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Harrington PD, Cantrell DL, Foreman MGG, Guo M, Lewis MA. Timing and probability of arrival for sea lice dispersing between salmon farms. ROYAL SOCIETY OPEN SCIENCE 2023; 10:220853. [PMID: 36778949 PMCID: PMC9905982 DOI: 10.1098/rsos.220853] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 01/10/2023] [Indexed: 06/18/2023]
Abstract
Sea lice are a threat to the health of both wild and farmed salmon and an economic burden for salmon farms. With a free-living larval stage, sea lice can disperse tens of kilometres in the ocean between salmon farms, leading to connected sea louse populations that are difficult to control in isolation. In this paper, we develop a simple analytical model for the dispersal of sea lice (Lepeophtheirus salmonis) between two salmon farms. From the model, we calculate the arrival time distribution of sea lice dispersing between farms, as well as the level of cross-infection of sea lice. We also use numerical flows from a hydrodynamic model, coupled with a particle tracking model, to directly calculate the arrival time of sea lice dispersing between two farms in the Broughton Archipelago, British Columbia, in order to fit our analytical model and find realistic parameter estimates. Using the parametrized analytical model, we show that there is often an intermediate interfarm spacing that maximizes the level of cross-infection between farms, and that increased temperatures will lead to increased levels of cross-infection.
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Affiliation(s)
- Peter D. Harrington
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Danielle L. Cantrell
- California Department of Fish and Wildlife, Marine Region’s Fisheries Analytics Project, 20 Lower Ragsdale Drive, Suite 100, Monterey, CA 93940, USA
| | - Michael G. G. Foreman
- Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, British Columbia, Canada
| | - Ming Guo
- Institute of Ocean Sciences, Fisheries and Oceans Canada, Sidney, British Columbia, Canada
| | - Mark A. Lewis
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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2
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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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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3
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Parent MI, Stryhn H, Hammell KL, Fast MD, Grant J, Vanderstichel R. Estimating the dispersal of Lepeophtheirus salmonis sea lice within and among Atlantic salmon sites of the Bay of Fundy, New Brunswick. JOURNAL OF FISH DISEASES 2021; 44:1971-1984. [PMID: 34411315 PMCID: PMC9291781 DOI: 10.1111/jfd.13511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Abstract
The objective of this study was to estimate the impact of infestation pressures on the abundance of the parasitic sea louse, Lepeophtheirus salmonis, in the Bay of Fundy, New Brunswick (NB), Canada, using the Fish-iTrends database for the years 2009-2018. Infestation pressures were calculated as time-lagged weighted averages of the abundance of adult female (AF) sea lice within a site (internal infestation pressure: IIP) and among sites (external infestation pressure: EIP). The EIP weights were calculated from seaway distances among sites and a Gaussian kernel density for bandwidths of 5 to 60 km. The EIP with a bandwidth of 10 km had the best fit, as determined with Akaike's information criterion, and historical AF sea lice abundance. This estimated dispersal distance of 10 km was similar to previous studies in Norway, Scotland and in New Brunswick. The infestation pressures estimated from empirical AF sea lice abundance within and among sites significantly increased the abundance of AF sea lice (p < .001). This study concludes that sea lice burdens within Atlantic salmon farms in the Bay of Fundy, NB, are affected by within site management and could be improved by synchronizing treatments between sites.
