Search

[Display omitted] • Scenario simulations with coordinated production reduced mean salmon lice abundance. • The salmon lice problem increased in the second year of the production cycle. • Only strategies with less fish in open cages in spring resulted in low impact on wild fish. • Low impact was achieved by stocking larger fish, implying earlier slaughtering. Parasitic salmon lice (Lepeophtheirus salmonis) are a constraint to the sustainable growth of salmonids in open net pens, and this issue has caused production to level off in recent years in the most aquaculture-intensive areas of Norway. The maximum allowed biomass at a regional level is regulated by using the so-called "traffic light" system, where salmon louse-induced mortality of migrating wild salmon post-smolts is evaluated against set targets. As a case study, we have investigated how a specific aquaculture-intensive area can reduce its louse levels sufficiently to achieve a low impact on wild salmon. Analyses of the output from a virtual post-smolt model that uses data on the reported number of salmon lice in fish farms as key input data and estimates the salmon louse-induced mortality of wild out-migrating Atlantic salmon post-smolts, suggested that female louse abundance on the local farms must be halved in spring to reach the goal implied by the traffic light system. The outcome of a modelling scenario simulating a proposed new plan for coordinated production and fallowing proved beneficial, with an overall reduction in louse infestations and treatment efforts. The interannual variability in louse abundance in spring, however, increased for this scenario, implying unacceptably high louse abundance when many farms were in their second production year. We then combined the scenario with coordinated production with other louse control measures. Only measures that reduced the density of farmed salmonids in open cages in the study area resulted in reductions in salmon louse infestations to acceptable levels. This could be achieved either by stocking with larger fish to reduce exposure time or by reducing fish numbers, e.g. by producing in closed units. [ABSTRACT FROM AUTHOR]

A major challenge facing sustainable aquaculture governance are disputes raised by social conflicts, highlighting the need to better understand and incorporate social dimensions into more holistic planning and policy. This study applied an in-depth qualitative approach to investigate key drivers that influence social acceptance of salmon aquaculture, drawing from interviews in coastal communities in Nova Scotia, Canada. From interviews, four main perspectives towards the planning, management, and development of salmon farming emerged, revealing a complex discourse of conflicts and controversy. This study argues that social responses to aquaculture are driven by perceived legitimacy and trust of the sector. Conflicts over the perceived legitimacy of policies and processes emerged, including arguments around what motivates and informs decision-making and how participants are involved in decision-making processes. In addition, conflicting paradigms of knowledge and perceived fairness in engagement processes highlighted the need for transparency, communication, and relationship-building. Controversy over a diversity of perceived environmental and social impacts reflected nuanced perceptions of how aquaculture contributes to individual and community well-being. This study also found perceptions of legitimacy to be deeply intertwined with evaluations of trust in government, industry, and science, which is a key predictor of social responses. Understanding these perceptual factors, separately and with their interdependencies, can provide decision-makers with insights to guide their regulatory, operational, and engagement processes. Ultimately, this work can serve to facilitate a better understanding of the motivators behind public responses to salmon aquaculture which can help bring social considerations into more holistic aquaculture governance. • Aquaculture governance is considered "wicked", complicated by a controversy of differing opinions. • A spectrum of perspectives towards salmon farming highlights the complex nature of social acceptance. • Conflicts, concerns, and priorities were not homogeneous, even among those with similar overall opinions. • Perceptions of legitimacy and trust emerge as key drivers of social responses. • Legitimacy can act as a frame for analyzing social acceptance as embedded within particular social contexts. [ABSTRACT FROM AUTHOR]

Atlantic salmon (Salmo salar) farming is moving towards extended periods of land-based production to minimise the time at sea, but this increases the risk of unwanted male sexual maturation. As the timing of puberty is driven by genetics (e.g. vgll3) and the environment, optimising rearing strategies and broodstock management may help alleviate the problem. Subsequently, we used a domesticated strain of vgll3 heterozygous broodstock to produce three all-male half-sibling families using three different production regimes to assess the timing of first puberty. Firstly, "large smolts" were produced in a flow-through system on 13 °C freshwater and constant light from first feeding (day 0) up to 1 kg (day 354). The mean incidence of pubertal males increased from 2% at 30 g, up to 78% at 1 kg. Genetics explained a significant (p < 0.05) amount of the variation, with 93, 71, and 34% of the expected early, intermediate, and late maturing vgll3 genotypes being pubertal on day 354, respectively. In addition, pubertal males in the early vgll3 genotype were found at the first sampling at ≈30 g, while it was not observed in the heterozygous and late genotypes until the fish were ≈90 g and ≈280 g, respectively. Secondly, "post-smolts" were produced by switching half the large smolts to 13 °C seawater at 420 g (day 272) and growing them in tanks to 0.95 kg (day 354). This led to a significant 14% reduction in the total incidence of puberty by day 354 compared to the large smolts. However, the regulation of pubertal timing by vgll3 did not interact with salinity. Thirdly, traditional "under-yearling" smolts were produced using periods of natural or manipulated temperature and photoperiod, followed by transfer to a sea-cage at 150 g in December (day 290) where they stayed for one year until harvest at 4.75 kg (day 648). None of these fish were mature at sea transfer, but 9% were at harvest, with 22, 7, and 2% of the early, intermediate, and late vgll3 genotypes being mature, respectively. When comparing the regimes, family effects outside of vgll3 on the prevalence of sexual maturation were significant for the land-based regimes (family means from 46 to 93% on day 354), but not in sea-cages (family means from 7 to 11% on day 648) and evidence for either vgll3 allele being dominant was mixed. Vgll3 also had minimal effects on body size/growth in any regime/family. In conclusion, i) selecting for the late vgll3 allele is an effective method to delay puberty over a range of production regimes, ii) family effects outside of vgll3 were not consistent across regimes, and iii) using seawater reduced the incidence of precocious puberty during land-based production. • 3 families of all-male salmon were reared across 3 different environmental regimes. • Family interacted with regime on the prevalence of maturation. • Vgll3 regulated the prevalence of maturation consistently across all regimes. • The results can help the industry prevent pre-harvest male maturation. [ABSTRACT FROM AUTHOR]

Dissolved oxygen concentrations were monitored at 12 points distributed over 3 depths in one out of six cages in an Atlantic salmon farm and compared to the output of a mathematical model using the advection-diffusion equation and a model of the salmon's oxygen consumption to estimate spatial oxygen distributions. The effects of oxygen consumption in neighbouring fish cages on the oxygen levels observed in the monitored cage were found to be significant, and several model variants modified to better represent the real system were tested. Position data from 8 fish in the cage equipped with acoustic telemetry tags was used to refine the model configuration. Results show that simulating the full farm with all cages improves model fit significantly over simulating a single cage only. Even better fit was achieved in a single cage model with ad hoc modifications, indicating that there are additional non-modelled effects that should be investigated further. This study establishes the oxygen model as a suitable tool for monitoring and forecasting of oxygen conditions in salmon cages, and gives indications about he accuracy and limitations of the model. • DO in salmon cages can be predicted in 3D using a mathematical model. • Commercial scale field study using 15 DO sensors, current profiler and acoustic tags. • DO in each cage is significantly affected by consumption in neighbouring fish cages. • Clear improvement in model fit when simulating all cages in the farm. [ABSTRACT FROM AUTHOR]

In this study, a fatty acid dilution model was coupled with a dynamic nutrient demand model to provide an integrated model capable of predicting the whole-body and fillet lipid and fatty acid levels of Atlantic salmon (Salmo salar) following a change in dietary fatty acid profile. Based on knowledge of the initial fish and dietary fatty acid compositions, diet digestible energy density, the water temperature and duration of feeding, the model demonstrated that it was possible to predict a range of parameters, including the growth, feed utilisation, whole-body and fillet (Norwegian Quality Cut; NQC) total lipid, and fatty acid levels of the fish. The model was validated against five separate experiments, including two farm-based trials with harvest size fish. Validation experiments involved fish ranging in size (initial weights to final weights) from 138 g/fish to 5138 g/fish and running for durations of between 66 and 323 days. For the laboratory experiments, prediction of growth, feed utilisation and fatty acid deposition proved to be highly predictable (R2 > 0.998). Fatty acid profiles from both short and long-term cage trials were also highly predictable. Despite the reduced level of weight change in the short-term cage trial, and the higher variability that was observed in growth performance, the fatty acid deposition still showed high levels of correlation (R2 > 0.996), between the modelled and measured fatty acid levels in the fish fillet. Departure from linearity was more evident in the long-term cage trial, but correlation still exceeded R2 > 0.995 for all treatments. Prediction of whole-body and NQC total lipid levels was less accurate, with correlations being R2 = 0.962 and R2 = 0.909 respectively. Model outputs were generally more accurate with greater weight change and/or experiment duration. The outcome of this study shows that the model developed here provides a useful tool for the estimation of the fatty acid composition of Atlantic salmon following a change in dietary fatty acid composition. This could help assist in the more judicious use of dietary long-chain omega-3 fatty acids for commercial salmon farming. [ABSTRACT FROM AUTHOR]

Marine-based salmon farming faces a significant challenge in the management of sea lice infestations, particularly in high-density production areas. Multiple strategies have been employed on salmon farms to prevent and treat sea lice infestations, but they have widely varied in their effectiveness in reducing infestations and their associated impact on the marine environment and fish welfare. Typically, cost and effectiveness are crucial considerations for salmon industries and researchers when determining which practice is optimal for reducing sea lice infestations, but the public's views on sea lice management have not yet been fully assessed. Therefore, an online survey was conducted to examine how the English and Scottish public evaluate different sea lice management practices. Participants were randomly assigned to one of eight conditions: four different types of sea lice management practices (medical treatment, mechanical treatment, cleaner fish treatment, or barrier technology) with two types of information formats (basic information or detailed information). The results showed that participants were more accepting of barrier technology and cleaner fish treatment than medical treatment and mechanical treatment, regardless of whether the presented information was basic or detailed. However, providing detailed information about mechanical treatment and cleaner fish treatment negatively affected the participants' acceptance and perceptions compared to the basic information condition. Specifically, when detailed information was provided, mechanical treatment was evaluated as less natural and less welfare friendly for farmed salmon, and the corresponding salmon products were considered to be less healthy than when basic information was provided. Similarly, when detailed information was provided, cleaner fish treatment was rated as less natural, less environmentally friendly, and less welfare friendly for cleaner fish than when only basic information was provided. This study has implications for salmon industries and policymakers: the public encourages a natural way of managing sea lice that has a minimum negative impact on the environment and farmed salmon, which might clash with the current realities of salmon farming. • The public's acceptance and perceptions of sea lice management were assessed. • Providing varying information influenced public evaluations of sea lice management. • Barrier technology and cleaner fish treatments were favorably rated than other methods. [ABSTRACT FROM AUTHOR]

