Salmon Production Research Articles

The impact of varying EPA:DHA ratio on Atlantic salmon health and welfare

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential fatty acids (EFA) vital for Atlantic salmon health, growth performance, and product quality. Yet, DHA and especially EPA are in short supply as ingredients for aquafeeds. Whilst the role of EFA in salmonid nutrition has been well studied, clear guidelines for aquaculture nutrition practitioners are still missing. This article addresses this gap by testing different EPA:DHA ratios (0.15, 0.55, and 0.98) when these two EFA represent at least 10% of the total pool of fatty acids in aquafeeds. Grow-out trials revealed no differences in zootechnical performance between fish fed the different diets during the initial eight weeks before vaccination challenge, nor on the subsequent three weeks post-vaccination for fish truly vaccinated or sham vaccinated (used as control groups for each of the three diets tested). Nonetheless, the FCR of vaccinated fish was significantly higher than sham vaccinated conspecifics, but diet yielded no significant effect. The expression of most genes screened (e.g., Elongation Factor 1α (Elf-1α), Interleukin 10 (IL10), Interleukin 8 (IL8), Tumor Necrosis Factor (TNFα)) was not significantly affected by vaccination or diet, while Viperine and Mx genes were upregulated in sham vaccinated fish fed the experimental diet with an EPA:DHA ratio of 0.55. The fatty acid composition of head kidney was affected by diet, namely EPA, but not DHA. The fatty acid profile of white muscle was also significantly affected by diet, with contrasting results for EPA and DHA; EPA content was higher for fish fed diets with higher EPA:DHA ratios and DHA levels were significantly higher (peaking at 16% of the total pool of fatty acids) when fish were provided with the diet featuring the lowest EPA:DHA ratio (0.15). Interestingly, fish fed the diet with the highest EPA:DHA ratio showed a lower number of wounded fish at the end of the grow-out period post-vaccination. Despite the reduction was not statistically significant, given the severe impact of wounded fish on salmon farming productivity, our results indicate that the partial replacement of fish oil with algal oil in salmon feed contributed to achieving a balanced EPA:DHA ratio, an adequate profile of Omega-3 long chain polyunsaturated fatty acids and improved the overall health and welfare of fish. This approach creates the opportunity to increase the productivity of fish farming operations and foster a more sustainable growth of the aquaculture industry.

Hypoxia vulnerability in the salmon watersheds of Southeast Alaska

The frequency of dissolved oxygen depletion events (hypoxia) in coastal aquatic ecosystems has risen dramatically since the late 20th century, yet the causes and consequences of hypoxia for some culturally and economically important species remain poorly understood. In rivers, oxygen depletion can be caused by high densities of spawning Pacific salmon (Oncorhynchus spp.) consuming oxygen faster than can be replaced by reaeration. This process may be exacerbated when salmon densities are artificially inflated, such as when hatchery-origin salmon stray into rivers instead of returning to hatcheries. In Southeast Alaska, hatchery salmon production has increased rapidly since the 1970s, with over 553 million chum salmon (O. keta) and 64 million pink salmon (O. gorbuscha) released in 2021 alone. Straying is pervasive in streams with outlets <25 km from nearshore marine hatchery release sites. Using a previously ground-truthed mechanistic model of dissolved oxygen dynamics, we examined how water temperature and low-flow channel hydraulics contribute to hypoxia vulnerability. We then applied the model to predict hypoxia vulnerability for watersheds within 25 km of hatchery salmon release points, where straying salmon spawner densities are expected to be higher and promote dissolved oxygen depletion. Our model predicted that low-gradient stream reaches, regardless of water temperature, are the most prone to hypoxia due to low reaeration rates. Our spatial analysis determined that nearly 17,000 km of anadromous-accessible stream reaches are vulnerable to high densities of hatchery-origin salmon based on 2021 release sites. To our knowledge, this study is the first to map the spatial variation of hypoxia vulnerability in anadromous watersheds, identify habitat conditions most likely to promote hypoxia, and provide a repeatable analytical approach to identify hypoxia-prone stream reaches that can be updated as empirical data sets improve.

Norwegian Farmed Salmon: A Commodity in Need of Differentiation?

