Senior Research Scientist
Solveig Engebretsen
- Department Statistical modelling and machine learning
- Phone number +47 22 85 26 49
- E-mail solveige@nr.stage.dekodes.no
Publications
- 133 publications found
Løland, Anders; Engebretsen, Solveig og Rognebakke, Hanne. (2026).
Method for estimation of DRS and total collection rate by unit – 2026 update.
NVA
Rapport
Løland, Anders; Engebretsen, Solveig og Rognebakke, Hanne. (2026).
Estimation of DRS collection rate by unit and total collection rate by unit for 2025.
NVA
Rapport
Løland, Anders; Engebretsen, Solveig og Rognebakke, Hanne. (2026).
Beregning av pantegrad og innsamlingsgrad for 2025.
NVA
Rapport
Jemterud, Torkild; Engebretsen, Solveig; Kvellestad, Anders og Swang, Ole. (2026).
Hvem av oss har seg med flest?
Aasen, Nora Røhnebæk; Engebretsen, Solveig; Aldrin, Magne Tommy og Jansen, Peder A. (2026).
Estimating the effect of wrasses (Labridae) and lumpfish (Cyclopterus lumpus) as control measures against salmon lice in Norwegian fish farms.
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Cleaner fish are commonly used as a biological control measure against salmon lice infestations in salmonid farming. However, there have been few attempts at quantifying the effect of cleaner fish on the louse abundance at commercial farms. Our study estimates a delousing effect for wrasses (Labridae) and lumpfish (Cyclopterus lumpus) by fitting a partially stage-structured lice development model to historical production data on all salmonid farms in Norway. We investigate different models, and evaluate them according to a statistical model selection criterion (BIC). The final model includes temperature dependence for the delousing effect of cleaner fish, as a quadratic function. The estimated optimal temperature for lice grazing was found to be 6.7 °C for lumpfish and 15.3 °C for wrasses. The final model also included separate delousing effects for adult female and other motile salmon lice. In general, the estimated delousing effect was larger for wrasses than for lumpfish. However, for temperatures below 8.3 °C, the estimated delousing effect of other motile lice was larger when using lumpfish compared to wrasses. The estimated delousing effect was larger for lower abundances of salmon lice. This implies that cleaner fish should be used at low louse abundances, and not as a delousing method during outbreaks. Our study is an important contribution to quantifying the temperature-dependent delousing effect of cleaner fish, which can be used to guide the farmers in their decision-making when planning cleaner fish strategies.
Stige, Leif Christian; Aldrin, Magne Tommy; Engebretsen, Solveig; Rafoss, Trond og Jansen, Peder A. (2026).
The efficacy of lumpfish in controlling salmon lice in fish farms.
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Lumpfish (Cyclopterus lumpus) are frequently used as “cleaner fish” to control parasitic sea lice in salmonid fish farms, but it has been questioned whether the benefits in terms of sea louse control outweigh the economic and lumpfish-welfare costs involved. Here we estimated the efficacy of lumpfish in controlling salmon lice (Lepeophtheirus salmonis) in salmonid farms by combining analyses of occurrence of salmon lice in stomach contents of lumpfish and experimental results on digestion time. We then conducted scenario simulations of salmon louse dynamics in salmonid fish farms, by combining the lumpfish feeding model with a lumpfish growth model and a salmon louse population model. Results showed that at a mean lumpfish weight of 50 g and typical conditions for other factors (9 °C, 2 kg salmonids, and 0.8 pre-adult and adult salmon lice per salmonid), the estimated feeding rate was 0.17 salmon lice per lumpfish per day (95 % confidence interval: 0.12–0.22). This rate increased with salmon louse concentration, temperature and salmonid weight and decreased with lumpfish weight. Scenario simulations of salmon louse dynamics under conditions representative for salmonid farms in Norway suggested that stocking lumpfish from the start of the production cycle with a 1:10 lumpfish per salmon ratio on average postponed the first salmon louse treatment by 43 days. The longest postponement was at intermediate external infestation pressure. Scenario simulations for a network of farms suggested that coordinated and strategic use of lumpfish after a spring treatment may succeed in supressing salmon louse outbreaks through spring and summer.
Engebretsen, Solveig; Aldrin, Magne Tommy og Berg, Florian. (2025).
Parametric estimation and comparison of age-reading error matrices across species, stocks, and calcified structures.
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Stock assessments are often based on age-structured data obtained by interpreting calcified structures. Due to readability and human error, the observed age may be wrong. We propose a parametric model for age-reading error matrices, which is more realistic and robust than the commonly used empirical matrices. The parameters have meaningful interpretations, allowing for direct comparison of age-reading properties. We compare different species (Atlantic mackerel ( Scomber scombrus) and herring ( Clupea harengus)), stocks (North Sea autumn-spawning vs. Norwegian spring-spawning herring), and calcified structures (otoliths vs. scales). Three out of four data sets had an asymmetry tendency towards reading higher ages than the true age. The estimated probability of reading the wrong age was lower for scales than for otoliths. The true age is often unknown and assumed to be the modal age. We assess the systematic bias due to this assumption. Finally, when including age-reading error in stock assessment, the dominating age classes were estimated to be larger and spawning stock biomass lower. Our study contributes with methods and insight for including age-reading error in stock assessment.
Jansen, Peder A; Engebretsen, Solveig; Ghinassi, Noemi; Giskegjerde, Siri; Rafoss, Trond og Aldrin, Magne Tommy. (2025).
Gastric evacuation of salmon lice in ballan wrasse, Labrus bergylta, with estimates of predation rates.
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Current debate on the sustainability of using cleaner fish to control parasitic lice in salmon farming suffers from extremely variable scientific evidence on the efficacy of this practice. This paper presents novel experimental results on evacuation rates of salmon lice through the digestive tract of ballan wrasse. These results are combined with quantitative field data on contents of salmon lice in ballan wrasse, to derive a method to study the efficacy of ballan wrasse in cleaning salmon of salmon lice. From a fitted binomial regression model on the probability of finding lice in the digestive tract after ingestion, we found a median evacuation time of 11.0 h. The mean evacuation time was 12.2 h. Furthermore, by integration, we found that if a wrasse on average consumes one louse per day, then the expected number of observable lice in the digestive tract is 0.472. This gave an estimated daily consumption of salmon lice per wrasse expressed as the number of salmon lice in the digestive tract divided by 0.472. As an example, analyses of lice contents in the digestive tract of 6406 ballan wrasse used as cleaner fish in salmon farming revealed that salmon lice were found in 2.9% of the wrasses, with a mean number of 0.15 lice per fish. This translates to an estimate of 0.32 lice consumed per day per ballan wrasse. The present way of estimating the efficacy of wrasse as cleaner fish may contribute to a more robust evaluation of louse control effects of ballan wrasse.
Helgesen, Kari Marie Olli; Jansen, Peder A; Urke, Henning Andre; Aldrin, Magne Tommy og Engebretsen, Solveig. (2025).
Lakselus påvirker antall og alder på villaks som gyter.
