The oxygen requirement of Atlantic salmon (Salmo salar L.) in the on-growing phase in sea cages

Atlantic salmon aquaculture is a successful and growing industry, with a global production of more than 1.4 million tonnes in 2010. In the on-growing phase, Atlantic salmon are normally kept in sea cages, where both the water temperature and oxygen levels may fluctuate substantially over time and with depth. Oxygen is the main limiting factor of fish metabolism, and sufficient oxygen is therefore essential for all energy-demanding processes, including growth and basic life-supporting functions. Knowledge of the dissolved oxygen (DO) requirement of Atlantic salmon in the on-growing phase, and this species’ ability to cope with observed fluctuations in DO (30-120% O2) is however limited. The overall aim of this thesis was therefore to study the physiology and production performance of Atlantic salmon in response to changes in the oxygen availability, in order to establish knowledge that can be used to assess whether growth and welfare is compromised as a result of insufficient oxygen in the on-growing phase. Insufficient oxygen supply (environmental hypoxia) is primarily considered to be a problem in summer and autumn, and to occur in short/ frequent rather than prolonged periods. The studies of responses to oxygen fluctuations were therefore performed at 16 °C (a typical autumn temperature along the Western coast of Norway) and with hypoxia occurring in cycles corresponding to the turn of the tidal current, resembling previous observations in sea cages (2 h of hypoxia every 6 h, termed “cyclic hypoxia”). However, the oxygen requirement of fish is known to increase with temperature and with the level of activity. For the determination of the minimum DO requirement of Atlantic salmon, temperatures were therefore set to range between 6 and 18 °C, and the experimental conditions were set to induce activity levels as similar to fish in sea cages as possible. For the typical autumn temperature of 16 °C, the threshold for optimal feeding of Atlantic salmon post-smolts was ~70% O2. Feed intake, and presumably also the digestion rate, decreased with increasing hypoxia severity, reaching low levels as DO approached the hypoxia tolerance threshold of 47% O2. Below this DO threshold, fish were no longer able to maintain their oxygen uptake rate, and resorted to anaerobic ATP production to cover their energy demand. Further, a general stress response was induced at DO equivalent to 51-54% O2, and a few fish died during the first day of hypoxic periods (40 and 50% O2). The limited ability to maintain basic functions and the stress and compromised survival at DO below the hypoxia tolerance threshold, demonstrate that this is a limit for acceptable drops in oxygen in Atlantic salmon sea cages, both with regard to production performance and welfare. For postsmolts with low swimming speed and relatively low growth rates, this threshold increased exponentially with temperature, from 29 to 55% O2 at temperatures ranging from 6-18 °C. It was estimated that this threshold should be increased by approximately 40% (i.e. 41-77% O2) in order to serve as practical guideline for salmon farming, due to the higher level of activity (feed intake, swimming speed etc.) that can be expected for fish in sea cages. The reduced feed intake of post-smolts in hypoxic periods was to a large extent compensated for by increased feeding in normoxic periods. This compensation developed after the initial stress response was down-regulated (hypoxia tolerance threshold) may be fully alleviated if the hypoxic periods are of shorter duration and/or frequency. The hypoxia sensitivity of Atlantic salmon was not considerably reduced as a result of acclimation to cyclic hypoxia, as indicated by the persisting anaerobiosis and inhibited feed intake during the hypoxic periods. The main conclusions from this thesis is that reductions in DO below the hypoxia tolerance threshold is unacceptable both with regard to production performance and welfare, while negative effects of DO ranging between this threshold and the threshold for maintained feeding depend on hypoxia severity, frequency and duration. Acclimation to hypoxia did not reduce hypoxia sensitivity, while habituation to hypoxic stress was linked to an increased compensatory feeding in normoxic periods. Hypoxia occurring for ~2 h in tidal cycles (~every 6 h) was not fully compensated for, in spite of stress habituation and normoxic feeding

Effect of ectoparasite infestation density and life-history stages on the swimming performance of Atlantic salmon Salmo salar

-To overcome sustainability obstacles and improve operations, the Atlantic salmon farming industry is testing novel approaches to production. Redistributing farm sites to offshore locations is one such solution; however, tolerance to high-current velocity sites must be considered, particularly if fish health status is compromised by parasites. We tested the effect of parasite density and life-history stage on the swimming performance of Atlantic salmon Salmo salar using a swim flume. Salmon with 3 different salmon lice Lepeophtheirus salmonis densities (0, 0.02 ± 0.01 and 0.11 ± 0.01 lice cm-2 [mean ± SE]) were tested across the 4 major life-history stages of lice (copepodid, chalimus, pre-adult and adult) for critical swimming performance (Ucrit). Salmon Ucrit declined slightly by a mean of 0.04 to 0.10 body lengths s-1 with high parasite densities compared to uninfested and low densities, across the lice stages, while progression through the parasite life-history stages had little effect on swimming performance. Our results suggest that increasing infestation density of salmon lice incurs negative fitness consequences for farmed Atlantic salmon held in high-current velocity sites, with little difference in costs associated with attachment by different life-history stages of the lice

Boligprisutvikling og finansiell stabilitet : bør styringsrenten brukes mer aktivt som prisstabiliserende faktor i boligmarkedet?

