| 1. |
- Watz, Johan, 1977-, et al.
(författare)
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Atlantic salmon in regulated rivers: Understanding river management through the ecosystem services lens
- 2022
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Ingår i: Fish and Fisheries. - : John Wiley & Sons. - 1467-2960 .- 1467-2979. ; 23:2, s. 478-491
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Tidskriftsartikel (refereegranskat)abstract
- Known as the “king of fishes”, the Atlantic salmon (Salmo salar, Salmonidae) is an iconic freshwater species whose contribution to human wellbeing has long been recognized, as have widespread declines in its abundance, partly due to river regulation. To understand how salmon conservation has been addressed within the ecosystem services (ES) framework, we synthesized the peer-reviewed literature on ES provided by salmon in regulated rivers. We developed a search string to capture allusions to provisioning, regulating, supporting and cultural ES and assessed the results to identify knowledge gaps. The effects of hydropower on fisheries catches and on modelled populations were shown is several publications. Overall, few studies focused explicitly on ES from salmon and hydropower; this is surprising given the considerable body of literature on salmon in regulated rivers. Wild salmon as a food source and other provisioning services are less important today than historically. Because predators such as salmon are important for facilitating biodiversity by cycling nutrients and controlling food webs, there is a scope of work for future assessments of these regulating and supporting services. Few papers explicitly addressed cultural ES, despite the salmon’s longstanding iconic status; this is a knowledge gap for future ES assessments in relation to hydropower. The influence of ES assessments for policy makers is growing through the Intergovernmental Panel for Biodiversity and Ecosystem Services (IPBES) and the post-2020 biodiversity strategy. Explicitly addressing ES poses an opportunity for river managers to raise awareness of aquatic conservation efforts and well-informed decision-making for sustaining ES.
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| 2. |
- Watz, Johan, 1977-, et al.
(författare)
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Hur mycket vatten behöver havsöringen? En jämförelse av en korrelativ och en individbaserad modell för att förutsäga effekter av flöden på strömlevande fiskar : How much water do sea trout need? A comparison between a correlative and an individual-based model to predict effects of flow on stream fish populations
- 2022
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Ingår i: Vatten. - Lund : Föreningen Vatten. - 0042-2886. ; 78:2, s. 107-114
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Modeller för att simulera effekter av flöde på strömlevande fiskpopulationer är kraftfulla verktyg för att avväga miljönytta och kostnad i samband med åtgärder för att minimera vattenkraftens miljöpåverkan. Vi jämförde en korrelativ och en individbaserad fiskhabitatmodell med avseende på vilka flöden respektive modell bedömde var gynnsammast för en potentiell havsöringspopulation i naturfåran vid Blankaströms kraftverk i Emån. Den korrelativa modellen förutspådde att ett optimalt flöde för att maximera arean med högkvalitativt öringhabitat låg mellan 2 och 3 m3/s. Den individbaserade modellen fann att flöde spelade mindre roll för överlevnad hos den yngsta årsklassen (0+), samt att tillväxten hos dessa var som högst vid 3 m3/s. Högre flöden krävdes dock för lyckad reproduktion och att överlevnaden och tillväxten hos äldre juveniler (1+) gynnades av flöden mellan 5 och 8 m3/s. Korrelativa modeller kan vara användbara, då de är enkla att använda, men det är möjligt att de framförallt förutsäger habitatförekomst för 0+-öringar och sämre speglar de miljöförhållanden som krävs för 1+-öringars uppväxt samt lekfiskars reproduktionsframgång. Individbaserade modeller, å andra sidan, är något mer komplicerade, men genererar mångfacetterad data för olika livsstadier, ger mekanistiska förklaringar till observerade fenomen och kan anpassas till dynamiska flöden.
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| 3. |
- Addo, Louis, Doctoral Student, 1987-, et al.
(författare)
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Growth and mortality of sympatric Atlantic salmon and brown trout fry in fluctuating and stable flows
- 2023
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Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; :2, s. 282-290
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Tidskriftsartikel (refereegranskat)abstract
- Sub-daily fluctuations in streamflow may have adverse effects on the biota downstream of dams in hydropeaking-regulated rivers. Although the stranding of salmonid fry is one documented effect of hydropeaking, little is known about the species-specific behavioural and subsequent growth effects of sub-daily flow fluctuations. We investigated the effects of sub-daily flow fluctuation on growth, mortality and behaviour of sympatric Atlantic salmon (Salmo salar) and brown trout (S. trutta) fry (29–34 mm) in a laboratory experiment. The fluctuating flow treatment negatively affected growth and increased mortality for trout but not for salmon. The level of aggressive behaviour was similar in the fluctuating- and stable-flow treatments. Within the fluctuating flow treatment, there was a trend that more fishes were visibly active above the substrate during low than high flow. These findings suggest that hydropeaking-induced flow fluctuations may affect fry of different salmonid species in different ways and that brown trout fry may be more vulnerable to hydropeaking effects than Atlantic salmon fry. It can therefore be important to consider the possibility of divergent reactions by different fish species under hydropeaking situations and to incorporate species-specific strategies to conserve culturally and economically relevant riverine fish species.
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| 4. |
- Degerman, Erik, et al.
(författare)
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Occurrence and habitat use of European eel (Anguilla anguilla) in running waters : lessons for improved monitoring, habitat restoration and stocking
- 2019
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Ingår i: Aquatic Ecology. - : Springer. - 1386-2588 .- 1573-5125. ; 53:4, s. 639-650
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Tidskriftsartikel (refereegranskat)abstract
- To improve the management of the European eel (Anguilla anguilla) in freshwater, it is essential to define important lotic habitats. Electrofishing data from 289 wadeable, hard-bottom sites in 69 Swedish coastal rivers and streams, originally surveyed for salmonid monitoring, were used to evaluate the effects of sampling- and habitat-related factors on eel occurrence. Probability of eel occurrence, as influenced by sampling procedure (sampled area, number of consecutive runs and ambient water temperature) and habitat characteristics (size of catchment, dominating bottom substrate, shade, water velocity, mean depth), was evaluated for small (total length <= 150 mm) and large (>150 mm) yellow eels. Data were analysed in a mixed presence/absence generalized linear model with dispersal (distance to mouth from sampled site), habitat and sampling-related variables as covariates. The two models explained variation in occurrence to 81.5% for small eel and 76.2% for large eel. Probability of eel occurrence decreased with distance from the river mouth, and increased with sampled area, number of runs, water temperature, coarser substrate and size of river. We suggest that future eel habitat restoration should focus on lower reaches of larger rivers with suitable coarse bottom habitats. Stocking of young eel should be carried out in comparable accessible habitats in the upper reaches where eel densities are low. The results also strongly indicate that eel may be sampled together with young salmonids with DC electrofishing in wadeable habitats.
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| 5. |
- Eggers, Florian, et al.
(författare)
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Methods for the Assessment of Fishways (Upstream Fish Passage)
- 2024
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Ingår i: Advances in Hydraulic Research. - : Springer Science+Business Media B.V.. - 9783031560927 ; , s. 67-79
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Fragmentation of rivers by manmade barriers has impeded the ability of riverine fish to move freely. Barriers can be improved by fishways that can partially mitigate the negative impacts by acting as aquatic corridors. Effective fishways require knowledge about the physiological and spatial demands of fish species, but the existing knowledge largely derived from laboratory settings. Evaluating fishway performance is needed for optimisation of their hydraulic design and positioning. Qualitative methods include trapping, electrofishing, and camera observations to estimate the number of individuals passing (effectiveness). For quantitative assessment, the study of individual fish behaviour can identify fishway sections in need of improvement and estimate associated efficiencies. This can be accomplished by telemetric techniques such as PIT tagging, radio, and hydroacoustic telemetry.
