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Arctic charr has emerged as a valuable candidate for diversifying commercial salmonid products for human consumption. The selective process is ongoing and the species has not been fully domesticated yet. Considering these factors, the impact of fish meal replacement on Arctic charr may differ from that observed in other farmed salmonids. The aim of this multidiciplinary study was to determine whether enhancements to SBM (enzyme pre-treatment and prebiotic addition) facilitate beneficial changes in the growth performance, gut microbiome, and behavior of Arctic charr. The results show that juvenile Arctic charr can tolerate relatively high inclusion levels (25 %) of soybean when supplemented with a prebiotic. However, enzyme pre-treatment of SBM had no beneficial effect on this species. The gut microbiota, mainly consisting of one dominant taxon, Mycoplasma sp., did not appear to be influenced by feed-related bacterial remnants or by the type of feed applied. Behavioral differences and similarities were observed in fish fed different diets. High consistency in the exploration trait was noted, with no impact of diet treatment on its mean value. A response to light stress on swimming activity occurred, regardless of diet treatment. Fish fed the untreated soybean diet exhibited greater boldness, while those fed the enzyme pre-treated diet showed high consistency in boldness. A negative correlation between boldness and growth performance was identified; however, no relationship was found between exploration and growth performance, nor was there a boldness-exploration syndrome in fish fed any of the diet treatments. These differences could not be attributed to variations in the gut microbiome, but other mechanisms that remain to be elucidated might be involved. Further research is needed on the impact of dietary proteins on the behavior and welfare of Arctic charr to optimize existing and new protein sources. • Impact of enhancements to soybean meal is assessed on Arctic charr. • Traits such as growth, gut microbiome and behavior are examined. • High inclusion levels (25 %) of soybean, when supplemented with a prebiotic, could be successfully used. • Microbiota does not appear to be influenced by the diets. • Behavior consistency and mean value vary according to diets. [ABSTRACT FROM AUTHOR]

Abstract Biodensity is a major factor affecting the production and welfare of farmed fishes. Arctic charr (Salvelinus alpinus) (average mass 176.9 ± 3.9 g) were held at biodensities of 30, 60, 90, 120, and 150 kg/m3 (4 replicates per treatment) during a 91 day study which examined key growth, stress physiology, and welfare parameters. During experimentation fish were fed to near satiety, and a random subsample of 20 fish (5 per replicate tank) were collected from each treatment every 21 days. Biodensity was found to have no significant effect on mortality rates or physical fin damage. Growth rates were lower in charr reared at the highest biodensities (120, and 150 kg/m3), while feed efficiency was negatively affected at both the highest (120, and 150 kg/m3) and lowest (30 kg/m3) biodensities. Plasma cortisol indicated that Arctic charr are more stressed at lower biodensities, but was not correlated with growth or feed efficiency measures. The results support an optimal biodensity range for charr culture between 60 and 90 kg/m3 to optimize production and welfare. Highlights • The purpose of this study was to provide an estimation of an optimal biodensity for Arctic charr aquaculture, with emphasis on production performance and welfare. High intensity aquaculture operations rely upon high biodensities which may compromise the welfare of the animals being farmed (Browman et al., 2018 ; Moccia, 2013). Thus, there are two drivers at play in determining an optimal biodensity with respect to the economics of fish growth and production performance, and the ethics associated with welfare consideration. Ultimately, the determination of an optimal biodensity for Arctic charr aquaculture must be the result of the careful consideration of these two approaches. • Biodensity had no effect on mortality, plasma glucose or fin damage (caudal and dorsal). However the combination of reduced growth rates (i.e. lower TGC's) observed at the high densities (120, and 150 kg/m3) and reduced feed efficiency (0.56–0.83) at the extremes (30, 120, and 150 kg/m3) suggest a density between 60 and 90 kg/m3 for optimal economic gains. The morphometric data presented here also provide additional considerations for the choice of stocking density in terms of the potential commercial productivity for Arctic charr. • Alternatively, the results of the welfare analyses show evidence of reduced stress (as assessed by circulating levels of plasma cortisol) at higher biodensities, with fish stocked at 150 kg/m3 exhibiting the lowest levels of all treatments. • These two approaches provide slightly different result on which to base a suggestion of an optimal biodensity. The economics approach suggests stocking at densities >30 kg/m3 and <90 kg/m3 for the benefit of producing product of similar quality while improving feed efficiency and growth. However, stocking at higher densities (150 kg/m3) resulted in reduced stress which is associated with the welfare status of farmed animals (Turnbull et al., 2008). Therefore, using a combination of an economics and ethics based approach, the suggested biodensity for Arctic charr aquaculture is somewhere in the range of 60–90 kg/m3 (actuals 65.1–99.0 kg/m3). Within this range, Arctic charr exhibited optimal feed efficiency and growth while maintaining cortisol levels below the 10 ng/mL which is a nominal threshold of cortisol implied for stressed salmonids (Pickering and Pottinger, 1989). [ABSTRACT FROM AUTHOR]

Abstract The reproductive performance of farmed Arctic charr exhibits substantial individual variation. The causes behind this variation have not yet been properly explained, despite the species relatively long history in aquaculture. The aim of the present study was to provide better understanding of the issue by evaluating parent and gamete traits in relation to fertility and offspring viability under routine hatchery conditions. Are losses mainly due to failed fertilisation or mortality? Are maternal or paternal factor more predominant? The study covered sex hormone status of the broodstock, egg traits (egg size and wateriness of egg batches), milt traits (volume, density, and sperm motility characteristics), and symmetry of early cell division. We found that the majority of offspring loss occurred as embryo mortality, although a significant additional loss could be assigned fertilisation failure. Fertilisation and mortality rates were not inter-correlated. Neither of the evaluated egg traits, egg size and wateriness of newly stripped egg batches, proved to be useful indicators of egg quality. With regard to sperm traits, milt density as well as several computer assisted sperm analysis (CASA) parameters, i.e. swimming speed (VAP, VSL, and VCL) and beat cross frequency (BCF), were correlated with reproductive performance and could potentially be used as quality indicators for Arctic charr. Together, male 17,20β-P levels and BCF explained 69.5% of the between male variation in proportion of successfully eyed eggs. The results support previous indications that post-ovulatory aging of oocytes is contributing to the impairment of reproductive performance in farmed Arctic charr. In addition, a significant paternal factor to this impairment has been exposed. However, the cause and mechanism involved are still far from clear. Highlights • Broodstock and gamete traits were evaluated together with fertility and embryo viability under routine hatchery conditions. • Embryo mortality, rather than failed fertilisation, was the main cause for egg loss in the studied Arctic charr broodstock. • Besides post-ovulatory aging of oocytes, paternal fertility issues, which needs to be investigated further, were revealed. [ABSTRACT FROM AUTHOR]

