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Rodger JR, Lilly J, Honkanen HM, Del Villar D, Kennedy R, Maoiléidigh NÓ, Boylan P, Rosell R, Morris DJ, O'Neill R, Waters C, Cotter D, Wilkie L, Barkley A, Green A, Beck SV, Ribbens J, Henderson J, Parke D, Kettle-White A, Ballantyne L, Marshall S, Hopper P, Gauld N, Godfrey JD, Chapman LE, Thorburn J, Drumm A, Whoriskey F, Shields B, Ramsden P, Barry J, Milane M, Roche W, Armstrong JD, Wells A, Walton S, Fletcher M, Bailey DM, Whyte B, McGill R, Bilsby M, Whelan K, Bean CW, Adams CE. Inshore and offshore marine migration pathways of Atlantic salmon post-smolts from multiple rivers in Scotland, England, Northern Ireland, and Ireland. JOURNAL OF FISH BIOLOGY 2024. [PMID: 38679466 DOI: 10.1111/jfb.15760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 02/23/2024] [Accepted: 04/02/2024] [Indexed: 05/01/2024]
Abstract
The migratory behavior of Atlantic salmon (Salmo salar) post-smolts in coastal waters is poorly understood. In this collaborative study, 1914 smolts, from 25 rivers, in four countries were tagged with acoustic transmitters during a single seasonal migration. In total, 1105 post-smolts entered the marine study areas and 438 (39.6%) were detected on a network of 414 marine acoustic receivers and an autonomous underwater vehicle. Migration pathways (defined as the shortest distance between two detections) of up to 575 km and over 100 days at sea were described for all 25 populations. Post-smolts from different rivers, as well as individuals from the same river, used different pathways in coastal waters. Although difficult to generalize to all rivers, at least during the year of this study, no tagged post-smolts from rivers draining into the Irish Sea were detected entering the areas of sea between the Hebrides and mainland Scotland, which is associated with a high density of finfish aquaculture. An important outcome of this study is that a high proportion of post-smolts crossed through multiple legislative jurisdictions and boundaries during their migration. This study provides the basis for spatially explicit assessment of the impact risk of coastal pressures on salmon during their first migration to sea.
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Affiliation(s)
- Jessica R Rodger
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
- Atlantic Salmon Trust, Perth, UK
| | - Jessie Lilly
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Hannele M Honkanen
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | | | - Richard Kennedy
- Agri-food and Biosciences Institute, Hillsborough, Northern Ireland
| | | | - Patrick Boylan
- Chief Scientific Advisor's Office, Department of Agriculture, Environment and Rural Affairs (DAERA), Jubilee House, Ballykelly, UK
| | - Robert Rosell
- Agri-food and Biosciences Institute, Hillsborough, Northern Ireland
| | - David J Morris
- Freshwater Fisheries Laboratory, Marine Scotland Science, Pitlochry, UK
| | | | | | | | | | - Andrea Barkley
- Agri-food and Biosciences Institute, Hillsborough, Northern Ireland
| | - Amy Green
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Samantha V Beck
- Galloway Fisheries Trust, Station Industrial Estate, Newton Stewart, UK
| | - Jamie Ribbens
- Galloway Fisheries Trust, Station Industrial Estate, Newton Stewart, UK
| | - Jim Henderson
- The Nith Catchment Fishery Trust and Nith District Salmon Fishery Board, Dumfries, UK
| | - Debbie Parke
- The Nith Catchment Fishery Trust and Nith District Salmon Fishery Board, Dumfries, UK
| | | | | | - Shona Marshall
- West Sutherland Fisheries Trust, The Gardeners Cottage, Scourie, UK
| | - Paul Hopper
- Outer Hebrides Fisheries Trust, Marybank, UK
| | - Niall Gauld
- Freshwater Fisheries Laboratory, Marine Scotland Science, Pitlochry, UK
| | - Jason D Godfrey
- Freshwater Fisheries Laboratory, Marine Scotland Science, Pitlochry, UK
| | - Lauren E Chapman
- Freshwater Fisheries Laboratory, Marine Scotland Science, Pitlochry, UK
| | - James Thorburn
- Scottish Oceans Institute, St Andrews, UK
- School of Biology, Queens University Belfast, Belfast, UK
| | | | - Fred Whoriskey
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | | | | | | | | | | | - John D Armstrong
- Freshwater Fisheries Laboratory, Marine Scotland Science, Pitlochry, UK
| | - Alan Wells
- Fisheries Management Scotland, Edinburgh, UK
| | | | | | - David M Bailey
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | | | - Ross McGill