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| 6. |
- Enefalk, Åsa, 1972-, et al.
(författare)
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Winter sheltering by juvenile brown trout (Salmo trutta) : Effects of stream wood and an instream ecothermic predator
- 2017
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Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 62:1, s. 111-118
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Tidskriftsartikel (refereegranskat)abstract
- In boreal streams, juvenile salmonids spend substantial amounts of time sheltering in the streambed and in stream wood, presumably as a means of protection against the physical environment and from terrestrial endothermic predators. Relatively little is known about sheltering by salmonids in response to instream ectothermic predators.We tested the effects of burbot (Lota lota) on the winter sheltering behaviour of PIT-tagged 0+ brown trout (Salmo trutta) in daylight and darkness. Sheltering in the streambed by trout was studied in the presence and absence of fine wood bundles.We found that the use of streambed and fine wood was lower in darkness than in daylight. Availability of fine wood significantly decreased sheltering in the streambed, and this effect was more pronounced in daylight than in darkness. The presence of a burbot significantly decreased sheltering in the streambed, had no effect on use of fine wood and resulted in a higher number of exposed trout.Our results indicate that juvenile brown trout decrease streambed sheltering in response to a burrowing, ectothermic predator.
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| 7. |
- Erlandsson, Ann, 1968-, et al.
(författare)
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Infiltrating immune cells in prostate cancer tissue after androgen deprivation and radiotherapy
- 2023
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Ingår i: International journal of immunopathology and pharmacology. - : Sage Publications. - 0394-6320 .- 2058-7384. ; 37
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Androgen deprivation therapy (ADT) has long been a cornerstone in treatment of advanced prostate cancer (PCa), and is known to improve the results of radiotherapy (RT) for high-risk disease. The purpose of our study was to use a multiplexed immunohistochemical (mIHC) approach to investigate the infiltration of immune cells in PCa tissue after eight weeks of ADT and/or RT with 10 Gy.Methods: From a cohort of 48 patients divided into two treatment arms, we obtained biopsies before and after treatment and used a mIHC method with multispectral imaging to analyze the infiltration of immune cells in tumor stroma and tumor epithelium, focusing on areas with high infiltration.Results: Tumor stroma showed a significantly higher infiltration of immune cells compared to tumor epithelium. The most prominent immune cells were CD20(+) B-lymphocytes, followed by CD68(+) macrophages, CD8(+) cytotoxic T-cells, FOXP3(+) regulatory T-cells (Tregs), and T-bet(+) Th1-cells. Neoadjuvant ADT followed by RT significantly increased the infiltration of all five immune cells. Numbers of Th1-cells and Tregs significantly increased after single treatment with ADT or RT. In addition, ADT alone increased the number of cytotoxic T-cells and RT increased the number of B-cells.Conclusions: Neoadjuvant ADT in combination with RT results in a higher inflammatory response compared to RT or ADT alone. The mIHC method may be a useful tool for investigating infiltrating immune cells in PCa biopsies to understand how immunotherapeutic approaches can be combined with current PCa therapies.
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| 8. |
- Filipsson, Karl, et al.
(författare)
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Do predator odours and warmer winters affect growth of salmonid embryos?
- 2023
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Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; :1
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Tidskriftsartikel (refereegranskat)abstract
- Conditions early in ontogeny can have considerable effects later on in life. Many salmonids spawn during the autumn, and temperature during subsequent embryogenesis may have far-reaching effects on life-history traits, especially when considering ongoing climate change. Even biotic conditions during embryogenesis, such as predation threat, may affect later life stages. Here, we examined how predator odours and increased temperatures affect embryonic growth and development of a fish (brown trout Salmo trutta). We found that embryos had lower body mass and greater yolk volume close to hatching when subjected to predator odours. Trout embryos incubated at temperatures representing natural winter conditions were larger than embryos incubated at higher temperatures, although the latter hatched earlier. Fry sizes at emergence did not differ between treatments, perhaps because of compensatory growth during spring. This study shows that predator presence can have similar effects on embryonic growth of salmonids as warming winters, with possible impact later in ontogeny.
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| 9. |
- Filipsson, Karl
(författare)
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Early life stages of brown trout - Anti-predator responses under warming winters
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During winter, juvenile salmonids in boreal streams are vulnerable to predation, mainly from mammals and birds. Encounters with terrestrial predators can be reduced or avoided if fish limit activity to the darker periods of the day or to periods with surface ice. As piscivorous fish also are active in winter, they may be a threat under low light conditions when juvenile salmonids do not avoid terrestrial predators. Abiotic conditions, especially temperature, have major effects on fish in winter. High temperatures alter ice conditions in winter and lead to increased metabolism and physiological performance of fish. Water temperature also influences embryogenesis, with repercussions for fish throughout their life. Considering the rapid warming of winters in boreal regions, insights into how salmonids are adapted to winter conditions can aid in efforts to predict and mitigate anthropogenic effects that alter the winter environment.In this doctoral thesis, I explore anti-predator responses of brown trout (Salmo trutta) during its early life stages. I have examined the effects of predators, temperature, light and ice on the behaviour and physiology of juvenile trout during winter. In addition, I have studied how temperature and predators affect embryogenesis and the behaviour of fry after hatching. Anti-predator responses were evident in both the behaviour and physiology of juveniles and during embryogenesis. Trout exhibited diel behavioural changes when piscivorous fish were present, and were more vigilant towards piscivorous fish in darkness. Furthermore, temperature affected trout behaviour and physiology, with higher activity levels and lower mRNA expression of stress-related genes at higher temperatures. Trout also behaved differently depending on the temperature they experienced as eggs, as increased egg-incubation temperatures resulted in trout being more active and prone to risk taking.
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| 10. |
- Filipsson, Karl, et al.
(författare)
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Effects of temperature and a piscivorous fish on diel winter behaviour of juvenile brown trout (Salmo trutta)
- 2019
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 64:1+, s. 1797-1805
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Tidskriftsartikel (refereegranskat)abstract
- Low winter temperatures constrain predator-detection and escape capabilities, making poikilotherms vulnerable to predation. Investigations of temperature effects on predator-prey interactions can therefore be of special importance in light of ongoing climate change, where winter temperatures are predicted to increase substantially at northern latitudes. Behavioral responses of stream fishes to terrestrial predators in winter are well recognised, whereas responses to predatory fish have received little attention. Using stream flumes, we examined the anti-predator behaviour of one-summer-old brown trout (Salmo trutta) at 3 and 8 degrees C in the presence and absence of burbot (Lota lota) under night, dawn, and daylight conditions. Burbot was placed upstream of the trout, separated by net screens. Lower temperature and the presence of burbot reduced trout activity. Light increased trout shelter use, and trout sheltered more in the presence of burbot. An interaction between the presence of burbot and light conditions affected trout position in the flumes: at night and dawn, trout positioned themselves further downstream when burbot were present than when absent, whereas during the day, trout maintained the same position in the presence or absence of the predator. Our results suggest that piscivorous fish, in addition to terrestrial predators, shape the behaviour of prey fishes in streams during winter. We show how predator avoidance results in altered diel patterns of juvenile brown trout under winter conditions, and that temperature has additional effects on trout behaviour.
