1
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Vollset KW, Dohoo I, Lennox RJ. The paradox of predation studies. Biol Lett 2023; 19:20230354. [PMID: 37848051 PMCID: PMC10734775 DOI: 10.1098/rsbl.2023.0354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Accepted: 09/28/2023] [Indexed: 10/19/2023] Open
Abstract
Understanding the causal relationships that contribute to mortality in populations is a priority for epidemiology, animal husbandry and ecology. Of all the sources of mortality in nature, predation is perhaps the most important, while simultaneously being one of the most difficult to study and understand. In this opinion piece, we use the epidemiological concept of the sufficient-component cause model to outline why we believe that predation studies often misrepresent predators as sufficient cause of death (or natural mortality) in ecological studies. This is pivotal in conservation biology because such studies have often led to demands for predator removal throughout the world. We use the sufficient-component cause model to illustrate the paradox that multiple studies, each studying singular putative causes of mortality (including predation), will sum to more than 100% mortality when added together. We suggest that the sufficient-component framework should be integrated into both fundamental and applied ecology to better understand the role of predators in natural ecosystems.
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Affiliation(s)
- Knut Wiik Vollset
- Laboratory for Freshwater
Ecology and Inland Fisheries, NORCE Norwegian Research
Centre, Nygardsgaten 112, 5008 Bergen,
Norway
| | - Ian Dohoo
- University of
Prince Edward Island, Charlottetown,
Canada C1A 4P3
| | - Robert J. Lennox
- Laboratory for Freshwater
Ecology and Inland Fisheries, NORCE Norwegian Research
Centre, Nygardsgaten 112, 5008 Bergen,
Norway
- Ocean Tracking Network,
Dalhousie University, 1355 Oxford Street,
Halifax, Canada
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2
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Lennox RJ, Eldøy SH, Dahlmo LS, Matley JK, Vollset KW. Acoustic accelerometer transmitters and their growing relevance to aquatic science. Mov Ecol 2023; 11:45. [PMID: 37501158 PMCID: PMC10375738 DOI: 10.1186/s40462-023-00403-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 06/26/2023] [Indexed: 07/29/2023]
Abstract
There has recently been great interest in the use of accelerometers onboard electronic transmitters to characterise various aspects of the ecology of wild animals. We review use cases and outline how these tools can provide opportunities for studying activity and survival, exercise physiology of wild animals, the response to stressors, energy landscapes and conservation planning tools, and the means with which to identify behaviours remotely from transmitted data. Accelerometer transmitters typically send data summaries to receivers at fixed intervals after filtering out static acceleration and calculating root-mean square error or overall dynamic body action of 2- or 3-axis acceleration values (often at 5-12.5 Hz) from dynamic acceleration onboard the tag. Despite the popularity of these transmitters among aquatic ecologists, we note that there is wide variation in the sampling frequencies and windows used among studies that will potentially affect the ability to make comparisons in the future. Accelerometer transmitters will likely become increasingly popular tools for studying finer scale details about cryptic species that are difficult to recapture and hence not suitable for studies using data loggers. We anticipate that there will continue to be opportunities to adopt methods used for analysing data from loggers to datasets generated from acceleration transmitters, to generate new knowledge about the ecology of aquatic animals.
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Affiliation(s)
- Robert J Lennox
- Norwegian Institute for Nature Research, Trondheim, Høgskoleringen 9, 7034, Norway.
- NORCE Norwegian Research Centre Laboratory for Freshwater Ecology and Inland Fisheries, Nygaardsgaten 112, 5008, Bergen, Norway.
- Ocean Tracking Network, Dalhousie University, 1335 Oxford St, B3H 3Z1, Halifax, Canada.