- Loughs Agency, Londonderry, Northern Ireland
| | | | | | - Colin W Bean
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
- NatureScot, Clydebank, UK
| | - Colin E Adams
- Scottish Centre for Ecology and the Natural Environment, School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
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2
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Sandhu S, Mikheev V, Pasternak A, Taskinen J, Morozov A. Revisiting the role of behavior-mediated structuring in the survival of populations in hostile environments. Commun Biol 2024; 7:93. [PMID: 38216662 PMCID: PMC10786947 DOI: 10.1038/s42003-023-05731-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 12/20/2023] [Indexed: 01/14/2024] Open
Abstract
Increasing the population density of target species is a major goal of ecosystem and agricultural management. This task is especially challenging in hazardous environments with a high abundance of natural enemies such as parasites and predators. Safe locations with lower mortality have been long considered a beneficial factor in enhancing population survival, being a promising tool in commercial fish farming and restoration of threatened species. Here we challenge this opinion and revisit the role of behavior structuring in a hostile environment in shaping the population density. We build a mathematical model, where individuals are structured according to their defensive tactics against natural enemies. The model predicts that although each safe zone enhances the survival of an individual, for an insufficient number of such zones, the entire population experiences a greater overall mortality. This is a result of the interplay of emergent dynamical behavioral structuring and strong intraspecific competition for safe zones. Non-plastic structuring in individuals' boldness reduces the mentioned negative effects. We demonstrate emergence of non-plastic behavioral structuring: the evolutionary branching of a monomorphic population into a dimorphic one with bold/shy strains. We apply our modelling approach to explore fish farming of salmonids in an environment infected by trematode parasites.
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Affiliation(s)
- Simran Sandhu
- School of Computing and Mathematical Sciences, University of Leicester, LE1 7RH, Leicester, UK
| | - Victor Mikheev
- Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
| | - Anna Pasternak
- Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia
| | - Jouni Taskinen
- Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland
| | - Andrew Morozov
- School of Computing and Mathematical Sciences, University of Leicester, LE1 7RH, Leicester, UK.
- Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia.
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3
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Grenier G, Rochat EC, Muladal R, Jensen H, Knudsen R. Salmon-lice as a potential threat to anadromous Arctic charr populations. JOURNAL OF FISH DISEASES 2023; 46:465-475. [PMID: 36696463 DOI: 10.1111/jfd.13758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/05/2023] [Accepted: 01/06/2023] [Indexed: 06/17/2023]
Abstract
Salmon-lice have the potential to change the behaviour and growth of their salmonid host species. Here, the baseline infection levels of salmon-lice of post-smolts (n = 815) and veteran migrants (n = 875) of sea-run Arctic charr (Salvelinus alpinus Linnaeus, 1758) were monitored over two successive years in a sub-Arctic Norwegian fjord without farming of salmonids. All Arctic charr were collected after the sea-migration period from a trap placed in the river, ascending to their overwintering freshwater habitat (Lake Laksvatn). The sea-lice infection showed a stable infection across the 2 years while increasing through the migration period and with the size of the wild sea-run Arctic charr. The prevalence of sea-lice infection was intermediate to high, and the intensities of sea-lice infections observed were generally modest, although some individuals had high infections. The relatively high infection of salmon-lice highlights the potential detrimental effects these parasites can have at both the individual and population level of such endangered sub-Arctic life-history strategies. A comparative study should be performed in fjords with aquaculture activity as focal points for salmon-lice, to investigate the impact farming have on sea-run Arctic charr populations.
