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Many lacustrine charrs of the genus Salvelinus were described as separate species, and their origin and phylogenetic relationships are still under debate. In this study, we described the genetic variation of charrs from Lake Grand (Elikchan Lake Group, the mainland coast of the Sea of Okhotsk, Russia) and several locations outside of this system based on eight microsatellite (ms) loci and mitochondrial (mt) DNA control region. We tested the hypothesis of the resident charr membership to (a) the Arctic lineage of Salvelinus taranetzi sensu (Oleinik et al., Russian Journal of Genetics, 51, 2015, 55); (b) the Bering lineage of the Northern Dolly Varden Salvelinus malma malma; and (c) the Atlantic lineage of the Arctic charr Salvelinus alpinus. Analysis of phylogenetic relationships based on the mtDNA control region showed that all individuals from Lake Grand grouped with the Bering lineage. Bayesian analysis using msDNA supports the clustering together of charrs from Lake Grand and Arctic lineage, regardless of their mtDNA haplotypes. Incongruence between mtDNA and msDNA markers provided strong evidence of historical mtDNA introgression from S. malma malma to S. taranetzi. Patterns of divergence confirm a postglacial secondary contact of the representatives of Arctic and Bering lineages in the area of the Sea of Okhotsk coast and past hybridization in Lake Grand with the following features: (a) complete fixation of introgressed mtDNA of one species within populations of another and (b) absence of modern population of S. malma malma in the lake. [ABSTRACT FROM AUTHOR]

Currently, no information is available on the effect of progressively decreasing temperatures on the sensory quality of Arctic charr. The objective of this study was to investigate if and how different and progressively changing rearing temperatures affect the sensory quality of cooked and raw fillets of Arctic charr. The effects of rearing temperature on the sensory quality of Arctic charr (weight range 622–888 g) were investigated. Rearing temperature was changed during the experimental period as the fish were reared at constant or decreased temperature during October to April and subsequently reared at two constant temperatures from April to August establishing six different rearing temperature combinations. Significant differences were seen in all four main sensory attributes groups, that is odour, appearance, flavour and texture. Freshness characteristics such as sweet odour and flavour, and metallic odour and flavour increased with decreasing rearing temperature, whereas musty odour and flavour decreased. Rearing temperature had a clear effect on the colour of the fillets. Lower rearing temperature increased colour intensity substantially. Softness, juiciness and tenderness increased with decreased rearing temperature. A trend was seen towards more effect from final rearing temperature than initial temperature on the sensory attributes studied. Spoilage characteristics, that is, sour and rancid odour and flavour, and off‐odour and flavour were either very weak or not noticeable in all sample groups. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The short‐ and long‐term effects of altered photoperiods during winter on growth and final gonadosomatic index (GSI) were investigated in 178 individually tagged 2‐year‐old smolt Arctic charr from an anadromous strain. The fish were reared at ambient temperature (2.3–12.5°C) for 18 months and reared at five different photoperiods. One group was reared on constant LD16:8 (light–dark, N = 40) photoperiod and a second group on continuous light (LD24:0, N = 32) throughout the experimental period. Three groups of fish were moved from LD16:8 to LD24:0 for 44 days and subsequently back to LD16:8, that is early winter light group (Early WL: 17 November–5 January; N = 35), Mid WL group (5 January–23 February; N = 38) and Late WL group (23 February–6 April; N = 33). No differences in growth were found for females, whereas males reared at constant LD24:0 were larger (mean ± SEM, 1,780 g ± 180) compared with the Late (1,264 g ± 101) and Mid WL (1,413 g ± 120) groups towards the end the study. Exposure to continuous light during early winter significantly influenced the GSI in female Arctic charr, whereas no differences were found in the males. Female GSI (%) was lowest in the Mid WL group (1.7) and highest in the LD24:0 group (7.0). In conclusion, the present study demonstrated that application of brief continuous light treatments during January and February can possibly be used as a tool to lower subsequent female maturation in Arctic charr farming. [ABSTRACT FROM AUTHOR]

Summary: Growing interest of Arctic char (Salvelinus alpinus) aquaculture in Europe, and the fact that it can easily hybridize with brook trout (Salvelinus fontinalis) resulting in fertile progeny, led us to investigate fish from the farmed stocks. Chromosomes of sampled Arctic char were examined using conventional and molecular cytogenetic (FISH) techniques in order to determine possible contamination of genomic elements of brook trout. Investigated fish possessed karyotypes composed of 80–82 chromosomes and up to three chromosome fragments. Using staining methods and FISH approach enabled identification of the brook trout chromosomes in the eight out of twenty‐two examined Arctic char. Specific location of AT‐, GC‐ positive and NOR sites observed on chromosomes as well as chromosome fragments in the karyotypes of several individuals points on past chromosomal rearrangements in fish from examined broodstock. Based on our results, it may be assumed that individuals with the brook trout genomic elements, although phenotypically identified as Arctic chars, were hybrids. Our results highlights that special care should be taken to protect gene pools of brook trout and Arctic char in farms where both species are cultured. [ABSTRACT FROM AUTHOR]

Abstract: This experiment investigated a blood smear method as an alternative to flow cytometry for ploidy determination in Arctic charr, Salvelinus alpinus. Fertilized eggs were either treated with hydrostatic pressure (putative triploids) or untreated (diploid controls), and the embryos, alevins, and juveniles were then reared under identical conditions. Blood samples were collected from alevins (2 g average body weight) for blood smear analysis, and from juveniles (120 g average weight) for both blood smear analysis and flow cytometry. Student's t tests revealed significant (p < 0.0001) differences in mean erythrocyte length between the two groups, with pressure‐treated fish having higher values than the control group as alevins (20.43 ± 0.53 μm and 15.90 ± 0.45 μm respectively) and juveniles (22.83 ± 0.66 μm and 17.68 ± 0.45 μm respectively). Ploidy assignment obtained with blood smear analysis perfectly matched results obtained with flow cytometry. The blood smear method is therefore a valid, simple, and less expensive alternative to flow cytometry for the assessment of ploidy level in Arctic charr. [ABSTRACT FROM AUTHOR]

