Temporal and spatial variations in lice numbers on salmon farms in the Hardanger fjord 2004-06

The long and narrow Hardanger fjord in western Norway has a high density of salmon farms and has had severe salmon lice, Lepeophtheirus salmonis, problems. In the years 2004-06, salmon lice numbers were recorded in selected salmon farms in the fjord as part of a larger research project. Most farm sites participated in a strategic control programme and were deloused between November and January in each year. The aim of the programme was to achieve a mean abundance of <0.3 adult female lice at this time and to minimize the infection pressure on wild smolts in the spring. Dedicated teams carried out detailed counting of lice on farmed fish in April-September each year. Temperature conditions were fairly similar throughout the fjord and amongst years, but wide variations in salinities were observed. The two innermost zones, B and C, had the lowest lice mean abundances, whereas the outermost zones, D and E, consistently had more lice. General linear model analyses showed that differences in adult female lice abundance between the zones were associated with differing levels of salinity and emamectin benzoate treatments strategically administered. Mean fish weight was significantly positively correlated with mean abundance of adult female lice

Confidence in assessing the effectiveness of bath treatments for the control of sea lice on Norwegian salmon farms

The salmon louse Lepeophtheirus salmonis is the most important ectoparasite of farmed salmonids in the Northern hemisphere, having a major economic and ecological impact on the sustainability of this sector of the aquaculture industry. To a large extent, control of L. salmonis relies on the use of topical delousing chemical treatments in the form of baths. Improvements in methods for the administration and assessment of bathtreatments have not kept pace with the rapid modernization and intensification of the salmon industry. Bathtreatments present technical and biological challenges, including best practice methods for the estimation of the effect of licetreatment interventions. In this communication, we compare and contrast methods to calculate and interpret treatmenteffectiveness at pen and site level. The methods are illustrated for the calculation of the percentage reduction in mean abundance of mobile lice with a measure of confidence. Six different methods for the calculation of confidence intervals across different probability levels were compared. We found the quasi-Poisson method with a 90% confidence interval to be informative and robust for the measurement of bathtreatment performance

Semigroup analysis of structured parasite populations

Motivated by structured parasite populations in aquaculture we consider a class of size-structured population models, where individuals may be recruited into the population with distributed states at birth. The mathematical model which describes the evolution of such a population is a first-order nonlinear partial integro-differential equation of hyperbolic type. First, we use positive perturbation arguments and utilise results from the spectral theory of semigroups to establish conditions for the existence of a positive equilibrium solution of our model. Then, we formulate conditions that guarantee that the linearised system is governed by a positive quasicontraction semigroup on the biologically relevant state space. We also show that the governing linear semigroup is eventually compact, hence growth properties of the semigroup are determined by the spectrum of its generator. In the case of a separable fertility function, we deduce a characteristic equation, and investigate the stability of equilibrium solutions in the general case using positive perturbation arguments.Comment: to appear in Mathematical Modelling of Natural Phenomen

A new approach to assessing the risk to woodland from pest and diseases

Pests and diseases pose a growing threat to woodlands from both endemic sources, and increasingly, from inter-regional transmission. Strong comparative analyses of this threat are needed in order to develop preventative measures. Such analyses should include estimates of the potential worst-case loss from all relevant pest and disease threats to key tree species. Existing approaches tend to focus on individual assessments of the risk from a single pest or disease, or assessments of overall trends. Effective risk management requires more comprehensive quantified assessments of the overall threat to woodland, that includes comparisons of the threat to individual tree species and identification of the potentially most damaging pest and diseases. Such assessments support important policy and management decisions including: species selection; preventative action; and the size of buffers against losses from forest carbon projects. Here we present a new approach that supports a systematic, risk-based assessment of the future threat to a given woodland from all known individual pest and diseases, and to constituent individual tree species, based on a risk management approach taken from the finance sector, but hitherto not applied in an ecological context. Unknown or unidentified pests and diseases can systematically be added in future as identified. We demonstrate the method through a case study evaluating the threat to projects certified under the UK’s Woodland Carbon Code. The approach can be adapted to any woodland resource worldwide. Its novelty lies in the simplification of complex threats, from numerous pests and diseases, to measures that can be used by a range of forest stakeholders