| | - Sindre H Eldøy
- NTNU Vitenskapsmuseet, Erling Skakkes gate 47B, 7012, Trondheim, Norway
| | - Lotte S Dahlmo
- NORCE Norwegian Research Centre Laboratory for Freshwater Ecology and Inland Fisheries, Nygaardsgaten 112, 5008, Bergen, Norway
| | - Jordan K Matley
- College of Science and Engineering, Flinders University, Adelaide, SA, 5042, Australia
| | - Knut Wiik Vollset
- NORCE Norwegian Research Centre Laboratory for Freshwater Ecology and Inland Fisheries, Nygaardsgaten 112, 5008, Bergen, Norway
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3
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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4
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Lennox RJ, Dahlmo LS, Ford AT, Sortland LK, Vogel EF, Vollset KW. Predation research with electronic tagging. Wildlife Biology 2022. [DOI: 10.1002/wlb3.01045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Robert J. Lennox
- Norwegian Inst. for Nature Research Trondheim Norway
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries Bergen Norway
| | - Lotte S. Dahlmo
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries Bergen Norway
- Dept of Biological Sciences, Univ. of Bergen Bergen Norway
| | - Adam T. Ford
- Univ. of British Columbia Okanagan Kelowna BC Canada
| | - Lene K. Sortland
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries Bergen Norway
- Dept of Biological Sciences, Univ. of Bergen Bergen Norway
| | - Emma F. Vogel
- UiT − The Arctic Univ. of Norway, Faculty of Biosciences, Fisheries and Economics Tromsø Norway
| | - Knut Wiik Vollset
- NORCE Norwegian Research Centre, Laboratory for Freshwater Ecology and Inland Fisheries Bergen Norway
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5
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Lennox RJ, Barrett LT, Nilsen CI, Berhe S, Barlaup BT, Vollset KW. Moving cleaner fish from the wild into fish farms: A zero-sum game? Ecol Modell 2022. [DOI: 10.1016/j.ecolmodel.2022.110149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Lennox RJ, Stöger E, Dahlmo LS, Helle T, Wiers T, Hanssen EM, Vollset KW. Effects of tag type and surgery on migration of Atlantic salmon (Salmo salar) smolts. J Fish Biol 2022; 101:515-521. [PMID: 35668681 PMCID: PMC9545663 DOI: 10.1111/jfb.15116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Tagging salmon smolts to provide information about the timing of outmigration has been a common approach to monitor phenology and model the risk of encountering stressors. However, the validity of tagging has come under scrutiny because of the sensitivity of this parameter in various management systems. We studied the probability of migration, timing of migration and growth during migration for Atlantic salmon smolts tagged with three different tags in the River Dale, western Norway. Two groups were tagged with passive integrated transponder (PIT) tags via a small ventral nonsurgical incision, either a 12 mm or a new 16 mm PIT tag. Two groups were subjected to surgical implantation of either a dummy acoustic transmitter or a 12 mm PIT tag (a sham surgery). Overall, 71% of the tagged smolts were recaptured at the downstream Wolf trap. Smolts from the sham tagged group were recaptured most frequently (78%) compared to dummy acoustic transmitters and 16 mm PIT tags (both 68%), but the differences were not significant. Results agree with prior assessments that longer smolts migrated earlier, with about half a day earlier migration for each millimetre total length of the smolt, but did not suggest any difference in time of migration among the tag types. Growth in length was evident from release to recapture, with smaller smolts exhibiting greater growth and no effect of tagging treatment. Our findings suggest that inferences about the timing of outmigration for salmon smolts based on acoustic tagging should be made cautiously because of the relationship among tag size, suitable fish size and the timing of a tagged individual's migration.
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Affiliation(s)
- Robert J. Lennox
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Elisabeth Stöger
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Lotte S. Dahlmo
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Turid Helle
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Tore Wiers
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Erlend M. Hanssen
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
| | - Knut Wiik Vollset
- NORCE Norwegian Research CentreLaboratory for Freshwater Ecology and Inland FisheriesBergenNorway
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7
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Vollset KW, Urdal K, Utne K, Thorstad EB, Sægrov H, Raunsgard A, Skagseth Ø, Lennox RJ, Østborg GM, Ugedal O, Jensen AJ, Bolstad GH, Fiske P. Ecological regime shift in the Northeast Atlantic Ocean revealed from the unprecedented reduction in marine growth of Atlantic salmon. Sci Adv 2022; 8:eabk2542. [PMID: 35245115 PMCID: PMC8896796 DOI: 10.1126/sciadv.abk2542] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 01/13/2022] [Indexed: 06/14/2023]
Abstract
Ecological regime shifts are abrupt changes in the structure and function of ecosystems that persist over time, but evidence of contemporary regime shifts are rare. Historical scale data from 52,384 individual wild Atlantic salmon caught in 180 rivers from 1989 to 2017 reveal that growth of Atlantic salmon across the Northeast Atlantic Ocean abruptly decreased following the year 2004. At the same time, the proportion of early maturing Atlantic salmon decreased. These changes occurred after a marked decrease in the extent of Arctic water in the Norwegian Sea, a subsequent warming of spring water temperature before Atlantic salmon entering the sea, and an approximately 50% reduction of zooplankton across large geographic areas of the Northeast Atlantic Ocean. A sudden decrease in growth was also observed among Atlantic mackerel in the Norwegian Sea. Our results point toward an ecosystem-scale regime shift in the Northeast Atlantic Ocean.
