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Viral Haemorrhagic Septicemia Virus (VHSV) Isolated from Atlantic Herring, Clupea harengus, Causes Mortality in Bath Challenge on Juvenile Herring
Get PDFViral hemorrhagic septicaemia virus (VHSV) has been demonstrated to cause high mortalities in a wide range of teleosts, farmed as well as wild. In Europe, VHSV of genotypes Ib, Id, II, and III have been detected in wild fish, including Atlantic herring Clupea harengus, but disease outbreaks have not been observed in Atlantic herring and the effects on wild stocks are not well documented. Here, we have tested two VHSV isolates from herring (genotypes Ib and III, from the western coasts of Norway and Denmark, respectively) in a challenge experiment with herring (mean weight 2.59 g, SD 0.71 g) caught on the west coast of Denmark. The Norwegian genotype Ib isolate (NO-F-CH/2009) showed an accumulated mortality of 47% compared to 6% mortality with the Danish genotype III isolate 4p168 and zero in the unchallenged control group. In both groups, we found positive rt-RT-PCR and positive immunohistochemistry of VHSV from days 6 and 8 onward. With both isolates, the organs mainly affected were the heart and kidney. The results demonstrate the susceptibility of Atlantic herring to VHSV, and both genotypes gave pathological findings in several organs. Genotype III showed a low mortality rate, and the importance of this genotype for herring is therefore not determined. Genotype Ib showed both high prevalence and mortality, and this genotype is therefore likely to have a negative effect on wild Atlantic herring stocks. Further examinations to determine how VHSV can affect wild Atlantic herring stocks are needed.publishedVersio
Long-term persistence of piscine orthoreovirus-1 (PRV-1) infection during the pre-smolt stages of Atlantic salmon in freshwater
Get PDFPiscine orthoreovirus (PRV) causes heart and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon. During salmon production cycles, HSMI has predominantly been observed after seawater transfer. More recently, better surveillance and longitudinal studies have detected occurrences of PRV-1 in freshwater broodstock farms and hatcheries. However, very little is known about the viral kinetics of PRV-1 or disease development of HSMI during these pre-smolt stages. In this study, we conducted a long-term PRV-1 challenge experiment to examine the profile of viral load, infectiousness and/or clearance in Atlantic salmon during their development from fry to parr stage. Atlantic salmon fry (mean weight: 1.1 ± 0.19 g) were infected with PRV-1 (high virulent variant) via intraperitoneal (IP) injection. The viral load reached a peak at 2–4 weeks post-challenge (wpc) in heart and muscle tissues. The virus was detected at relatively high levels in whole blood, spleen, and head kidney tissues until 65 wpc. Heart and muscle lesions typical of HSMI were clearly observed at 6 and 8 wpc but then subsided afterwards resolving inflammation. Innate and adaptive immune responses were elicited during the early/acute phase but returned to basal levels during the persistent phase of infection. Despite achieving high viremia, PRV-1 infection failed to cause any mortality during the 65-week virus challenge period. Cohabitation of PRV-1 infected fish (10 and 31 wpc) with naïve Atlantic salmon fry resulted in very low or no infection. Moreover, repeated chasing stress exposures did not affect the viral load or shedding of PRV-1 at 26 and 44 wpc. The present findings provide knowledge about PRV-1 infection in juvenile salmon and highlight the importance of continued monitoring and management to prevent and mitigate the PRV-1 infection in freshwater facilities.publishedVersio
Panel-based Assessment of Ecosystem Condition of the North Sea Shelf Ecosystem
Get PDFThe System for Assessment of Ecological Condition, coordinated by the Norwegian Environment Agency, is intended to form the foundation for evidence-based assessments of the ecological condition of Norwegian terrestrial and marine ecosystems not covered by the EU Water Framework Directive. The reference condition is defined as “intact ecosystems”, i.e., a condition that is largely unimpacted by modern industrial anthropogenic activities. An ecosystem in good ecological condition does not deviate substantially from this reference condition in structure, functions or productivity. This report describes the first operational assessment of the ecological condition of the marine shelf ecosystem in the Norwegian sector of the North Sea and Skagerrak. The assessment method employed is the Panel-based Assessment of Ecosystem Condition (PAEC1) and the current assessment has considered to what extent the North Sea and Skagerrak shelf ecosystem deviates from the reference condition2 by evaluating change trajectories.Panel-based Assessment of Ecosystem Condition of the North Sea Shelf EcosystempublishedVersio
Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder Data
Get PDFMulti-frequency echosounder data can provide a broad understanding of the underwater environment in a non-invasive manner. The analysis of echosounder data is, hence, a topic of great importance for the marine ecosystem. Semantic segmentation, a deep learning based analysis method predicting the class attribute of each acoustic intensity, has recently been in the spotlight of the fisheries and aquatic industry since its result can be used to estimate the abundance of the marine organisms. However, a fundamental problem with current methods is the massive reliance on the availability of large amounts of annotated training data, which can only be acquired through expensive handcrafted annotation processes, making such approaches unrealistic in practice. As a solution to this challenge, we propose a novel approach, where we leverage a small amount of annotated data (supervised deep learning) and a large amount of readily available unannotated data (unsupervised learning), yielding a new data-efficient and accurate semi-supervised semantic segmentation method, all embodied into a single end-to-end trainable convolutional neural networks architecture. Our method is evaluated on representative data from a sandeel survey in the North Sea conducted by the Norwegian Institute of Marine Research. The rigorous experiments validate that our method achieves comparable results utilizing only 40 percent of the annotated data on which the supervised method is trained, by leveraging unannotated data. The code is available at https://github.com/SFI-Visual-Intelligence/PredKlus-semisup-segmentation.Deep Semi-Supervised Semantic Segmentation in Multi-Frequency Echosounder DatasubmittedVersionsubmittedVersionsubmittedVersionacceptedVersio
Advice on fishing opportunities for Barents Sea capelin in 2024 — ICES subareas 1 and 2 excluding Division 2.a west of 5°W
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Effect of dietary macronutrient composition and buffering capacity on chyme characteristics and digestion kinetics in the gastrointestinal tract of freshwater rainbow trout (Oncorhynchus mykiss)
Get PDFThe aim of this study was to investigate the impact of dietary macronutrient composition and buffering capacity (BC) on chyme characteristics and digestion kinetics in freshwater rainbow trout (Oncorhynchus mykiss). Dietary macronutrient composition was altered by changing the protein-to-energy ratio (P:E) while keeping the fat-to-starch ratio constant. Dietary BC was increased by supplementation of CaCO3. The experiment lasted for 6 weeks. Fish were fed four diets having high and low P:E ratio and high and low CaCO3 level. This experiment was planned according to a 2x2x2 factorial design. The three factors were dietary P:E ratio, BC and time sampling after feeding (3 and 7 h). Chyme was collected from four gastrointestinal tract (GIT) segments (stomach, proximal, middle and distal intestine) and analysed for dry matter (DM), pH, osmolality, crude protein (CP) and mineral content. Relative water fluxes (RWF), electrolyte fluxes, kinetic of digestion and faecal digestibility (ADCs) were measured using yttrium oxide (Y2O3) as an inert marker. All chyme characteristics (including water fluxes) were not influenced by the interaction effect between dietary factors and sampling time (p > 0.05). Both dietary treatments did not affect chyme DM in the stomach. Low P:E diet increased (p < 0.001) chyme DM in all the intestinal segments. Dietary CaCO3 only affected (p < 0.05) chyme DM in the distal intestine. Low P:E diet decreased (p < 0.001) chyme pH in all GIT segments compared to the high P:E diet. Low CaCO3 diet decreased chyme pH in the proximal and middle intestine (p < 0.05) compared to the high CaCO3 diet. RWF were affected only by the dietary P:E ratio in the stomach and in the proximal intestine. Fish fed the high P:E diet had a lower water influx in the stomach and a higher water influx in the proximal intestine than fish fed the low P:E diet. Dietary P:E ratio affected electrolyte fluxes in the GIT, while no effect of CaCO3 was detected. Both dietary factors had a minimal or no effect on the kinetic of digestion in the different GIT segments, while a significant effect was present in all ADCs. Our findings suggest that dietary macronutrient composition, rather than buffering capacity, is the primary factor responsible for changes in chyme characteristics, water and ion fluxes in the GIT of freshwater rainbow trout. Furthermore, changes in dietary macronutrient composition and buffering capacity significantly affect faecal digestibility but are not reflected in digestion kinetics.publishedVersio
The Distribution of IgT mRNA<sup>+</sup> Cells in the Gut of the Atlantic Salmon (Salmo salar L.)