Oxytetracycline (OTC) is used in Chilean salmonid farming for bacterial pathogens treatment, mainly orally administered. Oral bioavailability of OTC in salmonids is low, so a high percentage of the dose is excreted by fishes. To increase OTC oral absorption, Zn-alginate microparticles were developed by spray drying, with a yield of 59.09%. An in vivo study was performed using Oncorhynchus mykiss (Rainbow trout) to compare OTC Zn-alginate micro-particles oral absorption in plasma and muscle matrices. Seven sampling points for plasma and four for muscle were considered. OTC was quantified in both matrices by UPLC-MS/MS. Results indicated a statistically significant difference between plasma concentrations of the OTC microparticles with respect to the commercial OTC formulation, reflecting a higher absorption of the microencapsulated drug, reaching maximum concentration 4 h earlier than the commercial formulation. In addition, the microparticles showed a release of OTC that remained constant for 12 h. In muscle, OTC microparticles reached twice the maximum concentration than the commercial formulation at 8 h. In conclusion, OTC microparticles improve the oral absorption of the molecule, which could allow drug delivery optimization and dose reduction in bacterial pathogens treatment in salmon production, consequently, decrease contamination of the environment with OTC residues. • Zn-alginate microparticles were developed by spray drying for OTC delivery to salmonids • Rainbow trout were used to compare OTC Zn-alginate microparticles oral absorption in plasma and muscle matrices • Increased absorption would allow to optimize doses administered in salmon production • Encapsulation in aquaculture is an alternative to improving drug delivery, reducing doses and residues in the environment [ABSTRACT FROM AUTHOR]

Open-net finfish farms require monitoring to manage fish welfare and to mitigate risk for diseases and parasites which could threaten wild fish populations. In salmonid farming the ectoparasite copepod sea lice Lepeophtheirus salmonis (Caligidae) is a major concern. This paper's novel contribution is the application of sampling statistics to determine the number of sea lice which should be sampled per pen so as to report the abundance of sea lice with a given accuracy. It does so considering the different statistical distributions which occur at high- and low prevalence of sea lice and combines these considerations to guide the reader towards counting a number of sea lice which would be more inline with other statistical applications. Existing pen sampling routines are analysed and the sampling error is quantified. These findings need to be taken into account when sampling protocols for sea lice are designed as it is especially important for fish welfare. • The error in sample averages for common sea lice counting regimes is quantified. • Comprehensive sample estimates of sea lice abundance in finfish farming are provided. • Implications would improve welfare standards of salmonid farming. [ABSTRACT FROM AUTHOR]

The adoption of standardized metrics and indicators of antimicrobial use (AMU) in the food animal industry is essential for the success of programs aimed at promoting the responsible and judicious use of antimicrobials in this activity. The objective of this study was to introduce the use of standardized AMU metrics and indicators to quantify the use of florfenicol and oxytetracycline in the Chilean salmon industry, and in this way evaluate the feasibility of their use given the type of health and production information currently managed by the National Fisheries and Aquaculture Service (SERNAPESCA), the Chilean agency responsible for regulating aquaculture in Chile. The data available from SERNAPESCA allowed the construction and evaluation of the most data-demanding AMU metrics and indicators. Consequently, the use of florfenicol and oxytetracycline administered by oral and parenteral routes was quantified using the treatment incidence based on both animal defined daily dose (TI DDDvet) and animal used daily dose (TI UDDA). To that end, the study included information from 1320 closed production cycles from farms rearing Atlantic salmon, coho salmon and rainbow trout that were active between January 2017 and December 2021. By applying standardized AMU metrics and indicators, we were able to determine that the median of TI DDDvet for florfenicol was 75.1 (80 % range, 20.0–158.0) DDDvet per ton-year at risk for oral procedures and 0.36 (80 % range, 0.07–1.19) DDDvet per ton-year at risk for parenteral procedures. For oxytetracycline, the median TI DDDvet was 3.09 (80 % range, 0.74–42.8) and 0.47 (80 % range, 0.09–1.68) DDDvet per ton-year at risk for oral and parenteral procedures, respectively. The median TI UDDA for treatments with florfenicol was 45.6 (80 % range, 10.9–96.5) UDDA per ton-year at risk for oral treatments and 0.28 (80 % range, 0.05–0.80) UDDA per ton-year at risk for parenteral treatments. For oxytetracycline, the median TI UDDA was 2.63 (80 % range, 0.61–28.2) UDDA per ton-year at risk for oral treatments and 0.41 (80 % range, 0.08–1.29) UDDA per ton-year at risk for parenteral treatments. This study demonstrates that it is feasible to move from traditional AMU metrics and indicators to standardized ones in the Chilean salmon industry. This is possible because the competent authority requires salmon farms to report detailed health and production information at a high frequency. The use of standardized AMU metrics and indicators can help the authority to have a more comprehensive view of the antimicrobial use in the Chilean salmon industry. [ABSTRACT FROM AUTHOR]

Nutrients introduced to the environment by finfish aquaculture pose environmental risks, which can be mitigated by robust environmental monitoring. Biological communities in soft sediments are good indicators of aquaculture derived environmental changes. Traditionally, monitoring programs have visually surveyed macrofauna communities. However, DNA metabarcoding is a potentially more efficient alternative. We compared alpha diversity, multivariate dispersion and taxonomic composition of macrofauna communities with metabarcoding derived bacterial and eukaryote communities along an organic enrichment gradient at a salmon farm in Tasmania, Australia. Additionally, we conducted a cost-benefit analysis comparing the approaches. All methods identified indicator taxa that changed in abundance over the enrichment gradient. Macrofauna analysis was the most sensitive method for detecting changes in alpha diversity, while metabarcoding was most sensitive for multivariate dispersion. Taxonomic composition of animal communities derived from the two methods differed drastically. Metabarcoding was cheaper than macrofauna for ≥93 samples and quicker for ≥14 samples. • 16S and 18S rRNA metabarcoding both detect aquaculture derived organic enrichment. • Sediment metazoan communities derived from metabarcoding and visual methods differ. • Metabarcoding was faster than visual identification for 14 or more samples. • Metabarcoding was cheaper than visual identification for 96 or more samples. [ABSTRACT FROM AUTHOR]

Significant expansion in salmon production globally has been partially enabled through the establishment of large-capacity sea-farms in high-energy environments that collectively produce substantial quantities of organic waste with potential to cause regional scale environmental degradation. We analyse results from comprehensive spatial and temporal surveys of water column particulates and seabed environmental indicators for responses to farm production, and residual effects. Results confirmed that while the particles can and do reach a relatively wide area, benthic effects do not necessarily follow suit. There was limited evidence of longer-term environmental degradation at some near-field locations and spatially removed deeper sites. We concluded that evidence for regional biological effects was negligible, suggesting: i) modern waste tracing techniques are more sensitive than traditional effects indicators, and ii) waste fluxes in the far-field were being assimilated without causing environmental perturbation. Monitoring at potential accumulation points, especially for sites with complex bathymetry and hydrodynamics is advised. • Substantive novel investigation of far-field effects from large-scale salmon farming • Waste influence field relatively wide (1.3 km) but effects field spatially constrained • Negligible inter-year benthic degradation, assimilation capacity not exceeded • Spatial patterns of waste influence complex, high resolution modelling important [ABSTRACT FROM AUTHOR]

The Norwegian salmon farming industry is characterized by an increasing technological diversity with new production systems emerging. The objective of this paper is to provide knowledge about challenges and opportunities with new production systems as perceived by industry representatives with hands-on experience. Interviews and workshops with fish farmers and suppliers illustrate that even though environmental issues concerning salmon lice, escapes, and diseases can be reduced, and in some cases solved, new challenges might arise. Semi-closed containment and land-based system concerns pertained to water quality and fish welfare, while exposed and offshore systems were more concerned about harsh conditions and their effects on fish, structures, and work operations. However, possibilities for beneficial new production strategies, the potential for a more stable production environment, and increased biosecurity are seen as important advantages. These findings provide valuable perspectives for industry, technology suppliers, and regulators moving forward. • New production technologies may solve or reduce challenges in open net pen fish farming, but also have challenges on their own. • Valuable industry views of challenges and opportunities with the new technologies are presented. • Land-based and semi-closed containment systems might encounter challenges with water quality and fish welfare. • Exposed and offshore systems might encounter challenges with fish welfare, structural design, and safe work operations. [ABSTRACT FROM AUTHOR]

The proliferation of salmon lice is one of the most challenging problems in salmon farming, seriously affecting the welfare of both farmed and wild salmonids. The detection of salmon lice in seawater, especially in the (pre-) infectious stage, supports the accurate management of salmon lice proliferation. Methods for detecting salmon lice in seawater to date involve traditional light and fluorescence microscopy and Polymerase Chain Reaction (PCR) methods. However, these methods require sample pre-processing and are laborious and time-consuming, rendering them difficult to apply for the task of continuous, rapid salmon lice detection in large water volumes. This study aims to develop a rapid and easy-to-use method for the detection of salmon lice in seawater. A novel approach was introduced for the detection of salmon lice at different larval stages in seawater by leveraging machine learning. A setup for the rapid acquisition of images of salmon lice in seawater was developed, and a dataset comprising 8316 images encompassing salmon lice "Nauplius Live," "Nauplius Shell" and "Copepodite" was created. Then 16 object detection models including one- and two-stage Convolutional Neural Network (CNN-) based models and Transformer-based models were trained, tested, and compared on this comprehensive dataset. RT-DETR showed the best performance among all models tested with a precision of 0.972 and a recall of 0.978. The YOLO series models, except for YOLOv3, showcased remarkable inference speeds (ranging from 152 to 416 frames per second) while maintaining high precision (ranging from 0.968 to 0.977) and recall (ranging from 0.964 to 0.970). To our knowledge, this is the first time machine learning has been applied to the task of rapidly detecting salmon louse larvae at different stages in seawater samples. The results demonstrate that the machine learning approaches can achieve rapid easy-to-use and cost-effective detection of salmon lice in seawater. In the future, this study has the potential for application in measuring salmon louse larvae numbers in aquatic environments, supporting the enhancement of the welfare of both farmed and wild salmon. • We used machine learning to detect salmon louse larvae at different stages in seawater for the first time. • Our image dataset contained 8316 images with salmon louse "Nauplius live," "Nauplius shell" and "Copepodite". • A total of 16 object detection models were compared with the YOLO series and RT-DETR models having the best performance. • We preliminary tested YOLOv8n in real seawater samples with good results. • It seems feasible to monitor the presence of salmon lice in seawater as a possible solution to the risk of infection of both farmed and wild salmon. [ABSTRACT FROM AUTHOR]

