Salmon Farming Research Articles

Risk Assessment of Harmful Algal Blooms in Salmon Farming: Scotland as a Case Study

This study explored harmful algal bloom (HAB) risk as a function of exposure, hazard and vulnerability, using Scotland as a case study. Exposure was defined as the fish biomass estimated to be lost from a bloom event, based on the total recorded annual production. Hazard was estimated from literature-reported bloom events. Vulnerability was calculated from records of the number of employees (2020), as an estimate of aquaculture-based employment. The dinoflagellate Karenia mikimotoi was identified as the HAB species with the highest frequency of reported bloom events in Scotland, with variable spatial and temporal reports, but environmental and climatological variables regulating these events are currently unknown. The Shetland Islands region exhibited the highest combined HAB risk, with the highest scores in all three components. Vulnerability was particularly important to overall risk within an island setting, where a larger proportion of the population was dependent on aquaculture. The analysis demonstrated the potential to evaluate the economic and social consequences of HAB events on the aquaculture industry. As fish-killing HABs and fish health impacts are likely under-reported, more transparent reporting of events and related fish health and physiological consequences is recommended for a more quantitative application of this approach.

Methylation of foreign DNA overcomes the restriction barrier of Flavobacterium psychrophilum and allows efficient genetic manipulation.

Bacterial cold-water disease (BCWD) caused by Flavobacterium psychrophilum is a problem for salmonid aquaculture worldwide, and current control measures are inadequate. An obstacle in understanding and controlling BCWD is that most F. psychrophilum strains resist DNA transfer, thus limiting genetic studies of their virulence mechanisms. F. psychrophilum restriction enzymes that destroy foreign DNA were suspected to contribute to this problem. Here, we used F. psychrophilum DNA methyltransferases to modify and protect foreign DNA from digestion. This allowed efficient conjugative DNA transfer into nine diverse F. psychrophilum strains that had previously resisted DNA transfer. Using this approach, we constructed a gene deletion mutant that failed to cause disease in rainbow trout. Further genetic studies could help determine the molecular factors involved in pathogenesis and may aid development of innovative BCWD control strategies.

Infectious agent release and Pacific salmon exposure at Atlantic salmon farms revealed by environmental DNA

The potential risk posed by infectious agents (IAs) associated with netpen aquaculture to wild fishes is determined based on the “release” of IAs from netpens into the environment, the “exposure” of the wild fish to those released agents, and the “consequence” for wild fish experiencing infection by those agents. Information available to characterize these three factors is often lacking, and the occurrence of transmission from aquaculture to wild fish as well as potential consequences of such transmission are difficult to observe. In this study, we utilized environmental DNA (eDNA) to characterize the release of dozens of IAs from, and exposure of Pacific salmon to, Atlantic salmon aquaculture. We combined these factors with the consequence of infection, as determined by the literature, to identify IAs that may pose a risk to wild salmon exposed to aquaculture in British Columbia, Canada. Over an 18-month period, eDNA samples were collected from seven active and four inactive netpen aquaculture sites in the Broughton Archipelago, BC. A meta-analytical mean across 22 IAs showed that the odds of IA detection at active sites was 4.3 (95% confidence interval = 2.3:8.1) times higher than at inactive sites, with 11 IAs in particular demonstrating a pattern consistent with elevated release. Oncorhynchus tshawytscha was the only Pacific salmon species presenting eDNA detections more likely to occur around and within active netpens relative to inactive sites. After considering the evidence of negative consequences of infection (from previous literature) in tandem with release model results, we determined that Tenacibaculum maritimum, Tenacibaculum finnmarkense, Ichthyobodo spp., and Piscine orthoreovirus are potential risks to Pacific salmon exposed to marine netpen aquaculture. These IAs, and others demonstrating patterns consistent with release but with insufficient prior research to evaluate the consequences of infection, require further studies that identify the factors influencing the intensity of release, the spatial extent of release around netpens, and the prevalence of infection in wild fish within known distances from netpens.

