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A species-specific fractionation equation for Arctic charr ( Salvelinus alpinus (L.)) was developed experimentally for use in ecological studies of temperature-driven phenologies for the species. Juvenile Arctic charr were reared in controlled conditions at different temperatures (2–14°C), with three replicates of each temperature. Otoliths from the fish and water samples from the chambers were analysed for oxygen isotope composition and used to estimate temperature-dependent fractionation equations relating the isotopic ratio to rearing temperature. A linear and a second order polynomial relationship were estimated and validated using comparable Arctic charr data from another study. Temperatures predicted using the polynomial equation were not significantly different from recorded experimental temperatures, whereas with the linear equation there were significant differences between the predicted and measured temperatures. The polynomial equation also showed the least bias as measured by mean predictive error. Statistical comparisons of the polynomial fractionation equation to a similarly estimated equation for brook charr ( Salvelinus fontinalis (Mitchill)) indicated significant differences. Results imply the need for species-specific fractionation equations, even for closely related fish. Results further suggest the polynomial form of the fractionation equation will facilitate more accurate characterisation of water temperatures suitable for use in ecological studies of temperature-driven phenologies of Arctic charr. [ABSTRACT FROM AUTHOR]

The UK lies towards the southernmost distribution limit of the circumpolar Arctic charr ( Salvelinus alpinus), and native populations of high national conservation value occur in all four component countries. However, given the temperature requirements of this species and the already relatively mild UK climate, there is strong reason to expect a significant negative impact of climate change on local populations. Data were assembled from repeated Arctic charr population assessments using combinations of hydroacoustics, gill netting, entrapment records and fisheries catches at five Scottish populations, five English populations and one Welsh population. These data were then used to test the hypotheses that there has been a widespread decline of Arctic charr in the UK and that it can be attributed at least in part to climate change. Ten of the 11 studied populations exhibited significant 1990-onwards declines in abundance, while only the most northerly population showed a significant increase. Overall, there was a significant positive relationship between the observed population decline ranking and a vulnerability to climate change ranking based on water body latitude, altitude and mean depth. These observations support the hypothesis that this species has suffered a recent and widespread decline in the UK, and although additional factors are undoubtedly also involved in some specific cases, climate change is a significant factor. [ABSTRACT FROM AUTHOR]

Biological data from 66 populations of Arctic charr, Salvelinus alpinus, from eastern North America were analysed to test the applicability of the countergradient hypothesis as an explanation of differences in seasonally adjusted growth rates. Samples were obtained along a 37° latitudinal gradient and partitioned among anadromous, normal lacustrine, and dwarf lacustrine Arctic charr morphotypes. Models relating length-at-age or age-specific growth rates to latitude were estimated for each morphotype. Length-at-age declined with latitude for anadromous and lacustrine charr. Age-specific growth rates also varied with latitude, particularly for normal lacustrine charr. Results of analyses provide support for the countergradient hypothesis in growth performance of normal lacustrine morphotypes, where northern populations compensate for the shorter growth season with a greater rate of growth than southern populations. Anadromous charr exhibited equivocal evidence of countergradient variation, while results for dwarf lacustrine Arctic charr populations were inconclusive owing to the limited range of ages, and latitudes for which data were available. [ABSTRACT FROM AUTHOR]

Three ecologically and morphologically distinct forms of Arctic charr ( Salvelinus alpinus L.) have been identified in Loch Rannoch, Scotland, whose evolutionary status and origins are incompletely understood. A study was made of restriction fragment length polymorphism (RFLPs) detected variation in the D-loop, ND1 and cytochrome b regions of the mitochondrial genome, encompassing >3500 bp. Eight RFLP haplotypes were identified that clustered into three distinct clans based on restriction differences and into four clans based on sequence differences. Significant differences in RFLP frequencies were found among all morph groups. The pelagic morph was highly divergent from the two benthic forms, with the benthic forms having variants from only one genetic clan while the pelagic was dominated by a single variant from another clan. The relative divergence observed among benthic and pelagic forms is ~10 fold greater when nucleotide divergence among the haplotypes, as well as haplotype frequency differences, is taken into account. Sequence divergence between haplotypes in the two main clans is of a similar order to that between haplotypes in these clans and a charr from North America. In contrast, divergence among the two benthic morphs relates entirely to differences in haplotype frequencies. The study confirms the genetic distinctiveness of the pelagic and benthic forms as well as of the two benthic forms. It strongly supports previous evidence that the genetic divergence between the pelagic and benthic populations is allopatric in origin. Additionally, the results strongly suggest that the two benthic populations have undergone peripatric divergence through the sequential colonisation of the two basins by one lineage, followed by their spatial separation and reproductive isolation. [ABSTRACT FROM AUTHOR]

