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.
•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.
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.
This paper reviews the life history of brown trout and factors influencing decisions to migrate. Decisions that maximize fitness appear dependent on size at age. In partly anadromous populations, ...individuals that attain maturity at the parr stage typically become freshwater resident. For individual fish, the life history is not genetically fixed and can be modified by the previous growth history and energetic state in early life. This phenotypic plasticity may be influenced by epigenetic modifications of the genome. Thus, factors influencing survival and growth determine life-history decisions. These are intra- and interspecific competition, feeding and shelter opportunities in freshwater and salt water, temperature in alternative habitats and flow conditions in running water. Male trout exhibit alternative mating strategies and can spawn as a subordinate sneaker or a dominant competitor. Females do not exhibit alternative mating behaviour. The relationship between growth, size and reproductive success differs between sexes in that females exhibit a higher tendency to migrate than males. Southern populations are sensitive to global warming. In addition, fisheries, aquaculture with increased spreading of salmon lice, introduction of new species, weirs and river regulation, poor water quality and coastal developments all threaten trout populations. The paper summarizes life-history data from six populations across Europe and ends by presenting new research questions and directions for future research.
Possible effects of short‐term starvation on flesh quality in Arctic charr were studied in spring (March) and summer (August). Groups of juvenile Arctic charr (mean weight March 536 g ± 24; August ...461 g ± 15 SEM) were starved for 1, 2 and 4 weeks (March) and 1, 2 and 3 (August). After each starvation period, the fish were slaughtered, and flesh samples collected in order to investigate quality and textural properties in the different experimental groups. Starvation had a positive effect on flesh quality giving firmer texture and lower gaping scores. Starved fish had lower cathepsin activity at slaughter, and a similar difference was seen one‐week post mortem. The results showed that the effect of starvation period was seasonally dependent. Starvation had a larger effect in summer, where a three‐week starvation resulted in firmer texture, whereas this was not seen during spring.
•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.
Trophic polymorphism and temporal reproductive isolation are the drivers of sympatric differentiation in many fish taxa. We present a new case of ecologically based diversification of Arctic charr in ...a Transbaikalian mountain lake inhabited by reproductively isolated dwarf and normal forms. These forms differ in size, diets and morphology and breed, respectively, in April–May and in September–October representing a rare example of sympatric spring- and autumn-spawning charr pair. Microsatellite analysis reveals clear-cut genetic differences and low-level hybridization between them. Dwarf form charr are planktivorous and manifest uniform slow growth. Normal form charr, though genetically homogeneous, are highly heterogeneous in size-at-age. They are subdivided into omnivorous small-size and piscivorous large-size groups, which can be considered as incipient forms at an early divergence stage. As evidenced by back-calculated growth data, their size-at-age heterogeneity results from highly variable individual growth patterns, which include different combinations of slow and fast growth periods presumably associated with spawning and non-spawning years. Growth acceleration in late ontogeny may result in the transformation of some normal charr from the smaller into the larger group during their lifetime.
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.
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.
•A summary of 30 years of selective breeding in Arctic charr•The growth has been significantly improved and the seasonal growth capacity have changed over time.•A feeding management model is given taking the seasonality into account.•An adaptive model on the theoretical energy need of Arctic charr is presented.
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