No full textThe newly discovered IgT+ B cell is thought to play a dominant role in mucosal immunity, but limited studies have examined its distribution in fish species, hindering our understanding of its function. This study investigated IgT and poly Ig receptor (pIgR) mRNA+ cell distribution in Atlantic salmon (Salmo salar) gut using RNAscope in situ hybridization (ISH) and assessed the effects of vaccination. The pyloric caeca, mid-intestine (first and second parts), and posterior segment in two weight stages (Group 1: avg. 153 g, Group 2: avg. 1717 g) were examined in both vaccinated and unvaccinated fish. ISH revealed more IgT mRNA+ cells in the second part of the midgut compared to other intestinal segments, as well as a higher number of positive cells in Group 2 (older fish). In line with previous findings, intraperitoneal vaccination had no significant impact on the number of IgT+ transcripts. IgT mRNA+ cells were found mostly in the lamina propria and near capillaries, while pIgR was registered in both the lamina propria and mucosa. Interestingly, vaccinated fish presented adhesions and granulomatous tissue in the peritoneum, with both IgT and pIgR mRNA+ cells. Taken together, these results suggest that the distribution of IgT mRNA+ cells in the intestine of Atlantic salmon is region-specific and is not affected by intraperitoneal vaccination but varies with fish age.publishedVersio
Recovery of algal turfs following removal
Get PDFAs a consequence of the increasing human footprint on the environment, marine ecosystems are rapidly transforming into new configurations dominated by early-successional and weedy life forms. Algal turfs, in particular, are emerging as a common and widespread configuration of shallow temperate and tropical reefs, and are predicted to transform reef dynamics and ecosystem services. Restoration is an increasingly used approach to mitigate these transformations, with turf removal being proposed as a tool to shift back the competitive balance and facilitate the recovery of initial species, such as forest-forming seaweeds. Yet, our practical understanding of turf recovery trajectories following removal is limited, and removal success may be hindered by strong feedback mechanisms that reinforce turf dominance once turfs are established. Here we investigate the recovery of algal turfs and their properties (mean height, turf biomass and sediment load) to experimental clearance across six turf-dominated reefs at ca. 9 m in subtropical western Australia. Turf cover, mean height, and sediment loads exhibited a rapid recovery following experimental clearing, with all experimental sites reaching pre-clearing turf conditions between 28 and 46 days. This response was mostly driven by the growth of filamentous turf species, whose cover exhibited a positive relationship with sediment load, and are well-known to rapidly recover after disturbance. Turf abundance and turf properties remained relatively constant for the remaining experimental period. Our results suggest that clearing turfs creates only a small time window for recovery of seaweed forests, which limits the effectiveness of turf clearing as a restoration tool. System-specific quantitative evidence on the recovery capacity of turfs may thus be necessary to guide restoration initiatives and develop decision support systems that account for the risks, feasibility, and costs and benefits of restoring turf-dominated systems to previous configurations.publishedVersio
Assessments of epidemic spread in aquaculture: comparing different scenarios of infectious bacteria incursion through spatiotemporal hybrid modeling
Get PDFThe sustainable development of the aquaculture sector is at risk due to the significant challenges posed by many emerging infectious diseases. While disease prevention and control measures are becoming increasingly critical, there is a dearth of studies on the epidemiological aspects of disease transmission in aquatic ecosystems. This study aims to forecast the spread of a bacterial disease between fish farms in two regions, Romsdalsfjord in Norway and Gujwa in South Korea by applying a DTU-DADS-Aqua spatiotemporal hybrid simulation model. The simulation model assessed the pattern of disease transmission between fish farms under different degrees of transmission power based on the distance between farms (ScalingInf), host susceptibility (RelSusceptibility), the origin site of disease, and the capacity of culling fish. The distance between fish farms was found to have significant associations with disease transmission. In most simulation conditions, the disease transmission between different bay management areas (BMAs) was not evident in Romsdalsfjord. In the Guwja region, where there are relatively narrow distances between fish farms, the spread of infectious disease was greatly affected by ScalingInf. The impact of RelSusceptibility on disease transmission patterns is a critical factor to consider in simulation modeling. When RelSusceptibility ranges from 0.5–1, there is little impact on the likelihood of disease transmission. Conversely, lower ranges (0.2 and 0.05) of RelSusceptibility result in a significant decrease in the area affected by the spread of disease. Eradication measures could control the patterns of infectious disease transmission, but the effectiveness of the depopulation strategy can be dramatically changed depending on the geographical environment. In conclusion, through a comparative analysis of the disease transmission and management scenarios, this study demonstrates the potential use of existing simulation models in predicting the spread of infectious diseases under different epidemiological circumstances and quarantine actions.publishedVersio