Salmon Aquaculture Industry Research Articles

Development of an image binarization software tool for net occlusion estimations

Marine biofouling poses a set of challenges to the salmon aquaculture industry, where an accumulation of biota on pens can lead to significant net mesh occlusion. This can reduce flow rates, risking oxygen depletion. The industry currently manages this challenge through regular cleaning of nets, with sporadic manual visual estimations of net occlusion an important but time-consuming task. This study developed a simple automated desktop application to more regularly and more robustly quantify pen net occlusion caused by biofouling. This software application pre-processes and binarizes images collected from cameras currently used by the industry into water and non-water pixels. The percentage of net occlusion is then calculated from the binary image. Accurate binarization of representative images was achieved by training a deep learning network on images collected in situ. The resulting network attained a validation accuracy of 96.4 % and a mean test accuracy of 93.5 %. From the test images, 98.3 % of pixels annotated as non-water and 88.8 % of pixels annotated as water were correctly classified by the network. This automated tool has the capacity to better inform industry and create a more efficient cleaning framework based on the needs of individual pens, based on data that can be more readily obtained as compared to manual net inspections.

Current vaccination strategy against Piscirickettsia salmonis in Chile based only on the EM-90 genogroup shows incomplete cross-protection for the LF-89 genogroup

Piscirickettsia salmonis, the primary bacterial disease in Chilean salmon farming, necessitates a constant refinement of control strategies. This study hypothesized that the current vaccination strategy for SRS control in the Chilean Atlantic salmon aquaculture industry, which has been in place since 2017 (ALPHA JECT® 5.1 plus LiVac®), solely relies on vaccines formulated with the EM-90 genogroup of P. salmonis (PS-EM-90), triggering a partial cross-immunity response in fish infected with the LF-89 genogroup (PS-LF-89). Relative Percent Survival (RPS) and cell-mediated immune (CMI) response were evaluated in Atlantic salmon post-smolts vaccinated with the standard vaccination strategy but challenged with both PS-EM-90 and PS-LF-89, in addition to other vaccination strategies considering primo vaccination and booster with other commercial vaccines and the possible enhancing effects of the combination with a natural immunomodulator (PAQ-Xtract®) administered orally. The intraperitoneal (I.P.) challenge was performed after 2395°-days (DD) after the start of the immunostimulant delivery, 1905 DD after the primo vaccination, and 1455 DD after the booster vaccination. Unvaccinated fish showed 73.6 and 41.7 % mortality when challenged with PS-EM-90 and PS-LF-89, respectively. Fish infected with PS-LF-89 died significantly faster (21 days post-infection, dpi) than fish challenged with PS-EM-90 (28 dpi) (p = 0.0043) and had a higher probability of death (0.4626) than fish challenged with PS-EM-90. RPS had a significant positive correlation with the PS-EM-90 load of the P. salmonis genogroup (r = 0.540, p < 0.01) but not with the PS-LF-89 load (r = 0.155, p > 0.05). This demonstrated that the immunization strategies were more effective in lowering PS-EM-90 loads, resulting in higher survival rates in fish challenged with PS-EM-90. The current industry vaccination strategy recorded a 100 % RPS when fish were challenged with PS-EM-90, but the RPS dropped significantly to 77 % when fish were challenged with PS-LF-89, meaning that the strategy did not show complete cross-protection. But after adding PAQ-Xtract®, the RPS improved from 77 % to 92 % in fish that were vaccinated with the standard method but then challenged with PS-LF-89. The most effective vaccination strategy was based on LiVac® as primo vaccination and ALPHA JECT® 5.1 plus LiVac® as booster vaccination, with or without PAQ-Xtract®, in both PS-EM-90 (100 %) and PS-LF-89 (96 %) challenged fish. The serum concentration of anti-P. salmonis IgM did not show a correlation with the protection of immunization strategies expressed in survival. Low serum IL-12 and high serum IFNγ concentrations showed a correlation with higher bacterial loads and lower survival. Aggregate analysis showed a significant correlation between higher numbers of CD8+ cells in the head-kidney, higher fish survival, and a lower bacterial load. The immunization strategies were safe for fish and induced only mild microscopic lesions in the gut. Taken together, our results help to better understand the biological interaction between P. salmonis and post-smolt vaccinated Atlantic salmon to deepen the knowledge on vaccine-induced protection, CMI immune response, and cross-immunity applied to improve the current immunization strategy for SRS control in the Chilean salmon industry.

