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Arctic charr (Salvelinus alpinus) farming in southern Norway
Get PDFArctic charr (Salvelinus alpinus) is a stenothermic cold-water fish with a circumpolar distribution. The species features large variations in life history, as populations are anadromous, riverine or lake dwelling. It occurs in various different morphs, which differ in physical traits, such as body size, head shape, and mouth position. The ecological niches of different morphs exhibit great variation as well, e. g. in terms of feeding ecology. Arctic charr has potential as a cultured species, and interest in Arctic charr farming existed since the 1970s. The global production of Arctic charr in aquaculture was between 6000 and 10 000 tonnes in 2013, with all the largest producers located in northern Europe. Arctic charr is suitable for aquaculture, as it grows rapidly at low temperatures, and tolerates high stocking density. Its high fillet yield and amenability to niche markets are also advantageous. However, Arctic charr aquaculture is a relatively small industry, which has made slow progress during its development. Some of the main problems are connected to obtaining viable eggs and juveniles in terms of egg quality, fertilisation rates, and survival through first feeding. There have also been challenges connected to variable growth and flesh pigmentation, early maturation, and marketing. Despite the large volumes of freshwater available in Norway, freshwater fish farming in general, and Arctic charr farming in particular have remained small industries here. One underlying reason are strict environmental regulations connected to freshwater aquaculture in Norway. Parasites may cause harm to Arctic charr aquaculture by reducing growth rates and marketability, as well as causing mortalities in fish held in cages in freshwater. There is little information available on freshwater parasites in southern Norway, as well as parasites threatening Arctic charr aquaculture.
The aim of this thesis is to identify challenges, and propose solutions to problems connected to freshwater aquaculture of Arctic charr in southern Norway. As a general problem in Arctic charr aquaculture, pre-hatch survival has been investigated by reviewing relevant literature about brood-stock management, fertilisation, and egg rearing in aquaculture. A common disinfection protocol for eggs featuring chemical disinfection with formalin before the eyed stage, and hand-picking during the eyed stage, was re-examined. The protocol was tested on fish from a local population in Vestfold and Telemark County. Four different treatments were tested, formalin treatment before the eyed stage only, hand-picking during the eyed stage only, a combination of formalin treatments and hand-picking, and one untreated control group. The hatching percent of these four treatments was compared using a two-way ANOVA. Both formalin treatments and hand-picking increased the proportion of hatched larvae. Hand-picking was more effective, likely because of its timing during the eyed stage. The use of formalin during the entire incubation period is advised until more information on the dynamics of water mould infections is available. Such information allows timing the application of chemical treatments to times of higher infection risk.
To successfully produce offspring of Arctic charr in aquaculture, summer holding temperatures of the brood-stock should be kept low (< 12 °C). Results on the dietary fatty acid composition and its influence on egg survival remain inconclusive. Extensive knowledge has been gained on the timing of spawning, and its manipulation using photoperiod, temperature and hormone treatments. Year round spawning is possible in cultured Arctic charr, and the synchronisation of spawning is important for good egg quality. Suitable routines for fertilisation and egg incubation are being developed, and important factors are the identification of ripe females before spawning, “dry” fertilisation in ovarian fluid, and low incubation temperatures (< 8 °C). There are numerous studies on egg quality parameters, that identify e.g. egg size as important. Egg size is also correlated to female age up to six years. However, not all studies confirm egg size as a suitable quality parameter. Energy density is shown to be more variable in smaller eggs, and may be a better egg quality parameter. Not much information is available on sperm quality parameters, but sperm quality has been identified as limiting factor for reproductive success.
To test conditions for Arctic charr aquaculture in the region, parasites were identified in a southern Norwegian lake, and factors determining their abundance were identified. The lake is located in Telemark and Vestfold County, in a different watercourse than the population of Arctic charr for the formalin experiment. Macro-parasites were identified, and their abundance was modelled in relation to age, length, weight, δ13C, δ15N, C/N-ratio, location, season, and sex in negative binomial generalised linear models. The most prevalent parasites in the investigated host species were determined by the habitat of the host. Arctic charr was the most pelagic species investigated, followed by European whitefish (Coregonus lavaretus) and European perch (Preca fluviatilis), according to stable isotope signatures. The abundance of parasites were most often increasing with increasing age or length of the host, and short-lived parasites exhibited seasonal variations.publishedVersio
Arctic charr (Salvelinus alpinus) farming in southern Norway
No full textArctic charr (Salvelinus alpinus) is a stenothermic cold-water fish with a circumpolar distribution. The species features large variations in life history, as populations are anadromous, riverine or lake dwelling. It occurs in various different morphs, which differ in physical traits, such as body size, head shape, and mouth position. The ecological niches of different morphs exhibit great variation as well, e. g. in terms of feeding ecology. Arctic charr has potential as a cultured species, and interest in Arctic charr farming existed since the 1970s. The global production of Arctic charr in aquaculture was between 6000 and 10 000 tonnes in 2013, with all the largest producers located in northern Europe. Arctic charr is suitable for aquaculture, as it grows rapidly at low temperatures, and tolerates high stocking density. Its high fillet yield and amenability to niche markets are also advantageous. However, Arctic charr aquaculture is a relatively small industry, which has made slow progress during its development. Some of the main problems are connected to obtaining viable eggs and juveniles in terms of egg quality, fertilisation rates, and survival through first feeding. There have also been challenges connected to variable growth and flesh pigmentation, early maturation, and marketing. Despite the large volumes of freshwater available in Norway, freshwater fish farming in general, and Arctic charr farming in particular have remained small industries here. One underlying reason are strict environmental regulations connected to freshwater aquaculture in Norway. Parasites may cause harm to Arctic charr aquaculture by reducing growth rates and marketability, as well as causing mortalities in fish held in cages in freshwater. There is little information available on freshwater parasites in southern Norway, as well as parasites threatening Arctic charr aquaculture.
