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Temperature Dependent Depuration of Norovirus GII and Tulane Virus from Oysters (Crassostrea gigas)
Get PDFRaw oysters are considered a culinary delicacy but are frequently the culprit in food-borne norovirus (NoV) infections. As commercial depuration procedures are currently unable to efficiently eliminate NoV from oysters, an optimisation of the process should be considered. This study addresses the ability of elevated water temperatures to enhance the elimination of NoV and Tulane virus (TuV) from Pacific oysters (Crassostrea gigas). Both viruses were experimentally bioaccumulated in oysters, which were thereafter depurated at 12 °C and 17 °C for 4 weeks. Infectious TuV and viral RNA were monitored weekly for 28 days by TCID50 and (PMAxx-) RT-qPCR, respectively. TuV RNA was more persistent than NoV and decreased by 1.0 log10 at this time. For RT-qPCR there was no detectable benefit of elevated water temperatures or PMAxx for either virus (p > 0.05). TuV TCID50 decreased steadily, and reductions were significantly different between the two temperatures (p 3.0 log10 were observed at 17 °C, while at 12 °C reductions did not exceed 1.9 log10. The length of depuration also had an influence on virus numbers. TuV reductions increased from 4.0 log10 after 4 weeks. This implies that an extension of the depuration period to more than seven days, possibly in combination with elevated water temperatures, may be beneficial for the inactivation and removal of viral pathogens.publishedVersio
Distribution and biomass estimation of Antarctic krill (Euphausia superba) off the South Orkney Islands during 2011-2020
Get PDFAntarctic krill is a key species in the Southern Ocean and subject to the most extensive fishery in the Antarctic. The Norwegian Institute of Marine Research has conducted acoustic-trawl monitoring of krill off the South Orkneys annually since 2011 in collaboration with the krill fishing industry. Average krill biomass within the 60000 km2 survey area ranged from 1.4 to 7.8 million tonnes in the period 2011–2020, strongly supporting that this is among the regions in the Scotia Sea with consistently highest krill densities. There were no significant (p ≈ 0.18, non-parametric Mann–Kendall test) monotonic trends in estimated krill biomass over the 10 years. The highest krill densities were associated with the shelf edge and submarine canyons on the north side of the South Orkneys. Our comparison with the CCAMLR 9.3% reference exploitation rate suggests that management of the krill fishery in the South Orkneys region is precautionary. The monitoring is run on fishing vessels, so e.g. acoustic frequencies applied could not always be in compliance with the standard CCAMLR methodology. Estimated deviance in krill backscatter when comparing 38 kHz to the standard 120 kHz ranged from −1.1% to 12.8%. Our results show that industry-based surveys are cost-efficient approaches to high-quality monitoring of krill.publishedVersio
Resistant calcification responses of Arctica islandica clams under ocean acidification conditions
Get PDFOcean acidification (OA) directly impacts marine calcifying organisms including ecologically and commercially important shellfish species such as Arctica islandica (A. islandica). To test whether documented growth resilience of A. islandica to OA is a general response across ages and populations or a function of adaptation to local habitat, we cultured juvenile and adult clams collected from an environment with little pH variation under four pH levels (7.5, 7.7, 7.9, and 8.1) for three months and integrated our understanding with relevant literature. The average shell growth over the experiment among all (69) individuals was 57 ± 55 μm, and there were no statistically significant differences in growth among pH treatments, including the control treatment, despite the general growth rate differences between juveniles and adults. Our results show that A. islandica can maintain its shell growth even in aragonite undersaturated (Ω < 1) conditions (0.65 and 0.83 for pH 7.5 and 7.7 treatments, respectively), supporting the hypothesis that resistance to OA conditions is likely a generalized response across populations. Although the present results show A. islandica can maintain their shell growth under short-term OA, long-term impacts of OA on A. islandica shell growth and other physical parameters including shell density and microstructure are still needed to better assess the sustainability of A. islandica in a more acidified future and to provide guidance on managing this important shellfish stock.publishedVersio
Oljeforurensning i Mossesundet etter oljelekkasjen fra vraket av MS Nordvard 2022-2023
Get PDFDet ble i mars 2023 samlet inn prøver av overflatesediment (0-2 cm) fra ti lokaliteter, og av blåskjell (Mytilus edulis) fra under vannoverflaten fra 11 lokaliteter i Mossesundet i forbindelse med gjentakende oljeutslipp fra vraket av MS Nordvard. Det ble funnet lite eller ingen oljeforurensning i blåskjellene. I sedimentene er det funnet betydelig hydrokarbonforurensning i indre del av Mossesundet, opptil Miljødirektoratets tilstandsklasse V (svært dårlig tilstand) for PAH16. Forurensningen er høyest nærmest byen, og har i hovedsak andre kilder enn olje, knyttet til forbrenning. Det vurderes derfor at påvirkning av det nylige oljeutslippet i 2022-2023 på det marine miljøet i området har vært ubetydelig.Oljeforurensning i Mossesundet etter oljelekkasjen fra vraket av MS Nordvard 2022-2023publishedVersio
Fish community dynamics in a coastal no-take marine protected area compared to a harvested area before and after protection from fishing