Abstract: The effects of two plant ingredients (solvent‐extracted soybean meal [SBM] and high‐protein sunflower meal [HPSFM]) and three inclusion levels (0 percent, practical diet containing 25 percent fish meal; 12.5 percent; and 25 percent) of these ingredients were investigated on the growth, feed utilization, gut histology and gene expression in the distal intestine of Arctic charr Salvelinus alpinus (average initial weight, 330.1 ± 8.9 g per fish). Feeding experimental diets for 12 weeks resulted in no difference between HPSFM diets in body weight gain (BWG), thermal‐unit growth coefficient (TGC), feed efficiency (FE), feed intake (FI) or pro‐inflammatory mRNA expression (PIE) with increasing dietary inclusion and between SBM FE, FI and PIE. Differences in quadratic contrasts were observed for nitrogen deposition rate (NDR) and nitrogen retention efficiency (NRE) (p < .05), whereby HPSFM diets elicited the strongest positive response. SBM resulted in linear reduction in BWG, TGC and distal intestine simple fold length and width measurements (p < .05) with stepwise increases in dietary inclusion, whereas dietary HPSFM had no effect. Histological observations of individual villi indicated several symptoms of non‐infectious subacute gastrointestinal enteritis in tanks fed SBM, many of which were not present in tanks fed HPSFM. The dietary HPSFM seems to be more adequate to replace fishmeal in Arctic charr diet than SBM, when fed at a level of up to 25 percent at the grow‐out stage. [ABSTRACT FROM AUTHOR]

An evaluation of different thermal regimes during incubation of Arctic charr Salvelinus alpinus L. egg was conducted with regard to embryo survival and development. The study consisted of two major parts: In experiment A, a range of commonly used thermal regimes, constant and variable ranging from 2.7°C to 7°C, were tested for differences in embryo survival and developmental status of newly hatched alevins. Experiment B assessed the timing of a shift from autumn (6°C) to winter temperature (2.5°C) and its effect on embryo survival and the occurrence of spinal deformities in newly hatched alevins. In general, incubations that were initiated at temperatures below 3°C resulted in significantly higher mortality rates and spinal deformity frequencies than other treatments. Hence, Arctic charr eggs require an initial warmer period for unimpaired embryonic development. A general negative correlation was found between the duration of this warmer period (6°C) and both mortality rates and frequency of spinal deformities. The total absence of the 6°C period had the most detrimental effect, with deformity frequencies at least four times higher than all treatments with an initial warmer period. The upper incubation temperature threshold was not reached in the study. The highest temperature tested (7°C) did not result in excess mortality or increased deformity frequency. Higher incubation temperature resulted in less developed alevins at hatching, i.e. alevins were smaller with more yolk remaining. However, measurements on alevins from incubations at variable temperatures revealed different temperature effects on growth and yolk consumption during different parts of embryonic development. [ABSTRACT FROM AUTHOR]

Arctic charr ( Salvelinus alpinus) were fed for 99 days on experimental diets with 40% of fish meal replaced, on a crude protein basis, with intact yeast ( Saccharomyces cerevisiae) ( ISC), extracted yeast ( ESC), Rhizopus oryzae fungus ( RHO) or de-shelled blue mussels ( Mytilus edulis) ( MYE). The fish were evaluated for growth performance, nutrient digestibility and fish intestinal function. Growth performance, retention of crude protein and sum of amino acids were not affected in fish fed diets ISC or MYE compared with those fed the reference ( REF) diet. However, fish fed diet ISC displayed decreased digestibility of crude protein and indispensable amino acids and decreased intestinal barrier function compared with fish fed the REF diet. Fish fed diet ESC exhibited decreased growth performance and protein retention, but had comparable digestibility to fish fed the REF diet. Fish fed diets MYE and RHO showed similar performance in terms of growth, nutrient digestibility and intestinal barrier function. Overall, the results indicated that blue mussel and intact S. cerevisiae yeast are promising protein sources for Arctic charr. [ABSTRACT FROM AUTHOR]

Apparent digestibility coefficients ( ADCs) for four protein-rich alternative feed ingredients, intact baker's yeast ( Saccharomyces cerevisiae), extracted baker's yeast ( S. cerevisiae), zygomycetes ( Rhizopus oryzae) and blue mussel ( Mytilus edulis), were determined for Arctic charr ( Salvelinus alpinus) and Eurasian perch ( Perca fluviatilis). Diets contained 30% of test ingredients, and ADCs were compared to a reference diet containing fish meal. For Arctic charr, ADCs for dry matter ( DM, 71-99%), sum of amino acids ( SAA, 84-99%) and gross energy (70-99%) were significantly lower for intact S. cerevisiae than for extracted S. cerevisiae, R. oryzae and M. edulis. The ADCs for the indispensable amino acids ( IAA) in Arctic charr varied between 84% and 99%. Significant differences were found in ADCs for IAA between the test ingredients for Arctic charr, with higher values for extracted S. cerevisiae and M. edulis. The ADCs in Eurasian perch varied between 83% and 95% for DM, 89% and 98% for CP, 92% and 100% for SAA, 81% and 96% for gross energy. No significant differences were found for ADCs between the test ingredients in Eurasian perch, indicating a species effect on digestibility. Furthermore, the absence of intact cell walls had a positive effect on digestibility of S. cerevisiae for Arctic charr. [ABSTRACT FROM AUTHOR]

A 20-week feeding trial was conducted to measure growth, nutrient utilization and faecal/gut bacterial counts in triplicate groups of red hybrid tilapia, Oreochromis sp., when fed diets supplemented with 0.5% organic acids blend ( OAB), 1.0% OAB, 0.5% oxytetracycline ( OTC) or a control diet (no additives). At the end of the feeding trial, tilapia were challenged with Streptococcus agalactiae for 22 days. Fish fed the OTC diet had significantly higher ( P < 0.05) growth than the control treatment, while growth between fish fed the OTC or OAB diets was not significantly different ( P > 0.05). Phosphorus, dry matter and ash digestibility were significantly higher in the 1.0% OAB diet than the control diet. Fish fed the OAB diets had significantly lower colony-forming units of adherent gut bacteria compared to the control or OTC treatments while those fed the 1.0% OAB diet had the lowest total faecal bacterial counts. Tilapia fed the 0.5% OTC or OAB diet had significantly higher resistance to S. agalactiae than those fed the control diet. This study indicates that dietary organic acids can potentially replace OTC as a growth promoter and antimicrobial in tilapia feeds. [ABSTRACT FROM AUTHOR]

We investigated whether Fraser strain Arctic charr Salvelinus alpinus L. reared in fresh water ( FW) differed in survival and growth from full siblings transferred to brackish water ( BW) and whether family performance was consistent throughout 1 year of commercial growth. Fish were grown communally ( n = 3600) in either FW or BW from May 2008 to May 2009. Mean family survival in BW was moderately correlated with mean family survival in FW ( r = 0.342; P = 0.032). Fish which survived until the conclusion of the experiment were significantly heavier in body weight at the baseline assessment than their full-sibs which died. Family by treatment interactions were detected for body weight, condition factor and specific growth across all measurement dates (May 2008, October 2008 and May 2009) and growth intervals. Despite the varied response of families to treatment, mean family body weight in FW was correlated phenotypically with BW body weight in October 2008 ( r = 0.633, P < 0.0001) and marginally correlated in May 2009 ( r = 0.289, P = 0.061). These data suggest that body weight in FW and body weight in BW should be analysed as separate, but correlated traits in Arctic charr breeding programs. [ABSTRACT FROM AUTHOR]