Функционирование фитопланктона в Кондопожской губе Онежского озера в условиях садкового выращивания форели

The Kondopogskaya Bay of Lake Onego is under the influence of anthropogenic pressure due to the inflow of wastewater from a pulp and paper mill (the upper part) and trout farms (the central part). The primary production characteristics (photosynthesis, chlorophyll a, specific rate of photosynthesis, assimilation numbers) of the bay ecosystem during the “outbreak” of phytoplankton number and biomass in August 2021 are assessed. It is proved that the photosynthesis rate in the bay was determined by small diatoms during the research period. Diatom plankton cells with a volume of less than 600 µm accounted for 80-90% of the number of Bacillariophyta, the dominant group of the community. The photosynthesis values (150-330 µg/l•day) did not exceed the limits of oligo-mesotrophic ecosystems. The specific rate of photosynthesis (0.4-1.2 day–1) and daily assimilation numbers (22-40 µg C/µg Chl) were also temperate and did not indicate strong biogenic water pollution. It was revealed that the low content of chlorophyll a in phytoplankton biomass (0.13-0.39%) was mainly determined by a small number of productive green algae. The share of this phytoplankton group in the community biomass did not exceed 26%, in the number – 11%. At the same time, phytoplankton biomass (2.1-5.7 mg/l) and chlorophyll a concentrations (5.1-9.8 µg/l) reached values typical of meso-eutrophic ecosystems. Comparing the results of the study with long-term photosynthesis data showed that the trophic state of the central part of the bay, where large trout farms are located, has not changed. Long-term data on phytoplankton biomass indicate an increase in the trophic status of the central part of the bay at the present time. The inconsistency of the trophy level in terms of quantitative and functional indicators of phytoplankton may indicate the initial stage of eutrophication of the central part of the Kondopogskaya Bay as a result of the activities of trout farms.

QTL mapping provides new insights into emamectin benzoate resistance in salmon lice, Lepeophtheirus salmonis

BackgroundThe salmon louse (Lepeophtheirus salmonis) is a parasite of wild and farmed salmonid fish, causing huge economic damage to the commercial farming of Atlantic salmon (Salmo salar) in the northern hemisphere. The avermectin emamectin benzoate (EMB) is widely used for salmon delousing. While resistance to EMB is widespread in Atlantic populations of L. salmonis, the molecular mechanisms of resistance remain to be elucidated. The aim of the present work was to obtain insights into potential EMB resistance mechanisms by identifying genetic and transcriptomic markers associated with EMB resistance.ResultsCrosses were performed between EMB-susceptible and -resistant L. salmonis, sourced from two parental strains isolated in Scotland, producing fully pedigreed families. The EMB susceptibility of individual parasites was characterised using time-to-response bioassays. Parasites of two families were subjected to double digest restriction site-associated DNA sequencing (ddRAD-seq) for simultaneous discovery of single nucleotide polymorphisms (SNPs) and genotyping. Data analysis revealed that EMB resistance is associated with one quantitative trait locus (QTL) region on L. salmonis chromosome 5. Marker-trait association was confirmed by genotyping assays for 7 SNPs in two additional families. Furthermore, the transcriptome of male parasites of the EMB-susceptible and -resistant L. salmonis parental strains was assessed. Among eighteen sequences showing higher transcript expression in EMB-resistant as compared to drug-susceptible lice, the most strongly up-regulated gene is located in the above QTL region and shows high homology to β spectrin, a cytoskeleton protein that has roles in neuron architecture and function. Further genes differentially regulated in EMB-resistant lice include a glutathione S-transferase (GST), and genes coding for proteins with predicted roles in mitochondrial function, intracellular signalling or transcription.ConclusionsMajor determinants of EMB resistance in L. salmonis are located on Chromosome 5. Resistance can be predicted using a limited number of genetic markers. Genes transcriptionally up-regulated in EMB resistant parasites include a β spectrin, a cytoskeletal protein with still incompletely understood roles in neuron structure and function, as well as glutathione S-transferase, an enzyme with potential roles in the biochemical defence against toxicants.