The use of pyrethroids in aquaculture has been an important component of achieving a thriving salmon farming industry in Chile. While the residual presence of such substances is known to depend on environmental conditions, most ecotoxicological studies to date have not considered environmental context. Here, we conducted oceanographic monitoring combined with experiments aiming to estimate the effects of two pyrethroids on the feeding rates of larvae of farmed mussels, Mytilus chilensis. In additional experiments, mussel spats were exposed to both pyrethroids, but under contrasting temperature/pH so as to mimic winter and summer conditions. Experiments mimicking spring conditions revealed that both pyrethroid substances affected the feeding of mussel larvae as a function of concentration. Conversely, significant impact of pyrethroids on adults were not observed with regard to temperature and pH, but a significant impact of low temperature/low pH condition on ingestion rates was confirmed. Given the current status of increasing ocean acidification, the results of this study are expected to provide useful information with regard to achieving sustainable mussel aquaculture, especially considering both activities occur in similar geographic areas, and the expansion of salmon farming areas is ongoing in Chile. • We examine the interaction of natural environmental regimes of temperature and pH conditions, with pyrethroids concentration used by salmon farming industry in Chilean Patagonia, and its potential impact of mussel feeding (clearance and ingestion rate of newly-hatched larvae and juveniles). • We combined approaches, including oceanographic monitoring in a salmon and mussel farming area in Chilean Patagonia, with experiments aiming estimate the effects of two pyrethroids (deltamethrin and cypermethrin) on the clearance and ingestion rate of mussel larvae. • We also exposed to mussel spats to both pyrethroids, but at contrasting temperature and pH conditions mimicking winter and summer conditions. [ABSTRACT FROM AUTHOR]

Crowding is a necessary operation for moving fish out of or between sea cages in Atlantic salmon farming. These operations consist of gradually reducing available volume in the nets to increase the biomass density. This is known to stress the fish, increase risk of injury, and can in extreme cases increase mortality rates. To reduce the negative impacts of crowding, the operation must be adjusted based on real-time monitoring of fish welfare. Today, this is mainly done by manually monitoring surface activity, as the high fish density limits the use of available tools. In this paper a new approach for monitoring was applied to crowding of meso-scale cages containing 40 fish each, using automatic detection of passive acoustic signatures. Four synchronised hydrophones were deployed and the acoustic signature was defined from the recordings. The automatic detection algorithm recorded an extreme increase in registered acoustic events during crowding, as high as 1000 events per 10 min period, compared to only 20 events per 10 min period on the day following crowding. Correlating the number of acoustic events to recorded heart rate and activity measures from implants in the salmon indicate that automatically registering acoustic events is a promising method for monitoring farmed fish. • Detection algorithm applied to monitor acoustic signature of Atlantic salmon during crowding. • Drastic increase of occurrences of acoustic events during crowding. • Increase in number of acoustic events correspond well with increased activity measurements. • Monitoring acoustic events are a promising method for monitoring stress in farmed fish. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Industry camera systems were used to collect in situ images of biofouled nets. • A deep learning network was trained to binarize the images into water and non-water. • The binary segmentation network obtained high accuracy for both classes. • Net occlusion percentages were estimated after correcting for the net mesh area. • A desktop application was developed to determine the net occlusion of image folders. [ABSTRACT FROM AUTHOR]

Salmon aquaculture is the fastest growing food production system in the world. Deficiencies in the quality or safety of salmon can have global repercussions. Controlling food safety aspects during production is therefore essential. Here, we investigate the state of hygiene in a salmon processing plant using next generation sequencing and classical culture-dependent methods to characterize the surface microbiota before and after cleaning and disinfection (C&D) at ten surface sampling points. Total aerobic counts revealed an average reduction in the bacterial loads of 1.1 log CFU/cm2 by C&D. The highest relative abundance in the core microbiota before C&D was assigned to Acinetobacter , Mycoplasmataceae , Pseudomonas and Enterobacteriaceae in descending order. After C&D, we observed a significant increase in the relative abundance of Pseudomonas (p < 0.05). However, variations were found between conveyors, processing machines and drains. To assess the efficacy of commercial disinfectants, we performed susceptibility assays using advanced robotic high-throughput technologies and included foodborne bacteria which may affect food safety and spoilage. These included 128 Pseudomonas isolates, 46 Aeromonas isolates and 59 Enterobacterales isolates sampled from the salmon processing plant. Generally, minimum inhibitory concentrations (MICs) of the disinfectants were below the user concentration recommended by the producer for most isolates. BacTiter-Glo biofilm assays revealed that 30 min exposure to six out of eight commercial disinfectants resulted in an average reduction of relative luminescence >95 % in 59 single-species biofilms selected for screening. However, disinfection alone may not always be sufficient to eradicate biofilms completely. C&D routines must therefore be continuously assessed to maintain food safety and quality. The results from this study can contribute to understand and improve the state of hygiene in salmon processing environments. • C&D reduced the average bacterial loads from 2.7 to 1.6 log CFU/cm2 on food contact surfaces in a salmon processing plant • The relative abundance of Pseudomonas increased significantly after C&D • Members of the P. fluorescens group dominated the Pseudomonas consortia • BacTiter-Glo assays revealed that biofilms may survive the highest recommended concentrations of comercial disinfectants [ABSTRACT FROM AUTHOR]

The use of coastal-marine resources is currently based on an unsustainable development model that leads to deterioration of the environment and consequent reductions in economic activities and the well-being of coastal societies. According to the conceptual framework provided by the sustainable blue economy model, this paper evaluates the effects of anthropogenic activities on the ecosystem services (ESs) of the coastal areas of the island and the sea of Chiloe, an archipelago located in Chilean Patagonia. It also analyzes how the degradation of the environment ultimately affects the economy itself and human well-being. The methodology employed is based on the construction of three matrices that connect 12 economic activities identified in the study area, with three ESs groupings (provisioning, regulating, and cultural) and four components of human well-being (security, material assets, health, and social relations). The impacts are assessed using four categories: high impact (3), moderate impact (2), low impact (1), and positive impact (0). The results reflect the domination of economic sectors that negatively affect the environment, among which salmon farming, the main activity in Chiloe, stands out. In contrast, small-scale fishing has been the highest evaluated sector, largely because of the new management instruments that have been developed in Chile. The establishment of a sustainable blue economy in Chiloe requires the application of sustainability standards –such as those proposed for small-scale fisheries– in the sectors that generate the most socio-ecological impacts. [ABSTRACT FROM AUTHOR]

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. • Pre-infection with lice was associated with substantially higher number of DEGs during the co-infection process on fish skin. • Single infection with M. viscosa caused a moderate systemic impact and inhibited pathway for tissue repair on the skin. • C-type lectin receptor signaling pathway played an essential role for innate immunity in Atlantic salmon. • An intense inflammatory and immune responses were observed at M. viscosa lesion sites. [ABSTRACT FROM AUTHOR]

Aquaculture has been identified as a food sector with potential to provide protein and essential micronutrients to a growing global population, with salmon aquaculture often viewed as a leader in innovation and adoption of new technologies. Despite a broad range of negative externalities in salmon aquaculture, sea lice infestations remain the most harmful of environmental issues within the industry. In response to these challenges and driven by the need for a higher degree of control over the production conditions, salmon producers in Norway have been investing in new technologies that are often perceived as the last resort for sea lice abatement. The challenge is to design a regulatory regime that encourages innovation toward a sustainable mix of production technologies in the future. In this paper, we propose to use feed-in tariffs (FITs), a dynamic Pigouvian subsidy, as a regulatory instrument that can promote investments in abatement technologies by the salmon farming industry. We ground our discussion of FITs for aquaculture in experiences from the renewable energy sector in Spain and Germany. [ABSTRACT FROM AUTHOR]

Fish diseases in aquaculture constitute a significant hazard to nutriment security. Identification of infected fishes in aquaculture remains challenging to find out at the early stage due to the dearth of necessary infrastructure. The identification of infected fish timely is an obligatory step to thwart from spreading disease. In this work, we want to find out the salmon fish disease in aquaculture, as salmon aquaculture is the fastest-growing food production system globally, accounting for 70 percent (2.5 million tons) of the market. In the alliance of flawless image processing and machine learning mechanism, we identify the infected fishes caused by the various pathogen. This work divides into two portions. In the rudimentary portion, image pre-processing and segmentation have been applied to reduce noise and exaggerate the image, respectively. In the second portion, we extract the involved features to classify the diseases with the help of the Support Vector Machine (SVM) algorithm of machine learning with a kernel function. The processed images of the first portion have passed through this (SVM) model. Then we harmonize a comprehensive experiment with the proposed combination of techniques on the salmon fish image dataset used to examine the fish disease. We have conveyed this work on a novel dataset compromising with and without image augmentation. The results have bought a judgment of our applied SVM performs notably with 91.42 and 94.12 percent of accuracy, respectively, with and without augmentation. [ABSTRACT FROM AUTHOR]