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Affiliation(s)
- Knut Wiik Vollset
- Norwegian Research Centre (NORCE), Laboratory for Freshwater Ecology and Inland Fisheries, 5008 Bergen, Norway
| | - Kurt Urdal
- Rådgivende Biologer AS, 5059 Bergen, Norway
| | - Kjell Utne
- Institute of Marine Research, 5817 Bergen, Norway
| | - Eva B. Thorstad
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | | | - Astrid Raunsgard
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | | | - Robert J. Lennox
- Norwegian Research Centre (NORCE), Laboratory for Freshwater Ecology and Inland Fisheries, 5008 Bergen, Norway
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | - Gunnel M. Østborg
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | - Ola Ugedal
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | - Arne J. Jensen
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | - Geir H. Bolstad
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
| | - Peder Fiske
- Norwegian Institute for Nature Research (NINA), 7485 Trondheim, Norway
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8
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Vollset KW, Lennox RJ, Lamberg A, Skaala Ø, Sandvik AD, Sægrov H, Kvingedal E, Kristensen T, Jensen AJ, Haraldstad T, Barlaup BT, Ugedal O. Predicting the nationwide outmigration timing of Atlantic salmon (
Salmo salar
) smolts along 12 degrees of latitude in Norway. DIVERS DISTRIB 2021. [DOI: 10.1111/ddi.13285] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Knut Wiik Vollset
- Laboratory for Freshwater Ecology and Inland Fisheries at NORCE Norwegian Research Centre Bergen Norway
| | - Robert J. Lennox
- Laboratory for Freshwater Ecology and Inland Fisheries at NORCE Norwegian Research Centre Bergen Norway
| | | | | | | | | | - Eli Kvingedal
- Norwegian Institute for Nature Research (NINA) Trondheim Norway
| | | | | | | | - Bjørn Torgeir Barlaup
- Laboratory for Freshwater Ecology and Inland Fisheries at NORCE Norwegian Research Centre Bergen Norway
| | - Ola Ugedal
- Norwegian Institute for Nature Research (NINA) Trondheim Norway
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9
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Affiliation(s)
- Shad Mahlum
- NORCE Norwegian Research CentreLFI Bergen Norway
- Department of Biological Sciences University of Bergen Bergen Norway
| | | | | | | | - Gaute Velle
- NORCE Norwegian Research CentreLFI Bergen Norway
- Department of Biological Sciences University of Bergen Bergen Norway
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10
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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. Aquat Toxicol 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] [What about the content of this article? (0)] [Affiliation(s)] [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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11
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Vollset KW. Parasite induced mortality is context dependent in Atlantic salmon: insights from an individual-based model. Sci Rep 2019; 9:17377. [PMID: 31758025 PMCID: PMC6874588 DOI: 10.1038/s41598-019-53871-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 11/04/2019] [Indexed: 11/09/2022] Open
Abstract
An individual-based model was parameterized to explore the impact of a crustacean ectoparasite (sea louse, Lepeophtheirus salmonis & Caligus spp.) on migrating Atlantic salmon smolt. The model explores how environmental and intrinsic factors can modulate the effect of sea lice on survival, growth and maturation of Atlantic salmon at sea. Relative to other effects, the parasite infestation pressure from fish farms and the encounter process emerge as the most important parameters. Although small variations in parasite-induced mortality may be masked by variable environmental effects, episodes of high infestation pressure from fish farms should be observable in wild populations of Atlantic salmon if laboratory studies accurately reflect the physiological effects of sea lice. Increases in temperature in the model negatively influenced fish survival by affecting the development time of the parasite at a rate that was not compensated for by the growth of the host. Discharge from rivers was parameterized to increase migration speed and influenced parasite induced mortality by decreasing time spent in areas with increased infestation pressure. Initial size and growth of the host was inversely related to the impact of the parasite because of size-dependent parasite-induced mortality in the early phase of migration. Overall, the model illustrates how environmental factors modulate effects on the host population by impacting either the parasite load or the relative effect of the parasite. The results suggest that linking population-level effects to parasite infestation pressure across climatic and environmental gradients may be challenging without correctly accounting for these effects.