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Affiliation(s)
- Marianne I. Parent
- Department of Health ManagementAtlantic Veterinary CollegeUniversity of Prince Edward IslandCharlottetownPEICanada
| | - Henrik Stryhn
- Department of Health ManagementAtlantic Veterinary CollegeUniversity of Prince Edward IslandCharlottetownPEICanada
| | - K. Larry Hammell
- Department of Health ManagementAtlantic Veterinary CollegeUniversity of Prince Edward IslandCharlottetownPEICanada
| | - Mark D. Fast
- Department of Pathology and MicrobiologyAVCUPEICharlottetownPEICanada
| | - Jon Grant
- Department of OceanographyLife Sciences CentreDalhousie UniversityHalifaxNSCanada
| | - Raphaël Vanderstichel
- Department of Health ManagementAtlantic Veterinary CollegeUniversity of Prince Edward IslandCharlottetownPEICanada
- Department of Veterinary Clinical SciencesCollege of Veterinary MedicineLong Island UniversityBrookvilleNYUSA
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4
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Dean KR, Aldrin M, Qviller L, Helgesen KO, Jansen PA, Bang Jensen B. Simulated effects of increasing salmonid production on sea lice populations in Norway. Epidemics 2021; 37:100508. [PMID: 34656838 DOI: 10.1016/j.epidem.2021.100508] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 08/06/2021] [Accepted: 10/06/2021] [Indexed: 11/28/2022] Open
Abstract
Norway produces more than one million tonnes of salmonids every year, almost exclusively in open-water net pens. In 2014, the Norwegian government announced plans to increase salmonid production. However, increasing the number of farmed salmonids can have negative effects on the marine environment that threaten the industry's sustainability. In particular, production growth can lead to an increase in density-dependent diseases, including parasitic sea lice. The aim of this study was to simulate the effects of increased salmonid production on sea lice abundance using different scenarios for increasing the number of fish and for the management of sea lice. We used a previously developed, partly stage-structured model based on Norwegian production and environmental data to simulate the different scenarios. Our results show that increasing the marine farmed salmonid population at a national level by two or five times the current production leads to an increase in the sea lice abundance by 3.5% and 7.1%, respectively. We also found that by lowering the maximum allowable level of sea lice to an average of 0.049 adult females per fish, weekly treatments can be used to control sea lice population growth with a five times increase in production. However, this increases the number of farms treating per week by as much as 281.3%, which can lead to high costs and increased mortality among farmed salmonids. Overall, the results from our study shed light on the effects of increasing salmonid production in Norway with respect to the ongoing threat of sea lice infestations.
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Affiliation(s)
| | - Magne Aldrin
- Norwegian Computing Center, P.O. box 114 Blindern, N-0314 Oslo, Norway
| | - Lars Qviller
- Norwegian Veterinary Institute, P.O. box 64, 1431 Ås, Norway
| | | | - Peder A Jansen
- Norwegian Veterinary Institute, P.O. box 64, 1431 Ås, Norway
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5
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Romero JF, Gardner I, Price D, Halasa T, Thakur K. DTU-DADS-Aqua: A simulation framework for modelling waterborne spread of highly infectious pathogens in marine aquaculture. Transbound Emerg Dis 2021; 69:2029-2044. [PMID: 34152091 DOI: 10.1111/tbed.14195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/10/2021] [Accepted: 06/10/2021] [Indexed: 11/29/2022]
Abstract
Simulation models are useful tools to predict and elucidate the effects of factors influencing the occurrence and spread of epidemics in animal populations, evaluate the effectiveness of different control strategies and ultimately inform decision-makers about mitigations to reduce risk. There is a paucity of simulation models to study waterborne transmission of viral and bacterial pathogens in marine environments. We developed a stochastic, spatiotemporal hybrid simulation model (DTU-DADS-Aqua) that incorporates a compartmental model for infection spread within net-pens, an agent-based model for infection spread between net-pens within and between sites and uses seaway distance to inform farm-site hydroconnectivity. The model includes processes to simulate infection transmission and control over surveillance, detection and depopulation measures. Different what-if scenarios can be explored according to the input data provided and user-defined parameter values, such as daily surveillance and depopulation capacities or increased animal mortality that triggers diagnostic testing to detect infection. The latter can be easily defined in a software application, in which results are summarized after each simulation. To demonstrate capabilities of the model, we simulated the spread of infectious salmon anaemia virus (ISAv) for realistic scenarios in a transboundary population of farmed Atlantic salmon (Salmo salar L.) in New Brunswick, Canada and Maine, United States. We assessed the progression of infection in the different simulated outbreak scenarios, allowing for variation in the control strategies adopted for ISAv. Model results showed that improved disease detection, coupled with increasing surveillance visits to farm-sites and increased culling capacity for depopulation of infected net-pens reduced the number of infected net-pens and outbreak duration but the number of ISA-infected farm sites was minimally affected. DTU-DADS-Aqua is a flexible modelling framework, which can be applied to study different infectious diseases in the aquatic environment, allowing the incorporation of alternative transmission and control dynamics. The framework is open-source and available at https://github.com/upei-aqua/DTU-DADS-Aqua.