We examined trophic positions and fatty acid concentrations of riverine, lacustrine, and aquaculture diet and fish in Austrian pre-alpine aquatic ecosystems. It was hypothesized that dietary fatty acid (FA) profiles largely influence the FA composition of the salmonids Salvelinus alpinus, Salmo trutta, and Oncorhynchus mykiss. We analyzed trophic positions using stable isotopes (δ15N) and tested for correlations with polyunsaturated fatty acid (PUFA) concentrations. Gut content analysis revealed benthos (rivers), pellets (aquaculture), and zooplankton (lakes) as the predominant diet source. Results of dorsal muscle tissues analysis showed that the omega-3 PUFA, docosahexaenoic acid (DHA; 22:6 n − 3), was the mostly retained PUFA in all fish of all ecosystems, yet with the highest concentrations in S. alpinus from aquaculture (mean: 20 mg DHA/g dry weight). Moreover, we found that eicosapentaenoic acid (EPA; 20:5 n − 3) in fish of natural habitats (rivers, lakes) was the second most abundant PUFA (3–5 mg/g DW), whereas aquaculture-raised fish had higher concentrations of the omega-6 linoleic acid (18:2 n – 6; 9–11 mg/g DW) than EPA. In addition, PUFA patterns showed that higher omega-3/-6 ratios in aquacultures than in both riverine and lacustrine fish. Data of this pilot field study suggest that salmonids did not seem to directly adjust their PUFA to dietary PUFA profiles in either natural habitats or aquaculture and that some alterations of PUFA are plausible. Finally, we suggest that trophic positions of these freshwater salmonids do not predict PUFA concentrations in their dorsal muscle tissues. [ABSTRACT FROM AUTHOR]

The trophic niche and parasite infection of Arctic charr ( Salvelinus alpinus) were explored in two lakes with sympatric burbot ( Lota lota) and two lakes without burbot in subarctic Norway. The CPUE of burbot and charr were similar in one lake, but burbot had a low population density in the other. Burbot were benthivorous in both lakes. Other co-occurring species like brown trout ( Salmo trutta), Atlantic salmon parr ( Salmo salar), grayling ( Thymallus thymallus) and minnow ( Phoxinus phoxinus) were also benthivores. At high densities, benthivorous burbot forced the whole Arctic charr population to utilise mainly the limnetic trophic niche. In contrast, at low burbot density or without burbot present, Arctic charr were primarily benthivorous in the littoral zone. Thus, a clear interactive segregation in diet was observed between Arctic charr and burbot at high burbot densities. There was also a high predation pressure from burbot on young Arctic charr along the benthic zones. The extensive use of zooplankton as prey caused a high parasite infection pressure of copepod transmitted Diphyllobothrium spp. larvae, with the potential for high negative impact on the Arctic charr population. As the benthivore trophic niche was occupied by burbot, the ecological opportunities for polymorphism with benthivorous ecotypes or morphs of Arctic charr were probably prevented. Therefore, the sympatry with burbot seems to have large ecological and evolutionary consequences for this Arctic charr population compared with neighbouring lakes where burbot is absent. [ABSTRACT FROM AUTHOR]

Stable coexistence of Arctic charr and whitefish does occur in a number of native lake fish communities in Scandinavia. Even so, whitefish introductions into Arctic charr lakes have resulted in serious decline and possibly local extinction of Arctic charr. In this article, we analyze the habitat use and diet of the two species in five Norwegian lakes differing in basin shape and environmental conditions. In two of the lakes, both species are native, and appear to live in a relatively stable coexistence. Here, whitefish mainly occupy the littoral and upper pelagic zone, while Arctic charr live in the deeper habitats. Diets are generally quite different in terms of the zooplankton species eaten. In the three other lakes, either whitefish or both species have been introduced. In the shallowest lake, habitat segregation is similar to that seen in the pristine lakes, although Arctic charr appears to be on the brink of extinction. In the remaining two lakes, however, Arctic charr dominates, and occurs in higher numbers than whitefish in all the habitats. Our observations indicate that coexistence of the two species in oligotrophic and relatively pristine lakes requires an extensive profundal zone to serve as a refugium for Arctic charr. If the littoral zone is rendered inaccessible or unprofitable for whitefish due to dominance of a third competitor or predator, or as a result of lake regulation, then Arctic charr may be the dominant species. [ABSTRACT FROM AUTHOR]