Exposure of female lobsters to sediments spiked with emamectin benzoate: Effects on eggs and larvae early development

The salmon aquaculture industry is an important economic activity established on both the west and east coast of Canada. To control sea lice infestations, in-feed products like emamectin benzoate (EMB) are widely used. Due to its low solubility and persistence EMB can accumulate in marine sediments and be potentially bioavailable to non-target organisms from months to years. The American lobster (Homarus americanus) is a key species in the Northwest Atlantic with high economic and ecological value. It may be exposed to therapeutants considering lobster habitats overlap with aquaculture locations requiring a better understanding of the potential impact of these therapeutants through varied pathways of exposure. In this study, we investigated the exposure of gravid female lobsters to EMB spiked sediment to mimic the likely presence of these females at aquaculture sites for a 10-day period. We completed testing by assessing EMB effects on adult molting and quality, embryo hatching rates, and larval offspring quality and larval molting. Our results show that a single, 10-day exposure of ovigerous females to EMB concentrations higher than environmentally relevant values did not affect females or their offspring.

The First Report on Saprolegnia parasitica and Neoparamoeba perurans Isolated from Atlantic Salmon (Salmo salar) Reared in Korea

This study is the first report of parasite and fungal disease separated from domestically reared Atlantic salmon in Korea; the characteristics of the pathogens were identified, and histopathological analysis was conducted. Fungal and parasitic diseases were detected in Atlantic salmon and were isolated as Saprolegnia parasitica and Neoparamoeba perurans based on morphological and genetic analysis. External symptoms observed in Atlantic salmon infected with S. parasitica include fin ulcers and hemorrhage, abdominal hemorrhage, and necrosis of the gills and gill covers. The histopathological analysis results showed necrosis, hemorrhaging, and inflammatory cell infiltration in the abdominal muscles, while only inflammatory cell infiltration was observed in the gill covers. The clinical symptoms observed in Atlantic salmon infected with N. perurans included excessive mucus secretion in the gills, a dense amoebic presence on the gill filaments, respiratory distress, and opening of the mouth and gill covers after death. Through histopathological analysis, we observed lesions in epithelial cells, characterized by the proliferation of epithelial cells and the fusion of secondary lamellae. Numerous lamellae were observed to be attached or fused with each other. To ensure the successful establishment of the Atlantic salmon aquaculture industry in Korea, it is essential to swiftly quarantine infected fish based on the morphological characteristics of S. parasitica and N. perurans revealed in this study, along with the external symptoms of Atlantic salmon infected with these pathogens. Developing disease control strategies based on the findings of this research is imperative.

Synergies of co-infecting pathogens, sea lice (Lepeophetheirus salmonis) and Moritella viscosa, are impacted by exposure order, and host response to initial infection

Sea lice infestations and winter ulcer disease caused by Moritella viscosa are two major challenges for the Atlantic salmon (Salmo salar) aquaculture industry. Despite their common tropisms for the skin/muscle, we know very little about the interaction between these two significant pathogens. The objective of this study was to elucidate the transcriptomic response of Atlantic salmon to sea louse (Lepeophtheirus salmonis) and M. viscosa under single infection and different scenarios of co-infection (i.e., first, L. salmonis and then, M. viscosa and vice versa). After exposure, sampling was performed from the infestation site as well as the adjacent area on fish skin, followed by transcriptome analysis. RNA-seq analysis revealed that infection with either L.salmonis or M. viscosa induced a significant immune response from the skin and resulted in extensive transcriptomic changes. More differentially expressed genes (DEGs) were detected at M. viscosa lesion sites compared to L. salmonis attachment sites. In addition, the effect of the infection order was evaluated. Interestingly, we found that primary infection with lice was associated with a significantly higher number of DEGs during the co-infection process on fish skin compared to the fish first infected with M. viscosa (721 and 5336 DEGs from lice attachment and M. viscosa lesion sites, respectively, vs 291 and 3601 DEGs from lice attachment and M. viscosa lesion sites, respectively). We also found that lice infection caused localized effects on the skin of Atlantic salmon, while single infection with M. viscosa caused a moderate systemic impact and inhibited the tissue repair function of the skin, leading to severe ulceration. In addition, the C-type lectin receptor signaling pathway was drastically activated at the lice attachment sites during both lice alone- and co-infections, regardless of the order of infections, and similar results were observed in M. viscosa infection at both lesion and adjacent sites, indicating that this pathway played an essential role for immunity in Atlantic salmon. A more intense inflammatory and immune response was also observed at M. viscosa lesion sites. These results will promote our understanding of the immune interactions between L. salmonis and M. viscosa during the co-infection process and provide insights for the development of preventive and treatment strategies for these pathogens in salmonid aquaculture.