“Consumers’ Preferences Toward Farmed Salmon in China: Integrating Sensory and Choice Experiments”

ABSTRACTChina's growing demand for farmed salmon is apparent, with the country importing 190 thousand tonnes valued at over $1.12 billion in 2023. In response, the Chinese government allowed rainbow trout to be labelled and sold as salmon starting in 2018, bridging the gap between domestically produced trout and imported Atlantic salmon. This study aimed to explore how country‐of‐origin information influences Chinese consumers' sensory perceptions and willingness to pay (WTP) for salmon. Using a within‐subject design with two evaluation rounds (blind and informed) we combined hedonic liking where Chinese consumers rated three salmon samples (from Norway, Chile, and China) with a discrete choice experiment. The results indicated that under the blind taste test, Chinese consumers found no significant difference in sensory preference between domestic rainbow trout and imported Atlantic salmon from Norway and Chile. However, when informed of the product origins, consumer preferences shifted in favor of Norwegian and Chilean Atlantic salmon. Furthermore, consumers' WTP for salmon was unaffected by the country of production unless provenance was disclosed, at which point the origin significantly influenced their preferences. Ecolabels, price, overall liking, education, frequency of aquatic food consumption, and prior experience with salmon were also found to impact WTP for salmon. These insights offer valuable insights for salmon producers/importers/marketers to customize their approaches in response to consumer preferences, refine product positioning, and seize upon opportunities within the competitive salmon market in China.

The changes of the transit denudation in the river basin systems of the Eastern Carpathians

Two river basins were chosen for the research. Both of them are monitored by water levels, water discharge and suspended sediments runoff: the Oriava River (left tributary of the Opir River, the gauging station – Sviatoslav) and the Bystrytsia River (right tributary of the Dnister River, the gauging station – Velyka Ozymyna). Both river basins have similar catchment area, morphometric parameters, but different forestry coefficients and hydro-climatic conditions. By the research the relations between the water discharge, precipitation and suspended sediments runoff have been analyzed. The water discharge dynamics features testify about difference in the morphometric conditions of the river beds. The matching of the year precipitation and water discharges testifies about determinative role of the precipitation irregularity in the surface runoff forming. The mean annual suspended sediments runoff modules in the Bystrytsia catchment 2.3 times larger than in the Oriava catchment. But this data is not enough to conclude about lesser transit denudation and slope erosion in the Oriava basin. Therefore, with the aim of preliminary assessment of the relations between the analyzed parameters and influence of different factors including human activities the series of twin graphs for many years dynamics of the parameters. The differences in sediments granulometry of the two river systems have been ascertained. The disturbed equidistance between the graphs of testifies on some factors influences which is more characteristic for the Bystrytsia river than Oriava. This fact concords with the conclusions of the scientists concerning relatively higher level of man-made affection of the Bystrytsia River basin. Ascertaining of these factors and their quantitative assessment are the perspective task for the next research stages. The investigations also confirm the determinative influence of the granulomentric composition of sediments on the relations between the water discharge and suspended sediments runoff in the researched river systems. Since the portion of the smallest fractions of the suspended sediments is considerably bigger in the abounding in water years, this fact confirms the conclusion about high level slope erosion in such years. Absence of the fractions more than 0.5 mm in the suspended sediments load in the Oriava River may be caused by the cascade of the dams and ponds of the trout farm in its main river course. At the same time it can partly explain the higher parameters of the suspended sediments runoff in the Bystrytsia (Velyka Ozymyna) in comparison to the Oriava (Sviatoslav). To confirm such conclusions it is necessary to match and analyze the granulomentric composition of the not only suspended sediments, but also bottom ones and their transition through the river bed. Key words: river system; river catchment; water discharge; suspended sediments runoff; Bystrytsia River; Oriava River.

A governability lesson for the Blue Economy: the collapse of mobile salmon aquaculture in the Norwegian coastal zone

Inspired by governability and evolutionary governance theory, this paper studies innovative aquaculture technologies that aim to contribute to the transition toward a sustainable blue economy. By tracing path, inter-, and goal dependencies, we explore a case related to developing new production systems in the Norwegian salmon aquaculture industry. As further development using conventional production systems is deemed unsustainable, the government has incentivised technological innovation to alleviate environmental and spatial pressures limiting industry expansion. We describe the work behind enrolling one innovative technology into the coastal governance system. As we find, there are conflicts between the conditions in governance that technological innovations depend on for realisation versus the conditions the governance system depends on for governability. Through our relational approach, we display how innovation challenges governability and that achieving Blue Economy objectives may require considerable political and administrative reorganisation of the existing governance setup.