Abstract Governance of fisheries in Canada's North is shared between communities, Inuit land claim management boards and the Canadian Department of Fisheries and Oceans under co-management systems outlined in the Nunavut Land Claim Agreement and the Inuvialuit Final Agreement. The management, conservation and optimization of Arctic Charr resources remain complicated by data paucity; by biological complexity of Arctic Charr stocks; climate change impacts; and by the lack of adapted stock assessment tools and co-management frameworks linking Inuit traditional knowledge with scientific expertise. The current state of Arctic Charr fisheries in Nunavut and the Northwest Territories is reviewed and alternatives presented for the evaluation of Arctic Charr stocks using intra-specific life history diversity as a basis for risk and quantitative assessments. The approach fits well with the shared governance model in that the biological characteristics at the root of the analysis, such as size at spawning and maximum length (life history metrics), can be observed through Inuit knowledge and/or through scientific sampling carried out by community members. Assessment is developed as a two stage process using productivity-susceptibility analysis and life history invariant models to determine the maximum sustainable production. The resulting analytical model can but updated through further ecological observations from the community and field sampling. The approach provides for active engagement by the fishers in the process of stock assessment. These science alternatives can be used by managers within the co-management framework to maximize sustainability of Arctic Charr fisheries. [ABSTRACT FROM AUTHOR]

Abstract Refeeding, following a period of food deprivation will often lead to compensatory growth. Although many studies have focused on molecular mechanisms behind this accelerated growth response in fish, little is known on the roles of protein and metabolism. We also assessed, for the first time, the potential roles of miRNAs in regulating compensatory growth. Artcic charr, Salvelinus alpinus , a northern freshwater species, was deprived of food for 101 days and then fed to satiety for 126 days. The refeeding period resulted in compensatory growth, with a partial compensation of body mass. The feed deprivation period lead to a decrease in hepatosomatic index (HSI) and intestinal somatic index (ISI). HSI and ISI were then gradually replenished during early refeeding, following a lag phase prior to the compensatory growth response. mRNA transcripts regulating protein degradation via the autophagy pathway (Cathepsin D and Cathepsin L) in muscle were upregulated during feed restriction and downregulated after refeeding, which could allow for greater protein accretion in muscle, facilitating compensatory growth. Transcript levels from the ubiquitin proteasome pathway (Mafbx and Murf1) and the calpain system (Calpain 7 and Calpastatin) suggested that these pathways were not involved in regulating compensatory growth. Furthermore, we've shown that miRNAs (miR-29a and miR-223) could be involved in fish glycogen homeostasis during the early stages of refeeding. These findings provide a deeper understanding of the molecular mechanisms regulating growth in fish. [ABSTRACT FROM AUTHOR]

The Swedish breeding program for Arctic charr ( Salvelinus alpinus L.) has been running for 30 years and includes seven selected generations. In this study, we evaluated the differences in growth between the first generation of selected Arctic charr and the present generation. We demonstrate that not only has growth been improved through selective breeding but also that a change in the seasonal growth capacity has occurred. Selection has induced a high winter growth capacity, but the largest weight gain between generations was seen during summer. As a result of selective breeding, the production time to reach a slaughter weight of 600–700 g has been reduced by 10 months since the start of the breeding program in 1985, and improvements in the final weight have been of the magnitude of 11% per generation. To be able to keep up with the faster growth and altered seasonality of this strain, feeding management needs to be adapted. In this study, a model based on the theoretical energy need of the Arctic charr is presented, which makes it possible to make such adaptions in feeding management. [ABSTRACT FROM AUTHOR]

Limited knowledge exists about the residing microbiome in gamete-related samples in fish. A potential effect between the seminal microbiome composition and sperm quality traits has been previously suggested in humans and livestock. Using a metabarcoding approach, we aimed to gain insights into the structure of the residing prokaryotes and microbial eukaryotes in ovarian fluid (n = 10) and milt (n = 84) from farmed Arctic charr - a species with highly variable reproductive success in captivity. In addition, sperm quality traits were recorded on the sampled males to investigate potential associations with the residing seminal microbiome. Higher microbial diversity was found in the ovarian fluid compared to the milt habitat. Even though the residing microbiome showed distinct differences between the two habitats, substantial overlap was observed, with >70% of the milt core microbiome being found in the ovarian fluid habitat. Statistically significant associations were found between the Shannon diversity index and sperm motility-related traits. Additionally, a fungal operational taxonomic unit (OTU) potentially belonging to the Leotiomycetes class was associated with sperm concentration and motility. Overall, our study documents the microbiome structure of gamete-related samples from Arctic charr. Even though some associations were obtained between sperm quality parameters and either microbiome diversity or with a fungal OTU, follow-up studies on a larger scale with more tank replicates are needed to confirm the robustness and causality of these relationships. • First report of the residing microbiome structure in gamete-related samples on fish • Associations were found between the Shannon diversity index and sperm motility-related traits. • A fungal operational taxonomic unit was associated with sperm concentration and motility. [ABSTRACT FROM AUTHOR]

Traditional sources of protein in fish feed for salmonids, such as fishmeal, face sustainability problems. Therefore, ingredients not attractive for human consumption are increasingly being considered for the development of future feeds. However, it is uncertain how this alternative range of ingredients will affect fish growth, quality and consumer opinion. In this experimental study, we tested a new fish feed on Arctic charr, containing a protein mixture from the Baltic Sea and yeast, all ingredients unattractive for human consumption. This feed comprised of sprat ( Sprattus sprattus ) and herring ( Clupea harengus ), blue mussels ( Mytilus edulis ) and baker's yeast ( Saccharomyces cerevisiae ), in a ratio of three parts to the whole. Fish fed with this feed grew 11.5% less than the control group. The digestibility and microscopy analysis of the faeces suggested a lower digestibility of the test feed, presumably caused by the fish's inability to utilize the nutrients from the yeast cells. Consumers' perceptions of the final product were evaluated through a sensory evaluation, indicating no differences in scores of fillet quality between the two treatments. Potential implications of these results are discussed in context of feed composition, quality and other factors including species biology and season, which are relevant topics in the discussions on feed sustainability. Statement of relevance Evaluating a feed mix unattractive for human consumption. [ABSTRACT FROM AUTHOR]

Two lab-based trials quantified the effect of a range of continuous light (LL) treatments overwinter on the somatic growth and incidence of sexual maturation in the fall age 2 of individually identified under-yearling Arctic charr (Labrador strain) at constant 10 °C. Controls were maintained under simulated natural photoperiod (LDN; Latitude 45°N). In trial 1 ( n = 120/trt, mean 54 g initial body weight), LL starting the 1st day of either October, November, December, January or February (all returned to LDN on April l) resulted in a step-wise reduction in maturity of 43, 55, 59, 67 73% compared with 77% in the control (sexes pooled). In trial 2 ( n = 90/trt, mean 24 g initial body weight), LL starting either August 13 or October 1 and ending April 1 reduced maturity to < 10%, compared to 33% (LL Dec1-Apr1) and 50% in the LDN controls. LL starting October 1 and ending either February 1, April 1 or June 1 were equally effective, resulting in < 15% maturity. The importance of returning from LL to LDN in spring to reduce maturity was demonstrated by the LL constant (Oct–Oct) treatment which resulted in relatively high maturity, 31%. The reduction of maturity rate was independent of both somatic growth and condition factor during winter in all treatment groups. Among fish that matured, the timing of completion of sexual maturation was affected by both the LL start and end date. [ABSTRACT FROM AUTHOR]