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| 11. |
- Filipsson, Karl, 1991-
(författare)
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From behaviour to genes: anti-predator responses of brown trout (Salmo trutta) under winter conditions
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Temperature has major effects on the performance of poikilotherms. In encounters with predators, low winter temperatures constrain predator detection and escape capabilities in prey fishes. Most studies of the anti-predator responses of fish under winter conditions focus on endothermic terrestrial predators, whereas effects of piscivorous fish are generally overlooked. The studies presented in this thesis explore behavioural and physiological responses of juvenile brown trout (Salmo trutta) at winter temperatures of 3 and 8 °C in the presence and absence of a winter-active piscivorous fish (burbot, Lota lota). In Paper I, I report behavioural responses of trout in relation to the time of day. At the lower temperature and in the presence of burbot, trout reduced their activity. Trout used overhead shelter the most during the day and in the presence of burbot. Trout also spatially avoided burbot at night and at dawn but not during the day. In Paper II, I examined plasma cortisol and mRNA expression of stress-related genes. A redundancy analysis showed that both temperature and the presence of burbot explained a significant amount of the observed variation. Trout had higher cortisol levels when exposed to the burbot. Analyses of individual gene expressions revealed that trout had higher mRNA expression at 3 than at 8 °C for 11 of the 16 examined genes. Only one gene, RBP1, was expressed to a higher degree in the presence of burbot, but there were also interaction effects between temperature and burbot presence for two genes coding for serotonin and glucocorticoid receptors. My studies show that piscivorous fish shape anti-predator responses of juvenile brown trout, both behaviourally and at the gene level, under winter conditions. The observed thermal effects on mRNA levels underscore the importance of temperature in fish stress responses, with implications for stream salmonids in a warmer climate.
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| 12. |
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| 13. |
- Filipsson, Karl, et al.
(författare)
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Temperature and predator-mediated regulation of plasma cortisol and brain gene expression in juvenile brown trout (Salmo trutta)
- 2020
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Ingår i: Frontiers in Zoology. - : BioMed Central. - 1742-9994. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Temperature affects many aspects of performance in poikilotherms, including how prey respond when encountering predators. Studies of anti-predator responses in fish mainly have focused on behaviour, whereas physiological responses regulated through the hypothalamic-pituitary-interrenal axis have received little attention. We examined plasma cortisol and mRNA levels of stress-related genes in juvenile brown trout (Salmo trutta) at 3 and 8 degrees C in the presence and absence of a piscivorous fish (burbot,Lota lota). Results A redundancy analysis revealed that both water temperature and the presence of the predator explained a significant amount of the observed variation in cortisol and mRNA levels (11.4 and 2.8%, respectively). Trout had higher cortisol levels in the presence than in the absence of the predator. Analyses of individual gene expressions revealed that trout had significantly higher mRNA levels for 11 of the 16 examined genes at 3 than at 8 degrees C, and for one gene (retinol-binding protein 1), mRNA levels were higher in the presence than in the absence of the predator. Moreover, we found interaction effects between temperature and predator presence for two genes that code for serotonin and glucocorticoid receptors. Conclusions Our results suggest that piscivorous fish elicit primary stress responses in juvenile salmonids and that some of these responses may be temperature dependent. In addition, this study emphasizes the strong temperature dependence of primary stress responses in poikilotherms, with possible implications for a warming climate.
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| 14. |
- Filipsson, Karl, et al.
(författare)
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Temperature during embryonic development in brown trout influences juvenile behaviour in encounters with predators
- 2024
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Ingår i: Journal of Zoology. - : John Wiley & Sons. - 0952-8369 .- 1469-7998. ; 322:3, s. 241-250
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Tidskriftsartikel (refereegranskat)abstract
- Variation in thermal conditions during embryogenesis can have far-reaching impact throughout ontogeny and may give rise to behavioural variation. Many animals, such as salmonids, exhibit behavioural trade-offs related to foraging and predator avoidance. How embryonic temperature affects these behaviours has remained unexplored. Not only abiotic conditions during embryogenesis but also biotic factors such as predator conditioning may affect fish behaviour, especially anti-predator responses. We examined how elevated temperatures and predator odours throughout embryogenesis affect the behaviour of 28-37 mm young-of-the-year brown trout (Salmo trutta) in encounters with predators, namely Atlantic salmon (Salmo salar; 20 cm) and burbot (Lota lota; 40 cm). Juvenile brown trout were more active and aggressive if they were incubated in warmer water as eggs than if they were incubated in colder water, and trout remained inactive longer when encountering predators if they were cold incubated. Brown trout were less active and aggressive when an Atlantic salmon was present than when a burbot or no predator was present. Behavioural responses did not differ between trout that had been subjected to water with versus without predator odours during embryogenesis, possibly because brown trout were not subjected to conspecific alarm cues during egg incubation. This study shows that thermal conditions during embryogenesis can influence fish behaviour early in life and thus contribute to behavioural variation, with potential effects on life history. Considering the rapid warming of northern regions, elevated embryonic temperatures may contribute substantially to variation in salmonid behaviour in the near future. Variation in environmental conditions during embryogenesis of salmonids can have far-reaching impact throughout ontogeny and may give rise to variation in anti-predator behaviour. In a laboratory experiment, we showed that elevated temperatures throughout embryogenesis increased the activity and aggression of 28-37 mm brown trout fry and reduced the time to first movement in encounters with predators (burbot and Atlantic salmon). Predator odour during embryogenesis did not affect brown trout fry behaviour.image
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| 15. |
- Filipsson, Karl, et al.
(författare)
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Winter Behavior of Juvenile Brown Trout in a Changing Climate : How Do Light and Ice Cover Affect Encounters with Instream Predators?
- 2023
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Ingår i: Fishes. - 2410-3888. ; 8:10
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- During winter, stream fishes are vulnerable to semi-aquatic predators like mammals and birds and reduce encounters by being active in darkness or under surface ice. Less is known about the behavior of fishes towards instream piscivorous fishes. Here, we examined how surface ice and light affected the anti-predator behavior of juvenile brown trout (Salmo trutta Linnaeus, 1758) in relation to piscivorous burbot (Lota lota Linnaeus, 1758) and northern pike (Esox lucius Linnaeus, 1758) at 4 degrees C in experimental flumes. Trout had lower foraging and swimming activity and spent more time sheltering when predators were present than when absent. In daylight, trout's swimming activity was not affected by predators, whereas in darkness trout were less active when predators were present. Trout consumed more drifting prey during the day when ice was present, and they positioned themselves further upstream when under ice cover, regardless of light conditions. Trout stayed closer to conspecifics under ice, but only in the presence of pike. Piscivorous fishes thus constitute an essential part of the predatory landscape of juvenile trout in winter, and thus loss of ice cover caused by climate warming will likely affect trout's interactions with predators.
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| 16. |
- Hajiesmaeili, Mahboobeh, et al.
(författare)
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Individual-based modelling of hydropeaking effects on brown trout and Atlantic salmon in a regulated river
- 2023
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Ingår i: Rivers Research and Applications. - : John Wiley & Sons. - 1535-1459 .- 1535-1467. ; :3, s. 522-537
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Tidskriftsartikel (refereegranskat)abstract
- We developed an individual-based model (IBM) to understand the effects of hydropeaking on growth, survival and distribution of age 0+ to 1+ juveniles for high-conservation value populations of native brown trout (Salmo trutta) and Atlantic salmon (S. salar) in River Gullspång, Sweden. We parameterized and applied inSTREAM (7.2-SD) and calibrated the model by comparing predicted versus observed growth under the current hydropeaking regime (n= > 1,200 model fish for 365 days). Our objective was to model growth, survival and distribution under flow scenarios with and without hydropeaking. We observed that hydropeaking generally resulted in modest (~10%) negative effects on growth and survival of both species. Survival was more affected than was growth, smaller fish more affected than larger fish. On-peak (high) hydropeaking flows resulted in less profitable feeding conditions (less growth) and higher predation (lower survival). Thus, inSTREAM 7.2-SD appears to capture ecologically-relevant behavioral patterns under hydropeaking, e.g., habitat selection, in response to rapid flow changes. Understanding such patterns for large rivers via manipulative field studies, even if possible, would be time-consuming and costly. Our study demonstrates the potential of IBMs as powerful tools for testing research questions and assessing and prioritizing alternative management strategies in regulated rivers.