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En ny studie viser at mye lus på utvandrende laksesmolt har en klar sammenheng med at færre gytefisk vender tilbake etter ett år. Forskere ved AquaLife R&D, Norsk Regnesentral og Veterinærinstituttet har utviklet en statistisk modell for å undersøke sammenhengen. Vi tallfestet i vår modell i hvilken grad lusebelastningen fisken opplevde på sin smoltvandring har påvirket antall og alder på gytefisk i norske elver. Det vi fant var at mye lus på utvandrende laksesmolt har en klar sammenheng med at færre gytefisk vender tilbake etter ett år i sjø. På fisk som hadde vært to år i sjø var den samme effekten ikke til stede. På fiskene som hadde vært tre år i sjø fant vi motsatt effekt; det var en klar sammenheng mellom høy lusebelastning på utvandrende smolt og økt antall fisk som returnerte som gytefisk, men denne økninga var langt mindre enn den tilhørende nedgangen i antall fisk som hadde vært ett år i sjø. Dette vises i figuren under. Én mulig årsak til denne forskjellen i effekt mellom årsklassene er at lusepåkjenning kan forsinke vekst og kjønnsmodning.
Jansen, Peder A; Urke, Henning André; Engebretsen, Solveig; Aldrin, Magne Tommy og Helgesen, Kari Marie Olli. (2025).
Effects of salmon lice on numbers and size distributions of Atlantic salmon returning to spawn in Norwegian rivers.
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Abstract Negative effects of salmon lice from salmon farms on wild salmonids have been a controversial issue for decades and concerns are expressed from virtually all areas where salmon farming coexists with important fisheries for wild salmonids. A key question is to what extent lice infestation from farms reduce numbers of wild mature salmon returning to spawn in the rivers. Here, we study counts and recreational catches of small (<3 kg), medium‐sized (3–7 kg) and large mature salmon (>7 kg) returning to spawn in Norwegian rivers, in association with lice burdens on out‐migrating post‐smolt recruits. The expected number of returning mature salmon was modelled as a function of theoretical smolt production in the rivers, river catches one generation back in time, size‐classes of returning salmon, year as a factor, a non‐linear spatial effect and parasite‐induced mortality (PIM) of out‐migrating post smolts of salmon. PIM was attributed to small, medium‐sized and large salmon assuming they spend one, two or three winters at sea (SW), respectively. There was a significant negative effect of PIM on returns of one SW salmon and a negative but non‐significant effect on returns of two SW salmon. For three SW salmon, the effect of PIM was significantly positive, but for comparably low numbers, implying an overall negative effect of PIM on returning salmon. The size‐specific effects of PIM were manifested by decreasing proportions of one SW salmon in returning populations with increasing PIM, from ~0.6 for rivers exposed to low levels of PIM, to predictions of <0.2 for rivers exposed to high levels of PIM. Synthesis and applications . This study presents a quantitative relationship between infestations of post‐smolt recruits and size‐structured returns of mature salmon to Norwegian rivers, suggesting that louse infestation from farms may reduce returns of spawners and re‐structure the size distribution of mature river populations of Atlantic salmon. The presented relationship opens for a more targeted approach to obtaining sustainable salmon farming. To accommodate the Norwegian Government's goal for sustainable aquaculture, reductions in lice abundances in farms are necessary.
Engebretsen, Solveig; Aldrin, Magne Tommy; Ghinassi, Noemi; Giskegjerde, Siri; Rafoss, Trond og Jansen, Peder A. (2025).
Temperature effect of evacuation time of salmon lice in ballan wrasse.
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The present study is an extension of a study on the evacuation time of salmon lice (Lepeophtheirus salmonis) in ballan wrasse (Labrus Berggylta). In the already existing study, the evacuation time of salmon lice in ballan wrasse was studied through an experiment conducted at 10-11 °C. We here supplement their analysis with additional experiments conducted at 6.5 °C and 15 °C. Quantifying the evacuation time of salmon lice in cleaner fish is important in order to assess cleaning efficacy from gastric lice count data, which are routinely collected by salmon farmers. We fit a binomial logistic regression model for the probability of finding lice in the digestive tract over time after ingestion based on data from experiments at all three temperatures. The estimated median evacuation time was 12.0 hours (95% confidence interval (10.8, 13.1), and the estimated mean evacuation time was 12.6 hours. By integrating the estimated probability, we derive that dividing the average number of salmon lice per wrasse in their digestive tracts by 0.504 gives an estimate of the average number of salmon lice consumed per wrasse per day. Assuming 0.39 salmon lice per digestive tract of ballan wrasse, as was found in the previous study, we hence estimate 0.77 salmon lice consumed per ballan wrasse per day. Comparing with the previous study which is based only on the experimental data at 10-11 °C, our estimate is similar but lower, as they found 0.83 salmon lice consumed per ballan wrasse per day.
Engebretsen, Solveig; Aldrin, Magne Tommy; Jansen, Peder A; Aksnes, Vegard og Santi, Nina. (2025).
Scenariosimulering av skjermingstiltak, lokalitetsstruktur, tiltaksgrenser og utsettsmønster i PO6.
NVA
Rapport
Bjorå, Charlotte Sletten; Raklev, Are; Engebretsen, Solveig og Jemterud, Torkild. (2025).
Abels tårn.
NVA
Programdeltagelse
Løland, Anders; Engebretsen, Solveig og Aasen, Nora Røhnebæk. (2025).
Beregning av pantegrad og innsamlingsgrad for 2024.
NVA
Rapport
Engebretsen, Solveig; Aldrin, Magne Tommy; Klakegg, Barbo; Grøntvedt, Randi Nygaard; Jensen, Stig Rune; Nøst, Ole Anders og Selnæs, John. (2025).
Pilotprosjekt PO6: Scenariosimulering av lakselus i Midt-Norge.
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I dette notatet vurderer vi ulike tiltak mot lakselus i produksjonsområde 6 ved hjelp av scenariosimulering fra en lusemodell. Vi tilpasser lusemodellen til historiske data fra BarentsWatch. I modellen inngår smitte mellom lokaliteter, og her modelleres denne både som funksjon av sjøavstand og vannkontakt basert på en hydrodynamisk modell for havstrømmer. Vi definerer et basisscenario basert på historiske produksjonsdata for lokalitetsstruktur, tiltaksgrenser og utsettsmønster, og simulerer lus over tid. Vi simulerer deretter luseutvikling for ulike alternative scenarioer og sammenlikner med basisscenarioet. Vi undersøker effekten av innføring av stortsmoltsone, bruk av dypdrift, endret utsettsmønster, endret tiltaksgrense og endring av lokalitetsstruktur/lukking av anlegg på gitte lokaliteter eller i underområder i produksjonsområdet.
Engebretsen, Solveig. (2025).
Plassering av laks og rognkjeks over døgnet. Tekna
NVA
Vitenskapelig foredrag
Engebretsen, Solveig og Klakegg, Barbo. (2025).
Digitalisering gir bedre beslutningsstøtte for områdesamarbeid. Fiskeri- og havbruksnæringens forskningsfinansiering (FHF).
NVA
Vitenskapelig foredrag
Engebretsen, Solveig og Aldrin, Magne Tommy. (2025).
Scenariosimulering av lakselus i Midt- Norge. DigiSjømat
NVA
Vitenskapelig foredrag
Løland, Anders; Engebretsen, Solveig og Aasen, Nora Røhnebæk. (2025).
Method for estimation of DRS and total collection rate by unit – 2025 update.
NVA
Rapport
Løland, Anders; Engebretsen, Solveig og Aasen, Nora Røhnebæk. (2025).