In situ infestation of sea trout Salmo trutta with salmon louse Lepeophtheirus salmonis reveals parasite-induced behavioral modifications.

In areas with high densities of salmon farming, spillover of the ectoparasitic salmon louse Lepeophtheirus salmonis poses a major threat to wild anadromous salmonids. By combining experimentally salmon louse infestation (mean ± standard deviation = 0.25 ± 0.25 lice g-1 fish) with acoustic telemetry, we studied the behavior of wild first-time migrating sea trout Salmo trutta (n = 58, fork length = 138-204 mm) from late June to September in a marine area with naturally low infestation pressure. We observed that a similar proportion of sea trout from the control and exposed groups returned to fresh water both temporarily and permanently. However, sea trout from the control group spent nearly twice the amount of time in the fjord before first freshwater detection compared to exposed individuals (32 vs. 17 days), and statistical models indicated a dose-response of louse burden on the timing of freshwater return. This effect was combined with evidence of negative impacts of salmon louse burden on overall marine residency. Sea trout predominantly utilized waters within their natal fjord during the marine migration, with exposed fish spending significantly more time close to their home river than sea trout from the control group. In summary, the behavioral modifications caused by salmon lice could reduce individual marine growth, increase long-term mortality, and ultimately harm recruitment at the population level.

Dietary inclusion of black soldier fly, cricket and superworm in rainbow trout aquaculture: impacts on growth and nutrient profiles

Abstract Inclusion of fishmeal and fish oil in aquafeeds is unsustainable, prompting the need for alternative protein and lipid sources. This study evaluates the impact of diets incorporating defatted black soldier fly larvae (Hermetia illucens), adult cricket (Gryllodes sigillatus) and superworm (Zophobas morio) on the growth performance, nutrient digestibility, nutrient retention efficiency, fatty acid and amino acid profiles of juvenile rainbow trout (Oncorhynchus mykiss). Juvenile trout (100.5 ± 0.6 g; mean ± SD) were fed one of four diets: a control diet with 20% fishmeal, and three experimental diets containing a total of 15% defatted black soldier fly meal, full-fat adult cricket meal, or full-fat superworm meal, with partial replacement of fishmeal and fish oil. Growth performance and body indices were unaffected by dietary treatments. Whole carcass content and retention efficiency of protein were higher in fish fed the control and superworm diets compared to those on cricket and black soldier fly diets. Despite reduced retention efficiency of leucine, phenylalanine, glutamic acid, and serine, carcass amino acid contents were not affected by dietary treatment. Fatty acid retention efficiency was greater in fish on the black soldier fly diet, though overall lipid content was consistent across diets. Notably, lauric acid and myristic acid levels were elevated in the black soldier fly group, while linoleic acid was higher in fish fed the superworm and cricket diets. Phosphorus retention improved significantly with the black soldier fly treatment, yet nitrogen retention was reduced. These findings suggest that insect meals can partially replace fishmeal and fish oil in trout diets without compromising growth or fatty acid composition.

18S rRNA Metagenomic Analysis of Nodular Gill Disease in Swiss Rainbow Trout (Oncorhynchus mykiss).

Nodular gill disease (NGD) is a serious proliferative gill condition that affects farmed salmonids, particularly in Europe. While the cause of NGD remains unknown (and maybe multifactorial), various amoebae are often isolated from the gills of affected fish and can in some cases be seen associated with lesions by histopathology. The present study aimed to quantify the abundance of different amoeba species directly from the gills of rainbow trout affected by NGD and healthy controls. An 18S rRNA amplicon metagenomic approach was employed to profile the diversity and abundance of micro-eukaryotes (including amoebae) while suppressing the amplification of host DNA using a salmonid-specific C3 spacer blocking primer. The 18S rRNA metagenomics approach identified a diversity of micro-eukaryotes on the gills of rainbow trout, including the phylum's Amoebozoa, Diatomea, Platyhelminthes and Ciliophora. Rainbow trout clinically affected by NGD had a significantly higher abundance of a specific sequence (zOTU2) classified as Vannella sp. compared to healthy controls. A quantitative PCR assay was then developed and validated which accurately quantified the abundance of this Vannella sp. sequence from a NGD outbreak in a Swiss rainbow trout farm. Additional PCR and Sanger sequencing analysis of the zOTU2 sequence demonstrated that this sequence is most likely derived from Vannella mustalahtiana. Our study highlights the potential role of Vannella mustalahtiana in NGD in Switzerland and further describes a specific and validated diagnostic PCR assay for accurate detection of this Vannella species.