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| 17. |
- Hajiesmaeili, Mahboobeh, et al.
(författare)
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Sustaining high-value salmonid populations in regulated rivers : Insights from individual-based modelling of brown trout and Atlantic salmon
- 2024
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Ingår i: Global Ecology and Conservation. - : Elsevier. - 2351-9894. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- To combat climate change, societal pressure to develop fossil-free hydroelectricity is growing. There is a great need, however, for environmental assessment tools that can predict the effects of streamflow regulation on biodiversity in hydropower-regulated rivers. Ecological modelling lets practitioners: 1) set broad bounds on population-level responses of key species and 2) identify knowledge gaps and prioritize research needs. Individual-based models (IBMs) are powerful tools for assessing relative benefits of alternative management actions, and therefore help to develop more sustainable hydropower solutions. We applied the inSALMO 7.3-SD IBM for populations of brown trout (Salmo trutta) and Atlantic salmon (S. salar) in the lower Gullspång River, Sweden. We simulated the effects of various minimum hydropeaking flow releases (from 9 to 21 m3/s) on outmigration production. We found that the number of age-1 outmigrants of both species decreased with increasing minimum flow release of the hydropeaking scenarios. The number of age-2 trout outmigrants did not change considerably with increasing the minimum release, but decreased sharply at the highest flow. The most age-2 salmon outmigrants were produced by flow scenarios with minimum releases of 15 and 18 m3/s. The model predicts, therefore, varying species- and life stage-specific effects of flow regulation. Moreover, increased flow caused juveniles to stay in the river longer and outmigrate at larger size, which exposes them to simulated predation longer but could increase post-outmigration survival. By providing insights into mechanisms driving population dynamics, IBMs can help promote the sustainability of high-conservation-value fish species.
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| 18. |
- Hansson, Mattias, et al.
(författare)
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The suitability of Hester–Dendy macroinvertebrate samplers in fluctuating flows
- 2021
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Ingår i: Rivers Research and Applications. - Hoboken : John Wiley & Sons. - 1535-1459 .- 1535-1467. ; 37:6, s. 859-899
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Tidskriftsartikel (refereegranskat)abstract
- Reliable methods for assessing the ecological status of degraded rivers are essential for evaluating restoration efforts in lotic habitats. Several methods are based on biological indicators, such as benthic macroinvertebrates. The Hester–Dendy multi‐plate sampler is a commonly used tool for sampling macroinvertebrates, but its performance under different environmental conditions is not well understood. In a laboratory experiment, we assessed if fluctuating and increasing water velocity influences the performance of Hester–Dendy samplers, by studying colonization of the samplers in relation to a pre‐determined composition of benthic macroinvertebrates. Biodiversity (Shannon‐Wiener index) of colonizing macroinvertebrates was higher in a constant than in a fluctuating flow treatment, but there was no effect on the number of colonizing individuals. The results suggest a potential bias in the interpretation of biodiversity data from sites with sub‐daily flow changes, for example, downstream of hydropeaking power plants.
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| 19. |
- Harbicht, Andrew, et al.
(författare)
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Guiding migrating salmonid smolts : Experimentally assessing the performance of angled and inclined screens with varying gap widths
- 2022
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Ingår i: Ecological Engineering. - : Elsevier. - 0925-8574 .- 1872-6992. ; 174, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- The loss of longitudinal connectivity in regulated rivers, both up- and downstream, has been detrimental for biodiversity worldwide. While progress has been made regarding upstream fish passage solutions, many questions remain unanswered regarding downstream passage alternatives. To address these knowledge gaps, we used Atlantic salmon (S. salar) smolts to experimentally assess the guidance efficiency and passage rates produced by several common screen-and-bypass fish guidance systems. Vertical screens with horizontally oriented bars extending across a turbine intake channel at a shallow angle (angled guidance screens), combined with a single, full-depth bypass entrance at their downstream end, were on average 20% more effective and produced passage rates that were 10 times higher than screens which extended perpendicularly across a turbine intake channel with vertically oriented bars that rose gradually towards the surface (inclined guidance screens) and with a bypass at the surface, on either side of the screen. Among inclined screens, gap width was negatively associated with guidance efficiencies and the smallest gap width (15 mm) exhibited a 41% greater guidance efficiency than the largest (30 mm). Among angled screens, performance was more closely linked to construction material as metal racks produced passage rates over three times faster than flexible Kevlar netting. Overall, passage through the guidance screens, and therefore into a tentative turbine intake area, was positively associated with gap width and was twice as prevalent among the inclined relative to angled guidance screens. Ultimately, an angled guidance screen with a 30 mm gap width produced the highest guidance efficiency and passage rates (a 30% improvement over the next best screen), while an inclined screen with a 30 mm gap width produced the lowest guidance efficiencies and passage rates. These results have implications for the suitability and performance of downstream fish passage solutions at both large- and small-scale hydropower plants where passage solutions are currently lacking or inadequate.
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| 20. |
- Motyka, Roman, et al.
(författare)
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Downstream passage performance of silver eel at an angled rack : effects of behavior and morphology
- 2024
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Ingår i: Hydrobiologia. - : Springer. - 0018-8158 .- 1573-5117.
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Tidskriftsartikel (refereegranskat)abstract
- The European eel is critically endangered due to heavy impact of anthropogenic factors, such as habitat fragmentation, overexploitation and climate change. During downstream migration, silver eels may encounter hydropower plants, which often result in delay or mortality from impingement on trash-racks or turbine passage. These problems can be mitigated with downstream passage solutions, such as angled racks that guide downstream-migrating eels to safe passage routes. The importance of bar spacing and phenotypic diversity for passage performance is, however, largely unknown. In this study, we investigated how morphological parameters (body mass, eye and fin indices) and behavioral score (open field test) influenced passage rate at an experimental intake equipped with a bypass and angled racks with either 15 or 30 mm bar spacing. Both racks were efficient in guiding eels into a bypass. There was a strong positive effect of body mass and a weak positive effect of open field test score on passage rate. Other factors such as eye and fin indices played a minor role. These results demonstrate the performance of angled racks with bypasses and form a useful starting point for further research regarding the relationships between individual variation in behavior, morphology and passage solutions for silver eels.
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| 21. |
- Motyka, Roman, et al.
(författare)
-
Growth and behaviour of juvenile European eel (Anguilla anguilla) in sandy and stony bottom substrates
- 2023
-
Ingår i: Ecology of Freshwater Fish. - : John Wiley & Sons. - 0906-6691 .- 1600-0633. ; 32:3, s. 640-647
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding how the physical habitat influences growth and behaviour is essential for developing effective habitat restoration programmes of threatened and endangered fish species. In our study, we compared the growth and behaviour of juvenile European eel during 13 weeks in aquaria with either sand (0.8-2 mm) or pebbles (25-40 mm) as bottom substrate. In aquaria with the pebble substrate, eel grew significantly faster than in aquaria with sand (specific growth rate 0.15 vs. 0.11% day(-1)). Moreover, growth rates varied more for individuals inhabiting aquaria with sand than in those with pebbles (coefficient of variation 1.26 vs. 0.67). Habitat-dependent growth rates may partly be explained by the observed differences in behavioural patterns. In aquaria with sand, eel left the substrate more often and moved close to the bottom or freely in water column. In aquaria with pebbles, eel remained hidden in the substrate to a high degree, also during feeding. These results may be important for prioritising connectivity- and habitat-restoring measures and for optimization of restocking programmes.