Atlantic salmon aquaculture may benefit from improved tools for behavioural monitoring and data-derived models that predict behaviour in commercial scale production cages. In the present study, timeseries depth registrations from individual farmed Atlantic salmon in commercial cages have been compiled from various projects, with the aim to resolve general swimming depth behaviour during the marine production stage. By implementing acoustic depth sensor tags, swimming depth data from 126 individuals of Atlantic salmon from ten different cages and five different farm sites were analysed over study periods lasting from 195 to 316 days. The study covers all seasons and were conducted at a latitude where there is hardly daylight during winter solstice nor nighttime or dusk during summer solstice. Average hourly swimming depth registrations for individual salmon were analysed by applying generalized additive modelling (GAM), where the main effects, hour of the day, temperature and sunlight hours were modelled as smooth terms in a non-linear way. The main effects were further modelled conditioned on the presence or absence of submerged lights and/or skirts used to shield the fish from salmon lice infestations. The results reveal that Atlantic salmon generally resided higher in the water column during nighttime than in daytime in all seasons except in the summer. The general tendency for diurnal depth patterns was most pronounced in winter and spring in cages without submerged lights, where average swimming depths varied from about 10–12 m during daytime to about 5–6 m during nighttime. The use of submerged lights in the cages disrupted the diurnal depth patterns and lead the fish to swim deeper in the water column during night-time in months with few sunlight hours. There was no substantial effect of the use of skirts on swimming depths. In addition to these general diurnal and day of the year trends, there were large individual variations in swimming depth. The study emphasises the utility of behavioural traits, particularly in modelling expected depth patterns as a surveillance tool in conjunction with real-time biomonitoring during the ongrowing phase at sea for Atlantic salmon. • Atlantic salmon display strong diurnal depth profiles during winter months in industrial size cages. • Atlantic salmon generally reside higher in the water column during nighttime than in daytime over all seasons except summer. • Submerged lights disrupt diurnal depth patterns and lead the fish to swim deeper during night-time over winter months. • Observed depth patterns emphasises the potential use of behavioural traits as a biomonitoring surveillance tool. [ABSTRACT FROM AUTHOR]

The use of lumpfish as a "cleaner fish" in Atlantic salmon aquaculture is increasing. However, during the summer months, there have been large-scale mortalities of lumpfish at some North Atlantic salmon sea-cage sites. There is evidence that manipulating temperatures during early life can improve the thermal tolerance of fishes. Thus, we reared lumpfish embryos (eggs), larvae and juveniles under different temperature regimes, and measured their metabolic physiology and upper thermal limits, with the goal of better understanding their physiology and mitigating the effects of high summer water temperatures on their welfare. The specific incubation (egg) / rearing temperature combinations were 6 °C / 9 °C (normal production temperatures), 8.5 °C / 9 °C, 6–11 °C / 9 °C, 8.5 °C / 9–11 °C and 6–11 °C / 9–11 °C; with a range of temperatures indicating that fish were exposed to stochastic temperature changes. Hatching success was 61 % in the control (6 °C) group, as compared to ∼ 47 % and 26.5 % in the groups exposed to 8.5 °C and the stochastic temperature regime (6–11 °C), respectively. Groups exposed to stochastic incubation and rearing temperatures also had the lowest survival rate (33.7 %) as opposed to those incubated and reared at constant temperatures (66.1 and 50.7 %) when unexpectedly exposed to high, and variable, ambient water temperatures that were experienced for roughly 7 weeks during rearing (due to abnormal water temperatures in the bay supplying our aquaculture facility). Interestingly, the critical thermal maximum (CT Max), incremental temperature maximum (IT Max) and metabolic capacity (i.e., aerobic scope) of 30-40 g lumpfish did not differ between the groups, and the first two parameters on average were 22.85 ± 0.12 °C and 20.63 ± 0.02 °C, respectively. • Warmer, stochastic incubation temperatures reduced hatching success of lumpfish. • Raising incubation/rearing temperatures did not improve lumpfish thermal tolerance. • Mean lumpfish CT Max is 2 °C higher than their IT Max. • High temperatures are not responsible for lumpfish mass mortality events. [ABSTRACT FROM AUTHOR]

Sampling bias was investigated in New Zealand farmed king salmon (Oncorhynchus tshawytscha) at the end of a feed trial. Two sampling techniques - a non-lethal manual assessment (MA) and a lethal hook and line (HL), were evaluated for the representativity of their samples, with regard to two performance indicators, weight and skin health. Both sampling techniques assessed (MA n = 60, HL n = 4) were biased when compared to the analysis of all the fish in each pen. However, MA samples were biased towards fish with better skin health and higher weight (+ 0.20 kg), while HL selected fish with poorer skin health than the pen population average and lower Fulton's Condition Factor (− 0.25) than MA samples. Our results emphasised the significance of understanding sampling bias so research interpretation is correct. • Manual assessment was biased for weight and skin health when compared to the analysis of all the fish in each pen. • This study is novel as while most of fish sampling is biased it is rarely admitted and even more rarely investigated. • This work is highly relevant to any aquaculture research which relies on fish sampling [ABSTRACT FROM AUTHOR]

Infectious Hematopoietic Necrosis (IHN) is a viral disease that causes great economic losses in salmonid fish farming industry. It is known that the N-glycosylation site on the G protein affects the immune evasion and pathogenicity of the Infectious Hematopoietic Necrosis Virus (IHNV). In this study, a mutation in the N-glycosylation site of the G protein (438 amino acids) of IHNV resulted in an increased the survival rate of rainbow trout from 17.1 % to 75.3 %, and a decreased serum antibody IgM level after virus infection. In addition, this mutation decreased the expression of CD83 and CD209 on dendritic cells and enhanced the binding of G protein to TCR. This suggests that the activation of CD4+ T-cells was enhanced. We hypothesize that IHNV evades the host's immune system by impairing antigen presentation and T-cell responses through the N-glycosylation of G protein. This finding could provide new insights for developing live attenuated vaccines. • IHNV G protein N-glycosylation mutations expose antigenic epitopes of the virus increasing the immunogenicity of the virus and decreasing its pathogenicity. • IHNV G protein N-glycosylation mutations alter the tertiary structure of viral G proteins, increasing the ability of viruses to bind to host proteins. • The IHNV G protein N-glycosylation mutation improves viral binding to the TCR, which is ultimately recognized and cleared by CD4+ T cells. [ABSTRACT FROM AUTHOR]

Salmon farming plays an important role in the Norwegian food industry, supplying a large portion of the world's salmon. Despite its economic importance, salmon farming faces unique biological challenges impacting the health and welfare of the fish. These factors limit the growth of salmon and the full economic potential of salmon farms, highlighting the need for advanced techniques in aquaculture to enhance productivity and sustainability. A key technical challenge is the unavailability of effective monitoring tools, leading to greater difficulties assessing the condition of salmon in water compared to the assessment of the animal stock on land-based farms. To improve the observability of salmon farms, we designed and created a computer-vision based approach for salmon breathing rate estimation (SaBRE), which allows the automatic monitoring of the respiration frequency of each individual salmon in a group of fish, seamlessly covering the entire workflow from video-stream input to the final data output (end-to-end). We thoroughly evaluated the capabilities of our method in two ways. Firstly, we performed a quantitative analysis of the constituent modules of SaBRE, revealing that all modules were highly accurate, including a salmon re-identification module that achieved an accuracy of 99.51 %. Secondly, we analyzed data from a salmon experiment with SaBRE, demonstrating that our algorithm provides high-quality respiration frequency information that can be compared with other types of experimental data to infer biological relationships. For the fish in our experiment, we observed that the ranking of the respiration frequencies in individual salmon remains relatively unchanged both in the short term and over longer periods (i.e., a salmon with a high breathing rate consistently remains among those with the highest rates, regardless of changes in the environment). Furthermore, a significant negative correlation (Pearson correlation coefficients with r values between −0.61 and −0.90 and p values below 0.01) was observed between our algorithm's estimated respiration frequency and the dissolved oxygen (dO 2) content in the water. In addition, the average breathing rate of the salmon was observed to increase in response to incidents potentially causing stress. • The individual salmon breathing rate in a group of 7 can be automatically monitored. • Breathing rate increases measurably with a decrease of dO2. • Breathing rate increases measurably when objects are inserted into a tank. • The relative breathing rate between fish in a group is consistent. [ABSTRACT FROM AUTHOR]

In-situ data is essential in understanding climate change in coastal and marine environments, especially in nearshore locations that are challenging for models to simulate and are often lacking in downscaled climate projections. Environmental parameters such as sea temperature and oxygen are often recorded at fish farms, and this information could be useful for observing coastal changes and climate change assessment. For aquaculture, Norway's BarentsWatch portal is one of the most advanced open-data platforms in the sector. The aim of this study was to inspect the weekly sea temperature data collected from salmon lice monitoring within the Fish Health dataset in BarentsWatch and consider if the recorded temperatures could have value for monitoring climate change due to the spatial and temporal coverage of the farm data. Initial inspection of the dataset found many inconsistencies and suspected errors. In total there were 667 sites where suspected errors were removed. Suspected errors amounted to 7797 data points. Following data cleaning there were 1129 sites and 303,792 data points in total, covering much of the Norwegian coastline. The positions offered good insight into the range of conditions, with data from sheltered inner fjords as well as more exposed locations. Analysis of the BarentsWatch temperatures revealed some sites in southern and western Norway that have already experienced temperatures above 20 °C, challenging conditions for Atlantic salmon (Salmo salar) aquaculture. The results showed differences between sites within the same production regions due to site-specific characteristics, illustrating the need for more local-scale data that represents the actual conditions the fish experience, rather than a reliance on regional averages. Although the BarentsWatch platform provided some insight into the temperatures experienced at Norwegian salmon farms, the lack of standardised reporting and uncertainties about data collection and aggregated values meant that detailed analysis was not possible at present. The BarentsWatch analysis was complemented by data from two farms that further demonstrated the need for better guidance and standardised data collection and reporting. Standardised data collection and reporting would ensure that data from different farms is directly comparable. When considered in context with other conditions and fish health parameters, more standardised and robust monitoring of water temperatures at farms would aid the identification of potential challenging conditions and allow for more targeted adaptation responses. Improved data collection and reporting in the present day would have huge value in the future by facilitating the creation of long-term datasets spanning multiple decades at hundreds of locations along the Norwegian coastline, offering exceptional insight into coastal climate change. • Aquaculture can provide important information for climate change assessments. • Marine fish farms offer unique insight into coastal conditions. • Improvements to data collection, auditing, recording and processing are needed. • Common protocols and standards for data collection and reporting are essential. • Environmental data must be collected and stored to support climate change assessments. [ABSTRACT FROM AUTHOR]