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Affiliation(s)
- Knut Wiik Vollset
- NORCE Norwegian Research Centre, Laboratory for Freshwater ecology and Inland fisheries, Nygårdsporten 112, 5006, Bergen, Norway.
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12
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Kristoffersen AB, Qviller L, Helgesen KO, Vollset KW, Viljugrein H, Jansen PA. Quantitative risk assessment of salmon louse-induced mortality of seaward-migrating post-smolt Atlantic salmon. Epidemics 2017; 23:19-33. [PMID: 29233546 DOI: 10.1016/j.epidem.2017.11.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/26/2017] [Accepted: 11/29/2017] [Indexed: 10/18/2022] Open
Abstract
The Norwegian government recently implemented a new management system to regulate salmon farming in Norway, aiming to promote environmentally sustainable growth in the aquaculture industry. The Norwegian coast has been divided into 13 production zones and the volume of salmonid production in the zones will be regulated based on salmon lice effects on wild salmonids. Here we present a model for assessing salmon louse-induced mortality of seaward-migrating post-smolts of Atlantic salmon. The model quantifies expected salmon lice infestations and louse-induced mortality of migrating post-smolt salmon from 401 salmon rivers draining into Norwegian coastal waters. It is assumed that migrating post-smolts follow the shortest path from river outlets to the high seas, at constant progression rates. During this migration, fish are infested by salmon lice of farm origin according to an empirical infestation model. Furthermore, louse-induced mortality is estimated from the estimated louse infestations. Rivers draining into production zones on the West Coast of Norway were at the highest risk of adverse lice effects. In comparison, rivers draining into northerly production zones, along with the southernmost production zone, were at lower risk. After adjusting for standing stock biomass, estimates of louse-egg output varied by factors of up to 8 between production zones. Correlation between biomass adjusted output of louse infestation and densities of farmed salmon in the production zones suggests that a large-scale density-dependent host-parasite effect is a major driver of louse infestation rates and parasite-induced mortality. The estimates are sensitive to many of the processes in the chain of events in the model. Nevertheless, we argue that the model is suited to assess spatial and temporal risks associated with farm-origin salmon lice.
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Affiliation(s)
| | - Lars Qviller
- The Norwegian Veterinary Institute, PB. 750 Sentrum, N-0106 Oslo, Norway
| | - Kari Olli Helgesen
- The Norwegian Veterinary Institute, PB. 750 Sentrum, N-0106 Oslo, Norway
| | - Knut Wiik Vollset
- Uni Research Environment, LFI-Freshwater Biology, Nygårdsporten 112, N-5006 Bergen, Norway
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13
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Pulg U, Vollset KW, Velle G, Stranzl S. First observations of saturopeaking: Characteristics and implications. Sci Total Environ 2016; 573:1615-1621. [PMID: 27707575 DOI: 10.1016/j.scitotenv.2016.09.143] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 09/17/2016] [Accepted: 09/17/2016] [Indexed: 06/06/2023]
Abstract
During the monitoring of total dissolved gas (TDG) saturation in the Vetlefjordelva River in western Norway in 2014-2015, characteristic waves of supersaturated water were discovered. These waves were significantly correlated with hydropower operation, which was run by hydropeaking (R2=0.82, p<0.001). The TDG saturation varied between 99% and 108%, with a median of 105%. The term "saturopeaking" is introduced for these waves, defined as the artificial, rapid, periodic and frequent fluctuation of gas saturation caused by hydropeaking. Hydropeaking is recognized as hydropower operation that rapidly fluctuates according to the electricity market demand. Though the observed TDG saturation levels were moderate and not likely to cause acute effects on biota, we expect that the observed saturopeaking may have significant ecological impacts in general, especially in cases with TDG saturation levels >110^% which is considered as potentially lethal for fish in rivers.