The effects of dietary lipid oxidation on fish are diverse and contradictory. In this study, herring oil was oxidized to five different levels (peroxide values (POV): 20.44, 182.97, 56.12, 33.27 and 0.00 meq kg − 1 ) and used to formulate five experimental diets. Juvenile Arctic charr ( Salvelinus alpinus , mean body mass ± SD: 2.41 ± 0.11 g) were reared on the five diets for 67 days. In another experiment, juvenile Nile tilapia ( Oreochromis niloticus ) (1.71 ± 0.40 g) were reared on three diets formulated with oxidized oils having POV of 19.55, 447.27 and 32.72 respectively, for 90 days. Growth responses were monitored in quadruplicate groups of 60 individuals of Arctic charr and 100 for Nile tilapia, respectively. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were only studied in Arctic charr. At the end of the study, the Arctic charr group reared on a diet with oils in the primary oxidation state had significantly lower body mass and specific growth rate, but higher hepatosomatic index compared to the rest of the groups. The activities of CAT and GPx increased with dietary lipid oxidation while that of SOD remained fairly stable. In Nile tilapia, both final body mass and condition factor were significantly lower in the group fed fresh oil than in the groups fed oxidized oils. Fillet lipid content decreased with lipid oxidation while ash and protein did not differ amongst tilapia groups. The results suggest that Arctic charr are more susceptible to lipid oxidation than are Nile tilapia. These differences may be the result of species differences in tolerance to oxidized lipids, variable lipid intake or access to vitamin E/tocopherol in feed. Statement of Relevance Important for Arctic charr and Nile tilapia feed development. [ABSTRACT FROM AUTHOR]

To address the problem of high maturity at 2 years of age among Salvelinus alpinus (Labrador strain), PIT-tagged yearlings (ca. 110 g) were reared for 18 weeks overwinter (Nov. 16 to Apr. 1) under six treatments (90 fish per treatment) that combined three factors: photoperiod (natural day length, LDN or 24 h light, LL), temperature (10 or 5 °C), and food (fed daily or no food). On April 1 all fish were returned to LDN, 10 °C and fed daily for a further six months. In November, the maturity rate was very high among fish reared the previous winter under LDN and fed daily at both 10 °C (♀ 94%, ♂ 43%) and 5 °C (♀ 87%, ♂ 45%). Replacing LDN with LL overwinter, at 10 °C halved the maturity rate (♀ 49%, ♂ 19%), and at 5 °C eliminated maturity among females, and male maturity was 6%. Food deprivation for 18 weeks posed no health problems, and combined with LL also was highly effective at preventing maturation, both at 10 °C (♀ 0%, ♂ 2%) and 5 °C (♀ 0%, ♂ 7%). Compensatory growth following the suppression of growth overwinter indicates this approach to reducing maturity can be a commercially viable means to produce 1 kg immature product around 2 years old. A new two-step gating mechanism is proposed to explain the photoperiod prevention of maturation, one independent of somatic growth, the other dependent. Statement of relevance This study shows that the combination of LL, reduced temperature and food deprivation can significantly reduce the incidence of maturation and improve the productivity among diploid Arctic charr. This combination approach can potentially be applied to other farmed salmonids and non-salmonids to improve the efficacy of controlling sexual maturation. [ABSTRACT FROM AUTHOR]

The bacterium Aeromonas salmonicida ssp. achromogenes (Asa) causes atypical furunculosis in salmonids that may lead to extensive financial losses in intensive fish farming. The commercially available vaccine commonly used against the ssp. achromogenes in the production of Arctic charr in Iceland has been developed for Atlantic salmon (Salmon salar) against the subspecies salmonicida which causes typical furunculosis, but it has insufficient efficacy in Arctic charr. In response to this, a novel vaccine against Asa in Arctic charr was developed in cooperation with Spanish vaccine company; HIPRA, and the antibody response of Arctic charr against Asa investigated using enzyme-linked immunosorbent assay. Fish used for testing were vaccinated using the novel, monovalent autogenous experimental vaccine and a commercially available vaccine Alpha Ject® 3000 developed for Atlantic salmon that was used as a comparison. The study was conducted in commercial production units where the fish were continually exposed to natural outbreaks of atypical furunculosis. Blood samples were collected from the fish prior to vaccination and thereafter at approximately ten-week intervals in each production unit throughout the production period until the fish reached harvesting size. Fish growth and mortality was recorded throughout the study. The results indicated that both vaccines induced antibody response in fish against Asa antigens and that antibody titers obtained during the first weeks following vaccination were maintained throughout the production period. However, significantly higher antibody titers were observed in fish vaccinated with the experimental novel vaccine and fish mortality was significantly lower in production units containing fish vaccinated with the novel vaccine in comparison to the Alpha Ject 3000® vaccine. These results suggest that the novel vaccine may be a promising candidate for protective immunity against atypical furunculosis caused by Asa in Arctic charr. • The specific antibody responses in Arctic charr against Aeromonas salmonicida ssp. achromogenes were analyzed using ELISA. • A novel experimental vaccine developed for Arctic charr and a commercial vaccine developed for Atlantic salmon were compared. • The novel experimental vaccine induced a higher specific antibody response and with more extended duration. • Significantly reduced fish mortality was observed in the group vaccinated using the experimental vaccine. [ABSTRACT FROM AUTHOR]

The flooding dose technique of Garlick et al. ( 1980 ) has become the main method for measuring tissue and whole-animal rates of protein synthesis in ectotherms. However, single tissue samples are used to determine rates of protein synthesis and no studies have examined the pattern of flooding in large tissues such as the white muscle in fishes, which can comprise up to 55% of the wet body mass of a fish and which is poorly perfused. The present study has examined, for the first time, the patterns of flooding and measured rates of protein synthesis in five different regions of the white muscle in the Arctic charr Salvelinus alpinus ranging in size from 25 g to 1.6 kg following a flooding dose injection of L-[ 3 H]-phenylalanine. The results indicate that the degree of flooding ( i.e. free pool specific radioactivity relative to that of the injection solution) and elevation in free phenylalanine concentrations can vary between regions but the calculated fractional rates of protein synthesis were similar in four of the five regions studied. The variability in rates of protein synthesis increased with body size with greater variability observed between regions for fish > 1 kg in body mass. For consistency between studies, it is recommended that samples are taken from the epaxial muscle in the region below the dorsal fin when measuring fractional rates of white muscle synthesis in fishes. [ABSTRACT FROM AUTHOR]

The Swedish breeding programme for Arctic charr aims to improve traits that are important for farming. Selection has been ongoing since the 1980s, and the aim of this study was to re-estimate the genetic parameters in the selected population. In addition, the genetics of skin pigmentation was studied, as previous work indicated a relationship between pigmentation and the ability to cope with stress. One hundred twenty-five full sib families of Arctic charr were hatched and reared separately until they were individually tagged (n = 12,266). In connection with the tagging, three replicates were formed, which were subsequently reared at different sites. The genetic relationships were known from a seven-generation pedigree. Body weight and length were at one site measured at six occasions until 27 months old, and these measurements were used to estimate the DGC (daily growth coefficient) and condition factor. At a second site fish were measured at 21 and 27 months age and at a third site at 27 months age. Skin pigmentation was measured using image analysis. The final weight at 27 months of age varied widely between rearing sites, ranging from 529 g to 1443 g. Weight heritability differed among the sites, at 0.45, 0.11, and 0.07. At one of the sites, where growth was followed closely, weight heritability varied among growth periods, ranging from 0.01 to 0.25, and similar results were obtained for the DGC. In contrast, condition factor heritability did not show such pronounced variations within and among sites. The magnitude of the differences in heritability of weight and growth among different sites that was observed here was not observed previously with this charr population. In particular, the low heritability among the fastest growing fish is unprecedented. Skin pigmentation showed a high heritability of 0.76, indicating a strong additive genetic component. At most ages, pigmentation showed a weak positive genetic correlation with growth. The genotype environment interaction (GEI) was estimated using genetic correlations among sites. For the final weight, genetic correlations were high, indicating weak GEI, although the presence of GEI was suggested from the DGC data. Statement of relevance The ms will impact charr breeding for commercial farming. [ABSTRACT FROM AUTHOR]