The global increase of aquaculture production has caused an escalating demand for alternative protein feed ingredients. Agro-industrial by-products such as sunflower meal are relatively abundant and cheap, but the content of antinutritional factors and fiber in the raw products reduce nutritional value and limit the inclusion levels in the feed for nutritionally demanding species, including salmonids. Solid-state fermentation is a microbial processing method with the potential to reduce the content of fiber and antinutritional factors and improve nutritional value in plant protein raw materials. In this study, Atlantic salmon (Salmo salar) at two commercial-like fish farms were fed experimental diets containing either 5 % non-fermented sunflower meal (as a control diet), 5 % fermented sunflower meal or 10 % fermented sunflower meal. The aim was to compare the effects of fermented sunflower meal on growth performance, gut microbiota, distal intestine histology and gene expression of Atlantic salmon under different environmental conditions. The field trial lasted for 8 and 11 months in a coastal and fjord location, respectively. The findings revealed that diets with fermented sunflower meal sustained growth performance, improved intestinal health by reducing the prevalence of prominent inflammation and ectopic goblet cells, as well as down-regulated the expression of physiological pathways related to tissue damage and cell division. Additionally, 10 % fermented sunflower meal promoted the relative abundance of gut lactic acid bacteria Lactiplantibacillus and Lactobacillaceae after long-term feeding. Our results suggest that fermented sunflower meal is a suitable protein source for Atlantic salmon when included at a level of up to 10 % in the diet. • Fermented sunflower meal reduced prominent distal intestine inflammation. • Fermented sunflower meal reduced the number of distal intestine ectopic goblet cells. • Technical pellet quality was not adversely affected by fermented sunflower meal. • 10 % fermented sunflower meal supported high growth performance under field conditions. • Fish fed fermented sunflower meal had increased gut lactic acid bacteria. [ABSTRACT FROM AUTHOR]

Tenacibaculum maritimum is the main organism responsible for yellow mouth (YM) and the primary driver for the use of antibiotics in Canadian Atlantic salmon culture. This creates a potential for the generation of antibiotic-resistant strains and brings significant costs to aquaculture producers. YM only occurs in Atlantic salmon recently transferred to saltwater, wherein affected fish die rapidly with few clinical signs apart from small yellow plaques around the mouth. Interestingly, if fish survive the first three to four months following saltwater transfer, they appear to have long-lasting protection against YM suggesting that immune memory may play a role. As a result, this costly predicament might be solved with an intervention that induces proper immune stimulation prior to the transfer of smolts to saltwater. To explore this, the current study developed an indirect ELISA that was specific for both Atlantic salmon and rainbow trout serum-IgM production towards a North American strain of T. maritimum. This assay was then used to confirm that Atlantic salmon routinely cultured in sea pens develop T. maritimum specific serum IgM and that this antibody development significantly increases over 220 days. To determine whether this antibody production could be induced and possibly optimized, a formalin inactivated T. maritimum vaccine was developed and used for intraperitoneal vaccinations of naïve rainbow trout while being maintained at low (11 °C) and high (15 °C) water temperatures. Analysis of leukocyte recruitment to the injection site revealed that the vaccine significantly enhanced total leukocyte and specifically lymphocyte recruitment when fish were held at the higher water temperature. Pathogen-specific antibody development was also significantly enhanced by the higher water temperature 21 days after receiving the vaccine. However, when a booster was given at day 21, any temperature-related differences in T. maritimum antibody levels between vaccinated groups was eliminated. A better understanding of salmonid antibody development towards T. maritimum could provide valuable insight into the development of an effective vaccine to prevent YM. Such a vaccine intervention could replace currently used antibiotic treatments and drastically improve the sustainability of North American aquaculture. • First evidence that Atlantic salmon develop serum IgM towards T. maritimum (Tm) when routinely grown in commercial sea pens. • Elevated water temperature enhanced leukocyte recruitment to peritoneum after i.p. injection of a formalin-killed Tm vaccine. • Higher water temperature significantly increased early serum IgM antibody development towards Tm in vaccinated rainbow trout. • Temperature related differences in vaccine-induced antibody development were lost when a booster was administered at day 21. [ABSTRACT FROM AUTHOR]

This study examined salmon lice (Lepeophtheirus salmonis) numbers during different full-scale lice treatments of salmon, with focus on detachment during crowding and re-attachment post-treatment. Data was collected from 259 non-medicinal treatments (NMM) during 2018 and 2019. The dataset included data from thermal (Optilicer), mechanical (Flatsetsund Engineering, SkaMik, Hydrolicer) and freshwater treatments. Salmon lice were counted by the staff at the aquaculture sites, and registered in the following categories: sessile, preadult/adult male (PA/AM) and adult female. A counting protocol was established in collaboration with staff from the aquaculture companies taking part, where the time for counting the parasitic salmon lice was: Sample 0: before crowding; Sample 1: at the end of the first crowding; Sample 2: during unloading of the salmon after treatment; and Sample 3: after delousing of the salmon, in the net pen. In addition to the treatments registered directly according to the protocol, we retrieved data for additional treatments directly from the aquaculture companies' own registration system. The objectives of this observational study was (1) investigate whether salmon lice detach during crowding before an NMM; (2) investigate the effect of NMM; and (3) investigate possible re-attachment after delousing. We observed an overall trend of a reduction of salmon lice numbers, with a median percentage decrease of 22% for PA/AM and 29% for adult female lice during crowding. A likely explanation for these observations is that lice detach from the salmon due to mechanical action associated with the increased density of crowding. One-sided Wilcoxon tests corroborated the hypothesis of a reduction in lice counts during crowding for PA/AM and adult female lice (p < 0.05). As expected, we also observed a substantial reduction in lice numbers from Sample 1 to Sample 2, which is most likely due to the effect of the delousing treatment with the NMM. We observed an increase in sessile and PA/AM salmon lice when studying possible re-attachment after delousing. For sessile lice, the increase in lice numbers was most likely due to new infestation. For PA/AM, the increase can primarily be explained by re-infestation with lice that detached during crowding. The increase for PA/AM was greater when the salmon were placed in the same cage (a doubling of lice numbers), compared to placing them in a new cage (p < 0.05), indicating that the salmon lice could re-infest to a greater extent when the salmon were moved a shorter distance. The results presented in this article shed light on the possible dispersal of parasitic salmon lice, which is largely an unexplored topic. • Salmon lice (Lepeophtheirus salmonis) numbers during different full-scale lice treatments of salmon with focus on detachment during crowding and re-attachment post-treatment. • A reduction of salmon lice numbers during crowding. • Increase of sessile and preadult/ adult male salmon lice when studying possible reattachment after delousing. • The increase for preadult/ adult male was larger when placing the salmon in the same cage compared to in a new cage. [ABSTRACT FROM AUTHOR]

Managing pathogens is a challenge in biological production processes. To manage private risks and reduce externalities, biological controls leverage the technology of natural ecosystems and are often considered environmentally friendly alternatives to chemical controls. In salmon farming, parasitic sea lice reduce own-firm profitability by stressing fish and slowing growth and generate externalities by spreading to neighboring farms and threatening wild fish populations. Cleaner fish are a form of biological control based on ecological interaction that can be used instead of chemical control of sea lice, but little is known about their efficacy and value in commercial use. We estimate efficacy of cleaner fish using facility-level data. To identify exogenous variation in cleaner fish usage, we instrument site-level cleaner fish stocks using distance to cleaner fish farm with a commercial license. Cleaner fish use significantly reduces likelihood of sea lice levels exceeding regulatory threshold levels. Combining efficacy estimates with cost data and a structural model, we provide estimates of cost-effectiveness. Our results show that cleaner fish are privately cost-effective, which is consistent with high levels of adoption. However, cost-effectiveness also suggests that policy could encourage even more adoption of biological controls to reduce externalities. [ABSTRACT FROM AUTHOR]

• An underwater exposure adjustment method using bio-vision is proposed. • An underwater color correction method using bio-visual perception is proposed. • A physical model for visibility recovery using underwater features is proposed. • We designed a perceptual fusion method using image quality evaluation. • The first deep sea netting enhancement datasets SBBD and SNBD are presented. Intelligent monitoring of deep-sea nets is affected by light attenuation, light scattering, and limited dynamic range factors of the camera, which can cause color shift, low visibility, and over/underexposure in monitoring, resulting in reduced farming efficiency, and misdetection of biological behavior. Therefore, we propose a method for underwater net tank scene enhancement and exposure using multicolor space and bio-vision, called DNIM. Specifically, we first propose an intelligent enhancement and exposure monitoring method for deep-sea nets using bio-vision, which eliminates the effect of exposure on underwater imaging by introducing a bio-vision system that uses a brightness transformation function to generate a series of exposure images. Inspired by the image fusion method, we designed a color correction and visibility recovery method using bio-vision. In the Lab color model, color shifts in bio-vision are corrected by guiding feature transformations with contrast-constrained adaptive histogram equalization; in the RGB color model, depth information is recovered by creating a linear model for the depth of field of underwater blurred images based on the characteristics of the bio-vision system. To obtain more qualified results, we also propose an efficient perceptual fusion module to mix the output of visibility recovery and color correction. Finally, we propose two deep-sea net tank culture datasets: salmon bait-eating behavior dataset (SBBD) and salmon non-bait-eating behavior dataset (SNBD). By comparing the experimental analysis in four real scenario datasets, our DNIM achieved superior results compared to 16 advanced underwater enhancement methods. The code is publicly available at: https://github.com/An-Shunmin/DNIM. [ABSTRACT FROM AUTHOR]