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Affiliation(s)
- João F Romero
- Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - Ian Gardner
- Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
| | - Derek Price
- Aquaculture Environmental Operations, Aquaculture Management Division, Fisheries and Oceans Canada, Ottawa, Ontario, Canada
| | - Tariq Halasa
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
| | - Krishna Thakur
- Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada
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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: 3] [Impact Index Per Article: 1.0] [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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Elghafghuf A, Vanderstichel R, Hammell L, Stryhn H. Estimating sea lice infestation pressure on salmon farms: Comparing different methods using multivariate state-space models. Epidemics 2020; 31:100394. [PMID: 32422519 DOI: 10.1016/j.epidem.2020.100394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 12/17/2019] [Accepted: 05/05/2020] [Indexed: 11/24/2022] Open
Abstract
Sea lice are ectoparasites of salmonids, and are considered to be one of the main threats to Atlantic salmon farming. Sea lice infestation on a farm is usually initiated by attachment of the free-living copepodid stage derived from the surrounding water, frequently originating from adult lice on the same farm or from neighboring salmonid farms, referred to as internal and external sources, respectively. Various approaches have been proposed to quantify sea lice infestation pressure on farms to improve the management of this pest. Here, we review and compare five of these methods based on sea lice data from 20 farms located near Grand Manan island in the Bay of Fundy, New Brunswick, Canada. Internal and external infestation pressures (IIP and EIP, respectively) were estimated using different approaches, and their effects were modeled either by a unique parameter for all production cycles or by different parameters for each production cycle, using a multivariate state-space model. Predictive variables, such as water temperature and sea lice treatments, were included in the model, and their effects across production cycles were estimated along with those of other model parameters. Results showed that models with only EIP explained the variation in the data better than models with only IIP, and that models with unique IIP and unique EIP for all cycles were generally associated with the best model fit. The simplest, fixed lag method for calculating infestation pressure had the best predictive performance in our models among the methods studied.
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Affiliation(s)
- Adel Elghafghuf
- Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada.
| | - Raphael Vanderstichel
- Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada
| | - Larry Hammell
- Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada
| | - Henrik Stryhn
- Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE, C1A 4P3, Canada
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8
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Mancilla-Schulz J, Marín SL, Molinet C. Dynamics of Caligus rogercresseyi (Boxshall & Bravo, 2000) in farmed Atlantic salmon (Salmo salar) in southern Chile: Are we controlling sea lice? JOURNAL OF FISH DISEASES 2019; 42:357-369. [PMID: 30644118 DOI: 10.1111/jfd.12931] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 10/19/2018] [Accepted: 10/22/2018] [Indexed: 06/09/2023]
Abstract
Caligus rogercresseyi generates the greatest losses in the salmon industry in Chile. The relationship between salmon farming and sea lice is made up of various components: the parasite, host, environment and farming practices, which make it difficult to identify patterns in parasite population dynamics to define prevention and control strategies. The objectives of this study were to analyse and compare the effect of farming, sanitary practices and environmental variables on the abundance of gravid females (GF) and juveniles (JUV) of C. rogercresseyi on Salmo salar in three Salmon Neighborhood Areas (SNAs) in Region 10, south of Chile. Linear mixed-effects models of the negative binomial distribution were used to evaluate the effect of the different explanatory variables on GF and JUV. Productive variables were the key drivers explaining the abundance of GF and JUV. Results suggest that C. rogercresseyi is not controlled and JUV are persistent in the three SNAs, and sanitary practices do not control the dissemination of the parasite among sites. Environmental variables had a low impact on sea lice abundance. There is a need to perform analysis for modelling of parasite population dynamics to improve Integrated Pest Management, including changes in the governance to achieve an effective prevention and control.