The evaluation of new diet composition is commonly achieved by performing time-consuming growth trials, which may negatively impact the welfare of a large number of fish if the feed is not accepted. Instead, the fish's behavioural responses to a new diet composition can be used as a first step in the evaluation of new diet composition. The taste acceptance of a new diet by Arctic charr ( Salvelinus alpinus ) was evaluated over 16 days based on the self-selection of a test diet and a control diet. The test diet contained ingredients from the nutrient-enriched Baltic Sea, and it is hoped that this diet can contribute nutrients to the nutrient-poor waters in northern Sweden in which Arctic charr are farmed. The main ingredients in the test feed were blue mussel meat ( Mytilus edulis ), meat from sprat ( Sprattus sprattus ) and herring ( Clupea harengus ), baker's yeast ( Saccharomyces cerevisiae ), fish oil and regionally produced rapeseed oil. Individual fish ( n = 15) were allowed to choose between abundances of both the test diet and a fishmeal based control diet that mimicked a standard feed for Arctic charr. After only a few days, the fish demonstrated a significant preference for the Baltic Sea test feed. These results may depend on betaine, which was found at concentrations that were four times higher in the test feed than in the control feed. Betaine is a known attractant for many fish species and is abundant in marine animals, such as mussels. Thus, the test diet can be evaluated further without additional taste stimulants before the new feed formula can be used commercially to ensure fish welfare, the product quality and the economic feasibility of the new formula. [ABSTRACT FROM AUTHOR]

• A novel evolutionary model (JBGP) was developed. • The JBGP classifies the presence of Arctic charr in the Teno River catchment. • The JBGP is superior to the jittered decision tree model. • Macroinvertebrates, mires and slope are the dominant indicators. Arctic charr is one of the fish species most sensitive to climate change but studies on their freshwater habitat preferences are limited, especially in the fluvial environment. Machine learning methods offer automatic and objective models for ecohydrological processes based on observed data. However, i) the number of ecological records is often much smaller than hydrological observations, and ii) ecological measurements over the long-term are costly. Consequently, ecohydrological datasets are scarce and imbalanced. To address these problems, we propose jittered binary genetic programming (JBGP) to detect the most dominant ecohydrological parameters affecting the occurrence of Arctic charr across tributaries within the large subarctic Teno River catchment, in northernmost Finland and Norway. We quantitatively assessed the accuracy of the proposed model and compared its performance with that of classic genetic programming (GP), decision tree (DT) and state-of-the-art jittered-DT methods. The JBGP achieves the highest total classification accuracy of 90% and a Heidke skill score of 78%, showing its superiority over its counterparts. Our results showed that the dominant factors contributing to the presence of Arctic charr in Teno River tributaries include i) a higher density of macroinvertebrates, ii) a lower percentage of mires in the catchment and iii) a milder stream channel slope. [ABSTRACT FROM AUTHOR]

A method was devised to measure the fractional rate of protein synthesis in fish using a stable isotope labelled tracer (ring-D 5 -phenylalanine) instead of radioactive phenylalanine. This modified flooding dose technique utilizes gas chromatography with mass spectrometry detection (GC-MS). The technique was validated by measuring the fractional rate of protein synthesis in the liver and white muscle of Arctic charr ( Salvelinus alpinus ) and then tested by comparing the fractional rate of protein synthesis of fed and starved Arctic charr. The modified technique met the assumptions of the flooding dose technique and was successfully used to detect alterations in the rate of protein synthesis in fed and starved fish. This modified technique allows for studies on protein metabolism to be carried out in situations where the use of radioactivity is difficult, if not impossible. [ABSTRACT FROM AUTHOR]

Anadromous and non-anadromous Arctic charr ( Salvelinus alpinus ) from multiple sample sites in Labrador, Canada were used to investigate possible differences in total mercury concentration ([THg]) between 1977–78 and 2007–09. The mean [THg] of anadromous Arctic charr was 0.03 μg/g wet weight (ww) in 1977–78 and 0.04 μg/g ww in 2007–09, while mean concentrations in non-anadromous conspecifics were 0.18 μg/g ww in 1977–78 and 0.14 μg/g ww in 2007–09. After correcting for the effects of fish age and fork-length, there was no widespread difference in the mean [THg] of anadromous or non-anadromous fish between the two time periods. However, at individual sites sampled during both time periods, [THg] increased, decreased, or did not change. The mean age of sampled fish declined from 9.0 years in 1977–78 to 8.2 years in 2007–09 for anadromous fish, and from 11.7 years to 10.5 years in non-anadromous Arctic charr. Similarly, mean fork-lengths decreased from 450 mm to 417 mm in anadromous and from 402 mm to 335 mm in non-anadromous fish between 1977–78 and 2007–09. The mean annual temperature at four Labrador weather stations increased by 1.6 °C to 2.9 °C between the two sampling periods. The lack of an overall trend in anadromous or non-anadromous Arctic charr [THg] despite warming temperatures that favour increased mercury methylation suggests that regional changes in climate-driven factors have had limited impacts on mercury exposure in Labrador freshwater or marine fish. [ABSTRACT FROM AUTHOR]

Behavioural traits have been shown to have implications in fish welfare and growth performances in aquaculture. If several studies have demonstrated the existence of repeatable and heritable behavioural traits (i.e., animal personality), the methodology to assess personality in fishes is often carried out in solitary context, which appears to somewhat limit their use from a selective breeding perspective because these tests are too time consuming. To address this drawback, group-based tests have been developed. In Nordic country, Arctic charr (Salvelinus alpinus) is widely used in aquaculture, but no selection effort on behavioural traits has yet been carried out. Specifically, in this study we examined if risk-taking behaviour was repeatable and correlated in group and solitary context and if the early influences of physical environment affect the among-individual variation of behavioural trait across time in order to verify whether a group risk-taking test could be used as a selective breeding tool. Here, we found that in both contexts and treatments, the risk-taking behaviour was repeatable across 7 days. However, no cross-context consistency was found between group and solitary, which indicates that individual Arctic charr express different behavioural trait in group and solitary. • Risk-taking behaviour was assessed in the Arctic charr. • Fish were raised in plain versus enriched environments. • Risk-taking were tested in solitary versus group contexts. • Risk-taking behaviour was repeatable across 7 days in both contexts. • No consistency was found between the solitaryand groupcontexts. [ABSTRACT FROM AUTHOR]