Salmon farming in Chile faces the dual challenge of maintaining growth while improving sustainability. One approach to advance sustainability involves the feeds without marine-fishery inputs. This study aimed to evaluate the effect of completely replacing fish oil (FO) on the performance of Salmo salar throghout marine grow-out. The investigation involved fish ranging from 400 g to 4000 g and explored three diets without fish meal, each which included 2.2% EPA + DHA from different sources: FO (control), transgenic canola oil (Can n-3) and Schizochytrium sp. oil (AOV) as unique type of oils. Each diet was randomly distributed in triplicate among nine tanks with a recirculation system maintained at 12 °C, with automatic feeding and a 24-h light photoperiod. Fish density was 29 fish m−3 at day 133 of the experiment and seven fish m−3 at day 319. The diets were isoproteic, isolipidic and isoenergetic. Fish were evaluated at 133 and 319 days of experiment in terms of productive performance, liver health, EPA + DHA and lipid retention efficiency, fatty acid metabolism, response to acute stress, and final product quality. The results showed similar productive performance and liver health among the three diets during both sampling periods. No differences were observed in lipid or EPA + DHA retention efficiency in the whole body or fillet. Eicosanoids and receptors for anti-inflammatory mediators derived from EPA and DHA showed similar or higher capacities in fish fed with Can n-3 and AOV than those fed FO. Responses to induced stress, measured through lactate, cortisol, sodium, potassium, chloride, glucose, and the liver profile were similar between the three diets. Similarly in fillet quality between the three diets. However, sensory analysis revealed a lower intensity of "global aroma" in Can n-3-fed fish fillets and lower evaluations in "typical salmon aroma", "oily aroma" and "fresh flavor" in AOV-fed fish fillets when they are compared with FO. The nutritional indicators of the final product were similar between the three diets, except for PUFA/SFA, the thrombogenicity index, hypercholesterolemia/hypocholesterolemia, and the health promotion index. In these specific indicators, fish fed with Can n-3 and AOV demonstrated more favorable results for consumer health than the FO-fed fish. • Lower "global aroma" for Can n-3 and lower "typical salmon and oily aroma" and lower "fresh flavor" for AOV compared to FO. • anti- inflammatory capacity from EPA and DHA is similar or higher in fish fed Can n-3 and AOV than those fed FO. • TI, and HPI revealed advantages for consumer in fish fed canola n-3 and algae oil compared to FO. [ABSTRACT FROM AUTHOR]

Biomarkers that give quantifiable information about disease development are valuable diagnostic indicators providing opportunities to thwart adverse outcomes through timely detection and initiation of countermeasures. Whereas human medicine already relies extensively on biomarker analysis, their application in the diagnostics of fish diseases is still at a tentative beginning. However, the increased utilisation of broad-range analytical approaches such as untargeted proteomics enhances the chances to discover changes in the levels of proteins, which are connected to fish health and could serve as novel biomarkers. In the present study, proteomic analysis accompanied by biostatistical data processing was employed with the aim of identifying plasma biomarker candidates for the onset of heart and skeletal muscle inflammation (HSMI) caused by Piscine orthoreovirus (PRV)-1 infection in Atlantic salmon. HSMI is a common viral disease and threat to fish welfare and productivity in Norwegian aquaculture, so that the early detection of HSMI development would allow a timely intervention to limit the damage. In the search for biomarker candidates, salmon plasma was sampled five and eight weeks after a PRV-1 cohabitation challenge experiment and from adequate control fish, and analysed by mass spectrometry-based proteomics. The proteome dataset contained 695 proteins with >90% probability of correct identification according to the set cut-off criteria for peptide quality. Time- and condition-related differences in protein abundance levels were revealed by multivariate analysis. Comparison of the proteins identified as significant using three different biostatistical models resulted in a short list of four potential biomarkers: galectin-3-binding protein (Gal-3BP), fucolectin-6, urokinase plasminogen activator surface receptor and ryanodine receptor 3. The physiological functions described for these proteins in mammals designate them as interesting indicators of inflammatory diseases also in other species, such as PRV-1 pathogenesis in salmon. In situ -hybridisation targeting Gal-3BP and PRV-1 mRNA in heart tissue sections from the same challenge trial showed a significant upregulation of Gal-3BP mRNA in infected salmon hearts as compared to controls, supporting the findings of the proteomic analysis and suggesting a role in the onset of heart- and skeletal muscle inflammation. • PRV-1 infection and HSMI affect the plasma proteome of Atlantic salmon. • Biostatistics revealed significant time- and condition-related proteome changes. • Four potential biomarkers for the onset of HSMI were identified. • Relevance of galectin-3-binding protein was confirmed by in situ -hybridisation. [ABSTRACT FROM AUTHOR]

The concept of a social licence to operate (SLO) that first emerged related to mining has been developed into several strands of theoretical models and used to study the social acceptance of industries in different contexts. There is an emerging literature on SLO for salmon-farming, but very few quantitative analyses are done to identify and assess factors that affect the level of social acceptance. Models that explain social acceptance levels from people's trust in an industry or company, their confidence in governance, and views on procedural and distributional fairness (trust models) are designed for quantitative analysis, and they have been successful in explaining social acceptance levels for mining. In this paper, we use survey data to test whether the factors in trust models can also explain the level of local social acceptance for salmon farming in Norway. From the structural equation modelling analysis, we conclude that these models at best have limited explanatory power in our case. We then develop an alternative model to analyse social acceptance, where factors of perception and attitudes and respondents' individual characteristics are tested as direct regression paths to influence level of acceptance. This model explains the variation in the data well. The factors that most strongly affect the level of acceptance, and which industry or authorities also can influence, are the perception of to what degree aquaculture is environmentally sustainable, whether the industry acts according to society's expectations, and if the industry is trustworthy. Practical implications for the industry and governance are discussed. • Social licence to operate (SLO) is studied in the context of Norwegian aquaculture industry. • Models developed in mining literature do not fit the data well, a simpler model provides a better fit. • Scale, structure and role in the local economy are among the sector-specific factors explaining the result. • Country-specific factors related to governance also influence SLO model in this case. [ABSTRACT FROM AUTHOR]

Fish feeding behaviour can be complicated and time consuming to observe, analyse and quantify. The conventional single ballotini X-radiography method was modified to determine the timing of feeding within a meal in farmed fish reared at commercial densities. Feed pellets containing two bead sizes were fed at different times during a single meal, either for the first half or second half of the meal. The two different ballotini sizes were differentiated on X-radiographs by human eye and semi-automated bead counting software was able to count the different bead sizes accurately. This dual ballotini method was used to assess whether fish ate earlier, later or during both halves of the meal and showed that individual fish feeding patterns were similar across two repeated meals. The method was applied to Chinook salmon (Oncorhynchus tshawytscha) , a premium farmed salmonid, to determine the relationship between feed conversion ratio (FCR) and the timing of feeding. Results showed that fish that ate smaller amounts of feed ate most of their meal at the end of the meal. There was no significant difference in when feed efficient or feed inefficient fish ate within the meal but, at the first dual ballotini assessment, there was a relationship between FCR and the timing of feeding where more efficient fish ate later in the meal. However, this relationship was absent at the second time point. Despite this, the dual ballotini method is a promising and versatile alternative method for the characterisation of fish feeding behaviours and can be applied under a range of conditions including higher rearing densities. • Two ballotini bead sizes can be fed. • Timing of feeding was identified. • Feed efficient fish eat later. [ABSTRACT FROM AUTHOR]

The environment in large aquaculture sea cages is never uniform. Abiotic factors such as oxygen level, water temperature, and ambient light, as well as farm operations such as feed distribution variate within a cage. Fish in cages look for the optimal conditions they can find, which results in higher stocking densities at specific areas. Understanding their spatial distribution patterns may help farmers to improve fish welfare, because unnormal distribution may imply sub-optimal living conditions, and the farmers can act for improvement. Good knowledge of fish distribution patterns in cages may also enable more efficient farm operations such as behaviour-based feeding. In the salmon farming sector, there has been a tremendous effort to understand fish behaviour by using diverse approaches. Much of the work was conducted in experimental cages which were smaller than the industrial scale sea cages commonly used nowadays, by using underwater cameras or single-beam echosounders. Every approach has its own pros and cons. Valuable knowledge about fish behaviour was brought by previous studies, but they had a disadvantage of seeing only a small proportion of fish in the entire cage. Consequently, their findings might be inapplicable to the industrial scale farming. Thus, there is a need for more representative information of fish behaviour in large cages, but we lack monitoring methods which can provide such information. The presented study aimed at filling this gap. The multi-beam sonar Wide Angle Sonar Seafloor Profiler , henceforth WASSP was used for the first time to understand fish distribution patterns in industrial aquaculture cages. The sonar had a 120° fan-shaped coverage, and it was rotated by the side wall of the cage to scan about 80% of the cage volume. The sonar data collected under three different farming conditions were used for 2D and 3D data visualization to test whether WASSP was able to capture changes in fish distribution patterns. The 3D distribution patterns captured by the sonar was validated by the optical data obtained by underwater cameras, which highlighted the suitability of the multi-beam sonar to monitor fish distribution patterns over the entire cage. Although the tested method exhibited some challenges such as noisy data near the water surface, it expanded our "vision" for the fish distribution in aquaculture cages. This innovative pilot study opened the possibility for continuous monitoring of 3D fish distribution in commercial scale cages, which will be focused in our future studies. • We visualized the 3D fish distribution in sea cages using a multi-beam sonar. • We can see the 3D fish distribution in good resolution. • The presented method can assist behaviour-based fish welfare assessment. [ABSTRACT FROM AUTHOR]

Conflict between stakeholder groups around social and environmental issues can fragment communities and disrupt development. For the past decade, salmon farming has globally been one of the most contentious issues within the aquaculture sector. Attempts to mitigate these conflicts have often been counterproductive due to high levels of distrust across stakeholder groups. A lower risk approach is to evaluate strategy options within a virtual socio-ecological system prior to real-world implementation. Using the Tasmanian salmon debate as a case study, this paper describes results from a social influence model that for the first time represents key stakeholder groups. This approach has allowed the responses of different stakeholders and their contribution to overall conflict to be explored and assessed under alternative communication strategies. Reductions in community conflict were achieved through improved marine literacy, collaborative learning amongst key stakeholder groups, and broad dissemination of information relating to industry performance on social and environmental issues. Model results further demonstrate that the perceived legitimacy of such initiatives depends on depoliticising the debate to address issues around regulatory capture. While applied here to salmon aquaculture, the modelling approach and lessons on effective communication strategies are likely to be relevant to a broad range of socio-ecological conflicts. [ABSTRACT FROM AUTHOR]