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Affiliation(s)
- Jorge Mancilla-Schulz
- Aquaculture Sciences, Universidad Austral de Chile, Puerto Montt, Chile
- Marine Harvest Chile, Puerto Montt, Chile
| | - Sandra L Marín
- Institute of Aquaculture, Universidad Austral de Chile, Puerto Montt, Chile
- Centro FONDAP de Investigación en Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Puerto Montt, Chile
| | - Carlos Molinet
- Institute of Aquaculture, Universidad Austral de Chile, Puerto Montt, Chile
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9
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Aldrin M, Jansen P, Stryhn H. A partly stage-structured model for the abundance of salmon lice in salmonid farms. Epidemics 2019; 26:9-22. [DOI: 10.1016/j.epidem.2018.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 07/12/2018] [Accepted: 08/16/2018] [Indexed: 11/28/2022] Open
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10
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Vollset KW, Qviller L, Skår B, Barlaup BT, Dohoo I. Parasitic sea louse infestations on wild sea trout: separating the roles of fish farms and temperature. Parasit Vectors 2018; 11:609. [PMID: 30497499 PMCID: PMC6267784 DOI: 10.1186/s13071-018-3189-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 11/06/2018] [Indexed: 11/10/2022] Open
Abstract
Background The causal relation between parasitic sea lice on fish farms and sea lice on wild fish is a controversial subject. A specific scientific debate has been whether the statistical association between infestation pressure (IP) from fish farms and the number of parasites observed on wild sea trout emerges purely because of a confounding and direct effect of temperature (T). Methods We studied the associations between louse infestation on wild sea trout, fish farm activity and temperature in an area that practices coordinated fallowing in Nordhordland, Norway. The data were sampled between 2009 and 2016. We used negative binomial models and mediation analysis to determine to what degree the effect of T is mediated through the IP from fish farms. Results The number of attached lice on sea trout increased with the T when the IP from fish farms was high but not when the IP was low. In addition, nearly all of the effect of rising T was indirect and mediated through the IP. Attached lice remained low when neighbouring farms were in the first year of the production cycle but rose substantially during the second year. In contrast to attached lice, mobile lice were generally seen in higher numbers at lower water temperatures. Temperature had an indirect positive effect on mobile louse counts by increasing the IP which, in turn, raised the sea trout louse counts. Mobile louse counts rose steadily during the year when neighbouring farms were in the first year of the production cycle and stayed high throughout the second year. Conclusions The estimates of the IP effect on louse counts along with the clear biennial pattern emerging due to the production cycle of fish farms clearly indicate that fish farms play an important role in the epidemiology of sea lice on wild sea trout. Furthermore, the mediation analysis demonstrates that a large proportion of the effect of T on louse counts is mediated through IP. Electronic supplementary material The online version of this article (10.1186/s13071-018-3189-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Knut W Vollset
- Uni Research Environment, LFI - Freshwater Biology, Nygårdsporten 112, 5006, Bergen, Norway.
| | - Lars Qviller
- Norwegian Veterinary Institute, P.O. Box 750, Sentrum, N-0106, Oslo, Norway
| | - Bjørnar Skår
- Uni Research Environment, LFI - Freshwater Biology, Nygårdsporten 112, 5006, Bergen, Norway
| | - Bjørn T Barlaup
- Uni Research Environment, LFI - Freshwater Biology, Nygårdsporten 112, 5006, Bergen, Norway
| | - Ian Dohoo
- Department of Health Management, University of PEI, Charlottetown, PEI C1A 4P3, Canada
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11
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Guarracino M, Qviller L, Lillehaug A. Evaluation of aquaculture management zones as a control measure for salmon lice in Norway. DISEASES OF AQUATIC ORGANISMS 2018; 130:1-9. [PMID: 30154267 DOI: 10.3354/dao03254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We evaluated the use of coordinated fallowing as a means to control salmon lice Lepeophtheirus salmonis infestation in farmed Atlantic salmon Salmo salar. In discrete management zones, aquaculture operations such as stocking, fallowing, treatments and harvesting are synchronized at all sites in coordinated areas within the zones. The expected benefit of synchronized generations is to reduce the presence of salmon lice larvae after a period of fallowing, as well as to minimize external infestation pressure from surrounding aquaculture sites. A regression analysis was used to evaluate the effectiveness of coordinated fallowing on the progression of external salmon lice infestation pressure and abundance in Atlantic salmon farming sites in 2 areas (zones) in Norway. The overall results show that external infestation pressure was higher inside than outside the management zones, and the external infestation pressure increased with increasing biomass throughout the production cycle. However, within the zones, the external infestation pressure at the beginning of a production cycle was high and in many cases even higher than the general external infestation pressure in the non-coordinated areas. This suggests that external infestation pressure from the neighboring areas has a considerable effect on the fallowed area. Higher numbers of salmon lice were recorded within the zones than outside and, as the production cycle progressed, this phenomenon became more evident. We conclude that the high infestation pressure from salmon lice at the beginning of the grow-out period after fallowing raises severe doubts about the effectiveness of coordinated fallowing practices.