Abstract: The present study aims to analyze several biological and environmental variables to explain the unpredictable reproductive success at the main aquaculture facility involved in the Swedish Arctic charr breeding program. Data from 540 egg batches, collected from the years 2000 to 2011, were analyzed for the effects of factors such as temperature conditions, female age and egg size on egg viability (% of eyed eggs). An exploratory factor analysis (EFA) reduced 12 variables into 4 factors. Factor 1 mainly explains the negative relationship between high temperature in summer and egg viability. Factor 2 mainly explains a significant relationship between increasing temperatures in autumn (September to November) and decreased egg viability. Factor 3 explains that an early stripping date and increased temperature during stripping and egg incubation together have a negative, although not statistically significant, relationship to egg viability. Factor 4 explains a significant positive relationship between female age and egg size on the proportion of eyed eggs. The most relevant factors in explaining egg viability identified by the EFA analysis were evaluated further, indicating how farming conditions need to be improved. The broodstocks have been subjected to critically high water temperatures during July and August, resulting in decreased egg viability. Access to sufficiently cool water during summer is crucial. Based on the negative correlations found between incubation temperature and egg survival we suggest that a more moderate water heating may be beneficial. Most females were used as broodfish for several years. By applying individual tagging, data on the individual reproductive performance of females for up to 5 consecutive years could be analyzed. In this analysis, both egg size and the proportion of eyed eggs increased with the mean female age. There was also a strong age-unrelated positive correlation between egg size and survival. [Copyright &y& Elsevier]

Abstract: Previous research has documented that total mercury concentrations ([THg]) are lower in anadromous Arctic charr than in non-anadromous conspecifics, but the two life-history forms have rarely been studied together. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual [THg] across a range of latitudes (49–81° N) in eastern Canada. Unadjusted mean [THg] ranged from 20 to 114ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations, ranging from 111 to 227ng/g ww. Within-population variations in [THg] were best explained by fish age, and were often positively related to fork-length and δ15N-inferred trophic level. Differences in [THg] were not related to differences in length-at-age (i.e., average somatic growth rate) among populations of either life-history type. Mercury concentrations were not related to site latitude in either the anadromous or non-anadromous fish. We conclude that the difference in Arctic charr [THg] with life-history type could not be explained by differences in fish age, fork-length, trophic position, or length-at-age, and discuss possible factors contributing to low mercury concentrations in anadromous, relative to freshwater, fish. [Copyright &y& Elsevier]

Abstract: Patterns of total Hg (THg) and methyl Hg (MeHg) biomagnification were investigated in six pairs of co-located lacustrine and marine food webs supporting a common predator, Arctic charr. Mercury biomagnification rates (the slope of log Hg concentration versus δ15N-inferred trophic level) did not differ significantly between the two feeding habitats for either THg or MeHg, but THg and MeHg concentrations at the base of the food web were higher in the lacustrine environment than in the marine environment. The proportion of THg as MeHg was related to trophic level, and the relationship was statistically similar in the lacustrine and marine habitats. The biomagnification rate of MeHg exceeded that of THg in both habitats. We conclude that the known difference in Hg concentration between anadromous and non-anadromous Arctic charr is driven by differential Hg concentrations at the base of the lacustrine and marine foodwebs, and not by differential biomagnification rates. [Copyright &y& Elsevier]

Abstract: A snapshot sample of Arctic charr (Salvelinus alpinus) from Heintzelman Lake (81°42′N, 66°56′W), Ellesmere Island, Canada was used to elucidate the biological and life-history factors potentially influencing individual total mercury (THg) concentrations. Migratory history was significant, with anadromous fish having a lower mean THg concentration (64μg/kg ww) than the non-anadromous Arctic charr (117μg/kg ww). The increase in individual THg concentration with age was shown to be independent of length-at-age when large and small individuals within the same age groups were compared. Similarly, the diets of individual Arctic charr were comparable regardless of size, and there was no apparent ontogenetic shift in diet that could explain differences in length-at-age or THg concentration among fast- and slow-growing groups of fish (i.e., fish of the same age but differing sizes). Maturity state was also not related to THg concentration, but appears to be related to differences in length-at-age, with slow-growing fish allocating more energy to reproduction than fast-growing conspecifics. The differences in THg concentration among individual Arctic charr were best explained by fish age. We suggest that the increase in mercury concentration with age can be altered by a shift in diet (e.g., to piscivory) or habitat (e.g., anadromy), but is otherwise unaffected by changes in size or length-at-age. [Copyright &y& Elsevier]

Abstract: The short and long term effects of short photoperiods on growth and maturity were investigated in 240 individually tagged juvenile Arctic charr (Salvelinus alpinus). The Arctic charr were reared at constant temperature (12°C) and on four different light regimes; one group on continuous light (LD24:0) as control and three groups experienced a period of short day (LD8:16) on a three subsequent 6week periods i.e. 24th September–6thNovember (LD8:16Sep–Nov), 6th November–19th December (LD8:16Nov–Dec), 19th December-29th January (LD8:16Dec–Jan). Before and after the short photoperiod treatment the groups were reared at continuous light. The growth of the fish was monitored over a period of 11months. At the termination of the experiment in September 2009, the body mass of the three groups receiving a short day period (LD8:16 Sep–Nov, LD8:16 Nov–Dec and LD8:16 Dec–Jan) was significantly higher (13.9%, 12.9% and 10.7% respectively) than that of the group reared at continuous light (LD24:0). The three groups receiving the short photoperiod did not differ in weight at the end of the trial so the time of the year at which the short photoperiod was applied did not seem to be of importance regarding the growth enhancement. The maturation rate did not appear to be affected by the photoperiod treatments. The improved growth was mainly a result of a higher feed intake and improved feed conversion efficiency for the period following transfer of the charr from a short photoperiod to the continuous light. Application of such a winter photoperiod during the juvenile phase can, therefore, be used as a tool to increase the biomass and growth rate in Arctic charr farming. [Copyright &y& Elsevier]

Abstract: Groups of Arctic charr (Salvelinus alpinus) were reared in duplicate tanks supplied with freshwater, and subjected to two different ration levels, 100% (full ration) and 50% (half ration) in two six week periods during autumn (Sept.–Nov.) and winter (Dec.–Feb.). In between the restricted ration periods and from February onwards, all fish were fed full ration. After the first and second 42day restricted feed periods, the 50% had lower mean weight than the 100% group in both sexes, but this size difference diminished as the trial progressed, and full final size compensation was seen for both males and females in the 50% group. Specific growth rates for both sexes were higher in the 100% group during the two reduced feeding periods, whereas growth was higher in the 50% group in the subsequent periods after feed restriction. No differences in growth were seen from May onwards. Feed conversion efficiency was higher in the 50% group during, and after, feed restriction, and daily feeding rate (F%) was higher in the 50% group in the periods subsequent to feeding restriction. In the following summer and autumn signs of lower maturation were seen for females in the feed restricted group. No differences were found in fillet water- and fat content in the experimental groups. The present findings indicate that intermittent feeding during autumn and winter could be a cost-effective strategy for Arctic charr farmers. [Copyright &y& Elsevier]

Abstract: Total mercury (THg) and methylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220mm, a standardized age of 5years or for individualuals did not exceed the 0.5mgkg−1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes. [Copyright &y& Elsevier]