The effects of three different temperatures on the growth and maturation of the offspring of cultured versus wild populations of juvenile arctic charr ( Salvelinus alpinus L.) were investigated. The fish (start weight 17 g) were reared for 5 months at constant temperatures of 12, 14 and 16°C under a continuous light regime ( LD24:0). Growth performance was significantly influenced by both temperature and source population. The offspring from the farmed fish displayed significantly higher mean weights at all temperatures compared with the offspring from the wild fish. The results indicate that the optimal temperature for growth ( Topt) decreases with increasing fish size in the offspring of both cultivated and wild fish. Significant differences in length-weight relationship were found, with the offspring of wild fish displaying higher condition factor throughout the experiment. The results demonstrate that the offspring from multiple generation farmed population of arctic charr are better adapted to high temperatures compared with the offspring (F1 generation) from a wild population of arctic charr, and the former are also able to maintain growth at higher temperatures. There was a significant difference in maturation between the two populations, as the offspring from cultured fish displayed significantly lower level of maturation: 0%, 4% and 2% mature compared with 24%, 40% and 42% in the offspring from wild fish at temperatures of 12, 14 and 16°C respectively. The offspring from farmed strains of arctic charr thus appear to be the most suitable population for aquaculture. [ABSTRACT FROM AUTHOR]

Alternative protein sources for aquafeeds need to be indentified in order to increase the efficiency of production. Many studies have examined terrestrial plant meals/protein concentrates as alternatives. Recently the focus has turned to aquatic protists and plants as well as by-products from other industries, such as breweries. Atlantic salmon, Salmo salar, and Arctic charr, Salvelinus alpinus, were fed diets containing canola meal, soybean meal, corn gluten meal, soy protein concentrate, barley protein concentrate, and solar dried algae included at 30% of the test diet. Barley protein concentrate had the highest apparent protein digestibility values for both species (96.3% for Atlantic salmon and 85.1% for Arctic charr), followed by corn gluten meal. Algae had the highest organic matter digestibility value for arctic charr (80.1%) while corn gluten meal had the highest organic matter digestibility value for Atlantic salmon (88.4%). Algae had a high energy apparent digestibility coefficient (82.4 salmon, 82.7 charr) along with corn gluten meal (78.5 salmon, 82.7 charr) for both species. In general, Atlantic salmon had higher apparent digestibility coefficients compared to Arctic charr for most of the tested ingredients. Both corn gluten and barley protein concentrate appear good candidates as alternative protein sources with both species. [ABSTRACT FROM AUTHOR]

We examined the amount and distribution of molecular variation at microsatellite loci in 21 broodstocks of Arctic charr Salvelinus alpinus derived from the Fraser River, Labrador and the Nauyuk Lake, Nunavut, Canada. Our goal was to assess the amount of genetic diversity and differentiation as broodstocks are subdivided and propagated in different hatcheries and grow-out facilities. We observed significant heterogeneity across pairs of ancestral and descendant broodstocks in the mean numbers of alleles at microsatellite loci. We detected a significant decrease in the observed heterozygosity between ancestors and descendants but the amount of decrease did not depend on either the degree of removal from the wild (number of sequential transfers) or the strain (Fraser vs. Nauyuk). Based on allele frequency distributions, there was little genetic evidence of bottlenecks during the creation of subsequent broodstock populations after the initial founding events. All broodstock samples were significantly differentiated from each other but those within the same strain were more similar to each other than to broodstocks from different strains. Broodstocks from the Nauyuk Lake broodstocks showed greater differentiation from each other than did Fraser River broodstocks, which could be attributed to differences in the number of founders. [ABSTRACT FROM AUTHOR]

Currently, there is an increasing interest in shipping live adult scallops to markets and broodstock to hatcheries; nevertheless, information about the shipping e!ect on live scallops physiology is very scarce. In a previous study, a method in emersion was developed to ship scallop seed out of water, but twas not known whether this method is useful to transport adult organisms. As a consequence, the purpose of this study was to evaluate the e!ects of transportation by the emersion method on the physiological status of the adductor muscle of adult giant lion’s paw scallop. Live specimens were packaged in a container and transported in emersion for 11h. Six scallops were frozen in a farm and a similar number were frozen as soon as they arrived to the laboratory. Physiological indices were determined in each lot and the survival was estimated 24 h after re-immersion. As a result of the transportation, a signi￠cant loss (P < 0.05) of total carbohydrates, glycogen, adenosine 50-triphosphate and adenilated energetic charge, and a significant increase (P < 0.05) in the free amino acids concentration were observed. Eighty-eight percent survival was achieved; therefore, we conclude that this method is appropriate for shipping live adult scallops of Nodipecten subnodosus. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to identify the effects of methanol in a glucose diluent on the fertility and viability of cryopreserved Arctic char spermatozoa, Salvelinus alpinus semen. It explores the cryopreserved semen in two thaw rates such as 25°C for 17 s and 5°C for 60 s. Results show that the levels of methanol higher than 10% are beneficial for cryopreserving Arctic char sperm.

The 'earthy' and 'muddy' off-flavours in pond-reared fish are due to the presence of geosmin or 2-methylisoborneol in the flesh of the fish. Similar off-flavours have been reported in fish raised in recirculating aquaculture systems (RAS); however, little information is available regarding the cause of these off-flavours. Our hypothesis was that earthy and muddy off-flavour compounds, found previously in pond-raised fish, are also responsible for off-flavours in fish raised in RAS. In this preliminary study, we examined water, biofilms in RAS and fillets from cultured arctic charr known to have off-flavours and requiring depuration using instrumental [solid-phase microextraction procedure and gas chromatograph-mass spectrometry (GC-MS)] and human sensory analyses. Geosmin was present in the samples taken from the biofilter and on the side walls of the tanks. Two-methylisoborneol was only found in low levels in the samples. The GC-MS results indicated the presence of geosmin in the fillets (705 ng kg), but lower levels were found in the water (30.5 ng L). Sensory analyses also detected an earthy flavour (i.e., geosmin presence) in the fillets, and, therefore, it appears that geosmin is the main compound responsible for the off-flavour in RAS. Further studies are being performed to identify the microorganisms responsible for geosmin production in RAS. [ABSTRACT FROM AUTHOR]