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Affiliation(s)
- Mario Guarracino
- Norwegian Veterinary Institute, PO Box 750 Sentrum, 0106 Oslo, Norway
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12
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Salama NKG, Dale AC, Ivanov VV, Cook PF, Pert CC, Collins CM, Rabe B. Using biological-physical modelling for informing sea lice dispersal in Loch Linnhe, Scotland. JOURNAL OF FISH DISEASES 2018; 41:901-919. [PMID: 28782801 DOI: 10.1111/jfd.12693] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 05/31/2017] [Accepted: 06/29/2017] [Indexed: 06/07/2023]
Abstract
Sea lice are a constraint on the sustainable growth of Scottish marine salmonid aquaculture. As part of an integrated pest management approach, farms coordinate procedures within spatial units. We present observations of copepodids being at relatively greater density than nauplii in upper waters, which informs the development of surface layer sea lice transmission modelling of Loch Linnhe, Scotland, for informing farm parasite management. A hydrodynamic model is coupled with a biological particle-tracking model, with characteristics of plankton sea lice. Simulations are undertaken for May and October 2011-2013, forced by local wind data collected for those periods. Particles are continually released from positions representing farm locations, weighted by relative farm counts, over a 2-week period and tracked for a further 5 days. A comparison is made between modelled relative concentrations against physical and biological surveys to provide confidence in model outputs. Connectivity between farm locations is determined in order to propose potential coordination areas. Generally, connectivity depends on flow patterns in the loch and decreases with increased farm separation. The connectivity indices are used to estimate the origins of the sea lice population composition at each site, which may influence medicinal regimens to avoid loss of efficacy.
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Affiliation(s)
- N K G Salama
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - A C Dale
- Scottish Marine Institute, The Scottish Association for Marine Science, Oban, UK
| | - V V Ivanov
- Arctic and Antarctic Research Institute, St. Petersburg, Russia
| | - P F Cook
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - C C Pert
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - C M Collins
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - B Rabe
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
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13
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Gislason H. Statistical modelling of sea lice count data from salmon farms in the Faroe Islands. JOURNAL OF FISH DISEASES 2018; 41:973-993. [PMID: 29148591 DOI: 10.1111/jfd.12742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 07/17/2017] [Accepted: 09/14/2017] [Indexed: 06/07/2023]
Abstract
Fiskaaling regularly counts the number of sea lice in the attached development stages (chalimus, mobiles and adult) for the salmon farms in the Faroe Islands. A statistical model of the data is developed. In the model, the sea-lice infection is represented by the chalimus (or mobile) lice developing into adult lice and is used to simulate past and current levels of adult lice-including treatments-as well as to predict the adult sea lice level 1-2 months into the future. Time series of the chalimus and adult lice show cross-correlations that shift in time and grow in size with temperature. This implies in situ the temperature-dependent development times of about 56 down to 42 days and the inverted development times (growth rates) of 0.018 up to 0.024 lice/day at 8-10°C. The temperature dependence DT=α1T+α2α3=17,840T+7.439-2.128is approximated byD1T=105.2-6.578T≈49 days at the mean temperature 8.5°C-similar to DchaT=100.6-6.507T≈45 days from EWOS data. The observed development times at four sites for a year (2010-11) were 49, 50, 51 and 52 days, respectively. Finally, we estimate the sea lice production from fish farms to discuss approaches to control the sea lice epidemics-preferably by natural means. This study is useful for understanding sea lice levels and treatments, and for in situ analysis of the sea-lice development times and growth rates.