Abstract: The Gram-negative fish pathogenic bacterium Aeromonas salmonicida possesses the LuxIR-type quorum sensing (QS) system, termed AsaIR. In this study the role of QS in A. salmonicida subsp. achromogenes virulence and pigment production was investigated. Five wild-type Asa strains induced the N-acyl-homoserinelactone (AHL) monitor bacteria. HPLC–HR-MS analysis identified only one type of AHL, N-butanoyl-l-homoserine lactone (C4-HSL). A knock out mutant of AsaI, constructed by allelic exchange, did not produce a detectable QS signal and its virulence in fish was significantly impaired, as LD50 of the AsaI-deficient mutant was 20-fold higher than that of the isogenic wt strain and the mean day to death of the mutant was significantly prolonged. Furthermore, the expression of two virulence factors (a toxic protease, AsaP1, and a cytotoxic factor) and a brown pigment were reduced in the mutant. AsaP1 production was inhibited by synthetic QS inhibitors (N-(propylsulfanylacetyl)-l-homoserine lactone; N-(pentylsulfanylacetyl)-l-homoserine lactone; and N-(heptylsulfanylacetyl)-l-homoserine lactone) at concentrations that did not affect bacterial growth. It is a new finding that the AHL synthase of Aeromonas affects virulence in fish and QS has not previously been associated with A. salmonicida infections in fish. Furthermore, AsaP1 production has not previously been shown to be QS regulated. The simplicity of the A. salmonicida subsp. achromogenes LuxIR-type QS system and the observation that synthetic QSI can inhibit an important virulence factor, AsaP1, without affecting bacterial growth, makes A. salmonicida subsp. achromogenes an interesting target organism to study the effects of QS in disease development and QSI in disease control. [ABSTRACT FROM AUTHOR]

Abstract: In a comparative experiment the effect of cortisol and growth hormone (GH) on the hypo-osmoregulatory ability of a landlocked and an anadromous strain of Arctic charr (Salvelinus alpinus) was investigated. Cortisol and GH were implanted either alone or in combination, and the fish were exposed to a 24 h seawater challenge test (SWT) on days 14 and 28 after implantation. Hypo-osmoregulatory ability, measured as plasma osmolality and chloride concentration after the SWTs, was better in the anadromous than in the landlocked strain, irrespective of treatment. However, cortisol provided a strong stimulation of hypo-osmoregualtory ability in both strains, and this stimulation seemed to be potentiated by GH in an additive manner. Improved hypo-osmoregulatory ability in GH+cortisol treated anadromous Arctic charr was accompanied by increased gill Na+, K+-ATPase activity and Na+–K+–2Cl− cotransporter protein abundance, but no changes in gill Na+,K+-ATPase α1a and α1b mRNA levels. For landlocked charr the improved hypo-osmoregulatory ability in GH+cortisol treated fish was accompanied only with an increase in gill Na+–K+–2Cl− cotransporter protein abundance. Hormone treatment caused an improvement of hypo-osmoregulatory ability that was of approximately the same magnitude in the landlocked as in the anadromous Arctic charr. This suggests that the lack of spontaneous development of hypo-osmoregulatory ability often seen in landlocked populations of Arctic charr may depend, at least partly, on a lack of the hormonal activation seen in anadromous populations. [Copyright &y& Elsevier]

Abstract: This study evaluated the survival and growth of juvenile Arctic charr in comparison to their diploid siblings. Eight triploid full-sib families were produced by hydrostatic pressure treatment of eggs (5 min at 65.5×103 kPa) beginning 210 °C-min post-fertilization. Diploid siblings came from the same eight families, but without pressure treatment. Mean survival from eyed-egg to first size-grading (at 1980 °C-days post-hatch) was 70% for triploids and 84% for diploids. In two growth studies using 4 m3 tanks containing 100 juveniles per ploidy level of each family, triploidization resulted in higher levels of phenotypic variance for growth traits. Specifically, triploids consistently had smaller mean body weight and fork length than their diploid siblings. Juveniles were first measured at 850 °C-dph and again every four weeks over a 24 week period. The proportion of the overall variance in weight was due to ploidy level in the first tank experiment whereas this variance was due to the effect of family in the second tank experiment. Mean specific growth rates of triploids and diploids were 2.01 and 2.09% for weight and 0.64 and 0.66% for length, respectively, which was not significant. The condition factor of triploids was less than that of diploids at every sampling date, except for the initial assessment. After transfer to a commercial site following completion of the tank trials, the same families were grown until market size (1 kg) and were measured again nine and 11 months after the conclusion of the growth studies. The condition factor of triploids improved at the commercial site and was not different from that of diploids. The difference in weight of triploid and diploid populations was significant at the conclusion of the study. These results indicate that as juveniles, triploids have reduced performance in important aquaculture traits. However, because triploid performance was reduced in a predictable fashion in comparison to sibling diploids, triploids of some full-sib families outperformed diploids of others. Any overall advantage of triploids may not be realized until the diploids begin to mature. [Copyright &y& Elsevier]

Abstract: This study investigates how simulation of condensed winter light conditions effects the growth of wild caught Arctic charr (Salvelinus alpinus L.) held in culture. After capturing from Altevatn, Northern Norway, juvenile Arctic charr were cultivated and subsequently individually divided into two groups. The fish were held under identical conditions from May to October including continuous light. Starting from week 41 after capture (October) one group was subjected to a winter light regime of 6 h light and 18 h dark per day (Winter Light group—WL), while light regimes in the second group remained continuous (Light group). After an eight weeks treatment period the WL-group was reverted to the continuous light regime until the experiment ended in May 2007. Results revealed no pre-treatment differences in growth between the two groups. However, starting from two months after the short day treatment, fishes from the WL group had significant higher growth rates compared to L group fish. At the end of the experiment, e.g. five months after the light treatment, fishes from WL group had increased their average body weight by 353 g as compared to 252 g in the L group. Consequently, results show that simulation of winter light conditions can increase the productivity of land-based Arctic charr (Salvelinus alpinus L.) cultivation by 25 to 30%. Thus, management of wild caught charr farming, great care should be taken as to what light regimes the fish are exposed to. [Copyright &y& Elsevier]

Abstract: Parr–smolt transformation and growth were studied in captive offspring of anadromous Arctic charr (Salvelinus alpinus) from the Hals watercourse in northern Norway (70°N), held either at a natural temperature (<1 °C until May) or at a temperature elevated to 6 °C in late March. In mid-May, 5 weeks after the increase in photoperiod from 8:16 h light:dark to continuous light, gill Na+, K+-ATPase activity started to increase in both temperature groups, concurrent with the final development of full seawater tolerance. Temperature had no effect on the development of gill Na+, K+-ATPase activity, or on hypoosmoregulatory ability. The fish in both treatments resumed growth in mid-May, but from then on growth was faster in the elevated than in the ambient temperature group. In the former group, fish mass doubled in 6 weeks (from 65 to 137 g), and growth ceased at the time when the fish were about to complete their parr–smolt transformation. These findings show that an early vernal temperature increase advances the seasonal growth cycle, but not the parr–smolt transformation, in anadromous Arctic charr. [Copyright &y& Elsevier]

Abstract: Arctic charr (Salvelinus alpinus L.) from Lake Thingvallavatn, Iceland occur as four distinct morphs: large benthivorous (LB), dwarf benthivorous (DB), piscivorous (PI) and planktonivorous (PL). The morphs differ with respect to body size, head morphology, growth rate, and life history. The aim of this study was to investigate the paired box protein 7 (Pax7) gene as a candidate for such polymorphisms due to its importance in cranio-facial, skeletal muscle, and central nervous system development. No variation in coding and intronic sequences was found between morphs. We identified 10 alternate Pax7 isoforms with insertions/deletions: a four-residue (GNRT) deletion, a GEASS insertion truncated by the first serine residue (GEAS), and a thirteen-residue insertion (GQYA/TGPEYVYCGT). The latter insertion with a threonine (T) contains a putative casein kinase II (CK-2) phosphorylation site. Pax7 spatial expression patterns were identical in embryos of DB-, LB-, and PL-morphs, and were similar to those described for zebrafish Pax7c, but a difference in temporal expression for segmentation was observed between DB and LB morphs. At the end of segmentation, novel expression was observed in the mandibular region as two bilateral domains. The potential role of multiple alternative splicing of the Pax7 gene for the generation of different Arctic charr morphs is briefly discussed. [Copyright &y& Elsevier]