Overweight and obesity as risk factors for chronic low back pain: a new follow-up in the HUNT Study

Background: Numerous studies have examined associations between overweight and obesity and risk of low back pain (LBP), but the exact magnitude of these associations is not yet clear. The purpose of this work was to assess such sex-specific associations in a community-based setting in Norway, taking into account potential relationships with other risk factors. Methods: A cohort study was conducted combining data from two waves of the Trøndelag Health Study, HUNT3 (2006–2008) and HUNT4 (2017–2019). Separate analyses were performed of risk of chronic LBP in HUNT4 among 14,775 individuals without chronic LBP in HUNT3, and of recurrence or persistence in HUNT4 among 5034 individuals with chronic LBP in HUNT3. Relative risks were estimated in generalised linear models for overweight and obesity compared to normal weight. Body size classification was based on values of BMI computed from measurements of height and weight. Chronic LBP was defined as LBP persisting at least 3 months during last year. Results: After adjustment for age, smoking, physical activity in leisure time and work activity, analysis of risk among women produced relative risks 1.11 (95% CI 1.00–1.23) for overweight, 1.36 (95% CI 1.20–1.54) for obesity class I and 1.68 (95% CI 1.42–2.00) for obesity classes II-III. Relative risks among men were 1.10 (95% CI 0.94–1.28) for overweight, 1.36 (95% CI 1.13–1.63) for obesity class I and 1.02 (95% CI 0.70–1.50) for obesity classes II-III, the last estimate being based on relatively few individuals. Analyses of recurrence or persistence indicated similar relationships but with smaller magnitude of relative risks and no drop in risk among obesity classes II-III in men. The change in BMI from HUNT3 to HUNT4 hardly differed between individuals with and without chronic LBP in HUNT3. Conclusions: Risk of chronic LBP increases with higher values of BMI in both sexes, although it is uncertain whether this applies to very obese men. Very obese women carry a particularly large risk. Probabilities of recurrence or persistence of chronic LBP among those already afflicted also increase with higher values of BMI. Adjustment for other factors does not influence relationships with overweight and obesity to any major extent.publishedVersio

Does the risk of chronic low back pain depend on age at menarche or menopause? A population-based cross-sectional and cohort study: the Trøndelag Health Study

Objective In most population-based studies of low back pain (LBP), women have a higher risk than men, possibly reflecting hormonal influences. The aim of this study was to explore associations between age at menarche and menopause and risk of chronic LBP. Design Population-based cross-sectional and cohort study designs. Setting The HUNT2 and HUNT3 medical surveys of the entire population of Nord-Trøndelag County in Norway. Main outcome measure Prevalence or risk of chronic LBP, defined as LBP persisting at least 3 months continuously during last year. Participants Associations between age at menarche and prevalence of chronic LBP were examined in cross-sectional data from HUNT2, comprising 27 697 women aged 20–69 years, with 7300 women reporting LBP. The corresponding cohort data included 11 659 women without LBP at baseline in HUNT2, with 2353 women reporting LBP at follow-up 11 years later in HUNT3. Cross-sectional data on age at menopause or premenopausal status included 11 332 women aged 40–69 years, with 3439 women reporting chronic LBP. Corresponding cohort data included 7893 women without LBP at baseline, of whom 1100 developed LBP. Methods Associations between age at menarche or menopause and risk of chronic LBP were examined by generalised linear modelling. Results A U-shaped association was indicated between age at menarche and risk of chronic LBP, both in the cross-sectional and cohort studies. Age at menarche ≤11 years was associated with an increased risk of chronic LBP, with a relative risk of 1.32 (95% CI 1.15 to 1.52), compared with age 14 years at menarche, after relevant adjustments. Corresponding cross-sectional crude absolute risks were 32% and 25%, respectively. No association was established between age at menopause and risk of LBP. Being premenopausal had no influence on risk. Conclusions In contrast to results for age at menopause, the association with age at menarche suggests that hormonal factors affect the risk of LBP.publishedVersio

A Multiple-Case Study on How Student Entrepreneurs Conduct Resource Development in Early-Stage Ventures Within a University Ecosystem