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Affiliation(s)
- Ulrich Pulg
- Uni Environment LFI Uni Research, Bergen, Norway.
| | | | - Gaute Velle
- Uni Environment LFI Uni Research, Bergen, Norway; Department of Biology, University of Bergen, Bergen, Norway
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14
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Vollset KW, Mahlum S, Davidsen JG, Skoglund H, Barlaup BT. Interaction between migration behaviour and estuarine mortality in cultivated Atlantic salmon Salmo salar smolts. J Fish Biol 2016; 89:1974-1990. [PMID: 27506320 DOI: 10.1111/jfb.13097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 06/28/2016] [Indexed: 06/06/2023]
Abstract
Migration behaviour and estuarine mortality of cultivated Atlantic salmon Salmo salar smolts in a 16 km long estuary were studied using two methods: (1) acoustic telemetry and (2) group tagging in combination with trap nets. Progression rates of surviving individuals through the estuary were relatively slow using both methods [0·38 LT (total length) s-1 v. 0·25 LT s-1 ]. In 2012, the progression rate was slow from the river to the estuary (0·55 LT s-1 ) and the first part of the estuary (0·31 LT s-1 ), but increased thereafter (1·45-2·21 LT s-1 ). In 2013, the progression rate was fast from the river to the estuary (4·31 LT s-1 ) but was slower thereafter (0·18-0·91 LT s-1 ). Survival to the fjord was higher in 2012 (47%) compared to 2013 (6%). Fast moving individuals were more likely to migrate successfully through the estuary compared to slower moving individuals. Adult recapture of coded-wire-tagged S. salar was generally low (0·00-0·04%). Mortality hot spots were related to topographically distinct areas such as the river outlet (in 2012) or the sill separating the estuary and the fjord (in 2013). At the sill, an aggregation of cod Gadus morhua predating on cultivated smolts was identified. The results indicate that slow progression rates through the estuary decreases the likelihood of smolts being detected outside the estuary. The highly stochastic and site-specific mortality patterns observed in this study highlight the complexity in extrapolating mortality patterns of single release groups to the entire smolt run of wild S. salar.
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Affiliation(s)
- K W Vollset
- Laboratory of Freshwater Ecology and Inland fisheries, Uni Research Environment, 5006, Bergen, Norway.
| | - S Mahlum
- Laboratory of Freshwater Ecology and Inland fisheries, Uni Research Environment, 5006, Bergen, Norway
| | - J G Davidsen
- NTNU University Museum, Norwegian University of Science and Technology, N-7491, Trondheim, Norway
| | - H Skoglund
- Laboratory of Freshwater Ecology and Inland fisheries, Uni Research Environment, 5006, Bergen, Norway
| | - B T Barlaup
- Laboratory of Freshwater Ecology and Inland fisheries, Uni Research Environment, 5006, Bergen, Norway
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Vollset KW, Skoglund H, Wiers T, Barlaup BT. Effects of hydropeaking on the spawning behaviour of Atlantic salmon Salmo salar and brown trout Salmo trutta. J Fish Biol 2016; 88:2236-2250. [PMID: 27125209 DOI: 10.1111/jfb.12985] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 03/03/2016] [Indexed: 06/05/2023]
Abstract
An in situ camera set-up was used to study the spawning activity of Atlantic salmon Salmo salar and brown trout Salmo trutta throughout two consecutive seasons in a spawning area affected by hydropower-related pulse flows due to hydropeaking. The purpose was to test whether the flow variation discouraged spawning in shallow areas or motivated spawning into areas with elevated risk of incubation mortality. There were more S. salar observed on the spawning ground during days with high discharge. The presence of S. salar in the spawning grounds was not affected by the hydropeaking cycles of the preceding night. Female S. salar were observed preparing nests within the first hour after water discharge had increased to levels suitable for spawning. In contrast, the number of S. trutta was not correlated with flow and nest preparation was also observed at a discharge corresponding to the lowest discharge levels during a hydropeaking cycle. Survival was generally high in nests excavated the following winter, with only 5·4% suffering mortality due to dewatering. The results suggest that S. salar may respond rapidly to variable-flow conditions and utilize short windows with suitable flows for spawning. Smaller S. trutta may utilize low-flow conditions to spawn in areas that are not habitable by larger S. salar during low flow.