An aquaculture risk model to understand the causes and consequences of Atlantic Salmon mass mortality events: A review

AbstractMass mortality events (MMEs) are defined as the death of large numbers of fish over a short period of time. These events can result in catastrophic losses to the Atlantic salmon aquaculture industry and the local economy. However, they are challenging to understand because of their relative infrequency and the high number of potential factors involved. As a result, the causes and consequences of MMEs in Atlantic salmon aquaculture are not well understood. In this study, we developed a structural network of causal risk factors for MMEs for aquaculture and the communities that depend on Atlantic salmon aquaculture. Using the Interpretive Structural Modeling (ISM) technique, we analysed the causes of Atlantic salmon mass mortalities due to environmental (abiotic), biological (biotic) and nutritional risk factors. The consequences of MMEs were also assessed for the occupational health and safety of aquaculture workers and their implications for the livelihoods of local communities. This structural network deepens our understanding of MMEs and points to management actions and interventions that can help mitigate mass mortalities. MMEs are typically not the result of a single risk factor but are caused by the systematic interaction of risk factors related to the environment, fish diseases, feeding/nutrition and cage‐site management. Results also indicate that considerations of health and safety risk, through pre‐ and post‐event risk assessments, may help to minimize workplace injuries and eliminate potential risks of human fatalities. Company and government‐assisted socio‐economic measures could help mitigate post‐mass mortality impacts. Appropriate and timely management actions may help reduce MMEs at Atlantic salmon cage sites and minimize the physical and social vulnerabilities of workers and local communities.

Insights from Hi-C data regarding the Pacific salmon louse (Lepeophtheirus salmonis) sex chromosomes.

Salmon lice, Lepeophtheirus salmonis (family Caligidae), are ectoparasites that have negatively impacted the salmon aquaculture industry and vulnerable wild salmon populations. Researchers have studied salmon lice to better understand their biology to develop effective control strategies. In this study, we updated the chromosome-level reference genome assembly of the Pacific subspecies of L. salmonis using Hi-C data. The previous version placed contigs/scaffolds using an Atlantic salmon louse genetic map. By utilizing Hi-C data from Pacific salmon lice, we were able to properly assign locations to contigs/scaffolds previously unplaced or misplaced. This resulted in a more accurate genome assembly and a more comprehensive characterization of the sex chromosome unique to females (W). We found evidence that the same ZW-ZZ mechanism is common in both Atlantic and Pacific subspecies of salmon lice using PCR assays. The W chromosome was approximately 800 kb in size, which is ∼30 times smaller than the Z chromosome (24 Mb). The W chromosome contained 61 annotated genes, including 32 protein-coding genes, 27 long noncoding RNA (lncRNA) genes, and 2 pseudogenes. Among these 61 genes, 39 genes shared homology to genes found on other chromosomes, while 20 were unique to the W chromosome. Two genes of interest on the W chromosome, prohibitin-2 and kinase suppressor of ras-2, were previously identified as potential sex-linked markers in the salmon louse. However, we prioritized the 20 unique genes on the W chromosome as sex-determining candidates. This information furthers our understanding of the biology of this ectoparasite and may help in the development of more effective management strategies.