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Affiliation(s)
- Gabrielle Grenier
- Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, Tromsø, Norway
| | - Eloïse C Rochat
- Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, Tromsø, Norway
| | | | | | - Rune Knudsen
- Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, Tromsø, Norway
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4
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Vollset KW, Lennox RJ, Skoglund H, Karlsen Ø, Normann ES, Wiers T, Stöger E, Barlaup BT. Direct evidence of increased natural mortality of a wild fish caused by parasite spillback from domestic conspecifics. Proc Biol Sci 2023; 290:20221752. [PMID: 36695034 PMCID: PMC9880801 DOI: 10.1098/rspb.2022.1752] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 11/30/2022] [Indexed: 01/26/2023] Open
Abstract
Parasite spillback from domestic animals can distort the balance between host and parasites in surrounding wildlife, with potential detrimental effects on wild populations. In aquatic environments, parasite spillback from aquaculture to wild salmon is one of the most contentious sustainability debates. In a 19 year time series of release group studies of Atlantic salmon, we demonstrated that (i) the effect of subjecting out-migrating salmon smolts to parasite treatment on marine survival has been reduced over a time, (ii) the relation between salmon lice levels in the out-migration route of the salmon and effect of treatment against the parasite is weak, but also (iii) the return rates in both treated and untreated groups of salmon are negatively correlated with salmon lice levels, and (iv) returns of wild salmon to the region are similarly negatively correlated with salmon lice levels during the out-migration year. Our study suggests that salmon lice can have a large effect on wild salmon populations that is not revealed with randomized control trials using antiparasitic drugs. This should be better accounted for when considering the impacts of farms on wild salmon populations.
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Affiliation(s)
- Knut Wiik Vollset
- Climate and Environment, NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5008 Bergen, Norway
| | - Robert J Lennox
- Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway
| | - Helge Skoglund
- Climate and Environment, NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5008 Bergen, Norway
| | - Ørjan Karlsen
- Institute of Marine Research, Nordnesgaten 50, 5005 Bergen, Norway
| | - Eirik Straume Normann
- Climate and Environment, NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5008 Bergen, Norway
| | - Tore Wiers
- Climate and Environment, NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5008 Bergen, Norway
| | - Elisabeth Stöger
- Institute of Marine Research, Nordnesgaten 50, 5005 Bergen, Norway
| | - Bjørn T Barlaup
- Climate and Environment, NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries, Nygårdsgaten 112, 5008 Bergen, Norway
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5
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Henriksen EH, Frainer A, Poulin R, Knudsen R, Amundsen P. Ectoparasites population dynamics are affected by host body size but not host density or water temperature in a 32‐year long time series. OIKOS 2022. [DOI: 10.1111/oik.09328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Eirik H. Henriksen
- Dept of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic Univ. of Norway Tromsø Norway
| | - André Frainer
- Norwegian Inst. for Nature Research (NINA), Framsenteret Tromsø Norway
| | | | - Rune Knudsen
- Dept of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic Univ. of Norway Tromsø Norway
| | - Per‐Arne Amundsen
- Dept of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic Univ. of Norway Tromsø Norway
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6
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Adams CE, Chavarie L, Rodger JR, Honkanen HM, Thambithurai D, Newton MP. An opinion piece: the evolutionary and ecological consequences of changing selection pressures on marine migration in Atlantic salmon. JOURNAL OF FISH BIOLOGY 2022; 100:860-867. [PMID: 35212396 PMCID: PMC9311443 DOI: 10.1111/jfb.15024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 02/10/2022] [Accepted: 02/22/2022] [Indexed: 06/14/2023]
Abstract