Estimation of DRS collection rate by unit and total collection rate by unit for 2024.
NVA
Rapport
Storvik, Geir Olve; Engebretsen, Solveig; Blasio, Birgitte Freiesleben De og Frigessi, Arnoldo. (2025).
Flaws in the Article “Nearly Instantaneous Time-Varying Reproduction Number for Contagious Diseases—a Direct Approach Based on Nonlinear Regression".
Engebretsen, Solveig; Thorarinsdottir, Thordis Linda; Palomares, Alfonso Diz-Lois; Storvik, Geir Olve; Frigessi, Arnoldo og Blasio, Birgitte Freiesleben De. (2025).
Contribution to the Discussion of 'Some statistical aspects of the Covid-19 response' by Wood et al.
Engebretsen, Solveig; Aldrin, Magne Tommy; Iversen, Nina Skorstad; Staven, Andreas R. og Staven, Fredrik. (2025).
Towards a better understanding of the evacuation time of salmon lice (Lepeophtheirus salmonis) in lumpfish (Cyclopterus lumpus).
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Cleaner fish are utilised as a preventive control measure against sea lice infestations in salmon farms. In recent years, lumpfish (Cyclopterus lumpus) has been the most commonly deployed cleaner fish species in Norway. However, there have been few studies aiming to quantify the cleaning effect of lumpfish. There are many studies which document the number of sea lice in lumpfish stomach contents. These numbers cannot be used to infer the cleaning efficacy of lumpfish without also knowing the evacuation time of sea lice in lumpfish. In this study, we aimed to replicate an experiment of the evacuation time for salmon lice (Lepeophtheirus salmonis) in lumpfish. We found a median evacuation time of 50 h, and a mean evacuation time of 65 h. Combining with the data from the previous experiment, we found a median evacuation time of 31 h, and a mean evacuation time of 49 h. Interestingly, we found significantly slower digestion for adult female salmon lice than for other motile salmon lice. This implies that if lumpfish consumed the same (absolute) number of lice in different stages of lice, then one would expect more adult female lice in the stomach contents, as these require a longer time to be fully evacuated. This study is an important contribution to further understand the digestion time of salmon lice in lumpfish, which ultimately can be combined with an estimated number of salmon lice in the stomach contents of lumpfish to estimate a cleaning effect.
Engebretsen, Solveig. (2025).
Parametric estimation and comparison of age-reading error matrices for fish stock assessments. The Nordic-Baltic Region of the International Biometric Society
NVA
Vitenskapelig foredrag
Engebretsen, Solveig; Aldrin, Magne Tommy; Jansen, Peder Andreas; Kristensen, Torstein; Bendiksen, Eskil og Urke, Henning Andre. (2025).
Rognkjeks i storskala merder: To eksperimenter med 0 og 10 % innblanding.
NVA
Populærvitenskapelig artikkel
Engebretsen, Solveig. (2024).
The effect of testing criteria for infectious disease surveillance: the case of COVID-19 in Norway. Statens Serums Institut
NVA
Faglig foredrag
Aasen, Nora Røhnebæk; Engebretsen, Solveig og Løland, Anders. (2024).
Beregning av bundet og forbrukt plast i et ombrukssystem og et resirkuleringssystem for PET-flasker.
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I denne rapporten estimerer vi mengden bundet og forbrukt plast i resirkuleringssystemet (dagens system) og et ombrukssystem for PET-flasker som drikkevareemballasje. Vi beregner og sammenligner forbrukt og bundet plast for PET-flaskene både isolert sett og når vi tar hensyn til lastbærere som plastkasser, -brett og -sekker som brukes til frakt og lagring av flaskene. Bundet plast er beregnet utfra antall flasker (med tilhørende lastbærere) som til enhver tid må innes for å holde det sirkulære systemet gående. Her finner vi at antall flasker som bindes opp er større i ombrukssystemet, hvilket skyldes en større følsomhet for sesongvariasjon og logistikkubalanse. Ettersom flaskene også veier mer i ombrukssystemet, blir effekten ytterligere forsterket når vi ser på mengden plast istedenfor antall flasker. Vi estimerer mer enn dobbelt så mye plast i ombrukssystemet som i resirkuleringssystemet. Hvis vi også tar hensyn til lastbærere i form av plastkasser, -brett og -sekker, blir forskjellen mellom systemene i bundet plast enda større. Forbruk av plast er her definert som mengden jomfruelig plast som må tilføres systemet for å dekke tapet av plast. Her finner vi at forbruket er større i ombrukssystemet enn i resirkuleringssystemet for små PET-flasker, og mindre for store PET-flasker. Dette skyldes blant annet at pantegraden er høyere for store PET-flasker enn for små PET-flasker. Totalt har ombrukssystemet størst plastforbruk når vi inkluderer forbruket fra plastkasser, -brett og -sekker. Plastforbruket fra PET-flasker i ombrukssystemet går ned ved høyere pantegrad. I resirkuleringssystemet får man en begrensende faktor i form av andel resirkulert plast som kan benyttes i nye flasker. Dette fører til at vi ved høy pantegrad ikke ser en nedgang i plastforbruket fra PET-flasker til tross for videre økning i pantegraden.
Engebretsen, Solveig. (2024).
Effekt av rensefisk basert på mageprøvedata. Fiskeri- og havbruksnæringens forskningsfinansiering (FHF) og Forskningsrådet.
NVA
Faglig foredrag
Engebretsen, Solveig; Sveinsson, Henrik Andersen; Dietrichs, Erik Sveberg og Jemterud, Torkild. (2024).
Abels tårn: Når kan vi overleve drukning?
NVA
Programdeltagelse
Engebretsen, Solveig. (2024).
Situational awareness and forecasting during the COVID-19 pandemic in Norway. Royal Statistical Society
NVA
Vitenskapelig foredrag
Chan, Yat Hin; Rø, Gunnar; Midtbø, Jørgen E.; Ruscio, Francesco Di; Watle, Sara Sofie Viksmoen; Juvet, Lene Kristine; Littmann, Jasper; Aavitsland, Preben; Nygård, Karin Maria; Berg, Are Stuwitz; Bukholm, Geir; Kristoffersen, Anja Bråthen; Engø-Monsen, Kenth; Engebretsen, Solveig; Swanson, David Michael; Palomares, Alfonso Diz-Lois; Lindstrøm, Jonas Christoffer; Frigessi, Arnoldo og Blasio, Birgitte Freiesleben De. (2024).
Modeling geographic vaccination strategies for COVID-19 in Norway.
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Vaccination was a key intervention in controlling the COVID-19 pandemic globally. In early 2021, Norway faced significant regional variations in COVID-19 incidence and prevalence, with large differences in population density, necessitating efficient vaccine allocation to reduce infections and severe outcomes. This study explored alternative vaccination strategies to minimize health outcomes (infections, hospitalizations, ICU admissions, deaths) by varying regions prioritized, extra doses prioritized, and implementation start time. Using two models (individual-based and meta-population), we simulated COVID-19 transmission during the primary vaccination period in Norway, covering the first 7 months of 2021. We investigated alternative strategies to allocate more vaccine doses to regions with a higher force of infection. We also examined the robustness of our results and highlighted potential structural differences between the two models. Our findings suggest that early vaccine prioritization could reduce COVID-19 related health outcomes by 8% to 20% compared to a baseline strategy without geographic prioritization. For minimizing infections, hospitalizations, or ICU admissions, the best strategy was to initially allocate all available vaccine doses to fewer high-risk municipalities, comprising approximately one-fourth of the population. For minimizing deaths, a moderate level of geographic prioritization, with approximately one-third of the population receiving doubled doses, gave the best outcomes by balancing the trade-off between vaccinating younger people in high-risk areas and older people in low-risk areas. The actual strategy implemented in Norway was a two-step moderate level aimed at maintaining the balance and ensuring ethical considerations and public trust. However, it did not offer significant advantages over the baseline strategy without geographic prioritization. Earlier implementation of geographic prioritization could have more effectively addressed the main wave of infections, substantially reducing the national burden of the pandemic.