Despite much innovation and development in the Norwegian salmon industry, the focus has largely been on building volume and reducing costs. Limited attention has been paid to develop value added products and differentiation strategies in Norway to reap stable profits associated with such strategies. In depth-interviews with a supply chain containing Norwegian salmon producers, one exporter and one feed producer, industrial buyers representing two Polish processing companies and two German retailers, aimed to provide insight into why more differentiation is not happening in the Norwegian salmon industry. Results from this supply chain reveals lack of communication and asymmetric power-dependence relations between the Norwegian salmon business actors and their industrial buyers.

Data fusion and multivariate analysis for food authenticity analysis

A mid-level data fusion coupled with multivariate analysis approach is applied to dual-platform mass spectrometry data sets using Rapid Evaporative Ionization Mass Spectrometry and Inductively Coupled Plasma Mass Spectrometry to determine the correct classification of salmon origin and production methods. Salmon (n = 522) from five different regions and two production methods are used in the study. The method achieves a cross-validation classification accuracy of 100% and all test samples (n = 17) have their origins correctly determined, which is not possible with single-platform methods. Eighteen robust lipid markers and nine elemental markers are found, which provide robust evidence of the provenance of the salmon. Thus, we demonstrate that our mid-level data fusion - multivariate analysis strategy greatly improves the ability to correctly identify the geographical origin and production method of salmon, and this innovative approach can be applied to many other food authenticity applications.

How Do Alternative Protein Resources Affect the Intestine Morphology and Microbiota of Atlantic Salmon?

The availability and cost of fishmeal constitute a bottleneck in Atlantic salmon production expansion. Fishmeal is produced from wild fish species and constitutes the major feed ingredient in carnivorous species such as the Atlantic salmon. These natural stocks are at risk of depletion and it is therefore of major importance to find alternative protein sources that meet the nutritional requirements of the Atlantic salmon, without compromising the animals' health. Terrestrial animal by-products have been used in aquaculture feed, but their use is limited by the lack of several essential amino acids and consumer acceptance. In the case of plant ingredients, it is necessary to take into account both their concentration and the extraction methodologies, since, if not dosed correctly, they can cause macro- and microscopic alterations of the structure of the gastrointestinal tract and can also negatively modulate the microbiota composition. These alterations may compromise the digestive functions, growth of the animal, and, ultimately, its well-being. An updated revision of alternative protein sources is provided, with the respective impact on the intestine health in terms of both morphology and microbiota composition. Such information may constitute the premise for the choice and development of Atlantic salmon feeds that guarantee fish health and growth performance without having a significant impact on the surrounding environment, both in terms of depletion of the fish's natural stocks and in terms of pressure on the terrestrial agriculture. The sustainability of aquaculture should be a priority when choosing next-generation ingredients.

Using skin mucus for the identification of ovulation biomarkers in North American Atlantic salmon (Salmo salar)

In Maine, North American Atlantic salmon production has experienced a 20% decrease in eye-up eggs, the point of embryo development where the black eye spot is visible. The maternal endocrine environment is suggested to be an important factor for ovulation and viable embryos but needs to be further investigated. Combining new sampling matrices (skin mucus) and advanced technologies (liquid chromatography tandem mass spectrometry (LC-MS/MS)) will advance the knowledge of the endocrine status in reproductively mature North American Atlantic salmon. The objectives of this study were to 1) identify mucus as a viable matrix to measure steroid hormones, 2) quantify steroid hormone profile of North American Atlantic salmon during ovulation and 3) compare hormone profiles of salmon with high and low eye-up rates. Mucus and plasma were collected from sexually mature female North American Atlantic salmon (n = 30). A group of females were sampled pre-ovulation (n = 9) and a separate group post-ovulation (n = 21) then analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Fish collected post-ovulation were slotted into groups based on eye-up rate, fish with ≥70% eye-up rate (high eye-up, n = 5) and fish with ≤70% eye up rate (low eye-up, n = 16). In mucus allopregnanolone (p = 0.01), 11-deoxycorticosterone (p = 0.05) and 11-deoxycortisol (p = 0.01) were significantly higher after ovulation. In plasma, allopregnanolone was significantly lower after ovulation (p = 0.01 and 17α, 20β-hydroxyprogesterone was significantly elevated (p = 0.05) after ovulation. Fish with a low eye-up rate had elevated mucus concentrations of corticosterone (p = 0.02). While fish with a high eye-up rate had elevated plasma testosterone concentrations (p = 0.04). Circulating androstenedione (r = 0.46, p = 0.03) and testosterone (r = 0.47, p = 0.03) were significantly correlated with eye-up rate. Mucosal concentrations of steroid hormone correlated with circulating concentrations of related steroids and reflect changes in reproductive physiology. The significant changes in mucosal and circulating steroid concentrations of the 5α reduced pregnane, allopregnanolone suggests a role of 5α-reduced pregnanes during ovulation in North American Atlantic salmon. To our knowledge this is the first time any 5α-reduced pregnane has been reported in teleosts. Mucosal concentrations of precursor glucocorticoids significantly elevated after ovulation combined with significant correlation with hydroxylated pregnanes suggests a dual mechanism needed for ovulation between glucocorticoids and pregnanes. Additionally, glucocorticoids and androgens appear to influence the viability of fertilized eggs highlighting the need for further research into the role's multiple hormones play in both oocyte maturation and embryo viability.