Abstract: This study aimed to test the hypothesis that diets containing relatively high amounts of the Δ6 desaturated fatty acids stearidonic acid (STA, 18:4n −3) and γ-linolenic acid (GLA, 18:3n −6), may be beneficial in salmonid culture. The rationale being that STA and GLA would be better substrates for highly unsaturated fatty acid (HUFA) synthesis as their conversion does not require the activity of the reputed rate-limiting enzyme, fatty acid Δ6 desaturase. Duplicate groups of two Arctic charr (Salvelinus alpinus L.) populations with different feeding habits, that had been reported previously to show differences in HUFA biosynthetic capacity, were fed for 16 weeks on two fish meal based diets containing 47% protein and 21% lipid differing only in the added lipid component, which was either fish oil (FO) or echium oil (EO). Dietary EO had no detrimental effect on growth performance and feed efficiency, mortalities, or liver and flesh lipid contents in either population. The proportions of 18:2n −6, 18:3n −3, 18:3n −6, 18:4n −3, 20:3n −6 and 20:4n −3 in total lipid in both liver and flesh were increased by dietary EO in both populations. However, the percentages of 20:5n −3 and 22:6n −3 were reduced by EO in both liver and flesh in both strains, whereas 20:4n −6 was only significantly reduced in flesh. In fish fed FO, HUFA synthesis from both [1-14C]18:3n −3 and [1-14C]20:5n −3 was significantly higher in the planktonivorous Coulin charr compared to the demersal, piscivorous Rannoch charr morph. However, HUFA synthesis was increased by EO in Rannoch charr, but not in Coulin charr. In conclusion, dietary EO had differential effects in the two populations of charr, with HUFA synthesis only stimulated by EO in the piscivorous Rannoch morph, which showed lower activities in fish fed FO. However, the hypothesis was not proved as, irrespective of the activity of the HUFA synthesis pathway in either population, feeding EO resulted in decreased tissue levels of n −3HUFA and 20:4n −6. This has been observed previously in salmonids fed vegetable oils, and thus the increased levels of Δ6 desaturated fatty acids in EO did not effectively compensate for the lack of dietary HUFA. [Copyright &y& Elsevier]

Abstract: Domestication and selection to enhance growth of animals is likely to affect social behaviour. Aggression may increase or decrease. A 4-generation selection programme on the salmonid species Arctic charr (Salvelinus alpinus L.) based on a well-defined population origin has made it possible to compare the social behaviour of its progeny with progeny from wild parents of the same population, thus excluding the effects of population differences. During 5 months, the within-group growth variation and specific, defined behaviour parameters were observed and analysed under experimental conditions where dominance hierarchies are promoted. In such conditions, which are opposite from farming conditions created to reduce dominance hierarchies, there was no difference in mean growth rate during the observation period and no difference in the social structure (number of dominant, subdominant and subordinate individuals) in the groups. Also, the level of within group aggression did not appear significantly different between level of domestication when observed between or during feeding periods. However, there was a significantly larger growth variation in the progeny of wild parents compared to the selected progeny. Also, the level of aggression increased significantly only in the groups with a selected origin during feeding events compared to periods in-between feeding. Individuals in the wild origin groups showed a significantly higher level of a passive low-profile behaviour compared to the selected origin groups. These differences suggest that selection for fast growth in farming conditions reduces the frequency of subordinate individual behaviour resulting in a smaller intra specific difference in growth in farm strains. [Copyright &y& Elsevier]

Abstract: A specific sex steroid-binding protein (SBP) is believed to be involved in regulation of circulating sex steroids, steroid delivery to target cells and intracellular signalling in sex steroid-sensitive tissues. In the present work, interactions between xenoestrogens and the plasma SBP in Arctic charr (Salvelinus alpinus L.) were determined using ligand–protein binding studies. The test compounds were all able to displace tritiated 17β-estradiol (E2) from the Arctic charr SBP (acSBP) in a competitive and dose-dependent manner. The acSBP affinities for the xenoestrogens ranged over several orders of magnitude (17β-estradiol≫ethynylestradiol (EE2)>zearalenone (ZEA)>diethylstilbestrol (DES)>genistein (GEN)>bisphenol A (BPA), 4-t-octylphenol (OP)≫o,p′-DDT, and dieldrin (DIN)), but were consistently lower than that of 17β-estradiol (about 4×102–106-fold less potent). The relative binding affinity (RBA) for selected chemicals were independent of both gender, age and maturation status, as well as variations of acSBP binding affinity. The affinity of endogenous steroids and estrogen mimics for the acSBP shows a high correlation to the affinity for the rainbow trout SBP, thus suggesting a phylogenetically conserved ligand-binding site between closely related species. Furthermore, it is argued that interaction with the acSBP- and SBP-mediated processes may introduce novel pathways for endocrine disruption, which may work in concert with the classical receptor-mediated effects. [Copyright &y& Elsevier]

The impacts of polychlorinated biphenyl (PCB) exposure on smoltification and subsequent seawater performance were investigated in hatchery-reared, anadromous Arctic charr (Salvelinus alpinus). The fish were subjected to a 2-month summer seawater residence, after which they were orally dosed with 0 (Control, C), 1 (Low Dose, LD) or 100 mg Aroclor 1254 kg−1 body mass (High Dose, HD) in November. They were then held in fresh water, without being fed (to mimic their natural overwintering in freshwater), until they had smolted in June the next year. The smolts were then transferred to seawater and fed to mimic their summer feeding residence in seawater, followed by a period without food in freshwater from August until maturation in October. Compared with C and LD charr, the HD charr had either a transient or a permanent reduction in plasma growth hormone, insulin-like growth factor-1, and thyroxin and triiodothyronine titers during the period of smoltification. These hormonal alterations in the HD charr corresponded with impaired hyposmoregulatory ability in May and June, as well as reduced growth rate and survival after transference to seawater. Consequently, fewer fish in the HD group matured in October compared to the other two treatments. The HD fish had a liver PCB concentration ranging between 14 and 42 mg kg−1 wet mass, whereas there were similar, and very low, liver PCB concentrations in LD and C fish throughout the smolting period. Our findings suggest that PCB might compromise mechanisms important for fitness in a fish species living in an extreme environment. [Copyright &y& Elsevier]

The serotonin1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) was administrated to juvenile Arctic charr either by intraperitoneal (i.p.) injections or through a permanent i.p. implanted catheter. 8-OH-DPAT induced an elevation of plasma cortisol in non-stressed fish (receiving the drug through a permanent i.p. catheter), whereas 8-OH-DPAT had the opposite effect when administrated through a standard i.p. injection, dampening the rise in cortisol induced by handling and injection, an effect which was most pronounced at low doses of 8-OH-DPAT. In both cases, plasma levels of adrenocorticotropic hormone followed the same general pattern as plasma cortisol. The results suggests that 5-HT1A receptors are involved in the regulation of hypothalamic–pituitary–interrenal axis activity in Arctic charr, but the effect of 5-HT1A stimulation seems to vary depending on the state of the fish. [Copyright &y& Elsevier]