Arctic charr is the only freshwater fish in most of the High Arctic, with both resident, anadromous, and landlocked populations present. The anadromous Arctic charr is particularly highly sought-after, and has been an important food source for people living in Arctic regions. A recent decline in harvest in many areas has been related to over-exploitation by extensive gillnetting. Very few studies, if any, have estimated the gillnet efficiency for harvesting anadromous Arctic charr. In this study, all anadromous Arctic charr ascending the lake, Linnévatn, in western Spitsbergen, Svalbard, were marked over a period of 5 weeks, in July–August 2008. Recaptures in the lake were obtained by gillnetting with three mesh sizes (39, 45, and 52 mm measured knot-to-knot) during three periods. The total number of anadromous charr in the lake was estimated by both Schnabel and Petersen mark-recapture methods. The catchability increased significantly with fish size. Anadromous charr in the length-class 40.0–56.9 cm captured by the legal mesh size in Svalbard lakes (52 mm) had a mean catchability of 0.0023 per gillnet per 2 h fishing effort, and the catch quota which is set at 40 charr for Linnévatn by the Governor of Svalbard, would have been filled by less than five gillnets, each used for 6 h. Although this short fishing time may give an overestimation of catchability due to the avoidance of gear saturation, the high catchability values still indicate that anadromous Arctic charr populations may be extremely vulnerable to gillnetting. Hence, in addition to catch quotas set for each population, a restriction on the number of gillnets allowed per harvester should also be considered. [ABSTRACT FROM AUTHOR]

This comparative study explores how low temperatures affect the mortality and growth of first generation hatchery-reared progeny of subarctic populations of Arctic charr ( Salvelinus alpinus L.) and European whitefish ( Coregonus lavaretus L.). Replicate fish groups where held under simulated natural light regimes (70°N) at three constant temperatures (1, 3 and 6°C). The mortality of Arctic charr was low (≤1.4%) at all temperature treatments, whereas the mortality of whitefish increased with decreasing temperature from 6% at 6°C to 33% at 1°C. The Arctic charr exhibited higher growth rates than whitefish at all three temperature regimes. All groups of Arctic charr increased in weight, whereas whitefish held at 1°C did not gain weight throughout the experimental period of 133 days. Arctic charr exhibited a large intraspecific variability in growth leading to large variations in size-structure, whereas whitefish in contrast showed very homogenous growth and size-structure patterns; a dissimilarity probably related to species-specific differences in antagonistic behaviour. Evidently, Arctic charr are more cold water adapted than whitefish and are able to maintain growth at extremely low temperatures. Arctic charr thus appear to be the most suitable species for aquaculture at low water temperatures. [ABSTRACT FROM AUTHOR]

Results and experiences from a selective breeding programme aiming at improving the performance of an Arctic charr strain in aquaculture are presented. The programme, which has been running since 1985, uses traditional quantitative genetic methods based on relatedness and trait measurements. Traits considered included growth, age at sexual maturity, flesh colour, fat content and other features. Estimates in the early phase of the programme showed promising heritabilities for most traits, e.g. growth heritabilities of 0.34–0.52, and suggested that improvement by selection was feasible. Several traits such as a high rate of early maturation and poor flesh colour that were considered problematic by the Arctic charr farming industry at the programme’s start no longer hamper farming. Considerable improvement of growth by selection, estimated at 8% per generation, has contributed to shortening the production cycle in commercial farming. Results from studies of genotype–environment interactions are presented and discussed. Poor survival of fertilised eggs is a major problem in Swedish Arctic charr farming as indicated by presented survival rates. Efforts have consistently been made to avoid inbreeding in the selected strain, and at the present seventh generation the accumulated increase in inbreeding is estimated from pedigree data to be only approximately 5%. [ABSTRACT FROM AUTHOR]

