets originating from different studies (in time and/or in space).
Hugo Flávio; Henrik Baktoft. actel: Standardised analysis of acoustic telemetry data from animals moving through receiver arrays. Methods in Ecology and Evolution 2020, 12, 196 -203.
AMA StyleHugo Flávio, Henrik Baktoft. actel: Standardised analysis of acoustic telemetry data from animals moving through receiver arrays. Methods in Ecology and Evolution. 2020; 12 (1):196-203.
Chicago/Turabian StyleHugo Flávio; Henrik Baktoft. 2020. "actel: Standardised analysis of acoustic telemetry data from animals moving through receiver arrays." Methods in Ecology and Evolution 12, no. 1: 196-203.
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.
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 StyleHenrik 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 StyleHenrik 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.
Different migratory species have evolved distinct migratory characteristics that improve fitness in their particular ecological niches. However, when such species hybridize, migratory traits from parental species can combine maladaptively and cause hybrids to fall between parental fitness peaks, with potential consequences for hybrid viability and species integrity. Here, we take advantage of a natural cross‐breeding incident to study migratory behaviour in naturally occurring hybrids as well as in their parental species and explore links between migratory traits and predation risk. To achieve this, we used electronic tags and passive telemetry to record detailed individual migration patterns (timing and number of migratory trips) in two common freshwater fish species, roach (Rutilus rutilus ), common bream (Abramis brama ) as well as their hybrids. Next, we scanned for tags regurgitated by a key avian predator (great cormorant, Phalacrocorax carbo) at nearby roosting sites, allowing us to directly link migratory behaviour to predation risk in the wild. We found that hybrid individuals showed a higher number of short, multi‐trip movements between lake and stream habitats as compared to both parental species. The mean date of first lake departure differed between bream and roach by more than 10 days, while hybrids departed in two distinct peaks that overlapped with the parental species’ averages. Moreover, the probability of cormorant predation increased with multi‐trip movement frequency across species and was higher for hybrids. Our data provide novel insights into hybrid viability, with links to predator‐mediated ecological selection. Increased exposure to predators via maladaptive migratory behaviour reduces hybrid survival and can thereby reinforce species integrity.
Varpu Pärssinen; Kaj Hulthén; Christer Brönmark; Christian Skov; Jakob Brodersen; Henrik Baktoft; Ben B. Chapman; Lars‐Anders Hansson; P. Anders Anders Nilsson. Maladaptive migration behaviour in hybrids links to predator‐mediated ecological selection. Journal of Animal Ecology 2020, 89, 2596 -2604.
AMA StyleVarpu Pärssinen, Kaj Hulthén, Christer Brönmark, Christian Skov, Jakob Brodersen, Henrik Baktoft, Ben B. Chapman, Lars‐Anders Hansson, P. Anders Anders Nilsson. Maladaptive migration behaviour in hybrids links to predator‐mediated ecological selection. Journal of Animal Ecology. 2020; 89 (11):2596-2604.
Chicago/Turabian StyleVarpu Pärssinen; Kaj Hulthén; Christer Brönmark; Christian Skov; Jakob Brodersen; Henrik Baktoft; Ben B. Chapman; Lars‐Anders Hansson; P. Anders Anders Nilsson. 2020. "Maladaptive migration behaviour in hybrids links to predator‐mediated ecological selection." Journal of Animal Ecology 89, no. 11: 2596-2604.
Citizen science platforms, including smartphone applications, that allow anglers to report information about fishing trips and catches may be a low-cost source of data that can feed into the science and management of recreational fisheries. However, information about potential biases in these data, such as the representativeness of user characteristics and retention patterns is largely lacking. Here, we examine the characteristics and retention patterns of the users of a Danish citizen science smartphone application and website that allow anglers to report data from fishing trips. Using data from a roving creel survey of sea trout (Salmo trutta) anglers as an independent source for calibration, we found that users of the citizen science platform were younger, more specialized, and had higher catch rates than non-users. On the citizen science platform, 21% of the users were active (i.e., contributed data at least once, three months after creating an account), with an additional 22% using the platform as a source of information (e.g., catch statistics or regulations) for at least three months. These sustained users were older and ascribed a higher importance to angling as a hobby compared to those who stopped using the platform within three months. Data from similar platforms are unlikely to be representative of all anglers and, as a result, research is required to determine what issues this will bring for population extrapolations.