In this paper, we critically assess two key shifts in the global salmon aquaculture sector: first, the development of large land-based salmon production facilities and, second, the increased reliance on land-based commodity crops in salmon feed. Proponents of this 'landing' of salmon aquaculture's infrastructure promise sustainable solutions to the environmental challenges of farming in and from the sea. But the firmness of land is no predictor of a given or stable form of capital accumulation, nor does it represent a straightforward 'sustainable solution' to the ecological challenges in conventional salmon farming. We show how productive and speculative capital underpin these new projects, but also how these projects meet varied frictions which raises questions about whether 'landing' infrastructures represents a sustainable alternative to conventional salmon aquaculture. We explore this development in the context of recent debates on infrastructures as they relate to environments, ecologies and the nonhuman. We argue that analysing industrial aquaculture, and more broadly industrial animal agriculture, through the lens of environmental or ecological infrastructures, helps to bring into focus the massive and global infrastructuring of nature and nonhumans. In turn, we are able to illuminate the political, social and ecological implications of the industrial containment and feeding of animals. This article contributes to the emerging field of scholarship on ecological infrastructures by critically assessing the landing of salmon in response to the socio-ecological crisis in conventional salmon aquaculture. [ABSTRACT FROM AUTHOR]

This study presents significant improvements in the culturing of Renibacterium salmoninarum , the causative agent of bacterial kidney disease (BKD) in salmonids. Our goal was to improve R. salmoninarum cultivation and its detection in salmon farming by adjusting to 1.5%wv−1 NaCl into kidney disease medium-2 (KDM2), which significantly expedited growth without further effects from varying NaCl concentrations. The reductions in incubation periods of cultivation, this approach enhances early and accurate bacterial and disease surveillance, enabling prompt intervention. The modified medium significantly accelerated R. salmoninarum growth, achieving an optical density at 600 nm of 0.5 within 5–6 days post-incubation, marking a notable improvement over traditional KDM2. Exploring a range of NaCl concentrations in solid and liquid media revealed distinct growth patterns of R. salmoninarum across various strains. Among these, 1.5%wv−1 NaCl proved highly effective in promoting rapid pathogen proliferation while preserving essential components roles in the medium, with an average of 75% of reduction in incubation times in plate agar culture media. Strains isolated from salmon organs in the Los Lagos and Magallanes region exhibited high pathogenicity, leading to 80–100% mortality within 30 days, underscoring the wide-ranging efficacy of NaCl in enhancing growth, irrespective of geographic origins. Moreover, the modified media, enriched with NaCl, demonstrated no compromise in the pathogenicity of R. salmoninarum strains. These results highlight the potential of NaCl supplementation, supporting its addition in the media of R. salmoninarum. This inclusion could expedite biomass growth within shortened timeframes, stimulate microbial aggregates, and enhance bacterial multiplication within the medium. These findings affirm the utility of KDM2-NaCl in enhancing R. salmoninarum effective cultivation and detection, offering cost-effective strategies for managing infections and supporting targeted interventions in the salmon industry. • Salinity concentration in culture media allow rapid growth of R. salmoninarum. • NaCl concentration enable 5-day exponential growth in agar and broth culture media. • Optimized culture medium allows maintaining the pathogenicity during in-vitro growth. [ABSTRACT FROM AUTHOR]

The objective of the research described here was to examine the policies, regulations, and instruments that directly or indirectly affect the coastal zones of the island and the sea of Chiloé (CZISC) and to evaluate the adequacy of the current political-administrative system concerning climate change. For this purpose, the Decalogue for Integrated Coastal Zone Management (ICZM) has been used as a methodological basis. Likewise, all policies, regulations, and instruments that have an impact on coastal management in Chiloé have been identified and classified based on their adaptation to problems that result from climate change. The documents have been grouped into seven numerical categories (1−7) that range from tools that omit the discourse on climate change (1) to those that focus exclusively on this subject and provide detailed information on the required actions and provisions (7). The lowest level (1) of the classification is predominant in the policies, regulations, and instruments studied, especially those that deal with subnational planning. Based on the strategic diagnosis presented, it was concluded that the lack of a holistic approach and the absence of discourse on climate change observed in Chiloé prevent the transition towards an ICZM model capable of improving human welfare and protecting socio-ecological systems in the long term. • Chilean policies, regulations and instruments are very unspecific in addressing the consequences of climate change. • Chiloé, an archipelago vulnerable to climate change, has a political-administrative system far from the ICZM model. • The lack of political will in Chile prevents the renewal of an outdated policy that ignores climate change. • The salmon farming generates socio-ecological conflicts that have their origin in the biased perception of regulations. [ABSTRACT FROM AUTHOR]

Sea lice infections cause significant economic losses in Atlantic salmon (Salmo salar) farming. The objectives of this study were to (1) estimate the heritability of resistance to sea lice in the USDA's breeding program for North American (N.A.) Atlantic salmon; (2) elucidate the genetic architecture of sea lice resistance; and (3) assess the accuracy and bias of predicted breeding values for sea lice resistance using cross-validation analysis (CVA) and progeny testing of selection candidates (PTSC). Fish from year-class (YC) 2014 n = 967 and YC 2018 n = 941 were challenged with sea lice (Lepeophtheirus salmonis) and genotyped with the new USDA 50K SNP chip developed for the N.A. Atlantic salmon. Heritability estimates for sea lice count in the two year-classes were between 0.07 and 0.10. GWAS with weighted ssGBLUP (wssGBLUP) highlighted the polygenic architecture of the trait. With CVA, the genomic prediction methods x ¯ = 0.54 had higher accuracy of predictions than the pedigree-based method x ¯ = 0.43 ; and ssGBLUP had the highest accuracy of BV predictions (0.50–0.62) among the genomic prediction methods. With PTSC approach, the pedigree-based method PBLUP had higher estimated accuracy than the genomic prediction methods (0.48 vs. 0.30). Bias of BV predictions with CVA x ¯ = 0.87 range 0.57 − 1.06 was lower than with PTSC x ¯ = 1.22 range 0.44 − 2.35. Our retrospective assessment of the accuracy of indirect sib-based selection to improve sea lice resistance in the St John River aquaculture stock that is commonly used for farming of Atlantic salmon in North America demonstrated that substantial genetic gains can be obtained. Due to the polygenic architecture of the trait, the estimated accuracy of the ssGBLUP model was better than the wssGBLUP model. In our assessment, a larger training sample size will be needed to achieve optimal results with the whole genome-enabled selective breeding method due to the polygenic architecture of sea lice resistance coupled with low heritability of the trait. • Polygenic architecture of sea lice resistance was confirmed in North American Atlantic salmon. • Substantial genetic gains for sea lice resistance can be achieved through indirect sib-based selection. • Larger training sample size will be needed to achieve optimal results with genome-enabled selective breeding method. • First report that evaluates the accuracy of genomic predictions for sea lice resistance using progeny performance data. [ABSTRACT FROM AUTHOR]

The sea lice control regulations on salmon farms in Chile require weekly monitoring of Caligus rogercresseyi populations and specifically recording the number of gravid females, mobile adult (male and female without eggs strings) and attached chalimus stages. The sea lice threshold to trigger treatment has been established to maintain the number of gravid females <3 per fish after the application of any antiparasitic treatment. However, because the non-gravid females are not considered in the count, this generates an underestimation of the real abundance of the total females on the fish and also an underestimation of the fecundity rate. This study shows that the number of females was higher than the number of males after the application of an anti-sea lice treatment, with the lowest sex ratio (1.2:1) for emamectin benzoate and the highest sex ratio (14.9:1) for azamethiphos. There were no significant differences in the proportion of females after an anti-sea lice treatment for the different products (p = 0.609) and the same for males (p = 0.864). The percentage of non-gravid females in the total females ranged from 11.2 to 51.7% and the non-gravid component of the mobile adults ranged from 15.0 to 77.6% after an anti-sea lice treatment. • To ignore the abundance of non-gravid females in the sea lice monitoring generate an underestimation of the fecundity rate. • To ignore the abundance of non-gravid females, cause an underestimation of the abundance of females on the fish. • To ignore the abundance of non-gravid females, cause an underestimation of the real epidemiological situation of sea lice. [ABSTRACT FROM AUTHOR]

Submerged cage technology may enable placement of salmon farms at more exposed sites whilst avoiding the impacts of damaging weather on farm structures. Field trials have demonstrated that Atlantic salmon grow well in submerged cages for a full production cycle if an air dome is provided to enable salmon to refill their swim bladders at depth, but on occasion submerged fish have slower growth and poorer fish welfare. This could be due to submerged fish experiencing less optimal environmental conditions, the physiological effects of holding fish submerged at depth, restricted access to surface air, or an interaction between these factors. Here, we designed an experiment to remove possible environmental and depth-related effects, which enabled a direct test of the effect of restricted surface access to air due to submergence. Atlantic salmon were cultured for 11 months in either standard surface cages or submerged cages with air domes installed with a ceiling at 1-m depth to stop normal surface access. Environmental conditions were similar in surface and submerged cages. Restricted surface access had minimal effect on fish behaviour, growth, condition, welfare and harvest quality of submerged fish relative to fish held in standard surface cages. Backscattering from echo signals showed that the volume of air in the swim bladders of submerged and surface cage fish was similar, indicating submerged fish captured enough air via the air dome to maintain neutral buoyancy throughout the production period. These findings help progress commercial use of air domes and submergence, as they show the feasibility of maintaining optimal growth rates in Atlantic salmon when submerged for long periods if environmental conditions during submergence are equivalent or better than surface conditions. • Full production cycle of Atlantic salmon in submerged sea cages fitted with air domes. • Salmon growth and welfare in submerged cages matched standard sea cage production. • Salmon exhibited normal swim behaviour and buoyancy over 11 months in submerged cages. • Optimal environmental conditions are critical for submerged sea cage aquaculture. [ABSTRACT FROM AUTHOR]