Identifying multiple configurations in global innovation system (GIS): lessons from the salmon farming industry

ABSTRACT The global innovation system (GIS) approach has until now focused on defining industries by a single GIS configuration at a given time. However, by analysing 739 innovation projects in the Norwegian global salmon farming industry, we find that the four ideal GIS configurations can be identified simultaneously. We argue that this is because we refer to an industry with a large diversity of innovation projects generating different resources along varied scales of interaction. Our analysis is based on text analysis of descriptive documents and interviews about innovation projects. With this information, we built four GIS configurations that illustrate how actors, networks and institutions form and are connected through different types of subsystems. The purpose is to understand why some actors have diverse priorities when participating in different types of innovation projects within the same industry and suggest relevant policy ideas.

Stakeholder perceptions of the Norwegian salmon farming industry and its future challenges

Aquaculture has emerged as the fastest growing sector in global food production, with salmon farming in the lead. Norway is responsible for over half of the world salmon production, but its industry faces significant challenges which must be addressed to achieve sustainability. One key issue is the lack of a unified understanding among stakeholders of how production affects the environment and intersects with the interests of other users. Given this context, this present study aims to understand the diverse perspectives of different groups of stakeholders regarding the expansion challenges faced by the Norwegian salmon farming industry. We assessed environmental, socio-economic, operational, and regulatory aspects, highlighting areas of agreement and disagreement among stakeholders using Q-methodology. Our results reveal four distinct stakeholder groups, two of which reveal polarized views, while the other two present more balanced opinions. We believe that our findings facilitate enriched dialogues among stakeholders and provide insights into the management of the industry, while addressing the dilemma of ensuring sustainability amid pressures for production growth.

Hydrobiological and Geochemical Responses to Trout Cage Aquaculture in Lake Ecosystem

This study investigates the seasonal dynamics and interrelationships between geochemical and hydrobiological parameters in lake ecosystems impacted by fish cage farming in Lake Ladoga, Russia. Environmental conditions at three trout farms were assessed, focusing on water and sediment quality as well as benthic and zooplankton communities. For each farm, two categories of sampling sites were designated: cage sites and reference sites located 100–600 m away from the cages. Fieldwork was carried out across four seasons in 2023: February, June, August, and November. The findings indicate that intensive fish feeding results in significant organic waste accumulation beneath trout cages, altering the composition and abundance of planktonic and benthic organisms. The organic matter content in sediments beneath the cages during periods of intensive feeding was found to increase 2–5 times compared to the reference sites. In winter, accumulated organic matter in the sediments underwent mineralization, bringing hydrobiological indicators closer to the reference values. The geochemical and hydrobiological parameters analyzed in this study serve as valuable indicators for developing ecological monitoring approaches in freshwater cage aquaculture.

Evaluating the Impact of Black Soldier Fly (Hermetia illucens) Larvae Meal on Growth Efficiency and Feed Utilization in Rainbow Trout (Oncorhynchus mykiss) Juvenile