There are strong signals that the selection forces favouring the expression of long-distance sea migration by Atlantic salmon (Salmo salar) are changing. Unlike many other behavioural traits, the costs of migration are incurred before any fitness benefits become apparent to the migrant. The expression of this behaviour has thus been shaped by selection forces over multiple generations and cannot respond to short interval (within a single generation) environmental change as many other behavioural traits can. Here we provide a framework to examine the evolutionary and ecological consequences of a sustained increase in migration cost. We argue that Atlantic salmon may have entered an evolutionary trap, where long-distance sea migration has become maladaptive because of shifting environmental conditions. We predict that if higher migration costs (affecting survivorship and ultimately fitness) persist, then shifting selection pressures will result in continuing declines in population size. We suggest, however, that in some populations there is demonstrable capacity for evolutionary rescue responses within the species which is to be found in the variation in the expression of migration. Under a scenario of low to moderate change in the selection forces that previously promoted migration, we argue that disruptive, sex-based selection would result in partial migration, where females retain sea migration but with anadromy loss predominantly in males. With more acute selection forces, anadromy may be strongly selected against, under these conditions both sexes may become freshwater resident. We suggest that as the migration costs appear to be higher in catchments with standing waters, then this outcome is more likely in such systems. We also speculate that as a result of the genetic structuring in this species, not all populations may have the capacity to respond adequately to change. The consequences of this for the species and its management are discussed.
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Affiliation(s)
- Colin E. Adams
- Scottish Centre for Ecology & the Natural EnvironmentInstitute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
| | - Louise Chavarie
- Scottish Centre for Ecology & the Natural EnvironmentInstitute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
- Faculty of Environmental Sciences and Natural Resource ManagementThe Norwegian University of Life SciencesÅsNorway
| | - Jessica R. Rodger
- Atlantic Salmon Trust FellowScottish Centre for Ecology & the Natural Environment, Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
| | - Hannele M. Honkanen
- Scottish Centre for Ecology & the Natural EnvironmentInstitute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
| | - Davide Thambithurai
- Atlantic Salmon Trust FellowScottish Centre for Ecology & the Natural Environment, Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
| | - Matthew P. Newton
- Scottish Centre for Ecology & the Natural EnvironmentInstitute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, RowardennanGlasgowUK
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7
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Strøm JF, Jensen JLA, Nikolopoulos A, Nordli E, Bjørn PA, Bøhn T. Sea trout Salmo trutta in the subarctic: home-bound but large variation in migratory behaviour between and within populations. JOURNAL OF FISH BIOLOGY 2021; 99:1280-1291. [PMID: 34184272 DOI: 10.1111/jfb.14832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 06/13/2023]
Abstract
Anadromous brown trout (sea trout), Salmo trutta, is currently in decline throughout its range, largely due to anthropogenic stressors in freshwater and marine habitats. Acoustic telmetry was utilized to study the marine migration of sea trout post-smolts from three populations in a relatively pristine subarctic fjord system. While at sea, the sea trout spent a substantial part of their time close to their natal river, preferred near shore over pelagic habitats and were strongly surface oriented. Despite a fidelity towards local areas, the sea trout utilized various parts of the fjord system, with maximum dispersion >30 km and total migration distance >300 km. Almost half of the sea trout (44%) migrated between river outlets, indicating that a metapopulation approach may be appropriate when managing neighbouring sea trout populations at high latitudes. Furthermore, the different populations displayed different migratory behaviours in terms of distance migrated, dispersion from origin and the likelihood of leaving their home area. This variation in migratory behaviour is likely influenced by spatiotemporal differences in habitat quality between sites, indicating that local habitat variations may promote population-specific behavioural responses even in relatively confined fjord systems.