Formålet med utredningen har vært å vurdere hvorvidt sentralbanken bør føre en mer kontraktiv pengepolitikk for å begrense veksten i boligprisene. Jeg finner at boligprisutviklingen de siste årene gir grunn til bekymring. Kombinert med sterk vekst i husholdningenes gjeld, skaper en potensiell boligprisboble finansiell sårbarhet. Et boligkrakk kan få store økonomiske konsekvenser som følge av redusert etterspørsel, dårligere evne til å betjene gjeld og tap på utlån i banksektoren. Dette taler for en økt styringsrente. Pengepolitikken har imidlertid begrenset handlingsrom. Norge er en liten åpen økonomi, og sentralbanken må ta hensyn til konsekvensene av store og vedvarende utslag i valutakursen. Kronekursen er i dag sterk. Hensynet til importert inflasjon, samt behovet for forutsigbare rammebetingelser i konkurranseutsatt sektor, legger derfor klare begrensinger for rentedifferansen mot utlandet. Basert på utviklingen i konkurranseevne og forventet inflasjon, konkluderer utredningen med at styringsrenten ikke bør brukes mer aktivt enn den gjør i dag. Andre virkemidler som regulering av banksektoren, endringer i skattesystemet og stimulans til økt priselastitet på tilbudssiden, vil være mer treffsikre, og kan gi mer langsiktig stabilitet i boligmarkedet

Assessing Sustainable Consumption in Packaged Food in Indonesia: Corporate Communication Drives Consumer Perception and Behavior

Sustainable consumption has been addressed in the literature in recent years, especially in relation to changing from a traditional consumption to sustainable consumption. Reducing environmental impacts from waste generation has been the focal point of sustainable consumption. However, a large number of attributes has caused a complexity in understanding which attributes effectively enhance the consumption. In particular, sustainable consumption has been facing a negative trend due to low levels of knowledge about packaging’s environmental impact, failed communication which leads to misperception and irresponsible behavior. This study contributes to proposing a set of attributes for enhancing sustainable consumption in the Indonesian food industry, to fulfill the lack of understanding of the attribute interrelationships using qualitative information. This study proposes a set of attributes to enhance sustainable consumption with qualitative information by assessing the interrelationships among the attributes employing the Delphi method and fuzzy decision-making trial and evaluation laboratory method to provide causal and effect relationships. As a result, corporate communication, consumer perception, consumer behavior, and product packaging are major aspects for sustainable consumption enhancement. Corporate communication becomes a major driver to affect perception and behavior. This study proposes a managerial insight for the packaged food industry on improving several criteria including green marketing, green consumerism, verbal features, and importance of information

Critical swimming speed in groups of Atlantic salmon Salmo salar

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Profit Maximization for Waste Furniture Recycled in Taiwan Using Cradle-to-Cradle Production Programming

This study proposes the use of cradle-to-cradle production programming for waste furniture and aims to achieve optimal efficiency by reusing waste furniture and maximizing the corresponding benefits so that the furniture industry is in line with cradle-to-cradle manufacturing. This study is increasingly important to manage products through a comprehensive green reverse logistics system that consists of three procedures, i.e., recycling, reuse, and remanufacturing of waste items. This study proposes a mathematical formula to establish a cradle-to-cradle production programming model for waste furniture. The fuzzy set theory is used to define the attributes that reflect production and market demands such as degree of damage, technical feasibility, market demands, environmental protection laws and regulations, and environmental performance. In addition, particle swarm optimization is adopted to ascertain the optimal profit from waste furniture sales. Through situational simulations and analyses, the fuzzy set information from Taiwan, Germany, and China is compared. The result reveals that the qualitative information proposed has a significant impact on the profit of waste furniture reuse. The production model can effectively assist in the production programming of waste furniture, thereby optimizing profit for cradle-to-cradle production planning

Tumeurs cérébrales et téléphonie mobile chez les jeunes

International audienceL’utilisation croissante du téléphone portable chez les adolescents, et plus récemment chez les enfants, suscite des inquiétudes quant à de possibles effets sanitaires des radiofréquences. C’est dans ce contexte que le projet de recherche international "MOBI-KIDS" a été initié, afin d’évaluer chez les jeunes de 10 à 24 ans le risque potentiel de tumeurs cérébrales lié à l’exposition aux radiofréquences

Temperature and size-dependency of lumpfish (Cyclopterus lumpus) oxygen requirement and tolerance

Under embargo until: 2023-10-09Lumpfish are currently produced and utilized as cleaner fish, to control sea lice infestation rates in salmon net pens, but information on environmental requirements is still limited. This study aimed to determine the zone of environmental hypoxia for two relevant fish sizes (15 and 60 g) and temperatures (5 and 12 °C), using intermittent flow respirometry (referred to as 15:5, 15:12, 60:5, 60:12), and to investigate parameters of stress in response to acute changes in dissolved oxygen (DO, % air saturation) from normoxia to 47, 63, 98 (control), 148 and 194% O2 at 10 °C. The standard and maximal metabolic rates (SMR and MMR) were measured in normoxia (n = 8), and MMR was measured at 5–6 DO levels ranging from 20−160% O2 (n = 8 per DO) to define the upper and lower boundaries of the hypoxic zone (DOlim and DOcrit). SMR, MMR and the aerobic metabolic scope (AS) increased with temperature and decreased with fish size. Similar effects of temperature and size were found on DOcrit – DOlim ranges: 20–55 (15:5), 35–147 (15:12), 21–53 (60:5) and 22–89 (60:12) % O2 air saturation. Results from acute exposure tests resulted in elevated cortisol levels at 63 and 47% O2, although not statistically significant at 47% O2. Other parameters of hypoxic or hyperoxic stress (lactate, pH, osmolality, lipid peroxidation rates, catalase activity) were not affected. Results from the present study suggest that lumpfish may experience oxygen levels in sea cages that restricts metabolism, performance and induce hypoxic stress.acceptedVersio