Engebretsen, Solveig og Aldrin, Magne Tommy. (2024).
Effect of testing criteria for infectious disease surveillance: The case of COVID-19 in Norway.
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During the COVID-19 pandemic in Norway, the testing criteria and capacity changed numerous times. In this study, we aim to assess consequences of changes in testing criteria for infectious disease surveillance. We plotted the proportion of positive PCR tests and the total number of PCR tests for different periods of the pandemic in Norway. We fitted regression models for the total number of PCR tests and the probability of positive PCR tests, with time and weekday as explanatory variables. The regression analysis focuses on the time period until 2021, i.e. before Norway started vaccination. There were clear changes in testing criteria and capacity over time. In particular, there was a marked difference in the testing regime before and after the introduction of self-testing, with a drastic increase in the proportion of positive PCR tests after the introduction of self-tests. The probability of a PCR test being positive was higher for weekends and public holidays than for Mondays-Fridays. The probability for a positive PCR test was lowest on Mondays. This implies that there were different testing criteria and/or different test-seeking behaviour on different weekdays. Though the probability of testing positive clearly changed over time, we cannot in general conclude that this occurred as a direct consequence of changes in testing policies. It is natural for the testing criteria to change during a pandemic. Though smaller changes in testing criteria do not seem to have large, abrupt consequences for the disease surveillance, larger changes like the introduction and massive use of self-tests makes the test data less useful for surveillance.
Engebretsen, Solveig; Aldrin, Magne Tommy; Staven, Fredrik Ribsskog; Bendiksen, Eskil; Stige, Leif Christian og Jansen, Peder Andreas. (2024).
Heterogeneous Weight Development of Lumpfish (Cyclopterus lumpus) Used as Cleaner Fish in Atlantic Salmon (Salmo salar) Farming.
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Lumpfish (Cyclopterus lumpus) are used as cleaner fish in Atlantic salmon (Salmo salar) aquaculture as one of multiple control measures against salmon lice (Lepeophtheirus salmonis). Numerous studies have documented weight as an important factor for characterising the cleaning efficacy of individual lumpfish. Hence, the efficacy of lumpfish in fish farms depends on the size at stocking and the weight development over time. Here, we aimed to quantify how weight developed over time for lumpfish deployed in salmon farming sea cages in Norway through modelling the daily growth rate. We found that the coefficient of variation for lumpfish weight increased over time, implying that the standard deviation increased more than the expected weight. The data thus showed heterogeneous growth for lumpfish in salmon farming cages, where some individuals exhibited no apparent growth, and others significant proliferation. We found that the daily growth rate was best described as bell-shaped functions of weight and temperature, consistent with a sigmoid-shaped growth curve and an optimal temperature around 10 °C. These results allow for more realistic modelling of the efficacy of lumpfish in controlling salmon lice in fish farms, as one can combine estimates of weight-dependent cleaning efficacy with weight development over time.
Engebretsen, Solveig. (2024).
Effekt av rensefisk mot lakselus. Norsk statistisk forening
NVA
Vitenskapelig foredrag
Aasen, Nora Røhnebæk; Engebretsen, Solveig og Løland, Anders. (2024).
Calculating tied up and consumed plastic for a reuse system and a single-use system for PET bottles.
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In this report, we estimate the amount of tied up plastic and plastic consumption in the single-use system (the current system in Norway) and a reuse system for PET bottles as beverage packaging. We calculate and compare the consumed and tied up plastic for PET bottles both isolated and when accounting for Transport Items such as plastic crates, trays, and bags that are used in shipping and storing of the bottles. Tied up plastic is calculated from the number of bottles (and corresponding Transport Items) that at all times must exist in order to keep the circular material system operational. Here we find that the number of bottles that are tied up is greater in the reuse system than in the single-use system, which is due to a higher sensitivity to seasonal variation and logistical imbalance. As the bottles weigh more in the reuse system, the effect is further reinforced when we consider the amount of plastic instead of the number of bottles. We estimate more than twice as much tied up plastic in the reuse system as in the single-use system. If we also take into account Transport Items in the form of plastic crates, trays, and bags, the difference between the systems becomes even greater. Plastic consumption is here defined to be the amount of virgin plastic that must be put in to the system to cover the loss of plastic. Here we find that consumption is greater in the reuse system than in the single-use system for small PET bottles, and smaller for large PET bottles. This is partly due to the fact that the DRS collection rate by unit is higher for large PET bottles than for small PET bottles. In total the reuse system has the highest plastic consumption when we take into account the consumption of plastic crates, trays, and bags. Plastic consumption from PET bottles in the reuse system decreases as the DRS collection rate by unit increases. In the single-use system there is a limiting factor in terms of the proportion of recycled plastic that can be utilized in new bottles. Hence, after a certain threshold of high DRS collection rate by unit we do not see a decrease in plastic consumption from PET bottles despite further increase in the DRS collection rate by unit.
Løland, Anders og Engebretsen, Solveig. (2024).
Beregning av pantegrad og innsamlingsgrad for 2023.
NVA
Rapport
Løland, Anders og Engebretsen, Solveig. (2024).
Estimation of DRS collection rate by unit and total collection rate by unit for 2023.
NVA
Rapport
Vandeskog, Silius Mortensønn; Aldrin, Magne Tommy; Engebretsen, Solveig; Sunde, Leif Magne og Venås, Birger. (2024).
Sammenlikning av automatiske lusetellingssystemer under varierende miljøforhold.
NVA
Fagartikkel
Engebretsen, Solveig; Aldrin, Magne Tommy; Lunde, Liss; Austad, Marthe; Rafoss, Trond; Danielsen, Ole Roald; Lindhom, Andreas; Boissonnot, Lauris Jeannine Ernestine og Jansen, Peder Andreas. (2024).
Condition factor tailored to lumpfish (Cyclopterus lumpus) used as cleaner fish in salmonid farms.