We present an overview of 27 years of experience of domestication and farming of Arctic charr ( Salvelinus alpinus) in Sweden. The domestication process included an evaluation of suitable strains for farming, a breeding programme and the study of the biological and behavioural characteristics of the species. Traits of three different Arctic charr populations differing in ecology and appearance were compared during initial 2-year trials under farming conditions. The best-performing population with respect to the growth rate and the lowest frequency of early sexual maturation was a piscivore form and this became the foundation for a breeding programme intended to select for an Arctic charr strain suitable for farming. After 23 years and 7 generations, our selective breeding has resulted in a fast-growing, late-maturing strain much appreciated by farmers. The biological and behavioural characteristics studied included annual and diel locomotor activity, feeding, social and thermal behaviour. Applying our findings in these areas has greatly improved both profits and conditions for the fish. Other investigations have focused on the application and further evaluation of the results from research in practical farming trials, such as evaluation of growth at different farms with different temperature conditions, optimal time and stocking density for start-feeding and evaluation of different feeding schedules. In Sweden, Arctic charr is mainly farmed in net pens situated in nutritionally depleted and extremely unproductive water reservoirs formed by damming rivers to create electric power. Judicious farming of Arctic charr in such reservoirs can restore their nutritional and productivity state to that which existed before regulation. Site selection criteria for Arctic charr farming in such waters have been developed. The development of intensive farming of Arctic charr in Sweden is discussed together with current limitations and future possibilities. [ABSTRACT FROM AUTHOR]

Two life-history variants of Arctic charr ( Salvelinus alpinus), anadromous and lake-resident, have been previously identified in lakes of Southern Baffin Island, Nunavut, Canada. In accordance with classical life-history theory, it is hypothesised that anadromous charr will delay maturation in both size and age, and have increased fecundity (per spawning event) in comparison with lake-resident charr. Sagittal otoliths and biological data were collected for both life-history variants within the three studied lakes: Iqalugaarjuit, Qasigiat and Qinngu. Sagittal otoliths were embedded in epoxy resin, cross-sectioned for age determination, and imaged for back-calculation (size and age). Back-calculated data in each lake were fit to von Bertalanffy growth models for each life-history variant and compared via analysis of residual sums of squares. Anadromous charr had greater mean size at maturity and experienced a delay in mean age at maturity in comparison with lake-residents. The relationship between size and fecundity or egg diameter did not differ between the two life-history variants. Growth models indicate that the overall growth coefficients of lake-resident and anadromous charr were different in all three studied lakes. The Brody growth coefficient for all lake-resident charr populations was greater than anadromous individuals indicating that maximum length was reached at a rapid rate, resulting in a smaller asymptotic length. Indirect evidence suggests that anadromous and lake-resident charr belong to one reproductive population. Future genetic analysis is necessary to further determine the degree of divergence between the life-history variants. [ABSTRACT FROM AUTHOR]

This article reports on the work of the Irish Char Conservation Group, a voluntary Non-Government Organisation set up in 2000 to promote the conservation of Arctic char Salvelinus alpinus in Ireland. The basic terms of reference of the group, its operations and achievements are outlined. Since 2001, the Irish Char Conservation Group has surveyed 47% of known Arctic char loughs in Ireland, updating records and recording previously undiscovered populations ( n = 8). Research in partnership with other agencies is ongoing, providing information necessary for informed management decisions concerning the species. The group interfaces with the relevant statutory bodies in Ireland on a number of levels and endeavours to be as proactive as possible in facilitating research by collecting material and archiving samples for scientific research. The group interfaces with the public through a range of media in an effort to promote understanding amongst the general public of issues affecting Arctic char and its importance from biodiversity and heritage perspectives. In some instances, specific targeted campaigns have been carried out in an effort to address issues affecting Arctic char in particular loughs. [ABSTRACT FROM AUTHOR]

Seasonal and ontogenetic shifts in the diet of Arctic charr Salvelinus alpinus were studied in a deep, ultra-oligotrophic lake in subarctic Finland from both stomach contents and the stable carbon ( δ13C) and nitrogen ( δ15N) isotope compositions of muscle and liver tissues. Both diet and isotope results indicated that the S. alpinus population relied mainly on littoral benthic energy sources. The strong littoral reliance appeared largely independent of season or fish size, although the data lacked small (total length, LT, <130 mm) and young (<3 years) S. alpinus. Liver isotope values of intermediate-sized S. alpinus (200–350 mm), however, suggested exploitation of the increase in the abundance of pelagic zooplankton in the late open-water season. The results suggest that, in general, a strong littoral reliance of fishes can be a feature in subarctic lakes throughout the year. Due to its faster isotopic turnover rate and thus higher resolution for temporal diet changes, liver could be more commonly used in stable-isotope studies of fish trophic niche shifts instead of using only the less responsive muscle tissue. [ABSTRACT FROM AUTHOR]