Casper Gundelund; Robert Arlinghaus; Henrik Baktoft; Kieran Hyder; Paul Venturelli; Christian Skov. Insights into the users of a citizen science platform for collecting recreational fisheries data. Fisheries Research 2020, 229, 105597 .
AMA StyleCasper Gundelund, Robert Arlinghaus, Henrik Baktoft, Kieran Hyder, Paul Venturelli, Christian Skov. Insights into the users of a citizen science platform for collecting recreational fisheries data. Fisheries Research. 2020; 229 ():105597.
Chicago/Turabian StyleCasper Gundelund; Robert Arlinghaus; Henrik Baktoft; Kieran Hyder; Paul Venturelli; Christian Skov. 2020. "Insights into the users of a citizen science platform for collecting recreational fisheries data." Fisheries Research 229, no. : 105597.
PIT‐tagging is commonly used in behavioural studies of fish, although long‐term evaluations of effects from tagging under natural conditions are scarce. We PIT‐tagged common bream Abramis brama, European perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus, released them in their lakes of origin and recaptured them after 103–3269 days. Overall, tagged fish did not differ in condition from non‐tagged fish, except for small R. rutilus that weighed less in one lake in one year. We conclude that PIT‐tagging in general has negligible long‐term effects on fish condition. This article is protected by copyright. All rights reserved.
Christian Skov; Joan Holst Hansen; Henrik Baktoft; Christer Brönmark; Jakob Brodersen; Ben B. Chapman; Lars‐Anders Hansson; Kaj Hulthén; P. Anders Nilsson. A field evaluation of long‐term effects of PIT tagging. Journal of Fish Biology 2020, 96, 1055 -1059.
AMA StyleChristian Skov, Joan Holst Hansen, Henrik Baktoft, Christer Brönmark, Jakob Brodersen, Ben B. Chapman, Lars‐Anders Hansson, Kaj Hulthén, P. Anders Nilsson. A field evaluation of long‐term effects of PIT tagging. Journal of Fish Biology. 2020; 96 (4):1055-1059.
Chicago/Turabian StyleChristian Skov; Joan Holst Hansen; Henrik Baktoft; Christer Brönmark; Jakob Brodersen; Ben B. Chapman; Lars‐Anders Hansson; Kaj Hulthén; P. Anders Nilsson. 2020. "A field evaluation of long‐term effects of PIT tagging." Journal of Fish Biology 96, no. 4: 1055-1059.
Remote underwater video systems (RUVS) are increasingly used in scientific studies to monitor marine ecosystems. RUVS can be deployed baited (BRUVS) or unbaited (UBRUVS) and allow for an estimation of the MaxN metric, a relative measure of species abundance. Recording species MaxN in a variety of marine habitats provides associations between species abundance and habitat type, known as ‘species-habitat relationships’. However, the introduction of bait in BRUVS could obscure such relationships by inadvertently attracting fish from neighbouring habitats. Here, we investigate the species-habitat relationships of seven temperate marine species: Atlantic cod (Gadus morhua), right-eyed flatfish (Pleuronectinae spp.), Atlantic herring (Clupea harengus), whiting (Merlangius merlangus), goldsinny wrasse (Ctenolabrus rupestris), two-spotted goby (Gobiusculus flavescens) and shore crab (Carcinus maenas) as revealed by BRUVS and UBRUVS. Video systems were deployed in coastal areas in the Western Baltic, with a cobble coverage ranging from 0% to 100%. Results show that all focal species responded to changes in cobble coverage, highlighting the importance of benthic habitat for a range of animals including benthopelagic species. Specifically, mean abundances of goldsinny wrasse and two-spotted goby were positively associated with cobble coverage, whilst right-eyed flatfish, herring, whiting and shore crab showed a negative association. Atlantic cod was found to be most abundant at intermediate cobble coverage between 65 and 70%, showing a unimodal trend with the mean abundance decreasing again at higher coverage. The relationships suggest that anthropogenic activities modifying benthic habitats, including extraction of material from the seabed and bottom trawling, likely change abundances of a range of marine species. Our comparative analysis suggests that both BRUVS and UBRUVS can identify previously documented species-habitat relationships. However, BRUVS demonstrated some superiority by confirming documented relationships for Atlantic cod and whiting, whilst UBRUVS failed to record any patterns for those species. Our data highlight the ability of BRUVS to identify changes in abundance across different habitats for a variety of species. Although the bait plume serves to attract organisms to the field of view, current results suggest that the use of BRUVS does not obscure species-habitat relationships in patchy coastal habitats. Therefore, future studies examining the importance of different marine areas may benefit from using BRUVS to quantify relationships between habitat variables and species abundance. Developing a better understanding of such relationships will be crucial in ensuring adequate management and protection of ecologically important marine habitats.