Aims: Black Soldier Fly (BSF) larvae meal is a promising alternative protein source in aquafeed, offering high nutritional value and essential amino acid profiles like fishmeal. Nepalese Rainbow trout (Oncorhynchus mykiss) farming currently relies on imported shrimp meal, presenting economic and ecological challenges. The focus of this research was to examines the potential of BSFL meal to replace the shrimp meal in trout feed. Place and Duration of Study: Fisheries Research Station (FRS), Trishuli Nepal, between May 1 to August 7, 2023. Methodology: A feeding trial was conducted using 750 healthy Rainbow trout (mean individual body weight 5.39±0.55 g) randomly divided into five experimental groups, each having three replicates. The control diet contained no BSFL meal (CON), while experimental diets replaced 25% (BSF25), 50% (BSF50), 75% (BSF75), and 100% (BSF100) of shrimp meal with BSFL meal. Fish were raised in flow-through raceway tanks (300L) and fed twice daily until satiation. The growth efficiency parameters were measured. Results: The results demonstrated that diets with 25-50% BSFL meal substitution (B25, B50) significantly enhanced growth efficiency compared to the control, reflected in higher final body weight and weight gain, and improved feed conversion ratios (P<0.05). Conversely, higher replacement levels (75% and 100%) negatively impacted growth, possibly due to increased chitin content affecting digestibility. Statistical analysis confirmed the optimal BSFL inclusion range for growth efficiency, with specific growth rates peaking in the B50 group. Conclusion: In conclusion, BSFL meal can effectively replace 25-50% of shrimp meal in rainbow trout feed, offering a viable and sustainable protein source for trout farming in Nepal. This substitution could reduce dependency on imported shrimp, promoting more sustainable practices.

Integrated miRNA-seq and functional analyses reveal the regulatory role of sha-miR-92a_L + 2R + 4 via targeting vegfaa in rainbow trout (Oncorhynchus mykiss) responding to acute hypoxia and reoxygenation stress

BackgroundHypoxia negatively affects the behavior, growth, reproduction and survival of fish, causing serious economic losses to aquaculture. Rainbow trout (Oncorhynchus mykiss), an important economic fish worldwide, belongs to a hypoxia-sensitive fish species, however, little is known about the regulatory mechanism of microRNAs (miRNAs) under hypoxia stress.ResultsRainbow trout were subjected to hypoxia stress for 3 h (H3h_L), 12 h (H12h_L), 24 h (H24h_L) and 3 h reoxygenation (R3h_L) to systemically evaluate the changes of miRNA expression profiles in liver, and functions of sha-miR-92a_L + 2R + 4 were investigated. We found 17, 144, 57 and 55 differentially expressed (DE) miRNAs in the H3h_L vs. control (N_L), H12h_L vs. N_L, H24h_L vs. N_L and R3h_L vs. N_L comparisons, respectively. Enrichment analysis revealed that the targets of DE miRNAs were significantly enriched in HIF signaling pathway, VEGF signaling pathway, FoxO signaling pathway and glycolysis/gluconeogenesis. Through miRNA-mRNA interaction and weighted gene co-expression network analysis (WGCNA), five key DE miRNAs (sha-miR-92a_L + 2R + 4, ssa-miR-128-3p, ssa-miR-101b-3p_R + 1, ola-miR-199a-5p_R + 2 and tni-miR-199_1ss18CG) were identified, which can target at least two hypoxia-responsive genes, such as vegfaa, ho, glut1a and junb. Functional analysis found that sha-miR-92a_L + 2R + 4 directly regulated vegfaa expression by targeting its 3′-UTR, overexpression of sha-miR-92a_L + 2R + 4 significantly decreased vegfaa expression in rainbow trout liver cells, while opposite results were obtained after transfection of sha-miR-92a_L + 2R + 4 inhibitor. Furthermore, overexpressed sha-miR-92a_L + 2R + 4 promoted rainbow trout liver cell proliferation and inhibited apoptosis.ConclusionThis study deepens our understanding of the crucial roles of miRNAs under hypoxia stress in rainbow trout. These results can contribute to devise strategies for improving rainbow trout survival rate and aquaculture production during hypoxia stress and help speeding up the selective breeding of hypoxia-tolerant rainbow trout.