Sustainable business model innovation, dynamic capabilities, and organizational design: Insights from Norwegian aquaculture

AbstractFirms must increasingly grapple with complex sustainability challenges. Business model innovation is needed to achieve radical sustainability improvements. Recent research highlights the interrelatedness between business model innovation, dynamic capabilities, and organizational design, calling for empirical work to better illuminate these relationships. These connections are relevant in sustainability contexts, where organizational barriers and drivers have been shown to either facilitate or hinder the development of dynamic capabilities for sustainable business model innovation (SBMI). This paper presents a case study of an emergent low‐carbon offshore aquaculture value chain in Norway to illuminate the importance and roles of these organizational factors. Based on our analysis, we identify those barriers and drivers present in the Norwegian salmon aquaculture industry; add to the body of theory around organizational design, dynamic capabilities, and SBMI; and offer insights for practitioners in the aquaculture sector aiming to develop dynamic capabilities for SBMI.

Improved 18S rDNA profiling of parasite communities in salmonid tissues using a host blocking primer

Sensitive screening of eukaryotic communities in aquaculture for research and management is limited by the availability of technologies that can detect invading pathogens in an unbiased manner. Amplicon sequencing of 18S ribosomal DNA (rDNA) provides a potential pan-diagnostic test to overcome these biases; however, this technique is limited by a swamping effect of host DNA on low abundance parasite DNA. In this study, we have adapted a host 18S rDNA blocking assay to amplify eukaryotic DNA from salmonid tissue for amplicon sequencing. We demonstrate that effective salmonid 18S rDNA blocking enables sensitive detection of parasite genera in salmonid gill swabs. Furthermore, 18S rDNA amplicon sequencing with host blocking identified enriched pathogen communities in gill swabs from Atlantic salmon suffering from severe clinical gill infections compared to those exhibiting no clinical signs of gill infection. Application of host 18S rDNA blocking in salmonid samples led to improved detection of the amoebic parasite Neoparamoeba perurans, a parasite of significant threat to the Atlantic salmon aquaculture industry. These results reveal host 18S rDNA blocking as an effective strategy to improve the profiling and detection of parasitic communities in aquaculture species. This assay can be readily adapted to any animal species for improved eukaryotic profiling across agricultural and veterinary industries.

Direction of salmon aquaculture development in the world

The growth of the world's population implies the search for alternative sources of nutrition. One such area is the development of aquaculture. The world aquaculture, as well as other branches of agriculture, has gone through stages of its formation from farming by primitive methods to use of modern technologies. Salmon farming occupies an important place in industrial fish farming, and the volume of farmed products is increasing every year. This review summarises the main milestones in the salmon aquaculture industry, describes the trends that have guided breeding programmes and shows the genetic approaches that have been used in fish farming. The introduction of genetic methods in salmonid fish breeding depends on the level of development of the countries where fish farms are located. Abroad there is a great experience of investment policy aimed at creation and introduction of projects up to the final (operational) stage of introduction of molecular genetics methods into salmon breeding, including the use of genomic selection. While in Russia the concept of genetic improvements in aquaculture is only being discussed. In this review an important place is given to generalisation of the accumulated material on genetic methods of salmonid fish research, as well as directions of application of genetic markers in salmon farming. The issues of searching for candidate genes, quantitative trait loci (QTL) associated with gaining muscle weight and fish resistance to diseases are discussed. The directions and ways of solving breeding problems are shown. Intensive development of scientific approaches to aquaculture development abroad is a vector for setting goals to expand business investment in the development of molecular genetic approaches to salmonid fish breeding in Russia.

Meta-analysis of GWAS for sea lice load in Atlantic salmon

Sea lice (Caligus rogercresseyi) are ectoparasites that cause significant production losses in the salmon aquaculture industry. Atlantic salmon (Salmo salar) is an important salmonid species for the aquaculture industry and highly susceptible to sea lice infestation. Sea lice load has been shown to be a polygenic trait, controlled by several quantitative trait loci (QTL) with small to medium effects. To improve the detection of QTL associated with sea lice load, we imputed single nucleotide polymorphism (SNP) data from medium- to high-density and conducted genome-wide association studies (GWAS). The imputation from 50 K to 600 K SNP genotypes was performed on 6144 fish from four different populations, which were challenged against sea lice. A metaGWAS was carried out for lice count, lice density, and log-transformed lice density. We identified two genomic regions highly associated with sea lice load on chromosomes (ssa) 3 and 12. Important functional candidate genes are mucin-16-like (ssa3), filamentous-growth-regulator 23-like (ssa3) and fibroblast growth factor receptor-like 1 (ssa12). Several other genes found here suggest that tissue repair, cytoskeletal modification and immune response may play an important role in the genetic variation of sea lice load. Our results confirm the highly polygenic architecture of sea lice load and provide novel insights into the genomic regions and candidate genes underlying the genetic variation for this trait in Atlantic salmon.

