Viser treff 231-250 av 271

    • Short-term tundra plant-community nutrient responses to herbivory and warming: New insights from Near infrared-reflectance spectroscopy methodology 

      Petit Bon, Matteo (Doctoral thesis; Doktorgradsavhandling, 2020-09-22)
      In the long-term, herbivores and climate warming have been shown to alter nutrient levels in tundra plant communities by changing the functional composition of the vegetation. Here, I asked the extent to which they affect tundra plant-community nutrient levels in the short-term by directly modifying the chemistry of plants. I first developed a time- and cost-effective method that allowed me to ...
    • Sjarkfiske og ressursforvaltning 

      Maurstad, Anita (Doctoral thesis; Doktorgradsavhandling, 1997-11-07)
      <p>Med utgangspunkt i feltarbeid fra fiskevær i Troms, samt intervjuer med flere fiskere i Troms og Finnmark, drøfter jeg det nordnorske sjarkfisket i lys av to motstridende teorier om ressurshøsting og -regulering. Den ene sier at små enheter er mer ressursvennlige enn store. I småskalaproduksjon finnes innebygde begrensninger i produksjonsmåten, dels fordi vi står ovenfor husholdsbasert produksjon ...
    • Some methodological issues in economic evaluation in health care 

      Olsen, Jan Abel (Doctoral thesis; Doktorgradsavhandling, 1993)
    • Spatial and temporal patterns of foraging of harbour seals (Phoca vitulina) in Porsangerfjord: from behavioural interpretation to resource selection. 

      Ramasco, Virginie (Doctoral thesis; Doktorgradsavhandling, 2015-09-24)
      The coastal cod stock of the Porsangerfjord has drastically declined in the 80’s and never fully recovered since. A population of harbour seals, known to be resident in the fjord all year round, has been hypothesised to act as predator-pit for cod in the area, affecting its lack of recovery. In order to understand the role of these seals in this local marine ecosystem, their foraging behaviour ...
    • Spatial and temporal variations in parasite communities of freshwater fish in the subarctic 

      Kuhn, Jesper Andreas (Doctoral thesis; Doktorgradsavhandling, 2015-11-03)
      Parasite communities are complicated systems believed to be affected by multiple ecological and environmental factors, both in time and space. These communities might be disrupted by anthropogenic host introductions which unfortunately appear to be a common practice e.g. in freshwater fish management. By addressing parasite occurrences in three of the most common freshwater fish species in subarctic ...
    • The speciation landscape of European whitefish in Northern Fennoscandia – the importance of deglaciation history, standing genetic variation and natural selection 

      Häkli, Katja (Doctoral thesis; Doktorgradsavhandling, 2019-12-10)
      <p>During the last deglaciation, one clade of European whitefish (<i>Coregonus lavaretus</i> L.) colonized the lakes in the three contemporary watercourses of northern Fennoscandia (Pasvik, Tana and Alta) and diverged thereafter in sympatry. This thesis investigates the interplay between evolutionary processes and standing genetic variation in shaping phenotypic and genetic divergence, and how ...
    • Speciation reversal in sympatric eco-morphs of European whitefish (Coregonus lavaretus. L) – phenotypic and genomic consequences 

      Bhat, Shripathi (Doctoral thesis; Doktorgradsavhandling, 2016-09-20)
      Anthropogenic activities, such as introduction of non-native species, is considered as one of the most significant causes for declining biodiversity, since such introduction may destabilise ecological barriers to gene flow between native populations. In the 1960s a salmonid fish, vendace, was introduced to the upper parts of Pasvik watercourse and during the early 1990s it invaded the entire ...
    • Species concepts and functional aspects of cold-water diatoms (Bacillariophyceae) 

      Degerlund, Maria (Doctoral thesis; Doktorgradsavhandling, 2011-10-18)
      The choice of species concept when delineating phytoplankton species is decisive for our knowledge of species diversity and distribution, but will also affect our understanding of the functioning of marine ecosystems. This is particularly true for so-called cryptic species, which may show high degree of genetic and physiological heterogeneity although being morphologically similar. A precise species ...
    • Spectral changes in fillet of Atlantic salmon as affected by freshness loss and spoilage during cold storage. 

      Sone, Izumi (Doctoral thesis; Doktorgradsavhandling, 2012-12-03)
      Spectral effects of microbial growth, packaging atmosphere and heme oxidation were investigated with fresh salmon. The presence of microorganisms and their growth have little effect on the development of spectral features in fresh salmon during storage prior to extensive spoilage. Important spectral changes occur at 606 and 636 nm in the spectra of fresh salmon during storage. Heme oxidation is the ...
    • The spread of salmon lice (Lepeophtheirus salmonis Krøyer) from Norwegian fish farms and their impact on sea trout (Salmo trutta L.) 