Commensal and Pathogenic Bacteria Associated with Farmed Rainbow Trout (Oncorhynchus mykiss Walbum) and Aquaculture Environment

The bacterial microflora associated with farmed rainbow trout (Oncorhynchus mykiss Walbaum) and its aquaculture environment was characterized. The counts of commensal, indicator and pathogenic bacteria were determined and bacterial colonies were characterized. The mean mesophilic counts were 4.5 log CFU g -1 and 7.6 log CFU g -1 in skin with muscle and intestine respectively. Significantly high densities of faecal coliform, E. coli and Enterococci was detected in pond sediment, fish intestine and feed when compared to pond water and trout tissues. A total of 110 randomly selected isolates from TSA were identified and characterized. Of the mesophiles, 70–75% were aerobic Gram-negative bacteria, both motile and non-motile, and members of the Enterobacteriaceae family. The skin microflora of trout was dominated by Gram-negative aerobic rods belonging to Enterobacteriaceae, Aeromonadaceae, Pseudomonas/ Shewanella, Moraxella, Acinetobacter and Flavobacterium. Psychrotrophic bacterial isolates of the genera Pseudomonas, Morganella, Hafnia were identified in trout. Pathogenic bacteria such as Clostridium botulinum, Yersinia enterocolitica could not be detected. However, Aeromonas hydrophila, A. veronii biovar sobria, A. veronii biovar veronii were prevalent in farmed trout. Presence of bacterial pathogens in the trout farm envisages a strict hygienic handling and processing of fish from such culture systems for ensuring public health safety.

Salmon Aquaculture in Chile: Production Growth and Socioeconomic Impacts

Salmon Aquaculture in Chile: Production Growth and Socioeconomic Impacts

Increased Liver Size and Dysfunction, Ionoregulatory Disturbance and Opportunistic Infections in Atlantic Salmon (Salmo salar) at Low Temperatures: A Case Study

ABSTRACTIn recent lab‐based experiments, some post‐smolt Atlantic salmon (Salmo salar) held at 3°C for 5 weeks exhibited a range of clinical signs. They became lethargic and swam at the water's surface, developed ulcers to the head and jaw (clinical signs similar to tenacibaculosis in Norwegian salmon aquaculture) and had fin erosion, and this was associated with significant mortalities. In addition, when fish with ‘early’ and ‘advanced’ stages of these different clinical signs were further examined, their livers were found to be large, pale and friable. Fish with this aetiology also had elevated aspartate aminotransferase levels (indicative of liver damage), elevated plasma [Na+], [Cl−] and osmolality (indicating osmoregulatory impairment), low glucose levels (likely limiting metabolic responses to maintain homeostasis) and high circulating cortisol levels (∼100 ng/mL). This suite of physiological disturbances is very similar to that observed in a condition referred to as ‘Winter Syndrome’ or ‘Winter Disease’ (WS/WD) in cultured gilthead sea bream (Sparus aurata) and other fish species. Thus, it appears that WS/WD described here for the first time in Atlantic salmon, alone or in combination with opportunistic infections, results in lipid deposition in the liver, compromising liver function and osmoregulatory capacity, and metabolic collapse that ultimately results in significant losses.

Status quo or giant ambitions? Norwegian Salmon farming SMEs' innovation responses to environmental regulations

Due to strict environmental regulations, the salmon farming industry needs to innovate to remain competitive. Despite the growing interest in how regulations impact innovation, few studies within the field of aquaculture have addressed the balancing act between tight environmental regulations and small and medium-sized enterprises' (SMEs') innovations for continued competitiveness. Here, SMEs refer to firms with less than 250 employees. To examine the innovation responses of firms, this paper applies an in-depth case study of four SMEs in the Norwegian salmon farming industry. We identify four innovation responses influenced by existing and anticipated regulations. These responses vary in terms of levels of innovation (incremental and radical), as well as ambitions and proactiveness towards innovations. When environmental regulations are uniformly imposed on all companies, smaller firms bear a disproportionate burden from these governmental regulations compared to their larger counterparts, particularly in their capacity to access regulatory incentives motivating radical innovation. However, our findings show that despite these constraints, some small firms pursue radical innovations, contrasting earlier studies on environmental regulations and innovation suggesting larger firms being the ones pursuing radical innovations in response to regulations. This study provides valuable insights for practice and policy regarding the regulatory regime of the Norwegian salmon farming industry and how and why different firms adapt to changing regulatory landscapes.