‘Finprint’ technopolitics and the corporatisation of global food governance

AbstractOur concern in this paper is the environmental ‘footprinting’ of food and its role as a source of technopolitical power in global food governance. Our case is the highly industrialised farmed salmon sector which currently generates metrics and carefully curated visualisations to promote this fish as a more sustainable and ‘climate friendly’ protein relative to animal protein produced on land. We show how these metrics and visualisations depend on an industrial production and measurement infrastructure. Significantly, this infrastructure and the metrics that it generates is being promoted as a ‘climate smart’ solution to small‐scale and extensive aquaculture in the Global South. Salmon aquaculture industry proposals for the transfer of technology from salmon farming to global aquaculture are explicitly articulated in global food governance and other institutional spaces. While there may be frictions in the transfer of salmon aquaculture's infrastructure of measurement to aquaculture in the Global South, our analysis suggests that environmental footprinting of food—and its associated measurement infrastructure—may be an emerging source of technopolitical power in increasingly corporatised global food governance systems.

The effects of SLICE®- and ivermectin-contaminated sediment on avoidance behaviour and oxygen consumption in marine benthic invertebrates

Pest management strategies to reduce sea lice infestations in the salmon aquaculture industry include in-feed treatments with ivermectin (IVM) and SLICE® (active ingredient [AI] emamectin benzoate [EMB]), which can result in local contamination of the environment. These compounds partition to sediments, have moderate persistence, and may pose a risk to non-target benthic organisms. The sub-lethal effects of EMB, IVM and a combination of both (EMB/IVM) on the benthic amphipod Eohaustorius estuarius and polychaete Nereis virens at environmentally relevant sediment concentrations were examined in subchronic exposures (28-30-d). E. estuarius avoided sediment containing >50 μg/kg IVM alone and in combination with EMB. N. virens avoided sediment with >50 μg/kg IVM and >0.5 μg/kg EMB/IVM and exhibited impaired burrowing and locomotory behaviour with both treatments. Oxygen consumption was significantly decreased in E. estuarius (up to 50% compared to controls) and increased in N. virens (by ∼ 200%) when exposed to EMB, IVM and EMB/IVM at concentrations <5 μg/kg. IVM, SLICE® and combination exposures at environmentally relevant concentrations caused adverse effects in E. estuarius and N. virens which could significantly alter organism fitness near salmon aquaculture operations.

Large sardine resource discovered off south-eastern Australia: Potential risks, challenges and benefits of establishing a new fishery

This paper documents the discovery of a large sardine (Sardinops sagax) resource off South-eastern Australia. We use information from three ichthyoplankton surveys for jack mackerel to apply the Daily Egg Production Method (DEPM) to the South-eastern sardine stock. Mean daily egg production was estimated from survey data. Spawning area was estimated from the surveys and using a habitat suitability model to predict presence/absence of eggs in unsurveyed areas. Spawning biomass was calculated using adult parameters from the adjacent Southern stock. The spawning biomass in the area surveyed was 262,564 t (95% CI 125,670–326–438 t). Habitat modelling using a conservative threshold suggested that the total spawning biomass was 346,388 t (95% CI 143,936–548,840 t). These results suggest this stock has the capacity to sustain an annual catch of several tens of thousands of tonnes, which is considerably larger than the recent catch of < 2500 t. Our findings provide further evidence that opportunities exist to increase Australia’s fisheries production. Risks and challenges associated with establishing a new large-scale sardine fishery, including bycatch and ecological impacts, and opposition from conservation groups and recreational fishers are discussed. We also outline the potential socio-economic and environmental benefits, including the use of marine protein and oil from a sustainable local source with low environmental impacts as an input to the AU$1.3B Tasmanian salmon aquaculture industry. We emphasize the need to adopt a precautionary approach to developing a new fishery and the critical importance of conducting comprehensive surveys to confirm our findings and inform ongoing management.