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Affiliation(s)
- H Gislason
- Faculty of Science and Technology, University of the Faroe Islands, Nóatún 3, FO-100 Tórshavn, Faroe Islands & Fiskaaling - Aquaculture Research Station of the Faroes, Við Áir 11, FO-430, Hvalvík, Faroe Islands
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14
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Using state-space models to predict the abundance of juvenile and adult sea lice on Atlantic salmon. Epidemics 2018; 24:76-87. [PMID: 29685498 DOI: 10.1016/j.epidem.2018.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 04/01/2018] [Accepted: 04/09/2018] [Indexed: 11/20/2022] Open
Abstract
Sea lice are marine parasites affecting salmon farms, and are considered one of the most costly pests of the salmon aquaculture industry. Infestations of sea lice on farms significantly increase opportunities for the parasite to spread in the surrounding ecosystem, making control of this pest a challenging issue for salmon producers. The complexity of controlling sea lice on salmon farms requires frequent monitoring of the abundance of different sea lice stages over time. Industry-based data sets of counts of lice are amenable to multivariate time-series data analyses. In this study, two sets of multivariate autoregressive state-space models were applied to Chilean sea lice data from six Atlantic salmon production cycles on five isolated farms (at least 20 km seaway distance away from other known active farms), to evaluate the utility of these models for predicting sea lice abundance over time on farms. The models were constructed with different parameter configurations, and the analysis demonstrated large heterogeneity between production cycles for the autoregressive parameter, the effects of chemotherapeutant bath treatments, and the process-error variance. A model allowing for different parameters across production cycles had the best fit and the smallest overall prediction errors. However, pooling information across cycles for the drift and observation error parameters did not substantially affect model performance, thus reducing the number of necessary parameters in the model. Bath treatments had strong but variable effects for reducing sea lice burdens, and these effects were stronger for adult lice than juvenile lice. Our multivariate state-space models were able to handle different sea lice stages and provide predictions for sea lice abundance with reasonable accuracy up to five weeks out.
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15
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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] [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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16
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The Phe362Tyr mutation conveying resistance to organophosphates occurs in high frequencies in salmon lice collected from wild salmon and trout. Sci Rep 2017; 7:14258. [PMID: 29079820 PMCID: PMC5660183 DOI: 10.1038/s41598-017-14681-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 10/13/2017] [Indexed: 12/02/2022] Open
Abstract
The parasitic salmon louse, and its resistance to chemical delousing agents, represents one of the largest challenges to the salmon aquaculture industry. We genotyped lice sampled from wild salmon and sea trout throughout Norway with the recently identified Phe362Tyr mutation that conveys resistance to organophosphates. These results were compared to data from lice sampled on farmed salmon in the same regions. The resistant (R) allele was observed in salmon lice from wild salmon and sea trout throughout Norway, although its frequency was highest in farming-intense regions. In most regions, the frequency of the R allele was higher in lice collected from wild sea trout than wild Atlantic salmon, and in all regions, the frequency of the R allele was similar in lice collected from wild sea trout and farmed Atlantic salmon. The R allele is only selected for in fish-farms where organophosphates are used for delousing. Therefore, our results suggest extensive exchange of lice between farmed and wild hosts, and indicate that in farming-dense regions in Norway, aquaculture represents a major driver of salmon louse population structure. Finally, these data suggest that the wild hosts within the regions studied will not delay the spread of resistance when organophosphates are used.
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17
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Aldrin M, Huseby R, Stien A, Grøntvedt R, Viljugrein H, Jansen P. A stage-structured Bayesian hierarchical model for salmon lice populations at individual salmon farms – Estimated from multiple farm data sets. Ecol Modell 2017. [DOI: 10.1016/j.ecolmodel.2017.05.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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18
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Groner ML, Rogers LA, Bateman AW, Connors BM, Frazer LN, Godwin SC, Krkošek M, Lewis MA, Peacock SJ, Rees EE, Revie CW, Schlägel UE. Lessons from sea louse and salmon epidemiology. Philos Trans R Soc Lond B Biol Sci 2016; 371:rstb.2015.0203. [PMID: 26880836 DOI: 10.1098/rstb.2015.0203] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Effective disease management can benefit from mathematical models that identify drivers of epidemiological change and guide decision-making. This is well illustrated in the host-parasite system of sea lice and salmon, which has been modelled extensively due to the economic costs associated with sea louse infections on salmon farms and the conservation concerns associated with sea louse infections on wild salmon. Consequently, a rich modelling literature devoted to sea louse and salmon epidemiology has been developed. We provide a synthesis of the mathematical and statistical models that have been used to study the epidemiology of sea lice and salmon. These studies span both conceptual and tactical models to quantify the effects of infections on host populations and communities, describe and predict patterns of transmission and dispersal, and guide evidence-based management of wild and farmed salmon. As aquaculture production continues to increase, advances made in modelling sea louse and salmon epidemiology should inform the sustainable management of marine resources.