Water Flow Requirements of Post-smolt Atlantic Salmon (Salmo salar L.) Reared in Intensive Seawater Flow-through Systems: A Physiological Perspective

Environmental challenges related to open sea cage production of Atlantic salmon have sparked interest in developing commercial-scale semi-closed sea systems for post-smolt Atlantic salmon (100–1000 g). Determining the mass-specific water flow required by post-smolts will largely influence the design and dimensioning of such systems. In this experiment, post-smolts were exposed to four levels of specific water flow: 0.2, 0.3, 0.4, and 0.5 L kg fish−1 min−1. All treatments involved flow-through seawater with full oxygenation, a salinity of 34‰, and a mean temperature of 9.3 °C. The stocking density was kept stable at 75 kg m−3. Water pH decreased with reduced flow, while partial pressure of carbon dioxide (pCO2) and total ammonia nitrogen (TAN) in the water increased. The increase in water CO2 was reflected in the blood with increased pCO2, HCO3−, and decreased Cl− in the lowest water flow treatment (0.2 L kg fish−1 min−1), indicating a typical regulatory response to increased water CO2 over the eight-week experimental period. No negative effects on osmoregulation, external macroscopic welfare, or performance indicators were observed, suggesting that within the time period of this experiment, post-smolts can compensate for reductions in water flow down to 0.2 L kg fish−1 min−1. However, to avoid activating and exhausting potentially energy-costly physiological regulatory mechanisms, it is suggested to keep specific water flow above 0.3 L kg fish−1 min−1 in large-scale operations with semi-closed sea systems at intermediate temperatures.

Detection of Salmonidae ingredient using mini-DNA barcoding in conjunction with a rapid visual inspection method

Using species outside Salmonidae to prepare salmon products has been widely revealed as a new type of fraud in China and other countries with less stringent labeling stipulations, highlighting the necessity to establish proper methods for rapid screening of Salmonidae ingredient. The present work selected mitochondrial Cytb gene as the target, and developed a novel mini-DNA barcoding assay to identify the salmonids ingredient in processed fish products. Results showed that the novel method is highly specific for salmonids detection and only the seven common salmonids species were successfully amplified. With the inclusion of HRM analysis, we can make an accurate differentiation of Salar salar, Oncorhynchus mykiss, and the other wild-caught Oncorhynchus species, which are deep in the scandal of species mislabeling. Moreover, a closed-tube visual detection can also be achieved by the preaddition of HNB (hydroxyl naphthol blue) and SYTO 9 in the reaction mixture, allowing an easy and rapid way to distinguish positive from negative. Finally, the novel assay was successfully applied on commercial products and the absence of salmonids ingredient indicated mislabeling with 4 commercial products. Overall, mini-DNA barcoding is a robust tool for fish species identification and the novel method is effective in screening Salmonidae ingredient.