Nicole Rhodes; Tim Wilms; Henrik Baktoft; Gesine Ramm; Jeannet Lillegaard Bertelsen; Hugo Flávio; Josianne G. Støttrup; Bo Mammen Kruse; Jon C. Svendsen. Comparing methodologies in marine habitat monitoring research: An assessment of species-habitat relationships as revealed by baited and unbaited remote underwater video systems. Journal of Experimental Marine Biology and Ecology 2020, 526, 151315 .
AMA StyleNicole Rhodes, Tim Wilms, Henrik Baktoft, Gesine Ramm, Jeannet Lillegaard Bertelsen, Hugo Flávio, Josianne G. Støttrup, Bo Mammen Kruse, Jon C. Svendsen. Comparing methodologies in marine habitat monitoring research: An assessment of species-habitat relationships as revealed by baited and unbaited remote underwater video systems. Journal of Experimental Marine Biology and Ecology. 2020; 526 ():151315.
Chicago/Turabian StyleNicole Rhodes; Tim Wilms; Henrik Baktoft; Gesine Ramm; Jeannet Lillegaard Bertelsen; Hugo Flávio; Josianne G. Støttrup; Bo Mammen Kruse; Jon C. Svendsen. 2020. "Comparing methodologies in marine habitat monitoring research: An assessment of species-habitat relationships as revealed by baited and unbaited remote underwater video systems." Journal of Experimental Marine Biology and Ecology 526, no. : 151315.
The R package yaps was introduced in 2017 as a transparent open source alternative to closed source manufacturer-provided solutions to estimate positions of fish (and other aquatic animals) tagged with acoustic transmitters.Although yaps is open source and transparent, the process from raw detections to final tracks has proved to be challenging for many potential users, effectively preventing most users from accessing the benefits of using yaps. Especially, the very important process of synchronizing the hydrophone arrays have proven to be an obstacle for many potential users.To make yaps more approachable to the wider fish tracking community, we have developed and added user-friendly functions assisting users in the complex process of synchronizing the data.Here, we introduce these functions and a six-step protocol intended to provide users with an example workflow that can be used as a template enabling users to apply yaps to their own data. Using example data collected by an array of Vemco VR2 hydrophones, the protocol walks the user through the entire process from raw data to final tracks. Example data sets and complete code for reproducing results are provided.
Henrik Baktoft; Karl Ø. Gjelland; Finn Økland; Jennifer S. Rehage; Jonathan R. Rodemann; Rolando Santos Corujo; Natasha Viadero; Uffe H. Thygesen. Opening the black box of high resolution fish tracking using yaps. 2019, 1 .
AMA StyleHenrik Baktoft, Karl Ø. Gjelland, Finn Økland, Jennifer S. Rehage, Jonathan R. Rodemann, Rolando Santos Corujo, Natasha Viadero, Uffe H. Thygesen. Opening the black box of high resolution fish tracking using yaps. . 2019; ():1.
Chicago/Turabian StyleHenrik Baktoft; Karl Ø. Gjelland; Finn Økland; Jennifer S. Rehage; Jonathan R. Rodemann; Rolando Santos Corujo; Natasha Viadero; Uffe H. Thygesen. 2019. "Opening the black box of high resolution fish tracking using yaps." , no. : 1.
Since in 1980s, the number of great cormorants (Phalacrocorax carbo sinensis) has increased all over its European distribution area. This has led to conflicts between bird conservation and fisheries. Mariager fjord in Denmark is an important feeding and transition area for a large population of migrating seatrout (Salmo trutta), but it also provides resting and breeding places for cormorants. Thus, juvenile anadromous salmonids migrating from the river to the sea may be exposed to high predation risk during a critical and vulnerable time in their development. A total of 31 123 down-migrating wild seatrout were tagged with Passive Integrated Transponder (PIT) tags in 2008, 2009, 2015, and 2016 in river Villestrup, the main tributary flowing into Mariager fjord. Tagged fish were measured and grouped by their developmental stage as parr, pre-smolt, or smolt. To quantify cormorant predation, nearby cormorant colonies and roosting sites were repeatedly scanned for PIT tags with a manual antenna to record tags from predated fish. Minimum predation rate was 27% but varied among years. Body length of the fish and predation risk were negatively correlated and the latter was dependent on the group of the fish. This study demonstrates a potential negative effect of predation by great cormorants on an important population of wild trout.