Groups of mature (5+ year old) Arctic charr Salvelinus alpinus held in sea water were exposed for 34 days to either a high (mean ± s.e. 0·15 ± 0·01 sea lice Lepeophtheirus salmonis g−1 fish mass) (HI), medium (0·07 ± 0·00 sea lice g−1 fish mass) (MI) or no [control (C)] sea-lice infection during early stages of gonad development (June to July). Infection with sea lice resulted in increased plasma cortisol concentrations and this was related to intensity of infection; females tended to have higher cortisol concentrations than males at high infection intensities (HI group: female c. 130 ng ml−1; male c. 80 ng ml−1). Plasma osmolality (C c. 330, MI c. 350 and HI c. 415 mOsm) and chloride concentrations (C c. 135, MI c. 155 and HI c. 190 mM) increased significantly with infection intensity, indicating osmoregulatory problems in infected fish. A strong positive relationship between plasma osmolality and cortisol concentration was recorded. Plasma sex-steroid concentrations were influenced negatively by sea-lice infection, particularly in the HI group, and were inversely related to plasma cortisol concentrations. The most heavily infected fish postponed the initiation of reproductive development until exposed to fresh water and timing of ovulation tended to be delayed in these fish. Growth rate and condition were negatively influenced by sea-lice infection and growth rate was inversely related to plasma cortisol concentrations. Sea-lice infection resulted in mortality among females in the HI group, and the proportion of maturing females was lower in the MI group (46%) than in the controls (85%). Egg production in the MI and HI groups was c. 50 and 30% of the C group. Egg size, embryonic survival and fry mass did not differ across groups. Sea lice influence reproductive development and egg production in S. alpinus, and consequently these parasites may influence populations via sublethal effects on broodfish, affecting growth and condition, and their reproductive output. [ABSTRACT FROM AUTHOR]

The parental influences on three progeny traits (survival to eyed-embryo stage, post-hatching body length and yolk-sac volume) of Arctic charr Salvelinus alpinus were studied under two thermal conditions (2 and 7° C) using a factorial mating design. The higher temperature resulted in elevated mortality rates and less advanced development at hatching. Survival was mostly attributable to maternal effects at both temperatures, but the variation among families was dependent on egg size only at the low temperature. No additive genetic variation (or pure sire effect) could be observed, whereas the non-additive genetic effects (parental combination) contributed to offspring viability at 2° C. In contrast, any observable genetic variance in survival was lost at 7° C, most likely due to the increased environmental variance. Irrespective of temperature, dam and sire-dam interaction contributed significantly to the phenotypic variation in both larval length and yolk size. A significant proportion of the variation in larval length was also due to the sire effect at 2° C. Maternal effects were mediated partly through egg size, but as a whole, they decreased in importance at the high temperature, enabling a concomitant increase in non-additive genetic effects. For larval length, however, the additive component, like maternal effects, decreased at 7° C. The present results suggest that an exposure to thermal stress during incubation can modify the genetic architecture of early developmental traits in S. alpinus and presumably constrain their short-term adaptive potential and evolvability by increasing the amount of environmentally induced variation. [ABSTRACT FROM AUTHOR]

In the family Salmonidae, lake trout (Salvelinus namaycush) are considered the least tolerant of salt water. There are, however, sporadic reports of lake trout in coastal, brackish habitats in the Canadian Arctic. Otolith microchemistry analyses conducted on lake trout and Arctic char (Salvelinus alpinus) from four Arctic lakes in the West Kitikmeot region of Nunavut, Canada, revealed that 37 of 135 (27%) lake trout made annual marine migrations. Anadromous lake trout were in significantly better condition (K = 1.17) and had significantly higher C:N ratios (3.71) than resident lake trout (K = 1.05 and C:N = 3.34). Anadromous lake trout also had significantly higher δ15N (mean = 16.4‰), δ13C (mean = –22.3‰), and δ34S (mean = 13.43‰) isotope ratios than resident lake trout (means = 12.84‰, –26.21‰, and 1.93‰ for δ15N, δ13C, and δ34S, respectively); results were similar for Arctic char and agree with results from previous studies. Mean age of first migration for lake trout was 13 years, which was significantly older than that for Arctic char (5 years). This could be a reflection of size-dependent salinity tolerance in lake trout, but further research is required. These are the first detailed scientific data documenting anadromy in lake trout. Dans la famille des Salmonidae, ce sont les touladis (Salvelinus namaycush) qui sont considérés les moins tolérants à l’eau salée. On signale néanmoins de temps à autre la présence de touladis dans les habitats côtiers et saumâtres de l’Arctique canadien. Des analyses microchimiques des otolithes faites sur des touladis et des ombles chevaliers (Salvelinus alpinus) de quatre lacs arctiques dans la région du Kitikmeot occidental au Nunavut, Canada, montrent que 37 de 135 (27 %) touladis avaient fait des migrations annuelles en mer. Les touladis anadromes sont en significativement meilleure condition (K = 1,17) et possèdent un rapport C:N (3,71) relativement plus élevé que les touladis résidants (K = 1,05 et C:N = 3,34). Les touladis anadromes ont aussi des rapports d’isotopes δ15N (moyenne = 16,4 ‰), δ13C (moyenne = –22,3 ‰) et δ34S (moyenne = 13,43 ‰) plus élevés que ceux des touladis résidants (moyennes de 12,84 ‰, –26,21 ‰ et 1,93 ‰ pour respectivement δ15N, δ13C et δ34S); les résultats sont semblables chez les ombles chevaliers et concordent avec ceux des études antérieures. L’âge moyen de la première migration chez le touladi est de 13 ans, ce qui est significativement plus tard que chez l’omble chevalier (5 ans). Cela pourrait refléter une tolérance à la salinité reliée à la taille chez le touladi, mais il faut des recherches supplémentaires sur le sujet. Nos résultats représentent les premières données scientifiques détaillées sur l’anadromie chez le touladi. [ABSTRACT FROM AUTHOR]