Intestinal epigenotype of Atlantic salmon (Salmo salar) associates with tenacibaculosis and gut microbiota composition

It remains a challenge to obtain the desired phenotypic traits in aquacultural production of Atlantic salmon, and part of the challenge might come from the effect that host-associated microorganisms have on the fish phenotype. To manipulate the microbiota towards the desired host traits, it is critical to understand the factors that shape it. The bacterial gut microbiota composition can vary greatly among fish, even when reared in the same closed system. While such microbiota differences can be linked to diseases, the molecular effect of disease on host-microbiota interactions and the potential involvement of epigenetic factors remain largely unknown.The aim of this study was to investigate the DNA methylation differences associated with a tenacibaculosis outbreak and microbiota displacement in the gut of Atlantic salmon. Using Whole Genome Bisulfite Sequencing (WGBS) of distal gut tissue from 20 salmon, we compared the genome-wide DNA methylation levels between uninfected individuals and sick fish suffering from tenacibaculosis and microbiota displacement. We discovered >19,000 differentially methylated cytosine sites, often located in differentially methylated regions, and aggregated around genes.The 68 genes connected to the most significant regions had functions related to the ulcerous disease such as epor and slc48a1a but also included prkcda and LOC106590732 whose orthologs are linked to microbiota changes in other species. Although the expression level was not analysed, our epigenetic analysis suggests specific genes potentially involved in host-microbiota interactions and more broadly it highlights the value of considering epigenetic factors in efforts to manipulate the microbiota of farmed fish.

Trends in Chinook salmon spawner abundance and total run size highlight linkages between life history, geography and decline

AbstractChinook salmon (Oncorhynchus tshawytscha, Salmonidae) are foundational to social‐ecological systems of the Northeast Pacific Rim and exhibit a rich diversity of life histories including in their adult migration timing, age at critical life‐history transitions and marine feeding distributions. In recent decades Chinook have experienced declines across much of their native range; however, changes in productivity and abundance have rarely been evaluated in relation to life‐history variation. To understand trends in Chinook salmon production, and how they are related to life history, we compiled time series data from the Fraser River to the Sacramento River on total run size (pre‐fishery abundance) and escapement (post‐fishery spawner abundance) and fit time series models to estimate trends across this bioregion. Our analysis revealed that most Chinook populations are declining, with negative trends in escapement (57 of 79) and total run (16 of 23) size. Trends were most acutely negative for interior spring Chinook in the Fraser, Columbia and Snake Rivers and most populations in California. Summer and fall Chinook had mixed trends, with several summer and fall upriver bright populations in the interior Columbia and Fraser exhibiting increases in abundance from the 1990s to 2019. Our research reveals widespread declines of this important species, but local complexity in trends that are mediated by population‐level life history, migratory behaviours and watershed‐scale restoration actions. Understanding linkages between life histories and resilience should inform rebuilding efforts for Chinook salmon and highlight the need to conserve intraspecific biodiversity.

From farm sustainability to ecosystem sustainability: Exploring the limitations of farm-applied aquaculture eco-certification schemes

Aquaculture eco-certification schemes provide standards against which individual farms are assessed, and those farms that comply with eco-certification criteria receive certified status. These schemes aim to improve aquaculture sustainability, but the site-by-site approach of eco-certification can be a barrier to the inclusion of ecosystem perspectives in the evaluation of farm sustainability. However, the ecosystem approach to aquaculture demands a management approach that considers broader scale ecosystem impacts. This study explored how eco-certification schemes and processes account for potential ecosystem impacts of salmon farms. Interviews with eco-certification auditors, salmon producers, and eco-certification staff were conducted. The experience of participants and information from eco-certification scheme criteria and other eco-certification scheme documents were used to identify thematic challenges associated with the consideration of ecosystem impacts including: assessing far-field impacts, managing cumulative effects, and anticipating ecosystem risks. Results indicate that eco-certification schemes work within the limitations of farm-scale application of global eco-certification standards to address potential ecosystem impacts by: (1) including eco-certification scheme criteria that address ecosystem impacts, (2) relying on the experience, expertise, and judgement of eco-certification auditors, and (3) referencing and deferring to local regulations. Results indicate that eco-certification schemes can address ecosystem impacts to some degree, despite their site-by-site approach. The integration of additional tools while supporting the capacity of farms to apply those tools, as well as increasing transparency during compliance assessment could help eco-certification schemes shift from providing assurance of farm sustainability to providing assurance of ecosystem sustainability.