Kristi Källo; Henrik Baktoft; Niels Jepsen; Kim Aarestrup. Great cormorant (Phalacrocorax carbo sinensis) predation on juvenile down-migrating trout (Salmo trutta) in a lowland stream. ICES Journal of Marine Science 2019, 77, 721 -729.
AMA StyleKristi Källo, Henrik Baktoft, Niels Jepsen, Kim Aarestrup. Great cormorant (Phalacrocorax carbo sinensis) predation on juvenile down-migrating trout (Salmo trutta) in a lowland stream. ICES Journal of Marine Science. 2019; 77 (2):721-729.
Chicago/Turabian StyleKristi Källo; Henrik Baktoft; Niels Jepsen; Kim Aarestrup. 2019. "Great cormorant (Phalacrocorax carbo sinensis) predation on juvenile down-migrating trout (Salmo trutta) in a lowland stream." ICES Journal of Marine Science 77, no. 2: 721-729.
Anthropogenic structures in rivers are major threats for fish migration and effective mitigation is imperative given the worldwide expansion of such structures. Fish behaviour is strongly influenced by hydrodynamics, but little is known on the relation between hydraulics and fish fine scale-movement. We combined 3D Computational fluid dynamics modelling (CFD) with 2D and 3D fish positioning to investigate the relation between hydrodynamics and the downstream movement of Atlantic salmon smolts (Salmo salar). We show that fish use fine-scale flow velocity and turbulence as navigation cues of fine-scale movement behaviour. Tri-dimensional swimming speed and swimming direction can be explained by adjustments of fish to flow motion, which are linked to fish swimming mode. Fish diverge from the flow by swimming at speeds within or higher than their prolonged speeds (0.38–0.73 m s−1). Flow direction plays a pivotal role on fish swimming performance, with high upstream and downwards velocities impacting swimming the most. Turbulence is also influential, by benefiting swimming performance at low TKE (< 0.03 m2 s−2) or constraining it at higher levels. We show that fish behaviour is affected by interactions of several hydraulic variables that should be considered jointly.
Ana T. Silva; Kim M. Bærum; Richard D. Hedger; Henrik Baktoft; Hans-Petter Fjeldstad; Karl Ø. Gjelland; Finn Økland; Torbjørn Forseth. The effects of hydrodynamics on the three-dimensional downstream migratory movement of Atlantic salmon. Science of The Total Environment 2019, 705, 135773 .
AMA StyleAna T. Silva, Kim M. Bærum, Richard D. Hedger, Henrik Baktoft, Hans-Petter Fjeldstad, Karl Ø. Gjelland, Finn Økland, Torbjørn Forseth. The effects of hydrodynamics on the three-dimensional downstream migratory movement of Atlantic salmon. Science of The Total Environment. 2019; 705 ():135773.
Chicago/Turabian StyleAna T. Silva; Kim M. Bærum; Richard D. Hedger; Henrik Baktoft; Hans-Petter Fjeldstad; Karl Ø. Gjelland; Finn Økland; Torbjørn Forseth. 2019. "The effects of hydrodynamics on the three-dimensional downstream migratory movement of Atlantic salmon." Science of The Total Environment 705, no. : 135773.
Martin Lykke Kristensen; David Righton; Diego Del Villar-Guerra; Henrik Baktoft; Kim Aarestrup. Behaviour of adult sea trout Salmo trutta that survive or die at sea. Estuarine, Coastal and Shelf Science 2019, 227, 1 .
AMA StyleMartin Lykke Kristensen, David Righton, Diego Del Villar-Guerra, Henrik Baktoft, Kim Aarestrup. Behaviour of adult sea trout Salmo trutta that survive or die at sea. Estuarine, Coastal and Shelf Science. 2019; 227 ():1.
Chicago/Turabian StyleMartin Lykke Kristensen; David Righton; Diego Del Villar-Guerra; Henrik Baktoft; Kim Aarestrup. 2019. "Behaviour of adult sea trout Salmo trutta that survive or die at sea." Estuarine, Coastal and Shelf Science 227, no. : 1.