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Lumpfish (Cyclopterus lumpus) are extensively used as part of the control measures against salmon lice in fish farms. In recent years, there has been an increased focus on lumpfish welfare, and how to increase survival of lumpfish during production. To survey lumpfish welfare and compare welfare between different fish farms, welfare indicators are necessary. Condition factor is an attractive welfare indicator since it depends only on the length and weight of the fish, which is easy to measure and does not require euthanisation. Fulton’s K is commonly used to assess body condition for fish. However, this condition factor assumes isometric growth, which has been found not to be a reasonable assumption for lumpfish. In this study, we suggest an alternative expression for lumpfish body condition, which is based on almost 30 000 lumpfish sampled from Norwegian fish farms during production. The resulting condition factor is given as 5.85 ⋅ W∕L2.5016, where W is the lumpfish weight measured in grams, and L is the standard length measured in centimetres. We demonstrate that our proposed condition factor is more suitable for comparing body condition of lumpfish than Fulton’s K, since Fulton’s K is negatively correlated to length such that small fish tend to have high Fulton’s K factors. We conclude that Fulton’s K is an inappropriate indicator of lumpfish welfare, and propose to rather use a condition factor tailored to lumpfish, like the presently proposed condition factor. We also illustrate why standard length (length up to the caudal fin) is more appropriate for measuring body condition than total length (i.e. length including the caudal fin). For condition based on standard length, we found that caudal fin erosion was less prevalent among the lumpfish with comparatively higher body condition. The same relationship was not found for body condition based on total length.
Engebretsen, Solveig; Görbitz, Carl Henrik; Ellingsen, Kristian og Jemterud, Torkild. (2024).
Abels tårn: Hva er de ti sterkeste dyrene?
NVA
Programdeltagelse
Jansen, Peder A; Lindhom, Andreas; Danielsen, Ole Roald; Rafoss, Trond; Engebretsen, Solveig; Aldrin, Magne Tommy og Stige, Leif Christian. (2024).
Rensefiskbetingelser: Betingelser som fremmer lusespising hos rensefisk
Faglig sluttrapport for FHF-prosjekt Rensefiskbetingelser (P.nr.: 901766).
Løland, Anders; Engebretsen, Solveig og Aasen, Nora Røhnebæk. (2024).
Method for estimation of DRS and total collection rate by unit.
NVA
Rapport
Hellton, Kristoffer Herland; Løland, Anders og Engebretsen, Solveig. (2023).
Alt du kan lære om statistisk modellering og maskinlæring på en dag. Norsk Regnesentral
NVA
Faglig foredrag
Engebretsen, Solveig. (2023).
Situasjonsforståelse og framskrivning av COVID-19 i Norge. ADA
NVA
Faglig foredrag
Jemterud, Torkild; Engebretsen, Solveig; Knudsen, Julie Paus og Kvellestad, Anders. (2023).
Abels tårn.
NVA
Programdeltagelse
Neef, Linda Reiersølmoen; Engebretsen, Solveig og Aas, Kjersti. (2023).
Modellering av sannsynlighet for uførhet.
NVA
Rapport
Løland, Anders og Engebretsen, Solveig. (2023).
Estimation of DRS collection rate by unit and total collection rate by unit for 2022.
NVA
Rapport
Løland, Anders og Engebretsen, Solveig. (2023).
Beregning av pantegrad og innsamlingsgrad for 2022.
NVA
Rapport
Engebretsen, Solveig; Jullum, Martin og Løland, Anders. (2023).
Introduksjon til sentrale metoder i statistisk modellering og maskinlæring. Forsvarets forskningsinstitutt
NVA
Faglig foredrag
Hellton, Kristoffer Herland; Løland, Anders og Engebretsen, Solveig. (2023).
Alt du kan lære om statistisk modellering og maskinlæring på en dag. Norsk Regnesentral
NVA
Faglig foredrag
Kamineni, Meghana; Engø-Monsen, Kenth; Midtbø, Jørgen E.; Forland, Frode; Blasio, Birgitte Freiesleben De; Frigessi, Arnoldo og Engebretsen, Solveig. (2023).
Effects of non-compulsory and mandatory COVID-19 interventions on travel distance and time away from home, Norway, 2021.
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Background
Given the societal, economic and health costs of COVID-19 non-pharmaceutical interventions (NPI), it is important to assess their effects. Human mobility serves as a surrogate measure for human contacts and compliance with NPI. In Nordic countries, NPI have mostly been advised and sometimes made mandatory. It is unclear if making NPI mandatory further reduced mobility.
Aim
We investigated the effect of non-compulsory and follow-up mandatory measures in major cities and rural regions on human mobility in Norway. We identified NPI categories that most affected mobility.
Methods
We used mobile phone mobility data from the largest Norwegian operator. We analysed non-compulsory and mandatory measures with before–after and synthetic difference-in-differences approaches. By regression, we investigated the impact of different NPI on mobility.
Results
Nationally and in less populated regions, time travelled, but not distance, decreased after follow-up mandatory measures. In urban areas, however, distance decreased after follow-up mandates, and the reduction exceeded the decrease after initial non-compulsory measures. Stricter metre rules, gyms reopening, and restaurants and shops reopening were significantly associated with changes in mobility.
Conclusion
Overall, distance travelled from home decreased after non-compulsory measures, and in urban areas, distance further decreased after follow-up mandates. Time travelled reduced more after mandates than after non-compulsory measures for all regions and interventions. Stricter distancing and reopening of gyms, restaurants and shops were associated with changes in mobility.
Storvik, Geir Olve; Palomares, Alfonso Diz-Lois; Engebretsen, Solveig; Rø, Gunnar Øyvind Isaksson; Engø-Monsen, Kenth; Kristoffersen, Anja Bråthen; Blasio, Birgitte Freiesleben De og Frigessi, Arnoldo. (2023).
A sequential Monte Carlo approach to estimate a time-varying reproduction number in infectious disease models: the Covid-19 case.
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Abstract The Covid-19 pandemic has required most countries to implement complex sequences of non-pharmaceutical interventions, with the aim of controlling the transmission of the virus in the population. To be able to take rapid decisions, a detailed understanding of the current situation is necessary. Estimates of time-varying, instantaneous reproduction numbers represent a way to quantify the viral transmission in real time. They are often defined through a mathematical compartmental model of the epidemic, like a stochastic SEIR model, whose parameters must be estimated from multiple time series of epidemiological data. Because of very high dimensional parameter spaces (partly due to the stochasticity in the spread models) and incomplete and delayed data, inference is very challenging. We propose a state-space formalization of the model and a sequential Monte Carlo approach which allow to estimate a daily-varying reproduction number for the Covid-19 epidemic in Norway with sufficient precision, on the basis of daily hospitalization and positive test incidences. The method was in regular use in Norway during the pandemics and appears to be a powerful instrument for epidemic monitoring and management.
Engebretsen, Solveig; Løland, Anders og Lison, Pierre. (2023).
Alt du kan lære om statistisk modellering og maskinlæring på en dag. Norsk Regnesentral
NVA
Faglig foredrag
Engebretsen, Solveig; Løland, Anders og Lison, Pierre. (2023).
Alt du kan lære om statistisk modellering og maskinlæring på en dag. Norsk Regnesentral
NVA
Faglig foredrag
Engebretsen, Solveig; Bøckman, Petter; Røyne, Anja og Jemterud, Torkild. (2023).
Abels tårn - Hvorfor faller ikke skyene ned.
NVA
Programdeltagelse
Staven, Fredrik; Engebretsen, Solveig; Aldrin, Magne; Iversen, Nina Skorstad; Staven, Andreas R.; Egeland, Torvald B.; Stensby-Skjærvik, Silje; Imsland, Albert K. D. og Boissonnot, Lauris Jeannine Ernestine. (2023).
The digestion time for salmon louse (Lepeophtheirus salmonis) in lumpfish (Cyclopterus lumpus).
