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 54g 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 24g 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.
•24h light overwinter effectively reduced early maturation in diploid Arctic charr.•Gonadal maturation can be either stimulated or inhibited by 24h light dependent on both the start date and duration.•Photoperiod induced reduction of maturity rate was independent of somatic growth.
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.
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.
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.
Ecological opportunity is considered a crucial factor for adaptive radiation. Here, we combine genetic, morphological and ecological data to assess species and ecomorphological diversity of Artic ...charr in six lakes of a catchment in southernmost Greenland, where only charr and stickleback occur. Because the diversity of habitats and resources increases with lake size, we predict a positive association between lake size and the extent of ecomorphological diversity. The largest lake of the catchment harbours the largest Arctic charr assemblage known today. It consists of six genetically differentiated species belonging to five ecomorphs (anadromous, littoral benthic, profundal dwarf, planktivorous, piscivorous), of which the latter comprises two ecomorphologically extremely similar species. Lakes of intermediate size contain two ecomorphologically and genetically distinct species. Small lakes harbour one genetically homogeneous, yet sometimes ecomorphologically variable population. Supporting our prediction, lake size is positively correlated with the extent of ecomorphological specialization towards profundal, pelagic and piscivorous lifestyle. Furthermore, assemblage-wide morphospace increases sharply when more than one genetic cluster is present. Our data suggest that ecological opportunity and speciation jointly determine phenotypic expansion in this charr radiation.
The winter ecology of anadromous Arctic charr, an important fish species for Indigenous populations, has remained poorly detailed in the literature beyond descriptions of seasonal fasting and ...resulting declines in condition. However, prolonged periods of reduced feeding can have significant consequences for other variables, such as tissue contaminant levels. To more thoroughly detail seasonal changes, biological information (fork length, total weight, age, sex, somatic condition), stable isotopes (δ13C, % carbon, δ15N, % nitrogen), dorsal muscle % lipid, caloric densities, and total mercury (THg) concentrations were assessed in anadromous Arctic charr collected from Deception Bay, Canada, during the summer and over-wintering periods. Significant reductions in somatic condition, total weight, and % nitrogen, consistent with prolonged periods of fasting, were found for post-winter captured Arctic charr, but % lipid and caloric densities were significantly higher in these fish. THg also varied seasonally and was significantly higher in summer collected tissue. When tested individually via linear regression, significant relationships were seasonally dependent, but limited in number. All previously mentioned parameters were then incorporated into multi-variable models which better explained variations in the data. While there was no clear best model for explaining the % lipid values, caloric densities, and THg, season, condition, and stable isotope values (% carbon and % nitrogen) were the best indicators of % lipid content and caloric densities. THg concentrations were best explained by total weight, somatic condition, and δ13C. Seasonal variation in fish condition measures and THg may be indicative of condition selective mortality that yields apparent improvement through the disproportionate removal of poorer conditioned fish from the population during the over-wintering period. This hypothesis was further supported by mortality estimates and the results of the multi-predictor variable models. Collectively, this research highlights the importance of understanding seasonal dynamics for anadromous Arctic charr populations.
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•Anadromous Arctic charr are the most northerly distributed freshwater fish.•Charr are of significant cultural and economic importance to local communities.•THg concentrations and lipid/caloric values were investigated seasonally.•Tissue THg values varied seasonally and were significantly higher in summer.•Weight, somatic condition, and δ13C best explained variation in THg data.
Animal personality has been shown to be influenced by both genetic and environmental factors and shaped by natural selection. Currently, little is known about mechanisms influencing the development ...of personality traits. This study examines the extent to which personality development is genetically influenced and/or environmentally responsive (plastic). We also investigated the role of evolutionary history, assessing whether personality traits could be canalized along a genetic and ecological divergence gradient. We tested the plastic potential of boldness in juveniles of five Icelandic Arctic charr morphs (
), including two pairs of sympatric morphs, displaying various degrees of genetic and ecological divergence from the ancestral anadromous charr, split between treatments mimicking benthic versus pelagic feeding modalities. We show that differences in mean boldness are mostly affected by genetics. While the benthic treatment led to bolder individuals overall, the environmental effect was rather weak, suggesting that boldness lies under strong genetic influence with reduced plastic potential. Finally, we found hints of differences by morphs in boldness canalization through reduced variance and plasticity, and higher consistency in boldness within morphs. These findings provide new insights on how behavioural development may impact adaptive diversification.
Atlantic salmon Salmo salar, brown trout Salmo trutta (including the anadromous form, sea trout) and Arctic charr Salvelinus alpinus (including anadromous fish) provide important commercial and ...sports fisheries in Western Europe. As water temperature increases as a result of climate change, quantitative information on the thermal requirements of these three species is essential so that potential problems can be anticipated by those responsible for the conservation and sustainable management of the fisheries and the maintenance of biodiversity in freshwater ecosystems. Part I compares the temperature limits for survival, feeding and growth. Salmo salar has the highest temperature tolerance, followed by S. trutta and finally S. alpinus. For all three species, the temperature tolerance for alevins is slightly lower than that for parr and smolts, and the eggs have the lowest tolerance; this being the most vulnerable life stage to any temperature increase, especially for eggs of S. alpinus in shallow water. There was little evidence to support local thermal adaptation, except in very cold rivers (mean annual temperature <6·5° C). Part II illustrates the importance of developing predictive models, using data from a long‐term study (1967–2000) of a juvenile anadromous S. trutta population. Individual‐based models predicted the emergence period for the fry. Mean values over 34 years revealed a large variation in the timing of emergence with c. 2 months between extreme values. The emergence time correlated significantly with the North Atlantic Oscillation Index, indicating that interannual variations in emergence were linked to more general changes in climate. Mean stream temperatures increased significantly in winter and spring at a rate of 0·37° C per decade, but not in summer and autumn, and led to an increase in the mean mass of pre‐smolts. A growth model for S. trutta was validated by growth data from the long‐term study and predicted growth under possible future conditions. Small increases (<2·5° C) in winter and spring would be beneficial for growth with 1 year‐old smolts being more common. Water temperatures would have to increase by c. 4° C in winter and spring, and 3° C in summer and autumn before they had a marked negative effect on trout growth.
To address the problem of high maturity at 2years of age among Salvelinus alpinus (Labrador strain), PIT-tagged yearlings (ca. 110g) were reared for 18weeks overwinter (Nov. 16 to Apr. 1) under six ...treatments (90 fish per treatment) that combined three factors: photoperiod (natural day length, LDN or 24h 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 18weeks 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 1kg immature product around 2years old. A new two-step gating mechanism is proposed to explain the photoperiod prevention of maturation, one independent of somatic growth, the other dependent.
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.
•The ability to reduce the problem of early maturity using 24h light was maximized when combined with reduced temperature and food restriction.•Combined food deprivation with 24h light overwinter can be a cost-effective method for farming Arctic charr and potentially other species.•A two-step gating mechanism was proposed to explain the photoperiod controlled sexual maturation, one independent of growth, the other dependent.
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 CO2 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.
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