Reciprocal hybrids of Atlantic salmon (Salmo salar) x brown trout (S. trutta) confirm a heterotic response to experimentally induced amoebic gill disease (AGD)

Amoebic gill disease (AGD) affects global marine aquaculture production of Atlantic salmon, requiring costly reiterative treatment and negatively impacting fish performance and welfare. Although there has been gradual and ongoing progress in genetic selection to improve host resistance to the causative agent (Neoparamoeba perurans) there has been little focus on the response of interspecific hybrids to AGD challenge. Previous research has demonstrated that Atlantic salmon x brown trout hybrids had reduced requirement for freshwater bathing (based on gross gill signs) during chronic natural AGD exposure, yet there has been no histological or molecular evidence confirming differential host response or parasite abundance. In this study we exposed Atlantic salmon (SS), brown trout (TT) and their reciprocal interspecific hybrids (TS and ST) to a single laboratory challenge (∼700 amoebae.l−1 for 18 days) and compared the resultant infection and disease signs characteristic of AGD. Gill score was significantly higher in SS than in TT and hybrids. Copy number quantification of amoebae on gills was higher in salmon than in hybrids or trout but did not differ between hybrids and trout. Gill histopathology confirmed both an increased amoebae abundance and higher expression of host tissue reaction in SS with significantly higher percentages of lesions harboring hyperplastic lesions. Mid-parent and best-parent heterosis of resistance to N. perurans and host response (gill lesions) was confirmed but did not differ between hybrid crosses. Although limited to a single laboratory infection event, our results support previously reported observations (from natural infection/reinfection) of reduced AGD signs in trout and interspecies hybrids. We conclude that interspecies hybrids have potential to improve our understanding of salmonid resistance to amoebic branchitis and support future gene-based research toward fish disease management.

Algal oil gives control of long‐chain omega‐3 levels in full‐cycle production of Atlantic salmon, without detriment to zootechnical performance and sensory characteristics

AbstractThe levels of eicosapentaenoic (EPA) and docosahexaenoic (DHA) in salmon fillets have decreased because of the progressive replacement of fish oil (FO). This study contributes to enabling the sustainable growth of aquaculture by confirming the effects of partially or fully replacing FO with microalgal oil (AO) on growth, muscle fatty acid profiles, and muscle quality of farmed Atlantic salmon. Crucially, this is now done throughout the entire post‐smolt production cycle and up to a harvest weight of 3 kg. Three experiments were performed using fish ranging from 145 g to 3 kg and testing different diets, replacing FO up to 100%. Zootechnical performance was similar among treatments in all experiments. Changing the lipid source in the diet resulted in EPA and DHA digestibility of greater than 96%. Sensory characteristics of raw fish fillets were similar among treatments, supporting a similar sensorial experience with the replacement of FO with no impact on consumers. Overall, results confirm that the AO tested here enables the sustainable growth of Atlantic salmon aquaculture by helping to maintain a level of EPA and DHA in the fish fillets, without detriment to zootechnical performance and sensory characteristics, while simultaneously contributing to a reduced marine footprint for aquafeeds.

Welfare and survival of lumpfish (Cyclopterus lumpus) in Norwegian commercial Atlantic salmon (Salmo salar) production

Lumpfish are currently used as a part of the overall strategy for the prevention and control of sea lice in Atlantic salmon farming in Norway. Their use as biological delousers is advantageous as it exposes salmon to very little stress and injuries. However, there is a growing concern and criticism about the welfare and survival of lumpfish in salmon farms. This study monitored the welfare and survival of lumpfish from four commercial salmon farms for 6 to 12 months in 2019–2021. Environmental and production conditions were also registered. Lumpfish welfare decreased during the study period, mainly related to eye and skin injuries. Mortality rate was low in the first few months after transfer to sea, but increased thereafter. Mechanical delousing affected the welfare and survival most negatively of all monitored external parameters. Even though diseases are often pointed out as the main factor for mortality of lumpfish in sea cages, it was not the case in the present study. However, there were indications that diseases are more likely to occur when lumpfish is already weakened by other factors such as mechanical delousing. One to two thirds of lumpfish were assessed as underweighted or emaciated at all time during the monitoring period, suggesting that the nutritional requirements of lumpfish are not fully met in sea cages.