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Atlantic salmon aquaculture employs lumpfish as a control method to combat ectoparasites, given their unique cleaning behaviour. There are multiple studies which estimate the average number of salmon lice in the stomach contents of dissected lumpfish. However, these numbers cannot be used to assess the cleaning efficacy of lumpfish (e.g., the average number of lice consumed daily per lumpfish) without knowing the digestion time of lice in lumpfish. The aim of the study was to provide quantitative estimates of the degradation of salmon lice, through a blinded clinical study over a duration of seven days. Individually tagged lumpfish (45.8 g, SD ± 10.28) were randomly arranged in triplicate tanks (n = 28 per tank) and acclimatised for three days. Subsequently, lumpfish were fed using oral gavage dosing with counts of lice (0–6), feed pellets (0–6) or a combination of both. Lice used were recently captured and stored at −80 °C to prevent parasite transmission at the study location and photographed before and after digestion to estimate degradation. Samplings ranged from 6 h intervals during the first two days, to 24 h and eventually 48 h for the last two days. Analysis of salmon lice revealed an expected digestion time of 29 h while the median digestion time was estimated to 15 h at 9 °C. Pellets dissolved quickly and had no impact on the lice digestion time. The findings of this study can be used to estimate cleaning efficacy of lumpfish from stomach contents of salmon lice.
Engebretsen, Solveig; Palomares, Alfonso Diz-Lois; Rø, Gunnar Øyvind Isaksson; Kristoffersen, Anja Bråthen; Lindstrøm, Jonas Christoffer; Engø-Monsen, Kenth; Kamineni, Meghana; Chan, Yat Hin; Dale, Ørjan; Midtbø, Jørgen E.; Stenerud, Kristian Lindalen; Ruscio, Francesco Di; White, Richard Aubrey; Frigessi, Arnoldo og Blasio, Birgitte Freiesleben De. (2023).
A real-time regional model for COVID-19: Probabilistic situational awareness and forecasting.
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The COVID-19 pandemic is challenging nations with devastating health and economic consequences. The spread of the disease has revealed major geographical heterogeneity because of regionally varying individual behaviour and mobility patterns, unequal meteorological conditions, diverse viral variants, and locally implemented non-pharmaceutical interventions and vaccination roll-out. To support national and regional authorities in surveilling and controlling the pandemic in real-time as it unfolds, we here develop a new regional mathematical and statistical model. The model, which has been in use in Norway during the first two years of the pandemic, is informed by real-time mobility estimates from mobile phone data and laboratory-confirmed case and hospitalisation incidence. To estimate regional and time-varying transmissibility, case detection probabilities, and missed imported cases, we developed a novel sequential Approximate Bayesian Computation method allowing inference in useful time, despite the high parametric dimension. We test our approach on Norway and find that three-week-ahead predictions are precise and well-calibrated, enabling policy-relevant situational awareness at a local scale. By comparing the reproduction numbers before and after lockdowns, we identify spatially heterogeneous patterns in their effect on the transmissibility, with a stronger effect in the most populated regions compared to the national reduction estimated to be 85% (95% CI 78%-89%). Our approach is the first regional changepoint stochastic metapopulation model capable of real time spatially refined surveillance and forecasting during emergencies.
Boissonnot, Lauris; Engebretsen, Solveig og Aldrin, Magne Tommy. (2022).
Kondisjonsfaktor hos rognkjeks.
NVA
Populærvitenskapelig artikkel
Engebretsen, Solveig. (2022).
Covid-19 situational awareness and forecasting modelling. University of Oslo
NVA
Faglig foredrag
Przybyla, Weronika; Paulsen, Kirsti; Mishra, Charitra Kumar; Nygård, Ståle; Engebretsen, Solveig; Ruud, Ellen; Trøen, Gunhild; Beiske, Klaus og Baumbusch, Lars Oliver. (2022).
Whole exome sequencing of high-risk neuroblastoma identifies novel non-synonymous variants.
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Neuroblastoma (NBL), one of the main death-causing cancers in children, is known for its remarkable genetic heterogeneity and varied patient outcome spanning from spontaneous regression to widespread disease. Specific copy number variations and single gene rearrangements have been proven to be associated with biological behavior and prognosis; however, there is still an unmet need to enlarge the existing armamentarium of prognostic and therapeutic targets. We performed whole exome sequencing (WES) of samples from 18 primary tumors and six relapse samples originating from 18 NBL patients. Our cohort consists of 16 high-risk, one intermediate, and one very low risk patient. The obtained results confirmed known mutational hotspots in ALK and revealed other non-synonymous variants of NBL-related genes (TP53, DMD, ROS, LMO3, PRUNE2, ERBB3, and PHOX2B) and of genes cardinal for other cancers (KRAS, PIK3CA, and FLT3). Beyond, GOSeq analysis determined genes involved in biological adhesion, neurological cell-cell adhesion, JNK cascade, and immune response of cell surface signaling pathways. We were able to identify novel coding variants present in more than one patient in nine biologically relevant genes for NBL, including TMEM14B, TTN, FLG, RHBG, SHROOM3, UTRN, HLA-DRB1, OR6C68, and XIRP2. Our results may provide novel information about genes and signaling pathways relevant for the pathogenesis and clinical course in high-risk NBL.
Løland, Anders; Engebretsen, Solveig og Günther, Clara-Cecilie. (2022).
Beregning av pantegrad og innsamlingsgrad for 2021.
NVA
Rapport
Engebretsen, Solveig; Aldrin, Magne Tommy; Qviller, Lars; Stige, Leif Christian; Rafoss, Trond; Danielsen, Ole Roald; Lindhom, Andreas og Jansen, Peder A. (2022).
Salmon lice (Lepeophtheirus salmonis) in the stomach contents of lumpfish (Cyclopterus lumpus) sampled from Norwegian fish farms: Relationship between lice grazing and operational conditions.
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Cleaner fish are commonly used as a control measure against salmon lice infestations in salmonid farms. Lumpfish (Cyclopterus lumpus) is the most common cleaner fish species used in Norwegian farms. However, little is known about how different operational, including environmental, conditions affect the salmon lice grazing efficacy by lumpfish. In this paper, we analyse salmon lice (Lepeophtheirus salmonis) in the stomach contents of a large sample of more than 20,000 lumpfish from 80 different Norwegian farms. We investigate the proportion of lumpfish with salmon lice and the mean number of salmon lice in the stomach contents of the lumpfish. We further explore how the salmon lice contents vary with different factors like lumpfish weight, weight of salmonids, salmon lice abundance in the cage, cloud cover, and sea temperature. We find that 3.1% of the 24,693 lumpfish contained salmon lice. Most of the lumpfish with salmon lice in their stomach contents contained few (one or two) lice, while there were a few lumpfish which contained many salmon lice. We find more salmon lice in the stomach contents with increasing abundance of salmon lice in the sea cage, lower weight of the salmonids, and in clear weather. Interestingly, for the relationship between lumpfish weight and salmon lice in the stomach contents, we find increased salmon lice grazing from ca. 5 g up to an optimal weight of ca. 40 g, and then a decrease from 40 g. Surprisingly, we find no relationship between sea temperature and salmon lice per lumpfish. We find more salmon lice in the stomach contents of the lumpfish with comparatively high condition. By studying the factors associated with most efficient salmon lice grazing, our paper contributes to understanding how different operational factors affect salmon lice grazing by lumpfish. For controllable factors, the results thus contribute to guiding the best practice for use of lumpfish as a salmon lice control measure.