Policies to promote breeding for lice-resistant salmon: Incentives designed for resilient and sustainable growth in aquaculture.

Sea lice represent a persistent and growing problem, challenging the resilience and growth of the salmon aquaculture industry. In this Norwegian case study, we studied and discuss how the absence of policy instruments directed at stimulating breeding for lice resistance (LR) might be explained. We found well-documented opportunities for selection progress for LR. Hence, breeding on LR appears with an untapped potential. We discuss how market-based, legal, institutional and interest-based factors can explain the absence of policy instruments stimulating LR breeding. Methodologically, we obtained data from document and literature studies and interviews with key players (salmon breeders, farmers, nongovernmental organizations (NGOs) and governmental bodies in Norway). First, LR is a polygenic trait, which makes it poorly suited for patenting. Furthermore, if only a small proportion of fish farmers choose seeds with higher LR, other operators can easily take on the free-rider role because they will not suffer from reduced gain in growth performance as a result of a much stronger emphasis on LR in the breeding goal. The market is thus not expected to stimulate stronger selection for LR in Norwegian salmon breeding. Second, neither genetic engineering (e.g., gene editing), still struggling with consumer acceptance, nor the uncertainty associated with possible changes in the Norwegian Gene Technology Act stimulate investment in LR via, for example, CRISPR technology. Thirdly, public policy instruments in their entirety have targeted other types of innovations against salmon lice, and none have so far been used to stimulate breeding companies to emphasize LR more strongly in their breeding programmes. From a political point of view, it seems that breeding has been left to the market and the private sector. However, neither the NGOs nor the public seem to be aware of, or pay significant attention to, the breeding potential to improve LR and fish welfare. Fragmented management of the aquaculture sector can camouflage the close ties between political and business interests. The industry is hesitant to invest significantly in long-term breeding targets such as significantly higher genetic LR. This may strengthen the assumption that strong economic interests will reduce the role of science in knowledge-based management. As farmed salmon are increasingly being exposed to stressful delousing treatments, mortality and associated welfare problems have increased significantly. For instance, large fish die more often from cardiomyopathy syndrome (CMS), resulting in growing demand for CMS-resistant salmon. This gives rise to a paradoxical situation: increasing treatments with high mortality and fish welfare issues in farmed salmon, while the lice threat to wild salmon persists.

Dissolved Algal Toxins along the Southern Coast of British Columbia Canada.

Harmful algal blooms (HABs) in coastal British Columbia (BC), Canada, negatively impact the salmon aquaculture industry. One disease of interest to salmon aquaculture is Net Pen Liver Disease (NPLD), which induces severe liver damage and is believed to be caused by the exposure to microcystins (MCs). To address the lack of information about algal toxins in BC marine environments and the risk they pose, this study investigated the presence of MCs and other toxins at aquaculture sites. Sampling was carried out using discrete water samples and Solid Phase Adsorption Toxin Tracking (SPATT) samplers from 2017-2019. All 283 SPATT samples and all 81 water samples tested positive for MCs. Testing for okadaic acid (OA) and domoic acid (DA) occurred in 66 and 43 samples, respectively, and all samples were positive for the toxin tested. Testing for dinophysistoxin-1 (DTX-1) (20 samples), pectenotoxin-2 (PTX-2) (20 samples), and yessotoxin (YTX) (17 samples) revealed that all samples were positive for the tested toxins. This study revealed the presence of multiple co-occurring toxins in BC's coastal waters and the levels detected in this study were below the regulatory limits for health and recreational use. This study expands our limited knowledge of algal toxins in coastal BC and shows that further studies are needed to understand the risks they pose to marine fisheries and ecosystems.