      Serra-Llinares, Rosa Maria (Doctoral thesis; Doktorgradsavhandling, 2020-10-09)
      <p>The transmission of salmon lice (<i>Lepeophtheirus salmonis</i> Krøyer) from farm salmon to wild salmonids and the impact on wild populations are sources of intense debate in all salmon producing countries, and it is currently an issue of high political and economic relevance in Norway. Solid science-based evidence is therefore needed by decision makers to apply sound management strategies. Given ...
    • Stakeholder Involvement in the Governance of Fisheries in Europe: With perspectives of the result-based management 

      Msomphora, Mbachi Ruth (Doctoral thesis; Doktorgradsavhandling, 2016-05-27)
      The PhD project study is about ‘stakeholder participation’ in fisheries governance; a concept that has become acceptable in all areas of decision-making during the last few decades, partly due to dissatisfaction with the performance of fisheries management systems across the world. Among other issues, discarding, especially of marketable fish, is a serious and continuing problem despite the heavy ...
    • Staying alive : the survival and importance of Atlantic salmon post-spawners 

      Halttunen, Elina (Doctoral thesis; Doktorgradsavhandling, 2011-08-19)
      Summary Atlantic salmon (Salmo salar L.) repeat-spawners might play an important role in population persistence by increasing both total recruitment and long-term stability of a population. This is because repeat spawners return at larger sizes and with greater fecundity than first time spawners, and the large majority of repeat-spawners are females. Nevertheless, little knowledge exists of this ...
    • Stoichiometry of lipid synthesizing calanoid copepods in Arctic and sub-Arctic marine regions Insights into limitation and elemental cycling from characterization of C:N:P ratios 

      Aubert, Anaïs (Doctoral thesis; Doktorgradsavhandling, 2012-12-12)
      Calanoid copepods, Calanus finmarchicus, C. glacialis and C. hyperboreus, are key species in Arctic and sub-Arctic marine ecosystems. They represent important prey for a number of species such as juvenile herring and cod because of their high but seasonally variable calorific value: they synthesize and store lipids as part of their survival strategy. Limitations in food quantity and quality can have ...
    • Storytelling and story staging. Co-creating value in tourism. 

      Mathisen, Line (Doctoral thesis; Doktorgradsavhandling, 2014-04-01)
      This thesis is about tourism firms as co-creators of value in tourist activities. It will explore how tourism firms communicate, particularly by using storytelling, to enhance co-creation of value with tourists. A central perspective used in this thesis is Service Dominant Logic, a logic that posits that service providers can only co-create value with their customer, not for them (Vargo and Lush ...
    • Stress responses influencing fillet quality of trawled Atlantic cod and haddock 

      Svalheim, Ragnhild Aven (Doctoral thesis; Doktorgradsavhandling, 2018-12-12)
      In this thesis, an experimental swim tunnel and cod-end was used as a model to investigate how stress during various stages of trawl capture affects fillet quality in terms of residual blood, time and hardness of post-mortem muscle stiffness and muscle colour of cod and haddock. In addition, the effect of stress on importance of timing of euthanasia was also addressed. The first stage of trawl ...
    • Studies of infectious pancreatic necrosis virus (IPNV) and immune evasion strategies 

      Skjesol, Astrid (Doctoral thesis; Doktorgradsavhandling, 2009-10-23)
      Infectious pancreatic necrosis (IPN) is a highly contagious disease which causes huge economic loss to the salmon farming industry world wide. The causative agent, the IPN virus (IPNV), is a dsRNA, non-enveloped virus with two genomic segments encoding five viral proteins, VP1-VP5. <br>Available vaccines against this disease give only partial protection. In order to optimize vaccine efficacies, ...
    • Studies of JAK/STAT signaling in Atlantic salmon 

      Sobhkhez, Mehrdad (Doctoral thesis; Doktorgradsavhandling, 2014-06-27)
      In mammals the JAK-STAT pathway plays a significant role in mediating the biological activities of both type I and type II IFN, where JAKs are receptor associated kinases and STATs the transcription factors they activate. At the start of this project the knowledge of the JAK-STAT pathway in fish in general was scarce and there were few reports describing the function of any JAK-STAT family member ...
    • Studies on the amphipod genus Metopa (Stenothoidae) : Taxonomy, Ecology, Phylogeny 

      Tandberg, Anne Helene S. (Doctoral thesis; Doktorgradsavhandling, 2011-12-19)
      The Amphipod-genus Metopa is a relatively large genus, with currently 55 accepted species. This PhD thesis consists of redescriptions of 23 of these species based on typespecimens or specimens collected and identified by the original authors; this has been done to create consistent descriptions that could form a basis for a phylogenetic analysis of Metopa. For some species Scanning Electron ...
    • A study of economic efficiency, adaptive measures to extreme climatic events, and drivers of disease in Vietnamese white leg shrimp aquaculture 

      Le Thi Thanh, Ngan (Doctoral thesis; Doktorgradsavhandling, 2023-12-08)
      This thesis delves into three key research areas centered on shrimp farming: evaluating operational efficiency in shrimp farming, analyzing adaptive choices made by farmers, and forecasting disease occurrences in shrimp farms in the context of evolving climate and environmental influences. The research employed a blend of methodologies derived from pertinent literature, coupled with data acquired ...
    • Sublethal effects of environmental pollutant exposure in birds of prey: Evaluating biomarkers of health as indicators of contaminant-mediated effects in two sentinel raptor species 

      Hansen, Elisabeth (Doctoral thesis; Doktorgradsavhandling, 2023-11-02)
      Environmental pollution emerged as a major concern in the mid-20th century primarily due to the unrestricted release of industrial chemicals and pesticides. Among wildlife species, apex predators, like raptors, have been heavily exposed to environmental pollutants such as organo-halogenated contaminants (OHCs) and metals (e.g., mercury). Due to their high trophic position, harmful levels of these ...