The effect of rearing temperature on the growth and maturation of Arctic charr ( Salvelinus alpinus) was investigated. Arctic charr juveniles were reared for 6 months (phase I, October-April, size range 20-500 g) at constant temperatures of 9, 12 and 15 °C and according to two temperature-step groups ( T) i.e. fish transferred from 15 to 12 °C or from 12 to 9 °C. All the previous treatments were then reared either at 7 °C or at 12 °C for an additional 4 months (phase II, size range 300-1000 g) and then slaughtered in August 2008. The overall growth rate was the highest at a constant temperature of 15 °C for the first 6 months of the trial, with the fish in this group being 44% and 78% heavier than the fish reared at a constant temperature of 12 or 9 °C respectively. Arctic charr showed a negative response in terms of the growth rate when transferred from higher to lower temperatures, especially for groups previously reared at 15 °C. There was a trend for higher gonadosomatic index values at the end of the experiment for groups of fish that were exposed to higher rearing temperatures during the juvenile phase i.e. 4.18% (±0.79) and 7.29% (±0.89), for the temperature groups of 12 and 15 °C, respectively, compared with 2.49% (±0.74) for the 9 °C group. Our results suggest that for the production of fish >1000 g, moderate or low temperatures (here 9 °C) should be applied during the juvenile phase in order to reduce the negative effects arising from maturation. Farmers with access to heat sources should accordingly choose more moderate rearing temperatures during the juvenile stage, especially if the fish is to be moved down in the temperature regime during the on-growing period. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity has been demonstrated in fishes but rarely addressed with respect to skeletogenesis. The influence of water velocity on the sequence of chondrification and ossification is studied for the median fins of Arctic charr, Salvelinus alpinus,during a period of 90 days post hatching. Time of appearance, relative position within sequences, and direction of development among serially repeated elements are compared between two velocity treatments. Water velocity has induced changes in the timing of events and to a lesser extent on the relative sequence events in the locomotor system. Ossification is more responsive to water velocity than chondrification, and early-forming elements are less responding than late-forming elements. Directions of development are fairly conservative. It is suggested that a faster sustained swimming (behavioural adaptation to a higher water velocity) could induce differential mechanical stresses on developing skeletal elements involved in locomotion and therefore induce changes primarily in the timing of the ossification. [ABSTRACT FROM AUTHOR]

The article presents an experimental study which examines the positive effects of exposure to increased water velocity on the growth of newly hatched Arctic charr also known as Salvelinus alpinus L. The experiment used 1224 newly hatched fish with the aid of water velocity treatment which has an effect on growth in terms of length and weight. It was found out the use of a higher water velocity immediately after hatching is associated with a significant increase in growth. The study also suggests that environmental growth advantages achieved early in the life history of cod.

Embryo somatic tissues, non-somatic yolk-sac materials, and whole, individual fingerlings (age 0+) of Arctic charr, Salvelinus alpinus (L.), as well as a commercial trout diet, were analysed for a wide spectrum of amino acids. Analytical material consisted of prefeeding swim-up fry that were separated into discrete yolk sac and somatic embryo tissue samples. Amino acid concentrations in fry somatic tissue and whole fingerlings were generally very similar to each other, but were lower than those measured in yolk materials. Higher correlations were observed between the majority of specific amino acid concentrations in the trout diet when compared with fingerling data ( r2 = 0.91) and fry somatic tissue data ( r2 = 0.89), than when correlated with fry yolk sac material ( r2 = 0.76). These results indicate that the essential amino acid profiles of fry somatic tissue and whole fingerlings are closer to that of a commercial feed than they are to the endogenous profiles found in the embryonic yolk sac material itself. The dietary ratios of individual essential amino acids were also compared with the total essential amino acid concentrations (A/E ratios) in whole fingerling tissues, and these ratios could be used to accurately estimate the apparent essential amino acid requirements of Arctic charr. The rationale for using carcass amino acid composition data to estimate the dietary essential amino acid requirements of Arctic charr is discussed. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate whether dietary ration or diet composition influence the relationship between plasma growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in Arctic charr ( Salvelinus alpinus L.). The pattern of changes in plasma GH and IGF-1 concentrations was examined in fish fed at different ration levels (0%, 0.35% and 0.70% BW day−1) for 5 weeks, and in fish fed diets containing different lipid:crude protein (LCP) ratios. Ration level significantly affected plasma GH and IGF-1 concentrations; at 5 weeks the levels of both hormones in the food-deprived group were significantly lower than in fish fed the 0.70% BW day−1 ration. Also, plasma IGF-1 levels in fish of each ration treatment group were significantly correlated with individual final body weight; no such correlation was found for GH. To examine the effects of dietary LCP ratios, fish were fed for up to 18 weeks, with one of four formulated diets that had LCP ratios (dry matter basis) of 0.35 (Diet 1), 0.43 (Diet 2), 0.51 (Diet 3) or 0.59 (Diet 4), or a commercial diet (Diet 5) which had an LCP ratio of 0.38. Statistical differences in plasma GH and IGF-1 concentrations were found only after 18 weeks. Growth hormone was significantly lower in fish fed Diets 1 and 2 compared with Diets 3 and 5, and IGF-1 was significantly lower in fish fed Diet 1 compared with Diets 2 and 5. Significant correlations between plasma GH and IGF-1 concentrations were found only for fish fed Diets 1 and 5, suggesting that the influence of diet composition on the relationship between GH and IGF-1 varies with the dietary LCP ratio in this species. The decline in plasma IGF-1 concentrations during food deprivation is similar to that described in other species; however, the unexpected decrease in plasma GH during food deprivation in this study may represent a species-specific response. [ABSTRACT FROM AUTHOR]

The effects of extender composition and freezing rate on motility and fertility of frozen-thawed Arctic char, Salvelinus alpinus, spermatozoa were investigated. Three freezing rates, two semen diluents and three cryoprotectants were tested. Semen frozen in 0.3 mol L−1 glucose diluent with 10% methanol as a cryoprotectant or in a diluent described by Lahnsteiner with 10% N,N-dimethylacetamide (DMA) resulted in the highest sperm motility. Fertility was the highest for semen frozen in a glucose–methanol extender but was not significantly different than that for semen frozen in Lahnsteiner's diluent with 10% DMA. Dimethyl sulphoxide (DMSO) at 10% was a relatively ineffective cryoprotectant with either semen diluent. Semen frozen at 6 cm above the surface of liquid nitrogen resulted in a higher post-thaw sperm motility and fertility than semen frozen at 5 cm. The addition of 7% fresh egg yolk to glucose diluent containing methanol or DMSO did not improve the fertility of frozen-thawed spermatozoa. However, the addition of 7% fresh egg yolk to glucose–DMA extender significantly improved the fertilization percentages of frozen-thawed spermatozoa. In conclusion, dilution of semen 1:3 in 0.3 mol L−1 glucose with 10% methanol and freezing 6 cm above the surface of liquid nitrogen (freezing rate of 40±8°C min−1, mean±SD from −5 to −55°C) is a promising protocol for cryopreservation of Arctic char semen. [ABSTRACT FROM AUTHOR]