The aim of this thesis is to identify challenges, and propose solutions to problems connected to freshwater aquaculture of Arctic charr in southern Norway. As a general problem in Arctic charr aquaculture, pre-hatch survival has been investigated by reviewing relevant literature about brood-stock management, fertilisation, and egg rearing in aquaculture. A common disinfection protocol for eggs featuring chemical disinfection with formalin before the eyed stage, and hand-picking during the eyed stage, was re-examined. The protocol was tested on fish from a local population in Vestfold and Telemark County. Four different treatments were tested, formalin treatment before the eyed stage only, hand-picking during the eyed stage only, a combination of formalin treatments and hand-picking, and one untreated control group. The hatching percent of these four treatments was compared using a two-way ANOVA. Both formalin treatments and hand-picking increased the proportion of hatched larvae. Hand-picking was more effective, likely because of its timing during the eyed stage. The use of formalin during the entire incubation period is advised until more information on the dynamics of water mould infections is available. Such information allows timing the application of chemical treatments to times of higher infection risk.
To successfully produce offspring of Arctic charr in aquaculture, summer holding temperatures of the brood-stock should be kept low (< 12 °C). Results on the dietary fatty acid composition and its influence on egg survival remain inconclusive. Extensive knowledge has been gained on the timing of spawning, and its manipulation using photoperiod, temperature and hormone treatments. Year round spawning is possible in cultured Arctic charr, and the synchronisation of spawning is important for good egg quality. Suitable routines for fertilisation and egg incubation are being developed, and important factors are the identification of ripe females before spawning, “dry” fertilisation in ovarian fluid, and low incubation temperatures (< 8 °C). There are numerous studies on egg quality parameters, that identify e.g. egg size as important. Egg size is also correlated to female age up to six years. However, not all studies confirm egg size as a suitable quality parameter. Energy density is shown to be more variable in smaller eggs, and may be a better egg quality parameter. Not much information is available on sperm quality parameters, but sperm quality has been identified as limiting factor for reproductive success.
To test conditions for Arctic charr aquaculture in the region, parasites were identified in a southern Norwegian lake, and factors determining their abundance were identified. The lake is located in Telemark and Vestfold County, in a different watercourse than the population of Arctic charr for the formalin experiment. Macro-parasites were identified, and their abundance was modelled in relation to age, length, weight, δ13C, δ15N, C/N-ratio, location, season, and sex in negative binomial generalised linear models. The most prevalent parasites in the investigated host species were determined by the habitat of the host. Arctic charr was the most pelagic species investigated, followed by European whitefish (Coregonus lavaretus) and European perch (Preca fluviatilis), according to stable isotope signatures. The abundance of parasites were most often increasing with increasing age or length of the host, and short-lived parasites exhibited seasonal variations
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Seasonal variations in the use of profundal habitat among freshwater fishes in Lake Norsjø, southern Norway, and subsequent effects on fish mercury concentrations.
Get PDFThis study is based on monthly sampling of fish from an industrial water intake, located at the bottom of Lake Norsjø, at a depth of 50 m, during one year (2014). By this sampling strategy, we have obtained unique information about the seasonal use of the profundal habitat among > 15 fish species present in the lake. However, besides a very few individuals of perch (Perca fluviatilis, n = 4) and one individual of Nortern pike (Esox lucius) and brown trout (Salmo trutta L.), respectively, only Arctic char (Salvelinus alpinus), European smelt (Osmerus eperlanus) and whitefish (Coregonus lavaretus) were caught. While A. char was present in the profundal habitat all year, E. smelt were only absent in June, and whitefish was primarily present during the winter, December-March. The main reasons for searching to this poor, cold and dark habitat, are primarily predator avoidance, interspecific competition, hatching and subsequent feeding on row. The various use of the profundal habitat among fish species, have primarily been linked to age, length and weight, stomach analyses and stable isotope signatures, δ13C and δ15N, in fish muscle. By also comparing the number of gill rakers (NGR) in whitefish caught by gill nets in a nearby littoral area, we revealed two morphs of whitefish, a profundal morph (NGR = 26.5 ± 0.4) and a littoral morph (NGR = 32.0 ± 0.6). The varying degree of habitat use (profundal, pelagic, littoral) among fish species and morphs, has further been shown to have implication for the mercury (Hg) concentration in fish, as baseline Hg and fish growth differ between different lake habitats. Accordingly, these factors, besides the more classical factors as trophic position and age, are essential for Hg concentration in fish.Published versio
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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