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Affiliation(s)
- Maya L Groner
- Department of Health Management, Centre for Veterinary and Epidemiological Research, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, Canada C1A 4P3
| | - Luke A Rogers
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
| | - Andrew W Bateman
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0
| | - Brendan M Connors
- Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0 ESSA Technologies Ltd, Vancouver, British Columbia, Canada V6H 3H4 School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - L Neil Frazer
- Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0 Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
| | - Sean C Godwin
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
| | - Martin Krkošek
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2 Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0
| | - Mark A Lewis
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9 Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1
| | - Stephanie J Peacock
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9
| | - Erin E Rees
- Department of Health Management, Centre for Veterinary and Epidemiological Research, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, Canada C1A 4P3
| | - Crawford W Revie
- Department of Health Management, Centre for Veterinary and Epidemiological Research, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown, Prince Edward Island, Canada C1A 4P3
| | - Ulrike E Schlägel
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1
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19
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Evaluating the effect of synchronized sea lice treatments in Chile. Prev Vet Med 2016; 136:1-10. [PMID: 28010902 DOI: 10.1016/j.prevetmed.2016.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 11/14/2016] [Accepted: 11/21/2016] [Indexed: 11/23/2022]
Abstract
The sea louse is considered an important ectoparasite that affects farmed salmonids around the world. Sea lice control relies heavily on pharmacological treatments in several salmon-producing countries, including Chile. Among options for drug administration, immersion treatments represent the majority of antiparasitic control strategies used in Chile. As a topical procedure, immersion treatments do not induce a long lasting effect; therefore, re-infestation from neighbouring farms may undermine their efficacy. Synchronization of treatments has been proposed as a strategy to improve immersion treatment performance, but it has not been evaluated so far. Using a repeated-measures linear mixed-effect model, we evaluated the impact of treatment synchronization of neighbouring farms (within 10km seaway distance) on the adult lice mean abundance from weeks 2 to 8 post-treatment on rainbow trout and Atlantic salmon farms in Chile, while controlling for external and internal sources of lice before the treatments, and also for environmental and fish-related variables. Results indicate that treatment synchronization was significantly associated with lower adult lice levels from weeks 5 to 7 after treatment. This relationship appeared to be linear, suggesting that higher levels of synchronization may result in lower adult sea lice levels during these weeks. These findings suggest that synchronization can improve the performance of immersion delousing treatments by keeping sea lice levels low for a longer period of time. Our results may be applicable to other regions of the world where immersion treatments are widely used.
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20
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21
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Rittenhouse MA, Revie CW, Hurford A. A model for sea lice (Lepeophtheirus salmonis) dynamics in a seasonally changing environment. Epidemics 2016; 16:8-16. [DOI: 10.1016/j.epidem.2016.03.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 03/22/2016] [Accepted: 03/25/2016] [Indexed: 11/28/2022] Open
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22
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Salama NKG, Murray AG, Rabe B. Simulated environmental transport distances of Lepeophtheirus salmonis in Loch Linnhe, Scotland, for informing aquaculture area management structures. JOURNAL OF FISH DISEASES 2016; 39:419-428. [PMID: 25929159 DOI: 10.1111/jfd.12375] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Revised: 02/11/2015] [Accepted: 03/01/2015] [Indexed: 06/04/2023]
Abstract
In the majority of salmon farming countries, production occurs in zones where practices are coordinated to manage disease agents such as Lepeophtheirus salmonis. To inform the structure of zones in specific systems, models have been developed accounting for parasite biology and system hydrodynamics. These models provide individual system farm relationships, and as such, it may be beneficial to produce more generalized principles for informing structures. Here, we use six different forcing scenarios to provide simulations from a previously described model of the Loch Linnhe system, Scotland, to assess the maximum dispersal distance of lice particles released from 12 sites transported over 19 day. Results indicate that the median distance travelled is 6.1 km from release site with <2.5% transported beyond 15 km, which occurs from particles originating from half of the release sites, with an absolute simulated distance of 36 km observed. This provides information suggesting that the disease management areas developed for infectious salmon anaemia control may also have properties appropriate for salmon lice management in Scottish coastal waters. Additionally, general numerical descriptors of the simulated relative lice abundance reduction with increased distance from release location are proposed.