The primary aim of the present study was to evaluate the population level of adherent (autochthonous) aerobic and facultative anaerobic bacteria in the hindgut of healthy Arctic charr ( Salvelinus alpinus L.) fed dextrin or inulin. This was assessed by the dilution plate technique, and visualized using both transmission and scanning electron microscopy. A population level of 4.8 × 105 adherent bacteria per gram wet mass was found in the hindgut of fish fed a casein-based diet supplemented with 15% dextrin. However, substituting dextrin with 15% inulin reduced the bacterial population level in the hindgut (3.56 × 104). A total of 217 bacterial isolates were identified by key phenotypical and biochemical characteristics. In addition, 22 strains were also identified by partial sequencing of the 16S rRNA gene. The composition of bacteria colonizing the hindgut of Arctic charr fed dextrin was dominated by the genera Staphylococcus, Pseudomonas, Micrococcus, Psychrobacter glacincola and Streptococcus. However, bacteria colonizing the hindgut of fish fed inulin were dominated by Gram-positive bacteria of the genera Staphylococcus, Streptococcus, Carnobacterium and Bacillus. While Carnobacterium divergens-like strains were isolated from charr fed dextrin, Carnobacterium maltaromicus-like strains were isolated from the hindgut of fish fed inulin. Electron microscopical analysis of hindgut regions confirmed traditional culture-based microbial analysis as fewer bacterial cells were observed between microvilli and associated with the surfaces of enterocytes of fish fed inulin rather than dextrin. [ABSTRACT FROM AUTHOR]

Populations of heterotrophic bacteria present in the hindgut region of Arctic charr Salvelinus alpinus L. fed dietary soybean, linseed and marine oils before challenge with Aeromonas salmonicida ssp. salmonicida and marine oil after challenge were estimated using the dilution plate technique. There were differences in bacterial composition between the rearing groups before and after challenge, as well as interindividual variations. For example, carnobacteria were only isolated from the hindgut region of fish fed soybean oil and linseed oil before challenge, whereas Carnobacterium spp. and Carnobacterium funditum-like species were isolated from fish fed the same oils after challenge. Three non-motile Aeromonas spp. were isolated from infected fish fed marine oil. One of these isolates was identified as identical to A. salmonicida ssp. salmonicida used in&the challenge test by microbial fingerprinting (amplified fragment length polymorphism). Electron microscopic examinations of hindgut regions demonstrated substantial numbers of bacterial cells associated with enterocytes, but bacterial colonization of the enterocyte surface varied between different rearing groups. The potential of bacteria found associated with the hindgut region to inhibit the fish pathogens A. salmonicida, Vibrio salmonicida and Vibrio anguillarum differed between rearing groups. [ABSTRACT FROM AUTHOR]

Dominance hierarchy formation in groups of fish is thought to be a major reason for the development of size heterogeneity. The objective of the current experiment was to examine the influence of different feeding frequencies on growth and changes in size distribution in groups of Arctic charr Salvelinus alpinus (L.). The fish were fed equivalent excess rations continuously for 24 h a day, for 2 h twice a day (early morning and evening), for 2 h once a day in the morning or for 2 h once every other day also in the morning. Growth was measured by individual weighing of fish four times during the 130-day experiment. Coefficient of variation in size within rearing groups was used to assess size dispersion and the possible development of hierarchies within the groups. Feeding frequency did not influence variation in size within groups, and there were no signs of hierarchy formation. [ABSTRACT FROM AUTHOR]

Abstract Sexually immature Arctic charr, Salvelinus alpinus (Linnaeus), were fed one of five isoenergetic practical diets of differing lipid:protein ratios (0.98, 0.67, 0.41, 0.26, 0.19) for an 84-day period to examine the influence of diet composition on growth, and growth hormone (GH) and thyroid hormone physiology. All five diets supported growth at approximately the same rate, but the diet with a lipid:protein ratio of 0.98 had the lowest weight gain and highest food conversion ratios. A GH enzyme-linked immunosorbent assay (ELISA), developed for use with oncorhynchid fishes, was validated for use with Arctic charr. Plasma GH concentrations were significantly higher in fish fed the diet with a lipid:protein ratio of 0.98, and there were significant direct and inverse correlations between plasma GH levels and dietary lipid and protein content respectively. There were no significant differences in pre- and post-prandial plasma GH concentrations for any group. There were significant post-prandial elevations of plasma triiodothyronine (T[sub 3]) and thyroxine (T[sub 4]) for fish fed the lower lipid:protein ratio diets, but there were no differences related to the diets. The results are discussed in terms of GH as a factor in the regulation of lipid and protein homeostasis in fishes. [ABSTRACT FROM AUTHOR]

Abstract The effects of temperature and salinity on the reproductive success of Arctic charr, Salvelinus alpinus (L.), were examined by holding broodstock under the following conditions from mid-May until the end of September: fresh water at ambient temperature (NFW; 8–16 °C); salt water (25–30‰) at ambient temperature (NSW; 4–10 °C); fresh water cooled to saltwater temperature (CFW; 4–10 °C); or salt water heated to freshwater temperature (HSW; 8–16 °C). The relative fecundity of females was similar among groups (P > 0.05; 2685 ± 706 eggs), but females reared in NSW produced significantly larger eggs than those raised in NFW. The highest spermatozoa concentrations were found in milt from males reared in SW and the highest milt glucose concentration was from males kept under coldwater conditions (CFW, NSW). Eggs from NSW and HSW females contained more proteins than eggs produced by NFW females. Eggs from NSW females also contained 40% more lipids than was observed in the other groups, and total energy content was 27% higher in eggs from NSW females than in eggs from NFW females. When FW was cooled (CFW), females produced eggs with protein contents similar to those in NSW, but the lipid contents remained 30% lower. Finally, the best survival at the eyed stage and at hatch was observed in families produced by NSW broodstock. Intermediate values were observed in families from NFW or CFW while the highest mortality occurred in families from the HSW group. All these results suggest that, under the experimental conditions used in the present study, coastal seawater conditions offered the most favourable summer rearing conditions with respect to the reproductive success of Arctic charr. [ABSTRACT FROM AUTHOR]