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| 22. |
- Nilsson, Per Anders, 1968-, et al.
(författare)
-
Substrate-size choice in European eel (Anguilla anguilla) elvers is not altered by piscivore chemical cues
- 2020
-
Ingår i: Journal of Fish Biology. - : John Wiley & Sons. - 0022-1112 .- 1095-8649. ; 96:6, s. 1534-1537
-
Tidskriftsartikel (refereegranskat)abstract
- The European eel Anguilla anguilla Linnaeus 1758 is critically endangered with recruitment estimated at 5-10% of historical levels. Enhancing survival of recruits is pivotal for conservation, and restoration should consider habitat choice of elvers ascending river systems. We experimentally show that newly ascended elvers choose small pebble habitat over finer and larger substrates, regardless of the presence or absence of piscivore chemical cues, indicating no predator-induced change in substrate choice. Enriching habitats with this substrate fraction should enhance eel recruitment as well as biodiversity at large.
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| 23. |
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| 24. |
- Nyqvist, Daniel, et al.
(författare)
-
Dispersal movements of non-native and native terrestrial slugs in an urban environment
- 2023
-
Ingår i: Invertebrate biology.. - : John Wiley & Sons. - 1077-8306 .- 1744-7410. ; 142:4
-
Tidskriftsartikel (refereegranskat)abstract
- Animal movement varies from undirected dispersal to directed migration. Movement rates may have implications for conservation and resource management, as well as pest control, and they play a key role in invasion success. In slugs, long-distance dispersal is typically passive, whereas active movement is critical for local dispersal and determines access to resources such as food and shelter. Telemetry has recently been used to study individual slug movements in the wild, whereas movement in arena tests has explored mechanisms of interspecific competition and invasiveness in slugs. Studies that relate the performance of individual slugs in arena tests to their post-release behavior in nature are lacking. We measured individual short-term movement speed of commonly occurring native and non-native slugs of the genera Arion and Limax in arena tests and tracked their post-release dispersal movements in a garden by PIT telemetry. We demonstrate clear differences in movement behavior among the species, but non-native slugs did not display higher movement rates than their native congeners. In the arena test, slugs of the genus Limax displayed a higher short-term speed than slugs of the genus Arion, whereas in the field, individuals of Limax maximus showed lower dispersal rates compared to the other slug species. Moreover, there was a positive correlation between short-term speed in the arena test and movement in the field among individuals of L. cinereoniger, indicating the possible existence of behavioral syndromes in slugs, which may link movement ecology, animal personality, and the invasion ecology of pest species.
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| 25. |
- Piccolo, John, 1964-, et al.
(författare)
-
Experimental Data for Drift-Foraging Models : What's New and What's Next
- 2011
-
Konferensbidrag (refereegranskat)abstract
- Estimating net energy intake (NEI) of is a key requirement in a new suite of models being developed to assess habitat quality for stream fish. To estimate NEI, habitat quality models use a drift-foraging sub-model, typically based on Hughes and Dill's (1990, CJFAS) well-known model. The Hughes and Dill model estimates the energetic costs and benefits of a fish's position in the stream based upon swimming costs and prey capture success. The model includes a number of unrealistic assumptions about prey detection and capture, and swimming costs, however, some of which might be addressed through lab or field experiments. Here we present the results of some recent experiments on the effects of water depth and velocity, and cold temperatures, on the foraging success of juvenile salmonids. We demonstrate that prey capture success is reduced by both faster velocities and colder temperatures, and that swimming costs appear to play a minor role in estimating NEI. We also report on the effects of fish species and size. In general, much experimental work remains to be done in the area of drift foraging theory, however, and we will discuss ongoing research and future needs.
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| 26. |
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| 27. |
- Piccolo, John, 1964-, et al.
(författare)
-
Future rivers, dams and ecocentrism.
- 2019
-
Ingår i: The Ecological Citizen. - 2515-1967. ; 2:2, s. 173-177
-
Tidskriftsartikel (refereegranskat)abstract
- In this article the authors look at the subject of ecocentrism and future rivers, focusing mainly on the effects of hydroelectric production. Although rivers also have been dammed for irrigation and flood control in addition to hydroelectricity, the production of ‘carbon-free’ energy has recently been touted as a major solution to climate change. The trade-off between clean energy and the negative impacts of hydropower offers much food for thought for ecocentric theory – how much biodiversity loss are we justified in allowing now, for example, to avert complete ecosystem collapse in the future if we continue to rely on fossil fuel? The authors intend this article to be a starting point for discussion of rivers and ecocentrism in general, and they conclude with some specific suggestions regarding rivers and hydropower.
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| 28. |
- Rock, Sebastian L., et al.
(författare)
-
Effects of parasitic freshwater mussels on their host fishes : a review
- 2022
-
Ingår i: Parasitology. - : Cambridge University Press. - 0031-1820 .- 1469-8161. ; 149:14, s. 1958-1975
-
Tidskriftsartikel (refereegranskat)abstract
- Freshwater mussels in the order Unionida are highly adapted to parasitize fish for the primary purpose of dispersal. The parasitic larval stage affixes itself to the gills or fins of the host where it becomes encysted in the tissue, eventually excysting to develop into a free-living adult. Research on the parasitic interactions between unionids and their host fishes has garnered attention recently due to the increase in worldwide preservation efforts surrounding this highly endangered and ecologically significant order. With the exception of heavy infestation events, these mussels cause minor effects to their hosts, typically only observable effect in combination with other stressors. Moreover, the range of effect intensities on the host varies greatly with the species involved in the interaction, an effect that may arise from different evolutionary strategies between long- and short-infesting mussels; a distinction not typically made in conservation practices. Lower growth and reduced osmotic potential in infested hosts are commonly observed and correlated to infestation load. These effects are typically also associated with increases in metabolic rate and behaviour indicative of stress. Host fish seem to compensate for this through a combination of rapid wound healing in the parasitized areas and higher ventilation rates. The findings are heavily biased towards Margaritifera margaritifera, a unique mussel not well suited for cross-species generalizations. Furthermore, the small body of molecular and genetic studies should be expanded as many conclusions are drawn from studies on the ultimate effects of glochidiosis rather than proximate studies on the underlying mechanisms.
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| 29. |
- Schiavon, Alfredo, et al.
(författare)
-
Navigating the drought : upstream migration of a small-sized Cypriniformes (Telestes muticellus) in response to drying in a partially intermittent mountain stream
- 2024
-
Ingår i: Knowledge and Management of Aquatic Ecosystems. - : EDP Sciences. - 1961-9502. ; :425
-
Tidskriftsartikel (refereegranskat)abstract
- River flow intermittence is a natural phenomenon intensified by human activities, such as water abstraction and the effects of climate change. A growing number of rivers are predicted to experience intermittent flows, which may impact the diversity and abundance of freshwater species. Dry riverbeds directly diminish the availability of habitats for freshwater organisms, and suitable environments can turn into ecological traps with reduced survival rates, posing a significant threat to population persistence. Even though fish movements can enable drought-affected populations to persist, little is known about individual fish movement between intermittent and perennial reaches. Here, we study the movement of individual PIT-tagged Italian riffle dace (Telestes muticellus) in an intermittent and perennial river reach before, during and after two severe drying events. A high proportion of fish from the intermittent reach survived the drying riverbed through directed upstream migration. This was manifested in fish living in the intermittent reach of the river displaying significantly higher linear ranges, and net travelled distances during the monitoring period than fish in the perennial reach, which remained resident with limited linear range and net distances travelled. This finding underscores the importance of conserving longitudinal river connectivity in the face of increased water scarcity and intermittent flow patterns.