Get PDFAn ecosystem's ability to maintain key functions during environmental change is largely determined by its biodiversity. We compared fish species composition, richness, diversity, catch per unit effort (CPUE), and fish size between a 1.5 km2 no-take marine protected area (MPA) and a nearby fished area on the southern Norwegian coast annually for one decade (2011–2021), including before-protection status. In total, >26 thousand fish representing 31 species were sampled using a beach seine. No significant effect of protection was detected on either species richness, diversity, or evenness. For selected species of small-bodied intermediate predators, there was a significant decline in mean body size in the MPA area compared to the fished area, indicative of a response to protection involving trophic interactions. No significant effect of the MPA was detected on either CPUE or body size of Atlantic cod (Gadus morhua), a top predator mainly captured at the juvenile stage by our sampling. The limited responses seen in this study may be linked to the small size of the MPA compared to the dispersal and movement capabilities of species such as the cod.publishedVersio
Effects of airgun discharges used in seismic surveys on development and mortality in nauplii of the copepod Acartia tonsa
Get PDFSeismic surveys are conducted worldwide to explore for oil and gas deposits and to map subsea formations. The airguns used in these surveys emit low-frequency sound waves. Studies on zooplankton responses to airguns report a range of effects, from none to substantial mortality. A field experiment was conducted to assess mortality and naupliar body length of the calanoid copepod Acartia tonsa when exposed to the discharge of two 40-inch airguns. Nauplii were placed in plastic bags and attached to a line at a depth of 6 m. For each treatment, three bags of nauplii were exposed to one of three treatments for 2.5 h: Airgun array discharge, a boat control, or a silent control. After exposure, nauplii were kept in filtered seawater in the laboratory without food. Immediate mortality in the nauplii was approximately 14% compared to less than 4% in the silent and boat control. Similarly, there was higher mortality in the airgun exposed nauplii up to six days after exposure compared to the control treatments. Nearly all of the airgun exposed nauplii were dead after four days, while >50% of the nauplii in the control treatments were alive at six days post-exposure. There was an interaction between treatment and time on naupliar body length, indicating lower growth in the nauplii exposed to the airgun discharge (growth rates after 4 days: 1.7, 5.4, and 6.1 μm d−1 in the airgun exposed, silent control, and boat control, respectively). These experiments indicate that the output of two small airguns affected mortality and growth of the naupliar stages of Acartia tonsa in close vicinity to the array.publishedVersio
Annual report on health monitoring of wild anadromous salmonids in Norway 2022 - Screening of Atlantic salmon (Salmo salar) postsmolts from Boknafjorden, Hardangerfjorden and Romsdalsfjorden for viral infections
Get PDFThe Institute of Marine Research has investigated the prevalence of infectious salmon anaemia virus (ISAV), salmonid alphavirus (SAV, PD-virus), piscine orthoreovirus 1 (PRV-1), piscine myocarditis virus (PMCV) and infectious pancreatic necrosis virus (IPNV) infections in migrating wild Atlantic salmon postsmolts captured in 2021 in three fjord systems located in three aquaculture production areas (PO2, 3 and 5). The fish were collected as part of the national salmon lice monitoring program in the outer parts of Boknafjord (N = 50), Hardangerfjord (N = 57) and Romsdalsfjord (N = 73) by trawling during the period May-June. SAV was detected in 2 postsmolts from Romsdalsfjord. PRV-1 was detected in 11 (6%) of postsmolts (8 from Boknafjord, 1 from Hardangerfjord and 2 from Romsdalsfjord). Low concentrations of PMCV-RNA were detected in 19 (11 %) of postsmolts (13 from Boknafjord and 6 from Romsdalsfjord). ISAV and IPNV were not detected in any of the test fish. Generally, the virus-positive fish had high Ct-values which may indicate very low virus concentrations. The results in the current report showed that migrating postsmolts from fjords had a very low occurrence of virus infections common in Norwegian aquaculture. These findings complement and corroborate our previously reported data and may suggest that prevalence virus infections in wild salmon postsmolts is not significantly influenced by the occurrence of these infections in fish farming.Annual report on health monitoring of wild anadromous salmonids in Norway 2022 - Screening of Atlantic salmon (Salmo salar) postsmolts from Boknafjorden, Hardangerfjorden and Romsdalsfjorden for viral infectionspublishedVersio
Atlantic salmon male post-smolt maturation can be reduced by using a 3-hour scotophase when inducing smoltification