Possibilities for the Technology Improvement of Soft-Salted Sockeye Salmon Fillet with a Prolonged Shelf Life without Preservatives Use

Pacific salmon (Oncorhynchus) are an important object of fishing in the Russian Federation. Prolonged delay of fish before processing provokes the spoilage processes onset, and mi crobiological contamination of salmon fish. The research aim is to study the characteristics of sockeye salmon as a raw material for the delicatessen lightly salted products produc tion, to develop a technology for the production of delicatessen salted products without preservatives using vegetable additives. The research consists of sockeye salmon (Onco rhynchus nerka) characteristic, the size-mass and technochemical composition. The sock eye salmon peculiarity is the presence of a large parasites group that are long-term viable and capable of causing various diseases in humans. Thus, a man recommends to produce delicatessen low-salted sockeye salmon products only from frozen raw materials, using preservatives and re-freezing the finished products. The thesis demonstrates the possibil ity to eliminate preservatives, using dusting with vegetable components as barrier agents (bay leaf, black pepper, chili pepper, dill, garlic, lemon) and storing sockeye salmon frozen in vacuum packaging. The researchers developed six recipes, a technological production scheme of sockeye lightly salted frozen salmon fillets with spices. The authors suggested to combine the operations of raw materials defrosting and salting in order to preserve the raw materials quality, optimize salting, form a maturation “bouquet”, reduce the techno logical process duration. When studying the effect of storing frozen sockeye salmon fillets lightly salted with spices, a man revealed that after 1, 6, 8 months of storage, the pro tein solubility in the experimental sample decreased by 6, 12 and 35 %, respectively. The researchers determined the recommended mode: temperature from minus 2 to 0 °C for 4 days. According to the totality of the studied indicators (organoleptic, physico-chemical, microbiological), the recommended shelf life of lightly salted sockeye salmon fillet with vegetable additives is 8 months at a temperature no higher than minus 18 °C.

The skin mucosal barrier of lumpfish (Cyclopterus lumpus L.) is weakened by exposure to potential aquaculture production-related stressors.

Various cleaner fish species, such as the lumpfish (Cyclopterus lumpus L.), are used in the sea cage production of Atlantic salmon (Salmo salar L.) as a control measure against the ectoparasitic salmon louse (Lepeophtheirus salmonis). Nonetheless, during severe lice infestation, alternative treatments are required to control parasitic burden. The aim of this study was to gain insight into how lumpfish skin responds to different chemicals used to treat parasites. The authors collected skin from lumpfish from both research facilities (tank-reared fish) and commercial production (cage-reared fish) and used operational welfare indicators, in vitro models, histology and transcriptomics to study how the skin responded to two anti-parasitic oxidative chemicals, hydrogen peroxide (H2 O2 ) and peracetic acid. Lumpfish sampled from the farm were classified as clinically healthy or weak based on their morbidity status, and fish from each category were used to gain insight into how the therapeutics affect the skin barrier. Differences between healthy and weakened (moribund) fish, and between treated fish from each of the two groups, were observed. Histological examination showed an overall reduced skin quality in fish characterized as moribund, including different grades of exposed bony plates. In vitro oxidant-treated lumpfish skin had reduced the migration capacity of keratocytes, a weakened epidermal barrier, and altered gene transcription, changes that are known predisposing factors to secondary infections. Skin from non-treated, healthy fish sampled from commercial farms exhibited similar features and attributes to oxidant-exposed tank-reared fish from a research facility, suggesting that apparently healthy cage-held lumpfish exhibited stress responses in the epidermal barrier. The results of the study outline the risks and consequences lumpfish can face if accidentally subjected to potential anti-parasitic oxidant treatments aimed at Atlantic salmon. It also strengthens the evidence behind the requirement that lumpfish should be removed from the cages before being potentially exposed to this type of treatment and outlines the potential risks of differing husbandry practices upon lumpfish health, welfare and resilience.

The Role of Eco-Labels in Making Environmentally Friendly Choices: An Eye-Tracking Study on Aquaculture Products with Italian Consumers

Eco-labels are crucial in helping consumers make sustainable food choices. However, previous literature has shown that eco-labels lack visibility and, frequently, are not easy for consumers to see. The main goal of the present study was to analyse the influence of aquaculture eco-labels’ visual elements—size and saliency—on consumers’ visual attention and choice. The study uses an eye-tracking methodology, together with a choice experiment and a semiotic analysis. A word association (WA) task was used to explore how each eco-label’s graphic design influenced consumers’ perceptions. Sixty-one consumers’ eye movements were tracked while choosing smoked salmon and seabass products carrying different eco-labels. The results showed that size and saliency largely influence visual attention. The choice of aquaculture products was influenced only by the size of the eco-labels. According to the WA task, the shape, the symbols and the language in which the claim was written influenced consumers’ preferences. The findings contribute to marketing and food research, suggesting which visual elements should be considered to increase consumers’ interest in eco-labels.