Spring migrating sea trout juveniles can be classified as parr, pre-smolt or smolt based on body morphology and osmoregulatory capacity. In this respect, parr are assumed to be less prepared for a marine life and to have lower survival at sea than pre-smolts and smolts. However, the behaviour and survival of these trout phenotypes upon entering the sea is not well known. Using passive integrated transponder telemetry, this study found that the return rate from the sea to the natal river was higher for parr compared to pre-smolts and smolts. Additionally, trout classified as parr generally migrated earlier to the sea and a larger proportion returned to the river after less than one year at sea. The daily mortality rate at sea was comparable among the different phenotypes of trout, suggesting that the higher proportion of returning parr to the river was linked to their shorter duration at sea. These results provide evidence of different life-history strategies for seaward-migrating juvenile sea trout, ultimately affecting their return rate to the natal river. Investigations failing to consider downstream migrating parr and pre-smolts risks neglecting a large part of the anadromous population and may result in inaccurate assessments of sea trout stocks in rivers.
Diego del Villar-Guerra; Martin H. Larsen; Henrik Baktoft; Anders Koed; Kim Aarestrup. The influence of initial developmental status on the life-history of sea trout (Salmo trutta). Scientific Reports 2019, 9, 1 -13.
AMA StyleDiego del Villar-Guerra, Martin H. Larsen, Henrik Baktoft, Anders Koed, Kim Aarestrup. The influence of initial developmental status on the life-history of sea trout (Salmo trutta). Scientific Reports. 2019; 9 (1):1-13.
Chicago/Turabian StyleDiego del Villar-Guerra; Martin H. Larsen; Henrik Baktoft; Anders Koed; Kim Aarestrup. 2019. "The influence of initial developmental status on the life-history of sea trout (Salmo trutta)." Scientific Reports 9, no. 1: 1-13.
There is no generic solution to establish safe passage of downstream migrating fish passed hydropower facilities and mitigation measures are species‐ and site‐specific. Development of solutions is thus often based on “trial and error” and modelling based approaches may significantly reduce cost and time to arrive at successful mitigation. Here we explore such an approach by combining data on fish migration and hydraulic modelling. First, we performed a positional telemetry study at a dammed section of a Norwegian river, where 100 Atlantic salmon smolts were tagged to track their downstream movement at the vicinity of a hydropower intake channel and bypass gates. An explanatory model was developed to explore mechanisms of migration route, into the intake towards the turbines or through the bypass gates. Next, flow conditions during the smolt run was numerically modelled to explore the physical environment of the tracked smolts. The joint results from the two approaches supported the general assumption that downstream migration is strongly influenced by flow patterns and showed that fish entering the study site closer to the riverbank where the intake channel is located were more likely to enter the intake due to the strong currents towards the intake. Finally, a suite of measures to guide salmon smolts past the hydropower intake were proposed based on the findings and local conditions and tested by hydraulic modelling. We found that most of the measures, which were likely candidates for field trials would most likely fail at improving safe passage, and only a rack type guiding boom was promising. The presented combination of telemetry migration data and hydraulic modelling illustrates the value of evaluation of mitigation measures prior to implementation.
Marcell Szabo‐Meszaros; Torbjørn Forseth; Henrik Baktoft; Hans‐Petter Fjeldstad; Ana T. Silva; Karl Øystein Gjelland; Finn Økland; Ingebrigt Uglem; Knut Alfredsen. Modelling mitigation measures for smolt migration at dammed river sections. Ecohydrology 2019, 12, 1 .
AMA StyleMarcell Szabo‐Meszaros, Torbjørn Forseth, Henrik Baktoft, Hans‐Petter Fjeldstad, Ana T. Silva, Karl Øystein Gjelland, Finn Økland, Ingebrigt Uglem, Knut Alfredsen. Modelling mitigation measures for smolt migration at dammed river sections. Ecohydrology. 2019; 12 (7):1.
Chicago/Turabian StyleMarcell Szabo‐Meszaros; Torbjørn Forseth; Henrik Baktoft; Hans‐Petter Fjeldstad; Ana T. Silva; Karl Øystein Gjelland; Finn Økland; Ingebrigt Uglem; Knut Alfredsen. 2019. "Modelling mitigation measures for smolt migration at dammed river sections." Ecohydrology 12, no. 7: 1.