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Affiliation(s)
- N K G Salama
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - A G Murray
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
| | - B Rabe
- Marine Scotland Science, Marine Laboratory, Aberdeen, UK
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23
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Peacock SJ, Bateman AW, Krkošek M, Lewis MA. The dynamics of coupled populations subject to control. THEOR ECOL-NETH 2016. [DOI: 10.1007/s12080-016-0295-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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24
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Kristoffersen AB, Jimenez D, Viljugrein H, Grøntvedt R, Stien A, Jansen PA. Large scale modelling of salmon lice (Lepeophtheirus salmonis) infection pressure based on lice monitoring data from Norwegian salmonid farms. Epidemics 2014; 9:31-9. [PMID: 25480132 DOI: 10.1016/j.epidem.2014.09.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 09/19/2014] [Accepted: 09/21/2014] [Indexed: 11/29/2022] Open
Abstract
Infection by parasitic sea lice is a substantial problem in industrial scale salmon farming. To control the problem, Norwegian salmonid farms are not permitted to exceed a threshold level of infection on their fish, and farms are required to monitor and report lice levels on a weekly basis to ensure compliance with the regulation. In the present study, we combine the monitoring data with a deterministic model for salmon lice population dynamics to estimate farm production of infectious lice stages. Furthermore, we use an empirical estimate of the relative risk of salmon lice transmission between farms, that depend on inter-farm distances, to estimate the external infection pressure at a farm site, i.e. the infection pressure from infective salmon lice of neighbouring farm origin. Finally, we test whether our estimates of infection pressure from neighbouring farms as well as internal within farm infection pressure, predicts subsequent development of infection in cohorts of farmed salmonids in their initial phase of marine production. We find that estimated external infection pressure is a main predictor of salmon lice population dynamics in newly stocked cohorts of salmonids. Our results emphasize the importance of keeping the production of infectious lice stages at low levels within local networks of salmon farms. Our model can easily be implemented for real time estimation of infection pressure at the national scale, utilizing the masses of data generated through the compulsory lice monitoring in salmon farms. The implementation of such a system should give the salmon industry greater predictability with respect to salmon lice infection levels, and aid the decision making process when the development of new farm sites are planned.
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Affiliation(s)
- Anja B Kristoffersen
- Norwegian Veterinary Institute, PO Box 750, Sentrum, N-0106 Oslo, Norway; Department of Informatics, University of Oslo, PO Box 1080, Blindern, N-0316 Oslo, Norway
| | - Daniel Jimenez
- Norwegian Veterinary Institute, PO Box 750, Sentrum, N-0106 Oslo, Norway
| | - Hildegunn Viljugrein
- Norwegian Veterinary Institute, PO Box 750, Sentrum, N-0106 Oslo, Norway; Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066, Blindern, N-0316 Oslo, Norway
| | - Randi Grøntvedt
- Norwegian Veterinary Institute, PO Box 750, Sentrum, N-0106 Oslo, Norway
| | - Audun Stien
- Norwegian Institute for Nature Research, Fram - High North Research Centre for Climate and the Environment, NO-9295 Tromsø, Norway
| | - Peder A Jansen
- Norwegian Veterinary Institute, PO Box 750, Sentrum, N-0106 Oslo, Norway.
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25
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Murray AG. A game theory based framework for assessing incentives for local area collaboration with an application to Scottish salmon farming. Prev Vet Med 2014; 115:255-62. [DOI: 10.1016/j.prevetmed.2014.03.023] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 03/20/2014] [Accepted: 03/22/2014] [Indexed: 11/27/2022]
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