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Affiliation(s)
| | | | | | - Eivind Nordli
- Faculty of Biosciences, Fisheries and Economics, UiT the Arctic University of Norway, Tromsø, Norway
| | | | - Thomas Bøhn
- Institute of Marine Research, Tromsø, Norway
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8
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Dalvin S, Eichner C, Dondrup M, Øvergård AC. Roles of three putative salmon louse (Lepeophtheirus salmonis) prostaglandin E 2 synthases in physiology and host-parasite interactions. Parasit Vectors 2021; 14:206. [PMID: 33874988 PMCID: PMC8056522 DOI: 10.1186/s13071-021-04690-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Accepted: 03/16/2021] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The salmon louse (Lepeophtheirus salmonis) is a parasite of salmonid fish. Atlantic salmon (Salmo salar) exhibit only a limited and ineffective immune response when infested with this parasite. Prostaglandins (PGs) have many biological functions in both invertebrates and vertebrates, one of which is the regulation of immune responses. This has led to the suggestion that prostaglandin E2 (PGE2) is important in the salmon louse host-parasite interaction, although studies of a salmon louse prostaglandin E2 synthase (PGES) 2 gene have not enabled conformation of this hypothesis. The aim of the present study was, therefore, to characterize two additional PGES-like genes. METHODS Lepeophtheirus salmonis microsomal glutathione S-transferase 1 like (LsMGST1L) and LsPGES3L were investigated by sequencing, phylogenetics, transcript localization and expression studies. Moreover, the function of these putative PGES genes in addition to the previously identified LsPGES2 gene was analyzed in double stranded (ds) RNA-mediated knockdown (KD) salmon louse. RESULTS Analysis of the three putative LsPGES genes showed a rather constitutive transcript level throughout development from nauplius to the adult stages, and in a range of tissues, with the highest levels in the ovaries or gut. DsRNA-mediated KD of these transcripts did not produce any characteristic changes in phenotype, and KD animals displayed a normal reproductive output. The ability of the parasite to infect or modulate the immune response of the host fish was also not affected by KD. CONCLUSIONS Salmon louse prostaglandins may play endogenous roles in the management of reproduction and oxidative stress and may be a product of salmon louse blood digestions.
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Affiliation(s)
- Sussie Dalvin
- Institute of Marine Research, SLCR-Sea Lice Research Centre, Nordnes, P. box 1870, 5817, Bergen, Norway
| | - Christiane Eichner
- Department of Biological Sciences, SLCR-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway
| | - Michael Dondrup
- Department of Informatics, SLRC-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway
| | - Aina-Cathrine Øvergård
- Department of Biological Sciences, SLCR-Sea Lice Research Centre, University of Bergen, P. box 7803, 5020, Bergen, Norway.
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9
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Synchrony and multimodality in the timing of Atlantic salmon smolt migration in two Norwegian fjords. Sci Rep 2021; 11:6504. [PMID: 33753812 PMCID: PMC7985142 DOI: 10.1038/s41598-021-85941-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 03/08/2021] [Indexed: 11/23/2022] Open
Abstract
The timing of the smolt migration of Atlantic salmon (Salmo salar) is a phenological trait increasingly important to the fitness of this species. Understanding when and how smolts migrate to the sea is crucial to understanding how salmon populations will be affected by both climate change and the elevated salmon lice concentrations produced by salmon farms. Here, acoustic telemetry was used to monitor the fjord migration of wild post-smolts from four rivers across two fjord systems in western Norway. Smolts began their migration throughout the month of May in all populations. Within-population, the timing of migration was multimodal with peaks in migration determined by the timing of spring floods. As a result, migrations were synchronized across populations with similar hydrology. There was little indication that the timing of migration had an impact on survival from the river mouth to the outer fjord. However, populations with longer fjord migrations experienced lower survival rates and had higher variance in fjord residency times. Explicit consideration of the multimodality inherent to the timing of smolt migration in these populations may help predict when smolts are in the fjord, as these modes seem predictable from available environmental data.