Engebretsen, Solveig. (2022).
Situational awareness through mathematical modelling of COVID-19. Folkehelseinstituttet
NVA
Vitenskapelig foredrag
Løland, Anders; Engebretsen, Solveig og Günther, Clara-Cecilie. (2022).
Estimation of DRS collection rate by unit and total collection rate by unit for 2021.
NVA
Rapport
Engebretsen, Solveig; Rø, Gunnar Øyvind Isaksson og Blasio, Birgitte Freiesleben De. (2022).
A compelling demonstration of why traditional statistical regression models cannot be used to identify risk factors from case data on infectious diseases: a simulation study.
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Background: Regression models are often used to explain the relative risk of infectious diseases among groups. For example, overrepresentation of immigrants among COVID-19 cases has been found in multiple countries. Several studies apply regression models to investigate whether different risk factors can explain this overrepresentation among immigrants without considering dependence between the cases. Methods: We study the appropriateness of traditional statistical regression methods for identifying risk factors for infectious diseases, by a simulation study. We model infectious disease spread by a simple, population-structured version of an SIR (susceptible-infected-recovered)-model, which is one of the most famous and well-established models for infectious disease spread. The population is thus divided into different sub-groups. We vary the contact structure between the sub-groups of the population. We analyse the relation between individual-level risk of infection and group-level relative risk. We analyse whether Poisson regression estimators can capture the true, underlying parameters of transmission. We assess both the quantitative and qualitative accuracy of the estimated regression coefficients. Results: We illustrate that there is no clear relationship between differences in individual characteristics and group-level overrepresentation —small differences on the individual level can result in arbitrarily high overrepresentation. We demonstrate that individual risk of infection cannot be properly defined without simultaneous specification of the infection level of the population. We argue that the estimated regression coefficients are not interpretable and show that it is not possible to adjust for other variables by standard regression methods. Finally, we illustrate that regression models can result in the significance of variables unrelated to infection risk in the constructed simulation example (e.g. ethnicity), particularly when a large proportion of contacts is within the same group. Conclusions: Traditional regression models which are valid for modelling risk between groups for non-communicable diseases are not valid for infectious diseases. By applying such methods to identify risk factors of infectious diseases, one risks ending up with wrong conclusions. Output from such analyses should therefore be treated with great caution.
Engebretsen, Solveig. (2022).
Why traditional statistical regression models cannot be used to identify risk factors from case data on infectious diseases. Folkehelseinstituttet
NVA
Vitenskapelig foredrag
Engebretsen, Solveig; Goodwin, Morten; Fyhn, Marianne og Jemterud, Torkild. (2022).
Abels tårn.
NVA
Programdeltagelse
Løland, Anders; Engebretsen, Solveig og Günther, Clara-Cecilie. (2021).
Beregning av pantegrad og innsamlingsgrad for 2020.
NVA
Rapport
Engebretsen, Solveig; Raklev, Are; Gravensteen, Ida Kathrine og Jemterud, Torkild. (2021).
Abels tårn.
NVA
Programdeltagelse
Lindstrøm, Jonas Christoffer; Engebretsen, Solveig; Kristoffersen, Anja Bråthen; Rø, Gunnar Øyvind Isaksson; Palomares, Alfonso Diz-Lois; Engø-Monsen, Kenth; Madslien, Elisabeth Henie; Forland, Frode; Nygård, Karin Maria; Hagen, Frode; Gantzel, Gunnar; Wiklund, Ottar; Frigessi, Arnoldo og Blasio, Birgitte Freiesleben de. (2021).
Increased transmissibility of the alpha SARS-CoV-2 variant: evidence from contact tracing data in Oslo, January to February 2021.
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Background: Information about the contagiousness of new SARS-CoV-2 variants, including the alpha lineage, and how they spread in various locations is essential. Country-specific estimates are needed because local interventions influence transmissibility.
Methods: We analysed contact tracing data from Oslo municipality, reported from January through February 2021, when the alpha lineage became predominant in Norway and estimated the relative transmissibility of the alpha lineage with the use of Poisson regression.
Results: Within households, we found an increase in the secondary attack rate by 60% (95% CI 20–114%) among cases infected with the alpha lineage compared to other variants; including all close contacts, the relative increase in the secondary attack rate was 24% (95% CI −6%−43%). There was a significantly higher risk of infecting household members in index cases aged 40–59 years who were infected with the alpha lineage; we found no association between transmission and household size. Overall, including all close contacts, we found that the reproduction number among cases with the alpha lineage was increased by 24% (95% CI 0%−52%), corresponding to an absolute increase of 0.19, compared to the group of index cases infected with other variants.
Conclusion: Our study suggests that households are the primary locations for rapid transmission of the new lineage alpha.
Indseth, Thor; Fretheim, Atle; Ezzati, Rojan Tordhol; Gele, Abdi; Brekke, Jan-Paul; Elgersma, Ingeborg Hess; Godøy, Anna Aasen; Hussaini, Lema; Sheikh, Naima Said; Rø, Gunnar Øyvind Isaksson; Arnesen, Trude Margrete; Bjørbæk, Mona; Duahle, Hodon; Engebretsen, Solveig; Eide, Helena Niemi; Fevåg, Julie Salvesen; Flatø, Martin; Gawad, Mohamed; Grøtting, Maja Weemes; Hernæs, Kjersti Helene; Kjøllesdal, Marte Karoline Råberg; Kour, Prabhjot; Kristoffersen, Anja Bråthen; Labberton, Angela Susan; Lindman, Anja Elsrud Schou; Methi, Fredrik; Nordström, Charlott; Qureshi, Samera Azeem; Spilker, Ragnhild Anne Caroline Storste; Strand, Bjørn Heine; Tsige, Selam Andegiorgis; Vinjerui, Kristin Hestmann; Vold, Line og Telle, Kjetil Elias. (2021).
Koronapandemien og innvandrerbefolkningene, vurderinger og erfaringer.
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Pandemien har rammet innvandrerbefolkningene i Norge hardt. I denne rapporten redegjør vi for hva vi vet om testing, smitte, sykehusinnleggelser og død som følge av pandemien, om hvordan smittevernsarbeidet og tiltak har blitt utformet og opplevd av målgruppene og om effekter av noen tiltak
Hellton, Kristoffer Herland; Tveten, Martin; Stakkeland, Morten; Engebretsen, Solveig; Haug, Ola og Aldrin, Magne Tommy. (2021).
Real-time prediction of propulsion motor overheating using machine learning.
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Thermal protection in marine electrical propulsion motors is commonly implemented by installing temperature sensors on the windings of the motor. An alarm is issued once the temperature reaches the alarm limit, while the motor shuts down once the trip limit is reached. Field experience shows that this protection scheme in some cases is insufficient, as the motor may already be damaged before reaching the trip limit. In this paper, we develop a machine learning algorithm to predict overheating, based on past data collected from a class of identical vessels. All methods were implemented to comply with real-time requirements of the on-board protective systems with minimal need for memory and computational power. Our two-stage overheating detection algorithm first predicts the temperature in a normal state using linear regression fitted to regular operation motor performance measurements, with exponentially smoothed predictors accounting for time dynamics. Then it identifies and monitors temperature deviations between the observed and predicted temperatures using an adaptive cumulative sum (CUSUM) procedure. Using data from a real fault case, the monitor alerts between 60 to 90 min before failure occurs, and it is able to detect the emerging fault at temperatures below the current alarm limits.