The foraging activity of large-bodied benthivorous fish has been suggested to be of key importance for maintaining shallow lakes in a turbid state. Since especially the spring ecosystem dynamics determines the successive state of shallow lakes, such impact could depend on seasonality in benthivore activity patterns. However, we do not yet know to what extent the activity of large-bodied benthivorous fish affects lake turbidity across the year. In order to investigate seasonal dynamics in bream activity and its impact on water turbidity under natural conditions, bream daily activity was studied in a small (39 ha) shallow Danish lake using passive biotelemetry technology, i.e. a modified Passive Integrated Transponder (PIT)-tag antenna system. We tracked the activity of 448 benthivorous bream over a period of four years (2012 to 2016) and during the same period wind conditions, water turbidity and temperature was measured. Results showed a clear relationship between bream activity and water turbidity at water temperature below 15°C indicating that winter season activity of benthivorous bream may play an important role for maintaining lake ecosystems in a turbid state. Also wind speed and wind direction affected water turbidity, suggesting that wind induced resuspension can be important even in small shallow lakes. This is to our knowledge the first full-scale study under natural conditions to describe how bream activity influence lake turbidity on a day-to-day basis. Our findings also add a seasonal component to previous findings by showing that benthivorous feeding bream have the potential to increase water turbidity also in the winter season and thereby, ultimately, impact ecosystem functioning within shallow lakes.
Joan H. Hansen; Jakob Brodersen; Henrik Baktoft; Christian Skov. Relationship between bream (Abramis brama) activity and water turbidity in a shallow lake under different season conditions. Journal of Limnology 2019, 78, 1 .
AMA StyleJoan H. Hansen, Jakob Brodersen, Henrik Baktoft, Christian Skov. Relationship between bream (Abramis brama) activity and water turbidity in a shallow lake under different season conditions. Journal of Limnology. 2019; 78 (2):1.
Chicago/Turabian StyleJoan H. Hansen; Jakob Brodersen; Henrik Baktoft; Christian Skov. 2019. "Relationship between bream (Abramis brama) activity and water turbidity in a shallow lake under different season conditions." Journal of Limnology 78, no. 2: 1.
Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems.
Joan H. Hansen; Christian Skov; Henrik Baktoft; Christer Brönmark; Ben B. Chapman; Kaj Hulthén; Lars-Anders Hansson; P. Anders Nilsson; Jakob Brodersen. Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities. Ecosystems 2019, 23, 292 -306.
AMA StyleJoan H. Hansen, Christian Skov, Henrik Baktoft, Christer Brönmark, Ben B. Chapman, Kaj Hulthén, Lars-Anders Hansson, P. Anders Nilsson, Jakob Brodersen. Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities. Ecosystems. 2019; 23 (2):292-306.
Chicago/Turabian StyleJoan H. Hansen; Christian Skov; Henrik Baktoft; Christer Brönmark; Ben B. Chapman; Kaj Hulthén; Lars-Anders Hansson; P. Anders Nilsson; Jakob Brodersen. 2019. "Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities." Ecosystems 23, no. 2: 292-306.
Juvenile salmonids experience high mortality when negotiating lentic waters during their downstream migration to the sea. The development of artificial lakes and wetlands in streams has become a widely used management tool to reduce nutrient load to coastal areas. Such wetlands may threaten anadromous populations. In this study we quantify net ground speed of downstream migrating brown trout Salmo trutta smolts in equally long stream and lake sections in a Danish lowland stream and artificial lake. This was done by passive integrated transponder telemetry in 2016 and 2017. Mean net ground speed in the stream section was 36.58 km day–1 and 0.8 km day–1 in the lake section. This decrease of net ground speed through the lake may lead to prolonged exposure to predators and probably contributes to high mortalities threatening anadromous populations.
Michael Schwinn; Henrik Baktoft; Kim Aarestrup; Anders Koed. Artificial lakes delay the migration of brown trout Salmo trutta smolts: a comparison of migratory behaviour in a stream and through an artificial lake. Journal of Fish Biology 2019, 94, 745 -751.
AMA StyleMichael Schwinn, Henrik Baktoft, Kim Aarestrup, Anders Koed. Artificial lakes delay the migration of brown trout Salmo trutta smolts: a comparison of migratory behaviour in a stream and through an artificial lake. Journal of Fish Biology. 2019; 94 (5):745-751.
Chicago/Turabian StyleMichael Schwinn; Henrik Baktoft; Kim Aarestrup; Anders Koed. 2019. "Artificial lakes delay the migration of brown trout Salmo trutta smolts: a comparison of migratory behaviour in a stream and through an artificial lake." Journal of Fish Biology 94, no. 5: 745-751.