The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was significantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per fish respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected fish. Such behaviour has previously been interpreted as a response by the fish to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected fish, and 47% of the fish caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all fish from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance. High salmon lice infections may therefore have profound negative effects upon wild populations of sea trout. At the unexposed location, the infection intensities were low, and few fish carried more than 10 lice. These are probably within the normal range of natural infection and such intensities are not expected to affect the stock negatively. [ABSTRACT FROM AUTHOR]

Arctic charr (Salvelinus alpinus L.) were fed diets based on a commercial recipe supplemented with either linseed, soybean or marine oil prior to cohabitant challenge with Aeromonas salmonicida ssp. salmonicida. Mortality varied significantly between the three dietary groups. Highest mortality (48%) was observed in fish fed the marine oil and the lowest mortality (20%) was in the group fed soybean oil. Transmission electron microscopy (TEM) examination of the digestive tract of uninfected fish demonstrated substantial numbers of bacterial cells between microvilli. However, only a few bacteria were recovered that were associated with the microvilli of infected fish. Immunocytochemical staining/labelling investigations using TEM and an immunogold method were performed on mid-gut segments of fish fed the marine oil diet and showed augmentation of goblet cells and the presence of A. salmonicida ssp. salmonicida in the gastrointestinal tract of diseased fish after challenge with the pathogen. It is suggested that the gastrointestinal tract could be an infection route of A. salmonicida ssp. salmonicida. The greater prevalence of goblet cells supports the suggestion that sloughing off mucus is a protective response against bacterial infections. These results make an important contribution to our understanding of how nutrition can affect the disease resistance of fish. [ABSTRACT FROM AUTHOR]

Examines the effects of inulin on intestinal enterocytes of an Arctic charr. Increase of vacuoles caused by inulin; Discussion on the destructive quality of inulin diet to Arctic charr; Impact of the detrimental effect of inulin on aquaculture.

Abstract Groups of one-year-old smolts of Arctic charr (Salvelinus alpinus L.) reared under a simulated natural photoperiod were fed pelleted feed with a NaCl content of either 1.5% or 9.5% for 6 weeks before release in a river in northern Norway. There were no differences in growth before release between fish fed the two diets. Smolts fed the 9.5% NaCl diet had better hypo-osmoregulatory ability than those fed the 1.5% diet, and a level of gill Na[sup +]-K[sup +]-ATPase activity that was several times higher. One of the two groups that had been fed the 9.5% NaCl diet had both a significantly higher recapture rate and growth in sea than the two groups fed the 1.5% NaCl diet, whereas this was not true for the other 9.5% NaCl diet group. The results indicate that a NaCl-enriched diet could be used to ensure sufficient hypo-osmoregulatory ability of charr smolts that would otherwise have insufficient regulatory ability. [ABSTRACT FROM AUTHOR]

Abstract Triploid hybrids between female rainbow trout Oncorhynchus mykiss and male brook charr Salvelinus fontinalis, Arctic charr S. alpinus and lake charr S. namaycush, together with diploid and triploid rainbow trout controls from the same dams, were tested in freshwater farming up to their fourth year of life. All hybrids displayed lower survival rates than the controls, the weakest genotype being the Arctic charr hybrid. Mortalities were mostly observed at the embryonic and larval stages and at the adult stage as a consequence of male sexual maturation. Growth of all hybrids was hindered (compared with controls) during the first year, but only moderate differences remained after 3 years. Sexual maturation resulted in a weight inferiority of males in all genotypes. As to carcass traits, female hybrids displayed a slightly higher dressing percentage than female triploid rainbow trout, as a result of lower visceral losses. These results are discussed with reference to hybrid resistance to rhabdoviruses from the viewpoint of fish farming improvement. [ABSTRACT FROM AUTHOR]

AbstractCryopreservation of Arctic charr Salvelinus alpinus (L.) semen was investigated using three diluents, three cryoprotectants [10% dimethyl sulphoxide (DMSO), 10% dimethylacetamide (DMA) or 20% glycerol] and three sizes of straw. The three diluents and three cryoprotectants were combined, resulting in nine extenders. One part semen was added to three parts extender, and motility was evaluated to assess the toxicity of six of the extenders. Semen in nine extenders was frozen in 0.5-mL straws using liquid nitrogen vapour. Semen extended in 0.3 m glucose and each of the cryoprotectants was also frozen in 0.5-mL, 1.7-mL (flat) or 2.5-mL straws. The freezing rate in each size of straw was measured. Fertility trials were conducted to determine the post-thaw viability of the frozen semen. The motility of activated spermatozoa was higher in the DMA and DMSO extenders than in the glycerol extender. For the trial using 0.5-mL straws, post-thaw fertility results were higher for all extenders containing DMSO, or 0.3 m glucose and DMA, than for all other combinations of diluent and cryoprotectant. For the straw size comparison, the highest fertility was obtained for the 1.7-mL straw using either DMSO or DMA and for the 2.5-mL straw using DMSO. For all cryopreservation trials, fertility was low for extenders containing glycerol. [ABSTRACT FROM AUTHOR]

Abstract Arctic charr Salvelinus alpinus (L.) were individually tagged and maintained in circular tanks for 102 days in order to allow the development of dominance hierarchies. At the end of the trial period, the charr were anaesthetized in benzocaine and identified as dominant, beta (β) and subordinate according to a set of established criteria including size, coloration and bite marks. The gut contents were then collected and analysed for apparent digestibility coefficient of nutrients using the chromic oxide method. Subordinate fish had significantly lower specific growth rates and apparent nutrient digestibility coefficients of both dry matter and lipid compared with dominant fish. Although specific growth rate was significantly lower in the β fish compared with dominant charr, this did not influence the apparent digestibility coefficient of nutrients to any major extent. [ABSTRACT FROM AUTHOR]

Abstract The hypothesis that long-term energy intake is matched to energy expenditure arose during the 1950s, and this formed the basis of the lipostatic model for the control of food intake in mammals. This gave rise to an additional hypothesis that body weight varies little over adult life because body fat, a variable related to body mass, is regulated. There is now a large body of evidence that adipose tissue plays a role in the regulation of feeding and body weight in mammals, and the study of the mechanisms by which the brain monitors the signals arising from the adipose tissue is currently a major area of research. After a period of nutritional restriction, a number of compensatory responses are invoked, and these result in hyperphagia, rapid weight increase and the repletion of energy reserves. However, the extent to which animals recover lost body weight has been reported to vary between studies. It is hypothesized that the rate at which animals replete their lipid reserves during catch-up growth may influence the hyperphagic response and, hence, whether or not there is complete recovery of body weight. Preliminary tests carried out using some data collected in studies of catch-up growth in salmonids appear to provide support for the model, but more experimental studies are needed to provide rigorous testing. [ABSTRACT FROM AUTHOR]