Single-spawning (semelparous) anadromous fishes are known to transport contaminants from marine to freshwater habitats, but little research has been conducted on contaminant biotransport by multiple-spawning (iteroparous) anadromous fishes. We examined the effect of iteroparous, anadromous Arctic charr (Salvelinus alpinus) on mercury concentrations ([Hg]) in freshwater biota and compared [Hg] between species and life history types of Arctic charr and lake trout (Salvelinus namaycush). Data from six lakes and one coastal marine area in the Arctic territory of Nunavut, Canada, indicated that 1) lake trout had significantly lower [Hg] in lakes where anadromous Arctic charr were present; 2) [Hg] was significantly lower in recently discovered anadromous lake trout than in resident lake trout; and 3) regardless of life history, Arctic charr had significantly lower [Hg] than lake trout. These differences were explained by fish condition, age-at-size, and C:N. Biomagnification of Hg, measured as log10[Hg]-δ15N slopes, did not differ between lakes with and without anadromous Arctic charr but was significantly higher in freshwater food webs (∼0.2) than in the marine food web (0.08). Some biomagnification estimates were affected by correction for fish age and size. In contrast to semelparous anadromous species, biotransport of Hg by anadromous Arctic charr appears to be offset by increased growth of freshwater fishes. [ABSTRACT FROM AUTHOR]

Landmark-based geometric morphometric analysis was used to detect differences in scale shape between ecologically distinct phenotypes of Arctic charr Salvelinus alpinus coexisting in the same lake. Relative warp analysis and standard multivariate analyses of the partial warps, obtained after a Procrustes superimposition, showed that scale landmarks were efficient in discriminating among two closely related alternative phenotypes within each of the two lakes. In Loch Tay, S. alpinus exhibited a bimodal body size-frequency distribution among sexually mature fish, whereas in Loch Awe, S. alpinus are unimodal in body size but segregated into two distinct spawning phenotypes. In both lakes, alternative phenotypes showed significant differences in foraging ecology, habitat use and life history. It is probable that differences in scale shape reflect differences in ecology of these forms. [ABSTRACT FROM AUTHOR]

Gallagher CP, Dick TA. Trophic structure of a landlocked Arctic char Salvelinus alpinus population from southern Baffin Island, Canada. Ecology of Freshwater Fish 2010: 19: 39–50. © 2009 John Wiley & Sons A/S Stable isotopes, diet and parasites were used to investigate the trophic structure of landlocked Arctic char ( Salvelinus alpinus) from a small Canadian Arctic lake. Two trophic levels of char were identified. The lower trophic level comprised smaller char that consumed mainly invertebrates and harboured low numbers of the cestode plerocercoid Diphyllobothrium spp. while the higher trophic level char were larger, mainly piscivorous and had high numbers of plerocercoids. Procercoids of Diphyllobothrium spp. in copepods are eaten by char where the parasite then differentiates into a plerocercoid. Plerocercoids from smaller fish are transmitted to larger fish by piscivory where they encyst again as plerocercoids until the fish is eaten by a gull. These plerocercoids are a good indicator of trophic level as their numbers accumulate over time in larger fish. The three variables together provided a better resolution of trophic structure than applied separately. For example, plerocercoid numbers plus diet were better predictors of trophic status than stable isotopes in 4–7 year olds, but for char ≥8 years all three variables were complementary. Some char (≥10 years old) were placed in the lower trophic level based on their stable isotope values and had low Diphyllobothrium spp. abundance but were piscivorous and/or cannibalistic. The absence of sexually mature char in the higher trophic group was associated with high numbers of Diphyllobothrium spp. plerocercoids. [ABSTRACT FROM AUTHOR]