Biochemical composition of Hediste diversicolor (OF Müller, 1776) (Annelida: Nereidae) reared on different types of aquaculture sludge

IntroductionSustainable growth of the salmon aquaculture industry is highly dependent on the availability of new feed resources as well as improved management and utilization of waste streams from production. Polychaetes are capable of recapturing and recycling valuable biomolecules contained in aquaculture sludge and at the same time constitute a possible resource for aquafeeds.Material and methodsIn this study, the potential of Hediste diversicolor (OF Müller, 1776) to recover nutrients and energy contained aquaculture sludge was evaluated. Hereby, the effect of two different diets, smolt and post-smolt sludge, and different feed levels on polychaete growth, and biochemical and elemental composition was assessed.Results and discussionSurvival ranged from 80-90%, independent of treatment. Specific growth rates at the highest feed levels were significantly higher than at the lowest feed levels and growth was not affected by the type of diet. Similarly, total lipid and total fatty acid content of polychaetes were positively correlated with feed level while the type of diet had a limited effect. Fatty acid composition of polychaetes reflected feed levels: in both diet groups, polychaetes at lower feed levels showed a higher percentage of saturated fatty acids; monounsaturated fatty acids increased with increased feed supply for smolt sludge-fed group and polychaetes fed post-smolt sludge showed increased polyunsaturated fatty acid content with increasing feed levels. Neither diet nor feed levels affected protein content and amino acid composition of polychaetes. In conclusion, H. diversicolor could be successfully cultivated on both smolt and post-smolt sludge and was rich in proteins and lipids as well as essential amino and fatty acids. The species can be considered a promising candidate for recycling valuable nutrients from different types of side streams salmon aquaculture.

Exploring public perceptions and expectations of the salmon aquaculture industry in Norway: A social license to operate?

The aquaculture industry depends on the support of society to maintain and extend its activities. In Norway and elsewhere, such support cannot be taken for granted. The public has diverse expectations of the industry, and attitudes toward the industry are shaped by experiences with industry production, how the benefits and disadvantages of aquaculture production are distributed in society, and the kind and degree of information about industry issues that is available. This paper investigates public attitudes toward the Norwegian salmon aquaculture industry through a nationwide survey (N = 1183). The results reveal that the public is generally positive toward the industry; they tolerate and even accept it. However, respondents had more negative perceptions regarding the environmental consequences of aquaculture production and the fairness of the distribution of economic gains. Although the industry was seen as acceptable, respondents were more reluctant in terms of welcoming production growth, which points to a need for improvement if production increase is to be realized and the industry is to be able to meet society's expectations. Our results reveal differences in attitudes between respondents living in areas with and without aquaculture, which suggest that proximity to industry is, in general, positively related to industry perceptions. However, these differences vary in size, and it can be assumed that there are substantial contextual variances within the group of respondents living in aquaculture municipalities. One potentially important influence on attitudes is related to how industry is perceived to be financially significant in a particular local community. Further research could supply these data to offer a more detailed understanding of contextual variations and thus expand on the present results that explore public perceptions and expectations of the salmon aquaculture industry.

Aquaculture sustainability: Global challenges need local actions

Aquaculture sustainability: Global challenges need local actions

First detection of Cyclopterus lumpus virus in England, following a mortality event in farmed cleaner fish

Lumpfish are used routinely as cleaner fish to delouse farmed Atlantic salmon (Salmo salar) and are often translocated globally. In September 2021, an aquaculture production business in Dorset, England experienced considerable mortalities in consignments of lumpfish (Cyclopterus lumpus) imported from Norway. Following suspicion of infection with Cyclopterus lumpus virus (CLuV) by a veterinarian, commercial testing provided presumptive confirmation of a CLuV infection using reverse-transcription real-time polymerase chain reaction (RT-rPCR). Affected fish were later resampled by the Centre of Environment, Fisheries, and Aquaculture Science, Fish Health Inspectorate for screening of CLuV by RT-rPCR, and confirmation by conventional RT-PCR and sequence analysis. Additional samples were tested using isolation of viruses on cell cultures, bacteriology, histopathology, and PCR/rPCR techniques to investigate whether other pathogens of concern to the salmon aquaculture industry were also present. All samples tested negative for the presence of viral haemorrhagic septicaemia virus, infectious haematopoietic necrosis virus , nervous necrosis virus, infectious pancreatic necrosis virus , infectious salmon anaemia virus , ranavirus, and salmonid alphavirus. Four pools of ten samples tested positive by RT-rPCR for CLuV (Ct values between 19 and 29) and was confirmed using conventional RT-PCR. Sequence analysis showed that amplicons shared a 99.63 % match with the published sequences for CLuV. The CLuV has only recently been reported in aquatic animals and its full impact is not yet known. To the best of our knowledge this is the first report of CLuV in England.