Genetic data have great potential for improving fisheries management by identifying the fundamental management units—that is, the biological populations—and their mixing. However, so far, the number of practical cases of marine fisheries management using genetics has been limited. Here, we used Atlantic cod in the Baltic Sea to demonstrate the applicability of genetics to a complex management scenario involving mixing of two genetically divergent populations. Specifically, we addressed several assumptions used in the current assessment of the two populations. Through analysis of 483 single nucleotide polymorphisms (SNPs) distributed across the Atlantic cod genome, we confirmed that a model of mechanical mixing, rather than hybridization and introgression, best explained the pattern of genetic differentiation. Thus, the fishery is best monitored as a mixed‐stock fishery. Next, we developed a targeted panel of 39 SNPs with high statistical power for identifying population of origin and analyzed more than 2,000 tissue samples collected between 2011 and 2015 as well as 260 otoliths collected in 2003/2004. These data provided high spatial resolution and allowed us to investigate geographical trends in mixing, to compare patterns for different life stages and to investigate temporal trends in mixing. We found similar geographical trends for the two time points represented by tissue and otolith samples and that a recently implemented geographical management separation of the two populations provided a relatively close match to their distributions. In contrast to the current assumption, we found that patterns of mixing differed between juveniles and adults, a signal likely linked to the different reproductive dynamics of the two populations. Collectively, our data confirm that genetics is an operational tool for complex fisheries management applications. We recommend focussing on developing population assessment models and fisheries management frameworks to capitalize fully on the additional information offered by genetically assisted fisheries monitoring.
Jakob Hemmer‐Hansen; Karin Hüssy; Henrik Baktoft; Bastian Huwer; Dorte Bekkevold; Holger Haslob; Jens‐Peter Herrmann; Hans‐Harald Hinrichsen; Uwe Krumme; Henrik Mosegaard; Einar Eg Nielsen; Thorsten B. H. Reusch; Marie Storr‐Paulsen; Andres Velasco; Burkhard Von Dewitz; Jan Dierking; Margit Eero. Genetic analyses reveal complex dynamics within a marine fish management area. Evolutionary Applications 2018, 12, 830 -844.
AMA StyleJakob Hemmer‐Hansen, Karin Hüssy, Henrik Baktoft, Bastian Huwer, Dorte Bekkevold, Holger Haslob, Jens‐Peter Herrmann, Hans‐Harald Hinrichsen, Uwe Krumme, Henrik Mosegaard, Einar Eg Nielsen, Thorsten B. H. Reusch, Marie Storr‐Paulsen, Andres Velasco, Burkhard Von Dewitz, Jan Dierking, Margit Eero. Genetic analyses reveal complex dynamics within a marine fish management area. Evolutionary Applications. 2018; 12 (4):830-844.
Chicago/Turabian StyleJakob Hemmer‐Hansen; Karin Hüssy; Henrik Baktoft; Bastian Huwer; Dorte Bekkevold; Holger Haslob; Jens‐Peter Herrmann; Hans‐Harald Hinrichsen; Uwe Krumme; Henrik Mosegaard; Einar Eg Nielsen; Thorsten B. H. Reusch; Marie Storr‐Paulsen; Andres Velasco; Burkhard Von Dewitz; Jan Dierking; Margit Eero. 2018. "Genetic analyses reveal complex dynamics within a marine fish management area." Evolutionary Applications 12, no. 4: 830-844.
Removal of cyprinid fish is a widely used biomanipulation tool to transform turbid shallow eutrophic lakes in north temperate regions into a clear water state. We here evaluate the removal of cyprinids from streams as a supplement to lake fishing. Since cyprinids often aggregate in high densities in lake inlet/outlet streams during winter migration, removal of fish in this space-confined habitat may be cost-efficient as compared to fish removal in the lake habitat. In two consecutive years, we annually removed up to 35% of the dominant cyprinids from an inlet stream to a lake and argue that this could easily be increased with a more targeted fishing effort. Concurrently, we monitored species- and length-specific variation in migration propensity, to explore how this relates to efficient fish removal. Smaller planktivores generally had a much higher migratory propensity than larger benthivores. Hence, stream fishing specifically targets species and size groups that are less efficiently controlled with traditional lake fishing methods. As a rule of thumb, stream fishing is most efficient when water temperature is 2–6°C. Prior to implementing fish removals from streams, the potential evolutionary consequences of the targeted removal of migratory phenotypes should be considered.
