1,721,031 research outputs found
Investigating the presence of Tetracapsuloides bryosalmonae in River Sandvikselva by eDNA analysis
Full text linkTetracapsuloides bryosalmonae is a myxozoan parasite that poses a threat to salmonid fish populations leading to development of the potential lethal Proliferative Kidney Disease (PKD). The presence and effects of T. bryosalmonae has been studied through many surveys in Europe and in Norway with traditional methods and eDNA analysis over the last decades.
Optimizing study design in eDNA analysis is important to reduce detection errors and optimize detection reliability in both sampling and analysis stages. The advantage of using eDNA in ecological studies is that it is a non-invasive method, compared to the invasive sampling and killing the host to detect a potential hidden parasite. The myxozoan parasite is primarily found in rivers and lakes inside their salmonid and bryozoan hosts, where the host morbidity is often exacerbated by climate change and warmer temperatures.
This master-thesis aim to investigate River Sandvikselva for the presence of T. bryosalmonae by eDNA analysis during the summer months 2023. Water sampling was done using a Peristaltic pump and an enclosed filter to sample 10 L of water. For DNA extraction a protocol for isolation of DNA from water-filter to eDNA analysis, and a modified Qiagen Blood and Tissue-kit was used. To detect T. bryosalmonae qPCR was used targeting the 18S rDNA.
T. bryosalmonae presence was detected in River Sandvikselva in station 1 and station 2, the two stations in the lower part of the watercourse. In station 1, four out of four samples tested positive in Juli and August, whilst in station 2 only one of four samples tested positive suggesting that T. bryosalmonae has been established in the lower part of River Sandvikselva. Additionally, the results highlight a low sensitivity that may have contributed to limiting the detection rate in the upper stations
The battle against the introduced pathogenic monogenean Gyrodactylus salaris in Norwegian Atlantic salmon rivers and fish farms
Full text linkThe introduced salmonid ectoparasite Gyrodactylus salaris has been detected on Atlantic salmon in 53 Norwegian rivers and in 39 Norwegian fish farms. In affected rivers, the mortality of Atlantic salmon juveniles is very high, estimated to a mean of 86%. G. salaris has been considered one of the biggest threats to wild Norwegian Atlantic salmon stocks. With various measures, the authorities have reduced the potential for further spread of the parasite to new rivers and fish farms, and G. salaris has been eradicated from 43 rivers and all fish farms. Furthermore, the eradication process is almost completed in five affected rivers located at the Norwegian west coast, while preparations for the eradication in the remaining five rivers in the southeastern part of Norway have begun. The goal of Norwegian management is to eradicate the introduced pathogenic G. salaris strains from all occurrences in Norway. In fish farms, the parasite has been removed by mandatory slaughter of infected fish. In rivers, G. salaris has mostly been removed by killing all the fish hosts with rotenone. The indigenous genetic Atlantic salmon stocks are re-established after eradication of the parasite. New methods are developed using chemicals that kill the parasite without killing fish in the rivers. Norwegian authorities have so far used more than NOK 1.5 billion on research, monitoring and combating G. salaris. However, the benefits are considered many times greater than the spending. Without control measures, G. salaris would likely have spread to new Atlantic salmon rivers where the same catastrophic outcome had to be expected. The Norwegian authorities seem to meet the goal in their long-term work to halt the spread of G. salaris and to eradicate the parasite in affected rivers.publishedVersio
Distribution of the gill parasite Discocotyle sagittata (Monogenea: Polyopisthocotylea) in parr of Atlantic salmon Salmo salar and sea trout S. trutta in Norwegian rivers
Full text linkThe monogenean gill parasite Discocotyle sagittata is reported from parr of Atlantic salmon Salmo salar and sea trout S. trutta in the anadromous part of 86 out of 223 Norwegian rivers. The prevalence in each river varied from 1.5% to 88.9%. This study has significantly increased our knowledge about the occurrence of this salmonid parasite in Norway. Most likely, D. sagittata has a much wider distribution all over the country and probably also occur in numerous inland lakes, rivers and streams. ectoparasite, occurrence, salmonids, freshwater, NorwaypublishedVersio
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Påvisning av infeksjoner hos pukkellaks Oncorhynchus gorbuscha ved bruk av HT-qPCR
Full text linkMo, T.A., Karlsson, S. & Fossøy, F. 2025. Påvisning av infeksjoner hos pukkellaks Oncorhynchus gorbuscha ved bruk av HT-qPCR. NINA Rapport 2532. Norsk institutt for naturforskning.
I juli 2023, ble 20 pukkellaks fanget i en fiskefelle i munningen av Syltefjordelva på nordsiden av Varangerhalvøya i Finnmark, mens 20 laks og 10 pukkellaks ble fanget i to kilenøter i Varangerfjorden. Ulike vevsprøver fra hver fisk ble analysert for forekomst av 47 ulike infektive organismer ved hjelp en spesiell PCR-maskin som kan analysere opptil 9.216 qPCR- reaksjoner (96 x 96) per kjøring. Totalt ble det påvist 14 ulike infektive organismer hos pukkellaks og laks. Seks infektive organismer ble påvist hos begge fiskearter, mens fire bare ble påvist i pukkellaks og fire bare ble påvist i laks. Store antall pukkellaks kan bidra til å øke smittepresset av ulike infektive organismer til villaks, sjøørret og sjørøye i havet og i elvene, men også til regnbueørret og oppdrettslaks i merder langs norskekysten.Mo, T.A., Karlsson, S. & Fossøy, F. 2025. Detection of infective organisms in pink salmon Oncorhynchus gorbuscha using HT-qPCR. NINA Report 2532. Norwegian Institute for Nature Research.
In July 2023, 20 pink salmon were caught in a fish trap at the mouth of the River Syltefjord on the north side of the Varanger Peninsula in Finnmark, while 20 Atlantic salmon and 10 pink salmon were caught in two bag-nets in the Varanger Fjord. Different tissue samples from each fish were analysed for the presence of 47 different infective organisms using a special PCR machine that can analyse up to 9,216 qPCR (96 x 96) reactions per run. In total, 14 different infective organisms were detected in pink salmon and Atlantic salmon. Six organisms were detected in both fish species, while four were only detected in pink salmon and four were only detected in Atlantic salmon. Large numbers of pink salmon can contribute to increased infection pressure of various infectious organisms to wild salmon, sea trout and sea char in the ocean and in rivers, but also to rainbow trout and farmed salmon in cages along the Norwegian coast.publishedVersio
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