Abstract We examined the effect of social rank on plasma cortisol dynamics after handling stress in juvenile Arctic charr, Salvelinus alpinus L., reared in groups of 200 individuals in 1.5 m[sup 3] circular tanks (rearing density 0.022 kg L[sup –1]). Fish obtained by dip-netting were categorized as either socially subordinate, dominant or as holding an intermediate position on the basis of size, skin coloration and occurrence of bite marks. In undisturbed fish, the highest cortisol levels were found in fish ranked as intermediate and the lowest in dominant fish. In contrast to what has been found under conditions of artificial rearing in small groups (two to ten individuals), cortisol was not significantly elevated in subordinates compared with dominant individuals. In small groups of fish, aggressive interactions and restricted access to food may be significant factors leading to increased stress in socially subordinate individuals. Following stress by dip-netting and transfer, the quickest and largest cortisol response was seen in dominant individuals. These results suggest that hypothalamus–pituitary–inter-renal/adrenal axis responsiveness as well as baseline cortisol production is influenced by social rank in fish, as has been shown in other vertebrates. [ABSTRACT FROM AUTHOR]

The dietary methionine requirement of juvenile Arctic charr Salvelinus alpinus (L.) was assessed by feeding diets supplemented with graded levels of DL-methionine (9, 12, 15, 18, 21, and 24 g kg-1dietary protein) for 16 weeks at 12°C. All diets contained 400 g kg-1 protein, 170 g kg-1 lipid, 66 g kg-1 ash and an estimated 17.5 MJ digestible energy (DE) kg-1. When live-weight gain was examined using quadratic regression, the estimate of methionine requirement for optimal growth was 17.6 g kg-1 of dietary protein (DP) or 7 g kg-1 of the diet. Requirements estimated on the basis of carcass protein and energy gains were 18.8 and 17.9 g kg-1 DP, respectively. Plasma methionine concentrations and ocular focal length variability measurements did not provide a sensitive measure of requirement, because each responded in a linear fashion to increasing dietary methionine levels. Based on the prevalence of cataracts, the methionine level required to prevent lens pathology (26.7 g kg-1 DP) appears to be higher than that required for maximum growth. [ABSTRACT FROM AUTHOR]

Abstract To study the influence of temperature on the nutrient and fatty acid digestibility of salmonid fish, Arctic charr, Salvelinus alpinus L., were fed dry pelleted diets at 10 and 0.6 °C for 81 days. The diets had a carbohydrate/lipid content of 23.7/13% and 6.4/27% and a constant protein content of around 50%. At the end of feeding period, gut contents were collected from the mid- and hind-gut regions, and analysed for the apparent digestibility coefficient (ADC) of nutrients using chromic oxide as digestibility marker. Fish maintained at 0.6 °C had a lower ADC of protein, carbohydrate, lipid and dry matter compared to those maintained at 10 °C. This shows that increased gastrointestinal holding time following low temperature adaptation does not fully compensate for lowered digestive/absorptive metabolism. Feeding high carbohydydrate diets had no significant influence on nutrient utilization at 10 °C, but appeared to reduce the ADC of most macronutrients at 0.6 °C. The ADC of the individual fatty acids increased with decreasing chain length and increased with unsaturation. Maintaining the fish at 0.6 °C significantly reduced the ADC of saturated fatty acids, while the monounsaturated fatty acids, and in particular, the polyunsaturated fatty acids were hardly influenced by environmental temperature. It is suggested that the reason may be a shift in digestive lipase specificity caused by changes in the substrate state or lowered solubilization of saturated fatty acids in bile micelles, which thus reduces the uptake into the enterocyte. [ABSTRACT FROM AUTHOR]

To compare the rates of digestion and absorption of individual fatty acids, Arctic charr, Salvelinus alpinus (L.), were fed isoenergetic diets containing 40 g kg[sup -1] coconut oil, and various combinations of 10 g kg[sup -1] of polyunsaturated fatty acids (PUFA) (18:2n-6 or 18:3n-3) and monounsaturated fatty acids (MONO) (20:1n-9 or 22:1n-9) in the form of free fatty acids (FFA) or triacylglycerol (TAG). The average lipid digestibility for all diets measured by use of the chromic oxide method in the pyloric caeca area, midgut and hindgut were 72%, 83% and 88%, respectively, showing that lipid digestion and absorption occur mainly in the pyloric caeca area, but also extend throughout the intestinal tract. Analyses of digesta present in the intestinal segments suggest the predominance of non-specific lipolytic activity producing primarily FFA and glycerol from dietary TAG. Comparisons of the fatty acid composition of the lipid classes in the digesta showed that the utilization of dietary TAG was dependent both on the rate of release of the individual fatty acids from TAG, and their subsequent rate of absorption. When supplied as either FFA or TAG, the levels of PUFA (18:2n-6 or 18:3n-3) in the digesta were very low, indicating almost complete utilization. Both MONO used (20:1n-9 or 22:1n-9) were absorbed less efficiently than PUFA, but the rate of release from TAG seemed to be rate limiting only for 22:1n-9, which accumulated in the digesta. The rates of absorption of 20:1n-9 and 22:1n-9 when fed as FFA were the same. Comparisons of the levels of fatty acids in the dietary coconut oil TAG with those of the digesta lipids showed that 12:0 was a good substrate for intestinal lipase and was quickly absorbed. The lipolysis of 14:0 and 16:0 was intermediate while the longer-chain 18:0 appeared very resistant to digestion and was a major component of TAG, diacylglycerols and monoacylglycerols present in particularly the hindgut digesta. The absorption of 18:0 al... [ABSTRACT FROM AUTHOR]