Among-lake variation in mercury (Hg) concentrations in landlocked Arctic char was examined in 27 char populations from remote lakes across the Canadian Arctic. A total of 520 landlocked Arctic char were collected from 27 lakes, as well as sediments and surface water from a subset of lakes in 1999, 2002, and 2005 to 2007. Size, length, age, and trophic position (δ15N) of individual char were determined and relationships with total Hg (THg) concentrations investigated, to identify a common covariate for adjustment using analysis of covariance (ANCOVA). A subset of 216 char from 24 populations was used for spatial comparison, after length-adjustment. The influence of trophic position and food web length and abiotic characteristics such as location, geomorphology, lake area, catchment area, catchment-to-lake area ratio of the lakes on adjusted THg concentrations in char muscle tissue were then evaluated. Arctic char from Amituk Lake (Cornwallis Island) had the highest Hg concentrations (1.31 µg/g wet wt), while Tessisoak Lake (Labrador, 0.07 µg/g wet wt) had the lowest. Concentrations of THg were positively correlated with size, δ15N, and age, respectively, in 88, 71, and 58% of 24 char populations. Length and δ15N were correlated in 67% of 24 char populations. Food chain length did not explain the differences in length-adjusted THg concentrations in char. No relationships between adjusted THg concentrations in char and latitude or longitude were found, however, THg concentrations in char showed a positive correlation with catchment-to-lake area ratio. Furthermore, we conclude that inputs from the surrounding environment may influence THg concentrations, and will ultimately affect THg concentrations in char as a result of predicted climate-driven changes that may occur in Arctic lake watersheds. Environ. Toxicol. Chem. 2010;29:633–643. © 2009 SETAC [ABSTRACT FROM AUTHOR]

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to δ13C and δ15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The δ13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes. Environ. Toxicol. Chem. 2010;29:621–632. © 2009 SETAC [ABSTRACT FROM AUTHOR]

Abstract: Alternative ingredients in fish feeds such as vegetable oils need to be evaluated from several aspects in order to justify their use. This study investigated the effects of feeding a coldwater species, Arctic charr (Salvelinus alpinus L.), diets where 75% of the fish oil (FO) was replaced with either rapeseed oil (RO) or equal ratios of rapeseed oil and palm oil (ROPO) on swimming performance at three different temperatures (4, 10, 17°C). Fish fed ROPO had a significantly lower critical swimming speed (U crit ) at 4°C compared to fish fed FO and RO diets. Similar patterns of impeded performance of the vegetable oil fed fish compared to the FO fed fish, albeit non-significant, was observed at 10°C and 17°C. The dietary compositions had no effect on growth but the total lipid content in white muscle was significantly higher in ROPO fed fish (2.7%) compared to fish fed FO and RO (2.0% and 2.1%, respectively). Considerable changes in the fatty acid composition were found with a decrease in the highly unsaturated fatty acids (HUFA) 20:5n-3, 22:6n-3 and an increase in 18:2n-6 and 18:1n-9 in the vegetable oil fed fish. The ratio of n-3 HUFA and saturated fatty acids is suggested to be partly responsible for the alternations in swimming performance at different temperatures because they both are involved in temperature-influenced metabolic mechanisms in fish. [Copyright &y& Elsevier]

The article discusses a study on Candidatus Piscichlamydia salmonis in Arctic charr Salvelinus alpinus that was identified during a survey of charr production facilities in North America. Aside from production facilities, several nonproduction water sources and effluents in Canada and the U.S. were sampled. The gills that were processed for DNA extraction and histopathologic examinations came from 607 fishes from several sites. Results revealed that several fishes from one site had inclusions of epitheliocystis with gill lesions.