The quality of smolts is one of the key factors for successful salmon production. We compared growth performance, physiological traits, and environmental adaptation in Atlantic salmon (Salmo salar) after transfer into a sea cages farm site from recirculating aquaculture system (RAS) to a similar sized group of the same genetic linage and produced in the same husbandry facility but under flow through system (FTS) conditions. Fish vertical distribution within the sea cages and water environment were continuously recorded, while biometry data and biological samples were collected monthly. No significant difference in size and smolt development between the FTS and RAS-produced fish were observed at the end of the freshwater phase. However, after transfer into seawater, the RAS fish showed an array of physiological and molecular differences that were maintained and resulted in significantly increased mortality and lower growth over the full production cycle. The RAS smolts were characterized by lower body weight, length, K factor, HSI (indicator of energy reserve), NKA activity, plasma levels of lactate, triacylglycerol, sodium, calcium, and phosphorus than FTS fish in seawater. This implicated osmoregulatory and allostatic maladaptation for the RAS fish during the first months in seawater. Both FTS and RAS fish showed physiological and behavioral adjustments during the seawater production linked with predictable (e.g., seasonal, diurnal) and short-term unpredictable variation in water temperature and oxygen. However, the RAS fish were characterized by lower physiological response to stressful effects of unpredictable environmental variability. Based on our data, the freshwater history sets the basis for the performance success of the FTS and RAS smolts in seawater. FTS fish showed faster adaptation to the seawater environment, with higher osmoregulatory capacity, and higher physiological robustness to seasonal changes than RAS fish, which reflected in their difference in growth and harvest size. We emphasize the crucial role of the freshwater rearing conditions as the foundation for successful physiological adaptation to seawater, growth, and the success of salmon farming production. • Freshwater history affects fish ability to cope with seawater transfer. • RAS smolts show slower osmoregulatory adaptation in seawater than FTS smolts. • FTS and RAS smolts respond differently to seasonal changes in seawater. • RAS smolts show lower physiological response to seawater seasonal changes than FTS. • Seawater temperature is a major factor in modulating fish performance in sea cages. [ABSTRACT FROM AUTHOR]

Feed efficiency is a highly desirable breeding goal trait as it can potentially reduce the relative economic cost of feed and concurrently reduce the environmental footprint of fish production. However, recording feed intake is a bottleneck in Atlantic salmon production. We recorded feed intake in 700 Atlantic salmon parr from 34 full sibling families using the X-ray method, where fish were fed feed containing radio-opaque beads and subsequently X-ray imaged one time after a full meal corresponding to the daily ration. In parallel, we cultured siblings from the same 35 families in duplicate family tanks of 25 individuals per tank and recorded the daily feed intake of each family at the tank level, which is known as the gold standard tank-based method. The heritability estimate for daily feed intake in Atlantic salmon using the X-ray method was significantly different from zero (0.19 ± 0.06) and was genetically correlated to growth-related traits (r g = 0.48–0.81). Daily feed intake at the family level with the X-ray method was highly genetically correlated to the daily feed intake traits using the tank-based feeding method at 0.78–0.82, depending on whether the comparison was made at a common time, common weight, or cumulative feed intake for the entire period. Whilst the X-ray method holds promise for research on the genetic background of feed intake and feed efficiency, more studies are needed to investigate the feasibility during the sea phase of Atlantic salmon production. • Feed intake using the X-ray method is heritable in Atlantic salmon • Feed intake using the X-ray method ranks well with the gold stand tank-based feeding method for families of Atlantic salmon • Feed intake is genetically correlated to growth in Atlantic salmon [ABSTRACT FROM AUTHOR]

A goal of salmon aquaculture is to produce larger, physiologically robust smolts to improve performance at time of seawater transfer and reduce time spent in marine net pens. However, little is known about whether standard processes to induce smoltification provide benefits in the production of large smolts. In Atlantic salmon (Salmo salar) reared under continuous light (24 L:0D) we applied an artificial photoperiod treatment (8 weeks of 12 L:12D followed by 4 weeks of 24 L:0D before seawater transfer) at three sizes to produce fish of ∼150–200 g, ∼400–600 g, and ∼ 1200–1300 g at seawater transfer. We then measured O 2 consumption (a proxy for metabolic rate) of photoperiod treated and control salmon (kept in constant 24 L:0D until time of seawater transfer) at three time points (in freshwater prior to seawater entry, 24 h after seawater entry, and 1 month after seawater entry) to assess impacts of photoperiod treatment and seawater transfer on performance. Consistent with known higher metabolic rates in smolts vs parr, photoperiod treatment (12 L:12D) increased minimum O 2 consumption (ṀO 2min) by ∼13% across all three sizes and at all time points measured. Increased ṀO 2min was not solely a result of increased growth rates and was associated with lower hypoxia tolerance at time of seawater transfer in ∼500 g and ∼ 1200 g salmon. Transfer to seawater reduced maximum O 2 consumption (ṀO 2max) acutely in ∼200 g and ∼ 500 g salmon regardless of the photoperiod treatment (12 L:12D or 24 L:0D), consistent with potential ion and osmotic disturbances leading to an osmo-respiratory compromise 24 h after seawater transfer. For both sizes of ∼200 g and ∼ 500 g, ṀO 2max recovered to freshwater levels 1 month after seawater transfer. In contrast, ∼1200 g salmon showed no significant changes in ṀO 2max following seawater transfer. Overall, we showed little benefits of traditional photoperiod treatments (12 L:12D) on performance of large salmon following seawater transfer. In fact, photoperiod treatment (12 L:12D) may lead to negative impacts on large salmon by increasing ṀO 2min and sensitivity to environmental stress such as hypoxia. Our results, combined with other recent studies, suggest that traditional photoperiod manipulations may be unnecessary for the development of larger Atlantic salmon smolts. However, further research is needed to fully understand impacts of photoperiod manipulations on physiological performance of larger salmon at time of seawater transfer. • Photoperiod treatment increased minimum O 2 consumption in large Atlantic salmon. • Increased minimum O 2 consumption was linked to reduced hypoxia tolerance. • Acute seawater transfer reduced maximum O 2 consumption and hypoxia tolerance. • Few benefits of photoperiod treatment for large salmon across seawater transfer. [ABSTRACT FROM AUTHOR]

Due to intensified environmental challenges and industry growth, salmon aquaculture is expanding into regions with stronger currents and higher waves. This can expose sea cages to the elements and result in pronounced cage deformations. Such deformations diminish net volume, potentially jeopardizing fish welfare and survival. A prevalent approach to gauging these deformations involves attaching pressure sensors at strategic locations on the cage. This study presents a comprehensive analysis of methods for calculating the volume of deformed aquaculture cages, categorizing them into two main approaches. The first approach involves dividing the cage's surface into triangular sections to calculate the overall volume. The second approach dissects the cage's interior into distinct segments for individual volume assessments. The effectiveness of these methods was tested on a cage exposed to extreme wave and current conditions, followed by simulations to investigate optimal sensor configurations for precise volume determination. Among the evaluated methods, the Cylinder with Cone method is praised for its simplicity, whereas the Signed Volume and Projection methods emerge as the gold standard for accuracy. A pivotal finding is the imperative of sensor placement for precision in volume calculations, with an optimal configuration comprising four sensors on the rim and one at the bottom centre. For heightened precision, a distribution of sensors between the rim, bottom centre, and cage side is endorsed in tandem with the Signed Volume or Projection method. • Volume calculations accurate even with significant deformations and easy to implement. • Measurements of volume reduction in cages using pressure sensors are demonstrated. • The sensor count required for volume estimation is ascertained from simulations. [ABSTRACT FROM AUTHOR]

As the second biggest producer of salmon after Norway, Chile is one of the leading forces of aquaculture with a long history of being strongly focused on international markets. Based on contributions from critical geography, political ecology and the sociology of globalization, the article analyses the dominant narratives and policies deployed by the Chilean government and the salmon farming industry in successive contexts of boom and crisis of production activity in the archipelago of Chiloé (Los Lagos Region). In a context of a word-wide growing interest in the capabilities of the blue economy, a discourse analysis of governmental, industrial, and public-private institutional documents, together with semi-structured interviews to a broad number of stakeholders contributes to advance the understanding of and learn from the evolution and challenges faced by one the longest world's salmon aquaculture leaders. The research identifies five discursive and policies phases over more than four decades of development. From an initial narrative that defines the region as "empty" and uses the discourse on salmon farming to justify territorial integration policies (1973–1982); to a second period in which the fostering of the salmon farming in the southern region served as a catalyst of national economic growth interests (1983–1994). It follows a boom phase characterized by the capitalization on the blue revolution discourse (1995–2006), which lasted until the territorial crisis resulting from the ISA virus, and the expansion of the industry towards southern regions (2007–2015). The analysis reveals a fifth phase starting in 2016 and ongoing by 2023, which characterized by the emergency and implementation of a new administrative right over coastal-marine areas to safeguard the traditional uses of indigenous communities, starts to challenge the long-standing hegemony of the salmon farming industry in Chile. [ABSTRACT FROM AUTHOR]

Salmon aquaculture production has grown considerably in recent years, and parallel to this growth public interest in production and product has also increased. In most salmon producing countries there have been reports of both public dismay and support for the industry. In this paper we investigate and compare public perceptions, understood as to what degree the industry has a social license to operate, across three countries. In Tasmania (AU), Iceland and Norway, the salmon aquaculture industry has a varying foothold, something which is also reflected in public perceptions. An outline of the three contextual settings is therefore provided. We undertook surveys using a standardized questionnaire which was distributed to respondent panels in the three countries. The data was analyzed using descriptive statistics. The findings show some similarities and notably mostly differences between the respondent groups. A comparative approach as reported here requires understanding of contextual factors to offer explanatory power to the analysis. The results from the comparative survey is therefore discussed in light of the various contextual settings. We found that many respondents are supportive of the aquaculture industry in their respective countries (Iceland less so), but that there is something amiss, which the respondents feel is not achieved. While support is related to industry contributions of food production, employment, and business activity, the respondents also report acceptance of the industry and view the industry to be important. However, the respondents are less supportive of the industry with regards to sustainability, industry regulation, and distribution of economic benefits. We suggest that efforts to increase societal support for aquaculture must be adapted and related to the contextual environment the industry operates in, both locally and nationally. A pivotal element in this context is the public's knowledge of the industry, which is deemed important for their assessment of perceived advantages and challenges posed by the industry on both local and national level, and the necessary trade-offs between them in forming a supportive or critical opinion. • Aquaculture is growing worldwide in parallel with increasing public awareness of impacts • A cross-country comparison of social license to operate for aquaculture is reported and discussed • Survey data is combined with contextual case study descriptions • Efforts to increase societal support for industry should be adapted and related to the contextual environment [ABSTRACT FROM AUTHOR]