Summary: An atypical strain of Carnobacterium divergens, strain 6251, was isolated from the small intestine of Arctic charr (Salvelinus alpinus L.), fed high dietary carbohydrate. This strain showed marked growth inhibitory effects in vitro against the fish pathogens Aeromonas salmonicida subsp. salmonicida(furunculosis), Vibrio anguillarum(vibriosis) and Vibrio viscocus(winter ulcer). The strain is a non-motile Gram-positive psychrotrophic rod that lacks both catalase and oxidase, grows at pH 9.1 (CTAS agar), but not on acetate containing media (pH ≤ 5.4), on TCBS or at ≤6% sodium chloride content. Strain 6251 is facultatively anaerobic and utilises tryptone as a sole source of nutrient. Further characterisation showed the most abundant cellular fatty acid of strain 6251 to be oleic acid (18:1) (n-9) (36.0%). Sequencing of a 16S rDNA region of 578 nucleotides and AFLPTM microbial fingerprinting suggested that strain 6251 is not closely related to any carnobacteria known, however, DNA-DNA similarity determinations showed high similarity (96.2%) with the type strain of Carnobacterium divergens. The unique phenotypic attributes of this strain represent new information on the biodiversity and ecology of carnobacteria and especially of the species C. divergens. [Copyright &y& Elsevier]

Although Arctic charr side streams contain limited amounts of fish flesh, they are a rich fish oil source (46.3 ± 0.6%). The aim of the study was to investigate the potential for valorization of Arctic charr filleting side streams through the extraction of oil by supercritical CO 2 technology. The effect of temperature (40 °C and 80 °C) and pressure (20, 35 and 45 MPa) on the final extract after supercritical fluid extraction (SFE) was evaluated. Temperature increase enhanced the yield but decreased the antioxidant activity at 45 MPa, did not affect the yield and the antioxidant activity at 35 MPa, whereas yield was limited at 20 MPa and 80 °C. Extracts were rich in monounsaturated fatty acids (56.7–58.3%, especially oleic acid 37.2–38.0%), and polyunsaturated fatty acids (20.2–26.1%, especially DHA 7.3–11.4%). The presence of astaxanthin significantly preserved the extracts from oxidation. Supercritical carbon dioxide extraction is a green technology appropriate for the recovery of non-polar and heat sensitive compounds. The extracted Arctic charr oils were rich in polyunsaturated fatty acids and astaxanthin which inhibited oxidation in combination with the absence of oxygen and light during the process. This technology could be an excellent alternative for more sustainable valorization of fish processing side streams. • Valorization of Arctic charr side streams after filleting process. • Arctic charr oil was extracted by SC-CO2 under different pressures and temperatures. • Arctic charr oil extracted by SC-CO2 was rich in unsaturated fatty acids. • The extracted oil at 350 bar and 40 °C had the highest astaxanthin content. [ABSTRACT FROM AUTHOR]

• Whey protein hydrolysate (WPH) is a source of protein and has antioxidant ability. • Arctic charr were fed diets containing up to 51 g/kg (WPH) for 12 weeks. • There was no significant effect of dietary treatment on growth or oxidative stress. • A dietary inclusion of WPH at 51.0 g/kg showed some positive effects. • WPH is an effective protein source at dietary inclusion levels up to 51.0 g/kg in charr. Whey protein hydrolysate (WPH) is a potential functional ingredient in salmonid feeds, as a source of protein with a mixture of peptides of varying chain lengths and free amino acids, which possess antioxidative properties. A 12-week feeding trial was conducted to examine the effects of including low levels of WPH in Arctic charr diets and its effect on growth performance, feed intake and oxidative indicators. Six salmonid diets were formulated to contain WPH at inclusion levels of: 0.0, 1.0, 5.1, 10.1, 25.5 or 51.0 g/kg. Fish meal was included in the diets at a level of 81.6 g/kg and fish oil at 51.0 g/kg. Diets were fed to Arctic charr (average weight: 34.1 g; 30 fish / 130 l tank; 3 tanks / treatment). There were no significant differences in the overall body weight, weight gain, feed consumption, feed conversion ratio, protein efficiency ratio, specific growth rate, fork length, viscerosomatic index or hepatosomatic index of fish fed the experimental diets, nor were there any significant linear or quadratic effects related to WPH inclusion level. There were also no significant differences among treatments for the thiobarbituric acid reactive substances (TBARS) or ferric reducing antioxidant power (FRAP) in liver samples. Although there were no significant differences in the growth performance and antioxidative capacity as a result of WPH inclusion, biological results—particularly at 5.1 g/kg WPH—warrant further study to fully evaluate the potential of WPH when oxidative stress is induced. Benefits of the dietary inclusion level of 5.1 g/kg WPH under normal conditions include 9% higher weight gain and feed consumption, lower TBARS values, and induction of oxidative stress mechanisms. Based on growth performance results alone, however, it appears WPH is an effective protein source at dietary inclusion levels up to 51.0 g/kg for juvenile Arctic charr. [ABSTRACT FROM AUTHOR]

The general objective of this study was to establish a standardized procedure for the cryopreservation of Arctic charr milt and its use in the production of 'sparctic' hybrids. The specific objectives of this study were to determine: (i) the optimal final sperm concentration as well as (ii) the final glucose concentration, (iii) the effect of post-thaw storage time on sperm motility characteristics, and (iv) the fertilization ability of cryopreserved Arctic charr milt at 0 and 60 min after thawing at sperm:egg ratios of 500,000:1 and 1,000,000:1. We observed high post-thaw sperm motility (49–57%) at final sperm concentrations ranging from 0.5 to 2.0 × 109 spermatozoa ml−1 in straw. We determined that a final glucose concentration of 0.15–0.19 M in 7.5% methanol was optimal (post-thaw sperm motility 48–60%). Milt cryopreserved at optimal conditions (final concentrations: 0.17 M of glucose, 7.5% methanol and 1.5 × 109 spermatozoa ml−1) could be stored for up to 15 min after thawing without the loss of sperm motility. The ability of cryopreserved milt to fertilize brook trout eggs was high (68–72%) and did not differ between the tested sperm:egg ratios (500,000:1 and 1,000,000:1) when milt was used immediately after thawing or after 60 min of post-thaw storage. The milt used in this study was obtained from two hatcheries and was characterized by significantly different values of sperm concentrations. In conclusion, a standardized and efficient cryopreservation method for Arctic charr milt has been developed and used for the production of 'sparctic' hybrids. Species-specific requirements for final sperm and glucose concentrations and the post-thaw storage time were determined. The hatchery of origin of Arctic charr should be taken into consideration, as high variability in sperm characteristics may be expected. The development of this method and the positive results of the fertilization trials indicate promising potential for the implementation of cryopreserved milt in hatchery practice. • Glucose from 0.15 to 0.19 M and sperm concentration from 0.5 to 2.0 × 109 spermatozoa ml−1 resulted in high sperm motility. • High fertilization rates were obtained both at sperm:egg ratios (500,000:1 and 1,000,000:1) and at 0 or 60 min after thawing. • Post-thaw sperm motility was negatively affected by time of storage. [ABSTRACT FROM AUTHOR]