Universitetet er et knutepunkt for innovasjon og entreprenørskap, og det fokuseres stadig mer på aktiviteter og læring innenfor entreprenørskap, samt kommersialisering av teknologi. Mange studenter starter bedrifter som en del av et studieprogram, eller som en frivillig aktivitet utenom studieprogrammet. Selv uten arbeidserfaring eller et etablert nettverk klarer studenter å samle ressursene de trenger for å bygger bedrifter, innenfor universitetsøkosystemet. Denne oppgaven tar for seg hvordan studententreprenører klarer å bygge nye bedrifter ved å svare på følgende forskningsspørsmål: 1) Hvordan går studententreprenører frem i tidligfase-ressursutvikling? Og 2) Hva er studententreprenørens rolle innenfor universitetets entreprenørielle økosystem? Metoden som er valgt for å besvare forskningsspørsmålene er en kvalitativ multi-case studie. Fire studentdrevne oppstartsbedrifter fra Norges Teknisk-Naturvitenskapelige Universitet har blitt studert gjennom observasjoner og semistrukturerte intervjuer, etterfulgt av en kryss-analyse på tvers av casene. Analysen og diskusjonen bygger på et bricolage-rammeverk som har blitt konstruert for denne spesifikke studien, basert på eksisterende teori. Rammeverket består av tre hovedelementer: 1) Bero på tilgjengelige ressurser, 2) Ressursrekombinasjon for nye bruksområder, og 3) Å gjøre det beste ut av det man har, som relateres til studententreprenørens evne til å søke etter muligheter og løsninger i stedet for å anerkjenne hindringer. Resultatene tyder på at studentene aktivt bruker "student-kortet" for å bygge legitimitet mot ulike interessenter. Videre bygger studentene sitt eget studentøkosystem inne i det allerede etablerte universitetsøkosystemet, og studententreprenører vurderer andre studenter og studentøkosystemet som den mest verdifulle ressursen i universitetssammenheng. Følgelig anerkjenner vi en nedenfra-opp-tilnærming, initiert av studenter, i utviklingen av det entreprenørielle universitetsøkosystemet. Vi oppfordrer derfor videre forskning på universitets-økosystemer og studententreprenørskap til å se på hvordan studentene deltar i å bygge universitetsøkosystemet nedenfra-opp, og hvordan universiteter kan fasilitere dette med fysiske fasiliteter og økonomisk finansiering fra et topp-ned-perspektiv. Til slutt anbefales studententreprenører til å bruke hverandre aktivt når de navigerer i universitetets økosystem, da dette viser seg å være avgjørende for å bruke og utvikle (de rette) ressursene.Universities are hubs for innovation and entrepreneurship, and there is a deepening focus on entrepreneurial activities and commercialization of university technology. Many students start ventures as part of their study program, or even as a co-curricular activity. Without profound work experience or established professional networks they manage to gather the resources they need for venture creation within the university ecosystem. This thesis embraces how student entrepreneurs manage to do that, by addressing two research questions: 1) How do student entrepreneurs go about early-stage resource development?, and 2) What is the role of the student entrepreneur within the entrepreneurial university ecosystem? The method chosen for exploring the research questions is a qualitative multiple-case study. Four student-driven startups from The Norwegian University of Science and Technology were studied by the use of observations and semi-structured interviews, resulting in a cross-case analysis. Following, the analysis and discussion are carried out within a bricolage-framework that was created to this specific study, based on existing theory. The framework consists of three main elements: 1) Reliance on whatever resources are at hand, 2) Resource recombination for novel uses, and 3) Making do, relating to the student entrepreneur's ability to search for opportunities and solutions rather than acknowledging obstacles. Findings suggest that student entrepreneurs actively use the "student-label" to build legitimacy towards different stakeholders. Furthermore, they create their own student ecosystem inside the already established university ecosystem, and consider other students and the student ecosystem to be the most valuable resource within the university context. Consequently, a bottom-up approach initiated by students in the development of the entrepreneurial university ecosystem is recognized. We therefore encourage further research on university ecosystems and student entrepreneurship to consider how the students participate in building the university ecosystem bottom-up, and how universities can enable this with physical facilities and economic funding from a top-down perspective. Lastly, student entrepreneurs are recommended to use other student entrepreneurs actively when navigating the university ecosystem, as that proves to be vital in using and developing (the right) resources