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| 30. |
- Schiavon, A., et al.
(författare)
-
River Runs Dry : Movement Patterns of Telestes muticellus (Cypriniformes: Leuciscidae) in an Intermittent River Stretch
- 2024
-
Ingår i: Advances in Hydraulic Research. - : Springer Science+Business Media B.V.. - 9783031560927 ; , s. 341-351
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Intermittent flow is a natural phenomenon in many stream systems worldwide. At the same time, droughts are an increasing threat to ecosystems as a consequence of climate change and water diversion. Severe droughts can change once suitable habitats into ecological traps that cannot support fish communities. Although individual fish movements can allow populations affected by drought to persist, the knowledge about individual fish movement between intermittent and perennial stretches remains limited. Here we present Italian riffle dace (Telestes muticellus) movement patterns (n = 17) in an intermittent and a neighbouring perennial stream stretch before and after a severe summer drought. Fish initially resident in the intermittent section had similar summer survival as fish from the perennial section. The majority of fish from the intermittent river stretch survived the drought by upstream movements to perennially watered reaches (87.5%). Fish from the intermittent stretch showed an average upstream movement of about 100 m, whereas fish from the perennial stretch remained relatively stationary within the stream. Our result highlights the ability of Italian riffle dace to cope with drought by a directed migration to river reaches with the perennial flow. It also underscores the need to preserve longitudinal river connectivity in the face of increasing water scarcity and associated intermittent flows.
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| 31. |
- Tamario, Carl, et al.
(författare)
-
Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.) : Implications for conservation strategies regarding fish-passage solutions
- 2019
-
Ingår i: Aquatic conservation. - : John Wiley & Sons. - 1052-7613 .- 1099-0755. ; 29:4, s. 612-622
-
Tidskriftsartikel (refereegranskat)abstract
- Many diadromous fish populations are declining and at risk of collapse. Lack of river connectivity is a major contributor to these declines, as free migration routes between marine and freshwater habitats are crucial for life-history completion. For the conservation and ultimately recovery of such species, it is imperative that remedial measures aimed at increasing connectivity are effective. This study investigated the distribution patterns of ascending juvenile European eel (Anguilla anguilla L.) in rivers in south-western Sweden, with a focus on the effects of barriers and measures that aim to reduce the impact of barriers, i.e. fish-passage solutions (FPSs). Eel occurrence data were spatially and temporally integrated with the national databases of dams and FPSs in a Geographic Information System (GIS) environment to evaluate their effect on ascending eel distribution. The types of barriers assessed were: (i) dams with nature-like fishways; (ii) dams with eel ramps; (iii) dams with technical fishways; and (iv) dams without FPSs. Dams fitted with eel ramps or technical fishways, as well as dams without FPSs, produced a significant negative effect on the probability of eel occurrence upstream. This negative effect was not found for dams fitted with nature-like fishways, indicating that these solutions may function better than the other FPS types in this study. The probability of eel occurrence decreased with distance from the sea and increased with area sampled, number of electrofishing runs, water temperature, and with the size of the bottom substrate. We suggest that future conservation strategies for improving the natural immigration of juvenile eels should include optimizing FPS function (e.g. placement and design), the continued maintenance of FPSs, the construction of nature-like fishways, and preferably the removal of dams, which will also benefit the downstream migration of maturing eels as well as restoring other ecosystem services.
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| 32. |
- Watz, Johan, 1977-, et al.
(författare)
-
Artificial barriers against arionid slug movement
- 2021
-
Ingår i: Crop Protection. - Amsterdam : Elsevier. - 0261-2194 .- 1873-6904. ; 142, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Arionid slugs can be serious pests on horticultural and agricultural crops. Using slug movement barriers is a potentially effective method to control slug damage. We evaluated the performance of waterglass (sodium silicate) and copper foil as barriers against Arion vulgaris movement both in a controlled experiment and in a semi-field validation under natural conditions. We used strawberry fruits as baits behind the barriers and monitored slug movement and damage to the strawberries. In the controlled experiment, copper foil barriers delayed but did not prevent passage, whereas waterglass barriers completely hindered slugs from passing. Barrier width (3, 4 or 6 cm) did not affect the passability of the barriers. In the semi-field validation, there was no difference in slug damage events between pots with and without copper foil barriers. Waterglass barriers applied to the pots reduced slug damage events by 50 % compared with pots without a barrier. Using waterglass to hinder slug movement may prove to be a cost-effective method to control slug damage in horticulture without any adverse side effects on non-targeted organisms.
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| 33. |
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| 34. |
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| 35. |
- Watz, Johan, 1977-
(författare)
-
Climbing the ladder : an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers
- 2019
-
Ingår i: Animal Conservation. - : John Wiley & Sons. - 1367-9430 .- 1469-1795. ; 22:5, s. 452-462
-
Tidskriftsartikel (refereegranskat)abstract
- Conservation programmes for endangered, long-lived and migratory species often have to target multiple life stages. The bottlenecks associated with the survival of juvenile anguillid eels migrating into inland waters, the survival and growth of the freshwater life stage, as well as the recruitment and survival of silver eels, migrating back to the ocean to spawn, must be resolved. In this study, we focus on the efficiency of passage solutions for upstream migrating juveniles. Such solutions can consist of inclined ramps lined with wetted climbing substrata. We evaluated different commonly used substrata in a controlled experiment, recorded eel behaviour at the entrance of the ramp with infrared videography and validated the experimental results at a hydropower dam, where we also investigated the effects of ramp placement on performance. In the experiment on eel substratum selection, 40 % of the eels passed in lanes with studded substratum, whereas only 21 and 5 % passed using open weave and bristle substrata, respectively. Video analysis revealed that the studded substratum attracted more approaches and initiated climbs than the other substrata, but once a climb had been initiated, passage success rates did not differ between substrata. Eels using the studded substratum climbed 26 % faster than those using the bristle substratum and almost four times as fast as those climbing in the open weave. The superior performance of the studded substratum was supported by data from the field validation. Moreover, ramps positioned by the bank with low water velocities caught the most eels, but proximity to the dam had no effect on performance. To strengthen the European eel population, more juveniles need to reach their freshwater feeding grounds. A critical step to achieve this increase is to equip upstream passage solutions with suitable substrata and to optimize ramp placement at migration obstacles.
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| 36. |
- Watz, Johan, 1977-, et al.