Farmed Arctic charr, Salvelinus alpinus (L.), (n = 270) with a wide range of carotenoid muscle pigmentation were produced by feeding astaxanthin at different levels (0-120 mg kg-1 feed). Steaks were scored subjectively for pigment concentration (dark = high score). Internal reflectance spectra were measured with a relatively non-destructive 1-mm-diameter fibre-optic probe. Colour scores were only moderately correlated with reflectance (R = 0.66 and P < 0.01, using data at 500, 610 and 520 nm) because the small-diameter probe had a short light-path through the tissue and was highly responsive to scattering. However, in fish without astaxanthin in their diet, this sensitivity to microstructural causes of scattering revealed that fibre-optic reflectance increased (P < 0.01) with age from 400 nm (r = 0.68) to 440 nm (r = 0.40), and from 530 nm (r = 0.30) to 700 nm (r = 0.56). In agreement with these results, colour scores decreased with age (r = -0.52; P < 0.001; n = 85), as did electrical resistance 24 h post-mortem (r = -0.42 at 120 Hz, r = -0.39 at 1 kHz and r = -0.54 at 10 kHz; P < 0.001). Resistance was correlated with colour score (r = 0.40 and P < 0.001 for resistance at 10 kHz) and with fibre-optic reflectance (R = 0.42 and P < 0.01 for resistance at 120 Hz and 1 kHz versus reflectance from 420 to 680 nm). Thus, without astaxanthin in the diet, muscle colour and tissue integrity at 24 h deteriorated with the age of the fish. [ABSTRACT FROM AUTHOR]

The relationships between fillet colour (CIE L* a* b* and CIE L* C* H°ab) and carotenoid concentration were investigated using samples taken from Arctic charr, Salvelinus alpinus (L.), of different ages and sizes, which were held under a variety of rearing conditions. Relationships between colour parameters and carotenoid concentrations were nonlinear. Increasing carotenoid concentrations led to increased redness (a*), yellowness (b*) and chroma (C*), and decreased lightness (L*) and hue angle (H°ab). Redness was the colour parameter most highly correlated with carotenoid concentration of the Arctic charr fillets. For a given redness value, yellowness was higher in sexually mature than in immature Arctic charr. This was possibly a result of mature fish having higher proportions of idoxanthin in the fillet than immatures. Alternatively, the differences in yellowness may have been a consequence of differences in proximate composition of fillets of mature and immature charr. There were also differences in yellowness in fillets from Svalbard and Hammerfest charr, Svalbard fish having the most yellow fillets. Fish from the two strains did not differ in relative proportions of fillet carotenoids, indicating that differences in colour were mediated through differences in other chemical properties. [ABSTRACT FROM AUTHOR]

There would appear to be considerable potential for Arctic charr, Salvelinus alpinus (L.), to be cultured in marine conditions in countries where coastal winter salinity is below oceanic, and temperatures remain above freezing. Sea lochs on the west coast of Scotland represent one such environment where freshwater run-off leads to depressed salinities (20-30 practical salinity units) and the North Atlantic Drift leads to winter sea water temperatures typically around 6-8 °C. [ABSTRACT FROM AUTHOR]

The article presents a study examining the effect of hierarchy formation in Arctic char on intestinal microbiota of subordinate and dominant individual fish. Hatchery-reared Arctic char were derived from the River Hals stock in northern Norway. The feeding trials were conducted using triplicate groups of 50 fish in circular experimental tanks at 8 Celsius and fed a commercial feed. The study found that C. Divergens bacterial species belongs to the indigenous microbiota of Arctic char and are able to colonized the digestive track even when low food intake occurs.

For salmonid semen, the cryoprotective action of 10% methanol was compared with a 5% dimethyl sulphoxide (DMSO), 1% glycerol mixture, until now one of the most effective cryoprotectants. In Oncorhynchus mykiss (Walbaum), Salmo trutta L. f. fario, Salmo trutta L. f. lacustris and Salvelinus alpinus (L.), semen cryopreserved with both cryoprotectants yielded post-thaw fertilization rates of 90–100% of control with untreated semen at sperm-to-egg ratios of 1.8 ⊗ 106–2.4 ⊗ 106 spermatozoa per egg. However, at sperm-to-egg ratios of 0.9 ⊗ 106–1.2 ⊗ 106 spermatozoa per egg, semen cryopreserved with methanol had significantly higher fertilization rates than semen frozen with the DMSO/glycerol mixture. In other studies we obtained similar data for Coregonus sp., Salvelinus fontinalis (Mitchill). Thymallus thymallus (L.) and Hucho hucho (L.), proving that methanol is the most effective and generally applicable cryoprotectant for semen of the studied salmonid species. To facilitate the insemination of large egg batches we investigated the suitability of 1.2 ml and 5 ml straws for deep freezing of semen of Oncorhynchus mykiss, Salmo trutta f. fario, Salmo trutta f. lacustris and Salvelinus alpinus. With 1.2 ml straws the fertilization rates were similar to 0.5 ml straws when using lower freezing and higher thawing temperatures. The 5 ml straws resulted in a fertilization success of only about 40% of fresh semen control. [ABSTRACT FROM AUTHOR]

An experiment was performed to determine the relative importance of social and genetic factors on the development of size variation in tanks of Arctic charr, Salvelinus alpinus (L.). Growth and the development of size variation were monitored for approximately 300 days in one-year-old fish from 18 families of Nauyuk, Norwegian and hybrid charr. Initial mean weights ranged between 21 and 85 g. and initial CVs (CV = coefficient of variation = 10 × standard deviation / mean) were between 4% and 52%. The final mean fish weights and variances of weight in tanks were highly predictable in terms of initial mean weights, initial variances, and elapsed time, suggesting that the same social influences were present in test tanks. Changes in CV depended on both the initial mean weights and initial CVs. The largest increases in CV occurred in tanks of small fish with initially small CVs and the largest decreases in tanks of large fish with initially large CVs. In general, tanks tended toward CVs of 20–40%, with tanks of initially small fish tending toward the larger CVs. On the basis of the observed results, it is suggested that to optimize growth and minimize size variation, charr should be sorted to CVs between 25% and 35% and then cultured at high densities (> 40 kg m-3). As expected, there were significant differences in strain and family growth rates. However, the relationship between size variation and mean weight did not differ between strains, but differed slightly but significantly between families within strains. These effects were weak compared with social effects. It is concluded that social factors are the most important in determining the growth of individual charr, and may have confounded previous experiments examining the genetic basis of growth. [ABSTRACT FROM AUTHOR]

Arctic charr Salvelinus alpinus L. averaging 150 g were fed six diets containing from 0 to 192 mg astaxanthin per kilogram dry diet at two temperatures (8°C and 12°C). After reaching an average weight of 320 g (102 days at 12°C and 126 days at 8°C). the fish were killed for evaluation of flesh pigmentation using instrumental colour measurement. There was a positive relationship between dietary astaxanthin and muscle redness up to a dietary concentration of around 70 mg kg-1, where a plateau in pigmentation was reached. Tail sections were more intensely pigmented compared with the neck and dorsal regions. Within each temperature regime, flesh coloration was positively correlated to specific growth rate. Fish maintained at 8°C had significantly higher pigmentation compared to those grown at 12°C. [ABSTRACT FROM AUTHOR]