Engebretsen, Solveig. (2021).
Computational statistics for COVID-19. University of Oslo
NVA
Faglig foredrag
Engebretsen, Solveig. (2021).
Situational awareness through mathematical modelling of COVID-19. Oslo Data Science Meetup
NVA
Faglig foredrag
Løland, Anders; Engebretsen, Solveig og Günther, Clara-Cecilie. (2021).
Estimation of DRS collection rate by unit and total collection rate by unit for 2020.
NVA
Rapport
Stoltenberg, Camilla; Aavitsland, Preben; Rø, Gunnar Øyvind Isaksson; Blasio, Birgitte Freiesleben de; Rattalma, Arnoldo Frigessi Di og Engebretsen, Solveig. (2021).
Aftenposten bommer om prognoser. Igjen og igjen.
NVA
Kronikk
Engebretsen, Solveig. (2021).
Spatial modelling of COVID-19 for situational awareness and forecasting. NTNU
NVA
Vitenskapelig foredrag
Engebretsen, Solveig. (2021).
Modellering av R-tallet i sanntid. Når PhD-arbeidet plutselig blir beslutningsgrunnlag under en pandemi. Senter for digitalt liv Norge
NVA
Faglig foredrag
Engebretsen, Solveig. (2021).
Covid-19 situational awareness and forecasting modelling. University of Oslo
NVA
Faglig foredrag
Løland, Anders; Aldrin, Magne Tommy og Engebretsen, Solveig. (2021).
Episode 10: R-tallet for de avanserte. Hvorfor beregner Magne sin egen R? Med Solveig Engebretsen og Magne Aldrin.
NVA
Programdeltagelse
Engebretsen, Solveig. (2021).
Spatial modelling of COVID-19 in Norway using real-time mobility data. Big Insight
NVA
Faglig foredrag
Engebretsen, Solveig; Aldrin, Magne Tommy; Grøntvedt, Randi; Jansen, Peder A og Nøst, Ole Anders. (2021).
Vurdering av tiltak mot lakselus i PO3, for reduksjon av smittepress.
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I dette notatet vurderer vi ulike tiltak mot lakselus i produksjonsområde 3, et intensivt produksjonsområde som står i fare for å miste retten til produksjonsvekst, på grunn av høyt smittepress av lakselus. For å kunne vurdere effekter av ulike tiltak, tilpasser vi en eksisterende lusemodell til oppdaterte data. Deretter bruker vi den tilpassede lusemodellen til å simulere lus over tid. Vi undersøker effekten av ulike tiltaksgrenser for behandling, å slå sammen lokaliteter, mer bruk av storsmolt og økt bruk av forebyggende tiltak mot lus. Effekten av å slå sammen lokaliteter sammenliknes med tidligere resultater fra Havforskningsinstituttet og Veterinærinstituttet. Vi undersøker også hvordan lusemodellen kan ta i bruk strømkontakt mellom lokaliteter i stedet for smittekontakt basert på sjøavstander som er brukt fram til nå.
Engebretsen, Solveig. (2021).
Regional modelling of COVID-19 in Norway for situational awareness and forecasting. OCBE
NVA
Vitenskapelig foredrag
Bakken, Jari; Johansen, Per Anders; Sandberg, Hallvard; Skille, Øyvind Bye; Blasio, Birgitte Freiesleben De; Engebretsen, Solveig; Britton, Tom og Frigessi, Arnoldo. (2021).
Panel debate: Mathematical models,
statistical complexity,
uncertainty and decision
making in the Covid-19
pandemic: science,
society and the public.
A panel discussion with
journalists and modellers.
NVA
Programdeltagelse
Frigessi, Arnoldo; Britton, Tom; Engebretsen, Solveig; Kuhlmann-Berenzon, Sharon; Leino, Tuija og Leskelä, Lasse. (2021).
Panel debate: The role of mathematics and statistics in the political and health political decisions
in the covid crises.
NVA
Programdeltagelse
Stoltenberg, Camilla; Rattalma, Arnoldo Frigessi Di; Engebretsen, Solveig; Sandberg, Hallvard; Johansen, Per Anders og Gjuvsland, Elin Ruhlin. (2021).
Paneldebatt: HVA KAN VI LÆRE AV RUNDEN MED COVID: HVORDAN HÅNDTERER VI USIKKERHET OG ÅPENHET?
NVA
Programdeltagelse
Engebretsen, Solveig. (2021).
COVID-19 modelling in Norway for situational awareness and forecasting. University of Oslo
NVA
Faglig foredrag
Jemterud, Torkild; Engebretsen, Solveig; Bjorå, Charlotte Sletten og Joner, Erik. (2021).
Abels tårn.
NVA
Programdeltagelse
Engebretsen, Solveig. (2021).
Spatial modelling of COVID-19 in Norway. University of Oslo
NVA
Faglig foredrag
Ulvund, John Birger; Engebretsen, Solveig; Alfredsen, Jo Arve; Kristensen, Torstein; Urke, Henning André og Jansen, Peder A.. (2021).
Behavioural response of farmed Atlantic salmon (Salmo salar L.) to artificial underwater lights: Wavelet analysis of acoustic telemetry data.
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Biological, environmental, economic and ethical issues become increasingly pertinent as the scale of the aquaculture industry expands. This study used acoustic telemetry data and wavelet analysis to investigate behavioural patterns of Atlantic salmon when exposed to artificial underwater lights in fully stocked production cages located on the Norwegian coast. Using acoustic depth sensor tags, time series of depth registrations were gathered from 21 individual salmon distributed over three cages during a five-month experimental period. Underwater lights, normally used to suppress pre-harvest sexual maturation amongst Atlantic salmon, were installed at eight-metre depth and switched on in the middle of the experimental period. Swimming depth registrations initially showed a typical diurnal swimming behaviour, manifested by registrations generally in deeper waters during day-time than during night-time. The diurnal swimming behaviour abruptly ceased after the onset of lights. The change in swimming behaviour was detected by wavelet analysis and coincided with the introduction of underwater lights. Results from this study demonstrate the utility of wavelet analysis as a timely surveillance tool when investigating behavioural patterns of a periodic nature in fish, and specifically the individual response of farmed salmon to artificial lighting in a genuine industrial setting.
Engebretsen, Solveig. (2020).
Pandemimodellering for COVID-19 i Norge ved hjelp av mobildata. Norwegian Smart Care Cluster, Norway Health Tech, Tekna
NVA
Vitenskapelig foredrag
Engebretsen, Solveig. (2020).
Modellering av geografisk spredning av COVID-19 i Norge. Norsk matematikkråd
NVA
Vitenskapelig foredrag
Rognebakke, Hanne Therese Wist; Redelmeier, Annabelle Alice og Engebretsen, Solveig. (2020).
Introduksjon til R – verktøy for statistisk analyse og maskinlæring. Norsk Regnesentral
NVA
Faglig foredrag
Engebretsen, Solveig. (2020).
Spatial modelling of COVID-19 in Norway. the national research school in bioinformatics, biostatistic
NVA
Vitenskapelig foredrag