(författare)
-
Day and night drift-feeding by juvenile salmonids at low water temperatures
- 2014
-
Ingår i: Environmental Biology of Fishes. - : Springer Netherlands. - 0378-1909 .- 1573-5133. ; 97:5, s. 505-513
-
Tidskriftsartikel (refereegranskat)abstract
- Drift-feeding salmonids in boreal streams face temperatures below physical optima for extensive periods of the year. Because juvenile salmonids react to low water temperatures by becoming nocturnal, knowledge about their foraging ability at low light intensities in cold water is needed to accurately estimate energy intake during non-summer conditions. In a laboratory stream channel, we studied temperature effects on the drift-feeding behaviour of juvenile Atlantic salmon, brown trout, and European grayling in simulated daylight and moonlight at temperatures ranging from 2 °C to 11 °C. Prey capture probability was positively related to temperature, but the temperature dependence did not agree with predictions of the Metabolic Theory of Ecology. Furthermore, reaction distance was positively related to temperature for the three species, which may be one of the underlying mechanisms responsible for the temperature effects on prey capture probability. Overall, the three species had similar capture rates at the different temperature and light levels, although there were species differences. European grayling had a slightly higher prey capture probability than brown trout, and brown trout had a shorter reaction distance than Atlantic salmon and European grayling. These results have implications for both energetics-based drift-foraging theory and for studies of winter ecology.
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| 37. |
- Watz, Johan, 1977-, et al.
(författare)
-
Effects of fragmentation per se on slug movement
- 2021
-
Ingår i: Acta Oecologica. - : Elsevier. - 1146-609X .- 1873-6238. ; 112
-
Tidskriftsartikel (refereegranskat)abstract
- To predict the effects of habitat alterations on animal populations we need insight into how the habitat configuration influences local scale movements. This relationship may be particularly important for effective management of pest species. We tracked 80 PIT-tagged Spanish slugs (Arion vulgaris) in 16 × 16 m arenas with manipulated habitat fragmentation. The arenas had habitat patches consisting of high grass residing within a matrix of short grass, and the arenas with a high degree of fragmentation had 12 large (2 × 2 m), 13 medium-sized (1 × 1 m) and 12 small (0.5 × 0.5 m) patches, whereas the arenas with low fragmentation had four 4 × 4 m patches, resulting in equal amounts of total habitat patch area in the two treatments. The measured mean distance moved per day was 3.8 m, and between 0 and 25% of the slugs left the arenas each day. Fragmentation treatment had no effect on these two measurements. In the treatment with patches of different sizes, slugs distributed themselves among the patch size classes according to the total amount of habitat area for each habitat patch class, whereas patch edge did not explain the distribution pattern. All in all, fragmentation per se seems to play a minor role in the local movement and distribution of Spanish slugs.
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| 38. |
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| 39. |
- Watz, Johan, 1977-, et al.
(författare)
-
Effects of ice cover on the diel behaviour and ventilation rate of juvenile brown trout
- 2013
-
Ingår i: Freshwater Biology. - : John Wiley & Sons. - 0046-5070 .- 1365-2427. ; 58:11, s. 2325-2332
-
Tidskriftsartikel (refereegranskat)abstract
- Winter ice conditions in boreal streams are highly variable, and behavioural responses by fish to river ice may affect overwinter survival rates. One type of ice, surface ice, stabilises water temperatures, reduces instream light levels and may provide overhead cover.Because surface ice is believed to afford protection against endothermic predators, we predicted that metabolic costs associated with vigilance would be lower under surface ice than in areas lacking surface ice. This potentially favourable effect of ice cover was tested by observing ventilation rates of juvenile brown trout (Salmo trutta) in a laboratory stream at dawn, during the day and at night in the presence and absence of real, light-permeable surface ice. Further, we offered trout drifting prey during daylight to test whether ice cover increased daytime foraging activity.Ice cover reduced ventilation rates during the day, but not at night or dawn. Moreover, fish made more daytime foraging attempts in the presence of ice cover than in its absence.We suggest that the most plausible explanation for these results is that fish experience a reduced perceived predation risk under surface ice.
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| 40. |
- Watz, Johan, 1977-, et al.
(författare)
-
Egg-laying habitat selection of the invasive slug Krynickillus melanocephalus Kaleniczenko, 1851 (Gastropoda: Eupulmonata: Agriolimacidae)
- 2023
-
Ingår i: Folia Malacologica. - : Association of Polish Malacologists. - 1506-7629 .- 2300-7125. ; 31:4, s. 222-228
-
Tidskriftsartikel (refereegranskat)abstract
- Invasive slugs cause damage to biodiversity as well as to horticultural and agricultural crops. To develop methods to mitigate problems with recently emerging invasive species, basic ecological knowledge about them in their new environment is crucial. We investigated the egg-laying substrate preference of Krynickillus melanocephalus in a laboratory experiment in which the slugs could choose between four different substrates. Slugs were mainly observed in contact with birch leaf compost, and less so with gravel, potting soil and sphagnum moss. Almost 90% of the eggs were found buried in birch leaves, although eggs were found also in the other substrates. In addition, we tested the winter survival of the eggs by examining their susceptibility to low temperatures. Eggs subjected to freezing temperatures did not survive, and at 8 °C, 60–70% of the eggs hatched after three months (640 degree days). In areas where K. melanocephalus is present, transporting any soil, gravel or compost material could potentially contribute to spreading the species. Particularly, leaf composts may warrant attention in this areas.
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| 41. |
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| 42. |
- Watz, Johan, 1977-, et al.
(författare)
-
Enhancing upstream passage solutions for juvenile eels : Effects of climbing substrate and ramp placement
- 2018
-
Konferensbidrag (refereegranskat)abstract
- Juvenile anguillid eels migrating into inland waters often face migration barriers. Upstream passage solutions normally consist of inclined ramps lined with a wetted climbing substrate. In this study, we compared the performance of three commonly used substrate types in a controlled experiment, using European eel as the test species. We also analyzed climbing behavior with videography and validated the experimental results under natural conditions at a hydropower plant. In addition, we investigated the effects of ramp placement. Studded substrate attracted more approaches and climbs and passed more eels at a higher climbing velocity than open weave and bristle substrates, results that were confirmed by the field validation. Moreover, ramps placed in the tailrace caught more eels in low than in high water velocities. To conserve anguillid eels, both safe routes for downstream-migrating adult silver eels and improved recruitment at the freshwater feeding life stage must be achieved. Optimizing ramp position and equipping upstream passage solutions with functioning climbing substrate are key factors to enhance the performance of eel ramps.
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| 43. |
- Watz, Johan, 1977-, et al.
(författare)
-
Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers
- 2017
-
Ingår i: Fisheries Management and Ecology. - : John Wiley & Sons. - 0969-997X .- 1365-2400. ; 24:6, s. 512-514
-
Tidskriftsartikel (refereegranskat)abstract
- To improve the situation for the threatened European eel in regulated rivers, better methods need to be developed that more efficiently collect and transport juvenile eels past dams. In this study, a novel mobile, floating eel trap is described, and the results from an evaluation of the trap in two Swedish regulated rivers are presented. The mobile trap was designed to reduce the length of the climbing distance while maximizing the width of the entrance. The mobile trap caught more juvenile eels than a stationary eel ladder, serving as control. Furthermore, the mobility of the floating trap enables adaptive placement and thus offers managers the possibility to search for the spatial optimum for trapping efficiency.
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| 44. |
- Watz, Johan, 1977-, et al.
(författare)
-
Ice cover affects the growth of a stream-dwelling fish
- 2016
-
Ingår i: Oecologia. - Berlin Heidelberg : Springer Berlin/Heidelberg. - 0029-8549 .- 1432-1939. ; 181:1, s. 299-311
-
Tidskriftsartikel (refereegranskat)abstract
- Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.
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| 45. |
- Watz, Johan, 1977-, et al.
(författare)
-
Ice cover alters the behavior and stress level of brown trout Salmo trutta
- 2015
-
Ingår i: Behavioral Ecology. - Oxford : Oxford University Press. - 1045-2249 .- 1465-7279. ; 26:3, s. 820-827
-
Tidskriftsartikel (refereegranskat)abstract
- Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3–4 °C in indoor experimental flumes. We hypothesized that an individual’s resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.