INVASIVE POTENTIAL AND REGULATION EXPERIENCE OF USING TRANSGENIC ORGANISMS IN AQUACULTURE BY WAY OF EXAMPLE OF ATLANTIC SALMON

The article considers a 30-year history of the creation, state regulation and production of AquAdvantage transgenic salmon genetically modified (GM) with the growth hormone gene. The arguments of opponents and proponents of the concept of ecological safety of the use of transgenic fish in aquaculture are critically analyzed. It has been generalized that the adaptability of transgenic fish is lower than that of its wild relatives. On this basis, it is assumed that in the event of an accidental ingestion of GM fish from aquaculture to natural populations, transgenes are under the negative influence of natural selection. Strict security measures for the maintenance of GM fish, however, should not be weakened, since there are still unexplained cases of the survival of fluorescent transgenic aquarium fish in freshwater ecosystems.

Landscape characteristics influence projected growth rates of stream‐resident juvenile salmon in the face of climate change in the Kenai River watershed, south‐central Alaska

AbstractObjectiveClimate change is affecting the distribution and productivity of Pacific salmon throughout their range. At high latitudes, warmer temperatures have been associated with increased freshwater growth of juvenile salmon, but it is not clear how long this trend will continue before further warming leads to reduced growth. To explore the potential influence of climate warming on juvenile Chinook and Coho Salmon summer growth rates in southcentral Alaska, we coupled bioenergetics models with temperature sensitivity models for streams across the Kenai River watershed.MethodsWe measured diet (n = 772 stomachs) and growth (n = 3,791 weight/length values) under current conditions and used published air temperature projections to model growth for the 2030–2039 and 2060–2069 decades.ResultWe estimated direct effects of climate warming on juvenile growth (body mass at the end of May–September study period) will be primarily negative, ranging from +5.1% to −22.8% relative to a 2010–2019 baseline. Estimated effects depended on age cohort, feeding rate, and climate scenario. However, an extended growing season from warming could mitigate or offset predicted reductions in growth during midsummer.ConclusionOur results illustrate how diverse habitats are expected to produce variation in the magnitude of climate effects throughout juvenile salmon rearing environments.

Effects of functional ingredients on gut inflammation in Atlantic salmon (Salmo salar L)

Functional feed ingredients are frequently used in feeds for Atlantic salmon, often claimed to improve immune functions in the intestine and reduce severity of gut inflammation. However, documentation of such effects is, in most cases, only indicative. In the present study effects of two packages of functional feed ingredients commonly used in salmon production, were evaluated employing two inflammation models. One model employed soybean meal (SBM) as inducer of a severe inflammation, the other a mixture of corn gluten and pea meal (CoPea) inducing mild inflammation. The first model was used to evaluate effects of two packages of functional ingredients: P1 containing butyrate and arginine, and P2 containing β-glucan, butyrate, and nucleotides. In the second model only the P2 package was tested. A high marine diet was included in the study as a control (Contr). The six diets were fed to salmon (average weight of 177g) in saltwater tanks (57 fish per tank), in triplicate, for 69 days (754 ddg). Feed intake was recorded.The growth rate of the fish was high, highest for the Contr (TGC: 3.9), lowest for SBM fed fish (TGC: 3.4). Fish fed the SBM diet showed severe symptoms of inflammation in the distal intestine as indicated by histological, biochemical, molecular, and physiological biomarkers. The number of differently expressed genes (DEG) between the SBM and Contr fed fish was 849 and comprised genes indicating alteration in immune functions, cellular and oxidative stress, and nutrient digestion, and transport functions. Neither P1 nor P2 altered the histological and functional symptoms of inflammation in the SBM fed fish importantly. Inclusion of P1 altered expression of 81 genes, inclusion of P2 altered 121 genes. Fish fed the CoPea diet showed minor signs of inflammation. Supplementation with P2 did not change these signs. Regarding composition of the microbiota in digesta from the distal intestine, clear differences regarding beta-diversity and taxonomy between Contr, SBM, and CoPea fed fish were observed. In the mucosa the microbiota differences were less clear. The two packages of functional ingredients altered microbiota composition of fish fed the SBM and the CoPea diet towards that of fish fed the Contr diet.