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10
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Dalvin S, Are Hamre L, Skern-Mauritzen R, Vågseth T, Stien L, Oppedal F, Bui S. The effect of temperature on ability of Lepeophtheirus salmonis to infect and persist on Atlantic salmon. JOURNAL OF FISH DISEASES 2020; 43:1519-1529. [PMID: 32882750 DOI: 10.1111/jfd.13253] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 06/11/2023]
Abstract
The salmon louse (Lepeophtheirus salmonis) is an ecologically and economically important parasite of salmonid fish. Temperature is a strong influencer of biological processes in salmon lice, with development rate increased at higher temperatures. The successful attachment of lice onto a host is also predicted to be influenced by temperature; however, the correlation of temperature with parasite survival is unknown. This study describes the effects of temperature on infection success, and survival on the host during development to the adult stage. To accurately describe infection dynamics with varying temperatures, infection success was recorded on Atlantic salmon (Salmo salar) between 2 and 10°C. Infection success ranged from 20% to 50% and was strongly correlated with temperature, with the highest success at 10°C. Parasite loss was monitored during development at eight temperatures with high loss of lice at 3 and 24°C, whilst no loss was recorded in the temperature range from 6 to 21°C. Sea temperatures thus have large effects on the outcome of salmon louse infections and should be taken into account in the management and risk assessment of this parasite. Improving understanding of the infection dynamics of salmon lice will facilitate epidemiological modelling efforts and efficiency of pest management strategies.
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Affiliation(s)
- Sussie Dalvin
- SLRC - Sea Lice Research Centre, Institute of Marine Research, Bergen, Norway
- Department of Biological Sciences, SLRC - Sea Lice Research Centre, University of Bergen, Bergen, Norway
| | - Lars Are Hamre
- Department of Biological Sciences, SLRC - Sea Lice Research Centre, University of Bergen, Bergen, Norway
| | | | | | - Lars Stien
- Institute of Marine Research, Matredal, Norway
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11
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Lennox RJ, Salvanes AGV, Barlaup BT, Stöger E, Madhun A, Helle TM, Vollset KW. Negative impacts of the sea lice prophylactic emamectin benzoate on the survival of hatchery released salmon smolts in rivers. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2020; 224:105519. [PMID: 32502848 DOI: 10.1016/j.aquatox.2020.105519] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/07/2020] [Accepted: 05/10/2020] [Indexed: 06/11/2023]
Abstract
Emamectin benzoate (EB) is a prophylactic pharmaceutical used to protect Atlantic salmon (Salmo salar) smolts migrating out of rivers and into the ocean against sea lice parasites. Randomized control trials comparing the marine survival of smolts treated with EB to a control group is used to calculate the fraction of marine mortality attributable to sea lice parasitism. However, it is assumed that there is no baseline difference in survival induced by the application of EB treatment. We used a combined laboratory and field study approach to investigate the potential impacts of EB treatment on behaviour and survival of hatchery-reared Atlantic salmon in western Norway. In aquaria experiments, EB-treated salmon smolts did not differ significantly in exploratory behaviour. Fish from treated groups responded similarly to simulated predator attack with spontaneous escape and elevated gill beat rate. Three rivers in the Osterfjord system of western Norway were selected for field experiments, Dale, Vosso, and Modalen. Dale River smolts were treated with intraperitoneal EB injections and had lower probability of detection in a wolf trap downstream of the release site than control smolts. Salmon smolts raised in the Vosso River hatchery were treated with EB delivered in their food and were detected on PIT antennas at the rivermouth of Vosso and Modalen at lower rates than control fish, but only when released at downstream sites. Calculation of risk ratios suggested that the bias in mortality caused by treatment with EB decreased the estimated survival of treated fish from an expected 18%to 46%, reducing the observable negative impact of sea lice on Atlantic salmon smolts in randomized control trials. The results suggest that estimates of the fraction of mortality attributable to sea lice may be underestimated due to lower baseline survival of treated fish caused by treatment and bring urgent attention towards a potential systematic underestimation of the impacts of sea lice on wild salmon.
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Affiliation(s)
- Robert J Lennox
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway.
| | | | - Bjørn T Barlaup
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway
| | - Elisabeth Stöger
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway
| | | | - Turid M Helle
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway
| | - Knut Wiik Vollset
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries (LFI), Nygårdsporten 112, 5008 Bergen, Norway
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