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| 46. |
- Watz, Johan, 1977-, et al.
(författare)
-
Increased Temperature and Discharge Influence Overwinter Growth and Survival of Juvenile Salmonids in a Hydropeaking River : Simulating Effects of Climate Change Using Individual-Based Modelling
- 2023
-
Ingår i: Fishes. - : MDPI. - 2410-3888. ; 8:6
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change causes warming of rivers and may increase discharge, particularly during winter. Downstream of hydropower plants, fluctuating water temperature and flow create dynamic overwintering conditions for juvenile salmonids. We used inSTREAM 7.2-SD to simulate the effects of increased temperature (+2 & DEG;C) and discharge (+10%) on the overwinter growth and mortality of one-summer- and two-summer-old Atlantic salmon and brown trout in a river with a hydropeaking flow regime in a 2 x 2 design with replicated simulations. Water temperature had a major positive relationship with growth for both species and year classes, whereas increased flow alone had no major general effect on overwinter growth. For one-summer-old trout experiencing the high temperature regime, however, increased flow resulted in reduced growth. There were no major effects from temperature and flow on the survival rate of the two-summer-old fishes. On the other hand, there were significant interaction effects for the one-summer-olds, indicating that the effect of flow depended on temperature. For one-summer-old salmon, high flow resulted in increased survival in the low temperature regime, whereas it resulted in reduced survival in high temperature. In contrast, for one-summer-old trout, high flow resulted in reduced survival in the low temperature regime and increased survival in the high temperature. Different hydropower operation alternatives may interact with warming, affecting the relative competitive abilities of stream salmonids. Ecological models that predict the effects of different environmental conditions, such as temperature and flow regimes, may offer insight into such effects when in situ experiments are not feasible.
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| 47. |
- Watz, Johan, 1977-, et al.
(författare)
-
Interspecific competition among terrestrial slugs
- 2022
-
Ingår i: Journal of molluscan studies. - : Oxford University Press. - 0260-1230 .- 1464-3766. ; 88:2
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Tidskriftsartikel (refereegranskat)abstract
- Interspecific competition among terrestrial gastropods has previously been considered to have little effect on population dynamics and local distribution. Recent studies, however, demonstrate several cases in which interspecific competition plays a major role in structuring terrestrial gastropod communities. To explore the general importance of interspecific competition for the ecology of slugs, we conducted a semi-systematic literature review, synthesizing available peer-reviewed literature relating interspecific interactions to the following: (1) mortality and reproduction; (2) activity, movement, feeding and growth; and (3) habitat use and geographical distribution of slugs. To support the literature on slugs, we also reviewed literature on terrestrial snails. The body of available literature is relatively limited, but the effect of interspecific competition on survival, reproduction, movement and activity has clearly been demonstrated in laboratory experiments for different slug species. The occurrence of interspecific competition seems, however, to be species specific, and no negative effects due to the presence of heterospecifics have been reported for many of the species combinations investigated to date. Most of the studies demonstrating interspecific effects between slug species involved interference from a few aggressive species (mainly Limax maximus as the aggressor). In addition, several correlative studies have indicated that in terrestrial gastropods, habitat use and geographical distribution might be mediated by interspecific competition. Further, well-designed experiments are needed to explore the general importance of interspecific competition among slugs, potentially with a focus on interactions between invasive and native species, where the lack of a shared evolutionary history and niche separation may increase the intensity of competition. Such experimental studies may produce information that has implications for the conservation of native species, as well as for management of invasive pests, because interspecific competition may result in local extinction of vulnerable species and influence the possibility of non-native species establishing invasive populations in new areas.
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| 48. |
- Watz, Johan, 1977-
(författare)
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Overwintering behaviour of stocked brown trout : effects of the rearing environment and river habitat complexity
- 2017
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Ingår i: 50th Anniversary Symposium of the Fisheries Society of the British Isles, Exeter, UK, 3-7 July, 2017.
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Konferensbidrag (refereegranskat)abstract
- In channelized and structurally simple temperature streams and rivers, adverse winter conditions may challenge the ability of riverine fishes to adapt in terms of their behaviour and physiology. Access to shelter is a key habitat factor that may influence overwinter survival chances and, consequently, population dynamics. In many river restoration projects, structural elements are added to the river to increase the complexity of the physical environment. When this habitat enhancement is combined with a stocking programme, the stocked fish mayadopt different behavioural strategies to cope with the winter season depending both onthe rearing environment in the hatchery and the level of habitat complexity in the river. In this study, young-of-the-year brown trout were reared in either barren or structurally enhanced tanks, and the effects of the rearing environment on resting ventilation rate (proxy for resting metabolic rate) and score in an open field test (proxy for activity) were assessed. In side channels of a Swedish regulatedriver, trout were then released at untreated control sites or at sites that were structurally enhanced by adding whole trees to the water. Throughout winter, trout were tracked on a weekly basis, and their movements as influenced by the river habitat complexity and the previous hatchery environment were analysed. The rearing environment affected resting metabolicrates and activity, which resulted in different behavioural overwintering strategies, and adding trees to the side channels increased apparent survival. These results have implications for managing river restoration projects and further studies of stream fish winter ecology.
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| 49. |
- Watz, Johan, 1977-, et al.
(författare)
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Prey capture rates of two species of salmonids (Salmo trutta and Thymallus thymallus) in an artificial stream: effects of temperature on their functional response
- 2014
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Ingår i: Marine and Freshwater Behaviour & Physiology. - London, UK : Taylor & Francis. - 1023-6244 .- 1029-0362. ; 47:2, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- The foraging success of predators depends on how their consumption of prey is affected by prey density under different environmental settings. Here, we measured prey capture rates of drift-feeding juvenile brown trout and European grayling at different prey densities in an artificial stream channel at 5 and 11 °C. Capture rates were lower at 5 than at 11 °C, and the difference was most pronounced at high prey densities. At high prey densities, we also observed that European grayling had higher capture rates than brown trout. Type III functional response curves, i.e. sigmoidal relationships between capture rates and prey densities, fitted the data better than type I (linear) and II (hyperbolic) curves for all four combinations of temperatures and species. These results may explain the dominance of grayling in stream habitats with low water velocities and results such as these may be of use when developing foraging-based food web models of lotic ecosystems that include drift-feeding salmonids.
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| 50. |
- Watz, Johan, 1977-
(författare)
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Salmonid behaviour under winter conditions
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Winter conditions are believed to play an important role in the population dynamics of northern temperate stream fish, challenging the ability of fish to physiologically and behaviourally adapt. Climate change is predicted to increase both mean temperature and temperature fluctuations, especially during winter, leading to dynamic environmental conditions in terms of river ice production and flow. Therefore, knowledge about the winter ecology of stream fish is important for predicting and mitigating anthropogenic impacts on fish production in boreal streams. Stream salmonids are relatively active throughout winter, and behavioural responses to different winter conditions may be critical for survival. Yet, relatively little is known about overwintering behaviour of salmonids, particularly in streams with ice. In this doctoral thesis, I report the results from experimental field and laboratory studies on the behavioural ecology of juvenile salmonids under winter conditions. My results from the field show that salmonids grow more and use a broader range of habitats in the presence of surface ice than in its absence. Results from the laboratory experiments show that the presence of surface ice increases food intake rates, reduces stress and affects social interactions. These laboratory results may explain the positive effects of ice cover on growth that was found in the field experiment. Moreover, I show that drift-feeding ability is reduced at low temperatures, and that nocturnal drift foraging under winter conditions has a low efficiency.
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