Get PDFPhotoperiod regulates the occurrence of unwanted male post-smolt maturation during the production of large (>100 g) Atlantic salmon (Salmo salar) smolts. However, the optimal daylength for triggering smoltification, but not male puberty, has yet to be established. We used either continuous light (24:0 light/dark) or long days (18:6 and 21:3) after a six week “winter” zeitgeber (12:12) to induce smoltification in fish of around 120 g reared at 16 °C. The fish were sampled 1, 2, 3, and 6 weeks after the initiation of the three different photoperiod treatments (n = 153 males in total with 9–18 males/photoperiod/time point). As expected, the smoltification indicator gill Na+/K+-ATPase (NKA) was significantly (p < 0.05) elevated and peaked 2 to 3 weeks after the initiation of the different photoperiods. Pubertal males were identified in all treatments via the combined use of relative testis size and histology, plasma 11-ketotestosterone, changes in body condition, and growth rate. The total incidence of puberty was significantly higher among males on continuous light at 33% (n = 16/49) compared to 10% (6/61) and 12% (5/43) in 21:3 and 18:6, respectively. The incidence of puberty increased over time in all photoperiods, with 62% (8/13), 19% (3/16), and 38% (3/8) of the males from 24:0, 21:3, and 18:6 pubertal at week 6, respectively. The mean weight of males that went on to initiate puberty was significantly higher (13%) at the beginning of the trial compared to those that remained immature (mean weight, 127 vs 112 g, respectively), but there was no initial difference in body condition. Puberty significantly reduced gill NKA by 35% compared to immature males at week six but had no effect at earlier time-points. Photoperiod had no effect on the female GSI, and they were all considered immature. In conclusion, the incidence of male puberty during smoltification is regulated by photoperiod and leads to an earlier decline in a key indicator of seawater readiness. As such, photoperiods with a short scotophase (21:3 or 18:6) following the winter zeitgeber in a square-wave (long-short-long day) smolt regime are recommended to limit the incidence of male puberty.publishedVersio
Analysis of spatial conflicts of large scale salmonid aquaculture with coastal fisheries and other interests in a Norwegian fjord environment, using the novel GIS-tool SEAGRID and stakeholder surveys
Get PDFThe expansion of the Norwegian aquaculture industry has generated a need for balancing aquaculture with other societal interests in the coastal zone. The interactions, conflicts and synergies of different uses of a Norwegian coastal region heavily influenced by large-scale salmonid aquaculture was analyzed and mapped by means of systematic stakeholder participatory approach and a GIS-based spatial interaction analysis tool, SEAGRID. Our study focused on spatial conflicts/synergies, whereas non-spatial interactions were taken into account in order to elucidate the spatial effects. The questionnaire analysis showed that there was a large agreement across the respondents that aquaculture and fisheries compete for access to sea areas, which is also in agreement with the SEAGRID analysis. All but one of the interviewees thought that conservation issues will become more important in the future. We found that societal interests and infrastructure obstruct or displace private enterprises and economic interests, whereas environmental protection measures do so to a lesser extent; an exception are coral reefs which seem to be well protected against both fishing operations as well as new aquaculture facilities. Nature protection was not found to affect fisheries nor aquaculture to a large extent, with the exception of the single salmon fjord, which is protected from salmonid aquaculture, but otherwise open to other activities, such as fisheries, tourist fisheries and tourism in general. The restricted military areas had a limited extent, and were not viewed as a cause of conflicts. Stakeholder consultations, like our participatory GIS approach, combined with GIS-based tools for analysis of spatial conflicts/synergies may be useful in identifying areas where aquaculture production can increase with little increase in degree of conflict with fisheries, although some interactions are not strictly spatial. Our results indicated a certain degree of mistrust of management authorities since neither fishermen nor aquaculturists perceived that their own sector was given priority by management authorities, but thought the other sector was prioritized.Analysis of spatial conflicts of large scale salmonid aquaculture with coastal fisheries and other interests in a Norwegian fjord environment, using the novel GIS-tool SEAGRID and stakeholder surveyspublishedVersio
Salinity and temperature alter the efficacy of salmon louse prevention
Get PDFSeveral promising preventive tools and strategies have been developed to combat infestation of salmon in marine cages by parasitic salmon lice. While most of the prevention strategies tested have significantly reduced louse infestations in some trials, they have also had negligible impact in others. To better understand the observed performance variability a meta-analysis was conducted to examine the efficacy of physical barriers and behavior modification, the louse prevention tools with the strongest evidence base, in relation to local salinity and temperature conditions. Integrated prevention strategies which combine behavior modification with skirt barriers gave the most consistent protection, halving louse infestations through all measured environmental conditions with no negative impacts on growth or gill condition. Snorkel barriers provide the greatest potential protection from lice, with reductions of over 80% in ideal conditions when salinity is uniform throughout the water column, but are sensitive to environmental variation and accompanied by reduced growth and increased amoebic gill disease severity. Behavior modification alone did not significantly impact louse infestation, growth or gill health in any conditions. The results herein show that understanding the interrelationships between preventive tools and environmental conditions is central to optimizing tool choice and deployment strategy. Parasite prevention does not operate in a vacuum, and clear understanding of the risks and limitations of such tools is critical for them to have practical applicability.publishedVersio