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Affiliation(s)
- K W Vollset
- Uni Research Environment, Nygårdsgaten 112, 5020, Bergen, Norway
| | - H Skoglund
- Uni Research Environment, Nygårdsgaten 112, 5020, Bergen, Norway
| | - T Wiers
- Uni Research Environment, Nygårdsgaten 112, 5020, Bergen, Norway
| | - B T Barlaup
- Uni Research Environment, Nygårdsgaten 112, 5020, Bergen, Norway
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Folkvord A, Vollset KW, Catalán IA. Differences in growth and survival between cod Gadus morhua and herring Clupea harengus early stages co-reared at variable prey concentrations. J Fish Biol 2015; 87:1176-1190. [PMID: 26412336 DOI: 10.1111/jfb.12783] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 07/26/2015] [Indexed: 06/05/2023]
Abstract
It was hypothesized that the survival and growth strategies of herring Clupea harengus, displaying a flexible reproductive activity, are adapted to coping with longer periods of prey deprivation (i.e. more variable prey availability), in contrast to cod Gadus morhua, which are adapted to match growth and survival at high prey concentrations. Experimental larval growth and survival data for the two naturally co-occurring species reared either in separate tanks or in combination are presented to test this hypothesis. Natural zooplankton was supplied either ad libitum or in a periodically restricted manner to mimic natural suboptimal conditions. Periodically restricted feeding significantly reduced initial growth of G. morhua larvae co-reared with C. harengus, while no such initial effect was seen for co-reared C. harengus. Overall survival of G. morhua was higher when reared together with C. harengus (32 v. 24%), while C. harengus had higher survival without the presence of G. morhua (59 v. 44%), indicating that both species were affected by higher densities of G. morhua larvae. Furthermore, the final survival in G. morhua was inversely related to average final size, while in C. harengus an opposite trend was observed. How potential behavioural interactions may drive the present results are discussed and contended that a better insight into field vital rates may be gained from further exploration of co-rearing experiments.
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Affiliation(s)
- A Folkvord
- Department of Biology, University of Bergen and the Hjort Centre for Marine Ecosystem Dynamics, N-5020, Bergen, Norway
- Institute of Marine Research, N-5817, Bergen, Norway
| | - K W Vollset
- Department of Biology, University of Bergen and the Hjort Centre for Marine Ecosystem Dynamics, N-5020, Bergen, Norway
- Uni Research Environment, LFI, Thormøhlensgt. 49 B, NO-5006, Bergen, Norway
| | - I A Catalán
- Department of Ecology and Marine Resources, Mediterranean Institute for Advanced Studies (IMEDEA-CSIC/UIB), C/ Miquel Marques 21, CP 07190, Esporles, Balearic Islands, Spain
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Abstract
The global increase in the production of domestic farmed fish in open net pens has created concerns about the resilience of wild populations owing to shifts in host-parasite systems in coastal ecosystems. However, little is known about the effects of increased parasite abundance on life-history traits in wild fish populations. Here, we report the results of two separate studies in which 379 779 hatchery-reared Atlantic salmon smolts were treated (or not) against salmon lice, marked and released. Adults were later recaptured, and we specifically tested whether the age distribution of the returning spawners was affected by the treatment. The estimates of parasite-induced mortality were 31.9% and 0.6% in the River Vosso and River Dale stock experiments, respectively. Age of returning salmon was on average higher in untreated [corrected] versus untreated fish. The percentages of fish returning after one winter at sea were 37.5% and 29.9% for the treated and untreated groups, respectively. We conclude that salmon lice increase the age of returning salmon, either by affecting their age at maturity or by disproportionately increasing mortality in fish that mature early.
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Affiliation(s)
- Knut Wiik Vollset
- LFI, Uni Environment, Uni Research, , Thormøhlensgt. 49 B, Bergen 5006, Norway
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Vollset KW, Bailey KM. Interplay of individual interactions and turbidity affects the functional response of three-spined sticklebacks Gasterosteus aculeatus. J Fish Biol 2011; 78:1954-1964. [PMID: 21651543 DOI: 10.1111/j.1095-8649.2011.02963.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The effects of turbidity, size and the presence of conspecifics on the functional response, feeding latency and activity in the three-spined stickleback Gasterosteus aculeatus were examined. A significant interaction between standard length and presence of conspecifics demonstrated an increase in attack rates of larger individuals in the presence of conspecifics. Attack rate was also higher in turbid water. Feeding latency decreased with prey concentration and presence of conspecifics, but was not affected by turbidity. Activity level did not change with prey levels, but increased with turbidity. These results can help to better understand how individual flexibility in the functional response can affect prey mortality according to environmental perturbation and social interaction at the level of the predator.
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Affiliation(s)
- K W Vollset
- Department of Biology, University of Bergen, N-5020 Bergen, Norway.
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