Christian Skov; Joan H. Hansen; Henrik Baktoft; Jakob Brodersen; Christer Brönmark; Lars-Anders Hansson; Kaj Hulthén; Ben B. Chapman; P. Anders Nilsson. Biomanipulating streams: a supplementary tool in lake restoration. Hydrobiologia 2018, 829, 205 -216.
AMA StyleChristian Skov, Joan H. Hansen, Henrik Baktoft, Jakob Brodersen, Christer Brönmark, Lars-Anders Hansson, Kaj Hulthén, Ben B. Chapman, P. Anders Nilsson. Biomanipulating streams: a supplementary tool in lake restoration. Hydrobiologia. 2018; 829 (1):205-216.
Chicago/Turabian StyleChristian Skov; Joan H. Hansen; Henrik Baktoft; Jakob Brodersen; Christer Brönmark; Lars-Anders Hansson; Kaj Hulthén; Ben B. Chapman; P. Anders Nilsson. 2018. "Biomanipulating streams: a supplementary tool in lake restoration." Hydrobiologia 829, no. 1: 205-216.
Eutrophication of coastal areas as a consequence of the agricultural use of fertilizers is a widespread problem. The development of artificial lakes and constructed wetlands in nutrient‐rich rivers is a widely used management tool in the fight to decrease eutrophication. Juvenile salmonids that have to negotiate these lakes during their downstream migration to the sea are commonly subjected to high mortality due to increased predation pressure and delayed passage. In this study, we double tagged 39 brown trout smolts with passive integrated transponder and radio tags to gain further insight into predation rates and migration patterns during their passage of an artificial lake in a Danish lowland stream in the spring of 2016. Thirty‐four of the tagged smolts, caught and released upstream, entered the lake, of which 22 (65%) successfully exited the lake. Four smolts (12%) returned upstream to the river. Three smolts were predated in the lake by two northern pike (Esox lucius). Three tags were recovered from the lake bottom, and two disappeared out of the study area after a last detection in the lake. Tracking the smolts manually and by automatic listening stations showed highly erratic movement patterns during lake passage. Further, we observed long delays of up to 27 days after the smolts reached the river mouth and before they entered the sea, potentially due to low sea water temperature or due to the stocking of a large amount of hatchery‐reared brown trout smolts. The results are discussed in the context of abiotic and biotic factors, which differed considerably in the year 2016 compared with previous years.
Michael Schwinn; Henrik Baktoft; Kim Aarestrup; Martyn C. Lucas; Anders Koed. Telemetry observations of predation and migration behaviour of brown trout (Salmo trutta ) smolts negotiating an artificial lake. River Research and Applications 2018, 34, 898 -906.
AMA StyleMichael Schwinn, Henrik Baktoft, Kim Aarestrup, Martyn C. Lucas, Anders Koed. Telemetry observations of predation and migration behaviour of brown trout (Salmo trutta ) smolts negotiating an artificial lake. River Research and Applications. 2018; 34 (8):898-906.
Chicago/Turabian StyleMichael Schwinn; Henrik Baktoft; Kim Aarestrup; Martyn C. Lucas; Anders Koed. 2018. "Telemetry observations of predation and migration behaviour of brown trout (Salmo trutta ) smolts negotiating an artificial lake." River Research and Applications 34, no. 8: 898-906.
Ml Kristensen; D Righton; D Del Villar-Guerra; Henrik Baktoft; K Aarestrup; Dd Villar-Guerra. Temperature and depth preferences of adult sea trout Salmo trutta during the marine migration phase. Marine Ecology Progress Series 2018, 599, 209 -224.
AMA StyleMl Kristensen, D Righton, D Del Villar-Guerra, Henrik Baktoft, K Aarestrup, Dd Villar-Guerra. Temperature and depth preferences of adult sea trout Salmo trutta during the marine migration phase. Marine Ecology Progress Series. 2018; 599 ():209-224.
Chicago/Turabian StyleMl Kristensen; D Righton; D Del Villar-Guerra; Henrik Baktoft; K Aarestrup; Dd Villar-Guerra. 2018. "Temperature and depth preferences of adult sea trout Salmo trutta during the marine migration phase." Marine Ecology Progress Series 599, no. : 209-224.