Data describing Arctic char Salvelinus alpinus were collected in 2002 and 2004 and compared with historical data collected over the past 60 years from the Sylvia Grinnell River, Nunavut, Canada, to determine population status. The goal of the study was to provide information that could be used to manage the stock. Current subsistence harvest was estimated based on data collected from gillnetting, angling, and snagging. The Arctic char subsistence harvest was estimated at 8,364 kg in 2002 and 7,956 kg in 2004. The current population remains well below historic levels, but it has improved since 1976-1977. The improved status of the stock is based on increased length at age, increased mean weight, longer and older fish, decreased mortality rate, and improved catch indices from experimental gill nets and angling. Future benchmarks useful for evaluating the population's status include (1) proportion of females that have reached reproductive age, (2) proportion of older and longer fish, (3) mortality rate, and (4) catch per angler-hour. The fishery should be monitored by enumerating the harvest, quantifying fishing effort from all gear types, and recording biological data. Experimental gill nets should be periodically used to obtain biological data for comparison with the 2002 and 2004 data. Snagging should he prohibited since most young Arctic char (<200-300 mm) are injured and are not utilized by the fishery, and it is impossible to estimate the number of Arctic char larger than 200 mm that are struck and lost instead of landed. We recommend (1) closing all fishing at the base of the falls and at least 500 m into the estuary, (2) limiting gill-net mesh size to no less than 114 mm, 13) implementing benchmarks to evaluate population status, (4) obtaining an estimate of the population size, and (5) determining the exploitation rate. [ABSTRACT FROM AUTHOR]

Arctic charr are characterized by an extensive variability in growth and body size in natural waters. Although growth traits may involve a significant heritable component, most of this intraspecific variation presumably is environmentally induced and thus attributable to phenotypic plasticity. In the present study, size-at-age and length–weight relationship (body condition) were assessed for three Finnish Arctic charr populations of different geographical origins and extreme size forms (a stunted vs. two large-growing, predatory charr) held under standardized rearing conditions for 3 years (up to 37 months after hatching). In particular, our interest was to investigate whether the differences in growth between the large and the stunted charr as observed in the wild populations would diminish when the fish are offered suitable food in abundance. Population-specific mean body size and condition differed significantly in 0+, 1+, 2+ and 3+ fish. However, the identical rearing conditions resulted in the originally stunted charr reaching a comparable final mean size (317 mm/427 g) as the large charr populations (343 mm/510 g and 359 mm/497 g). Some individuals were of the same size as their parents at spawning already at the age of 0+ years. Furthermore, length–weight regression residuals of the stunted charr developed to a notably high level, indicating the largest final condition mean. The increase of size variation (CV of weight) in stunted charr lasted for over two growth seasons, whereas in large charr it remained stable since the end of the first summer. Variations in mortality and sexual maturation at age 2 seemed to be less relevant factors affecting overall growth performance. The study demonstrates an example of the high plasticity involved in the growth of fish: the stunted charr possess a tremendous capacity for growth in a benign environment, virtually corresponding to that observed in the large predatory populations. [ABSTRACT FROM AUTHOR]

Background: The adaptive significance of female polyandry is currently under considerable debate. In nonresource based mating systems, indirect, i.e. genetic benefits have been proposed to be responsible for the fitness gain from polyandry. We studied the benefits of polyandry in the Arctic charr (Salvelinus alpinus) using an experimental design in which the material investments by the sires and maternal environmental effects were controlled. Results: Embryonic mortality showed a strong paternal genetic component, and it was lower in polyandrously fertilized offspring (sperm competition of two males) than in monandrous fertilizations. We also found that high sperm velocity was associated with low offspring mortality, but not with the size of the offspring or their yolk volume. Although no male effect was found on the size of the offspring yolk reserves, yolk volume was higher in offspring from polyandrous matings than offspring of the either of the two males when mated monandrously. Conclusions: In support of the "good sperm hypothesis, we found that sperm velocity was positively associated with offspring fitness. In addition, our results suggest that polyandrous females gain genetic advantage (higher offspring survival) from this behavior, but that some benefits of polyandry (larger yolk volume) may not be explained solely by the additive genetic effects. This suggests that sperm competition environment may intensify the selection on genetically superior sperm which in turn may produce offspring that have superior yolk reserves. However, as high sperm velocity was not associated with larger yolk volume, it is possible that also some other non-genetic effects may contribute to offspring fitness. The potential role of polyandrous mating in inbreeding avoidance is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Anadromous (sea-migrating) Arctic charr (Salvelinus alpinus) display pronounced seasonal variations in food intake and growth and is an interesting model for studying mechanisms of appetite regulation. In this study cDNAs encoding for ghrelin (GHRL) and leptin (LEP) in Arctic charr were cloned, after which stomach GHRL and liver LEP mRNA expressions were examined by qPCR during a seasonal feeding cycle of semi-wild anadromous Arctic charr. The fish were captured as they returned from summer feeding in seawater and transferred to an indoor tank where they were fed in excess until October the year after. Growth rate was low in late winter, increased in late spring and reached a peak during summer, and then declined during autumn, when the fish became sexually mature. The changes in growth rate were associated with corresponding changes in the proportion of fish that had been eating at each sampling date, and whole body lipid status. Stomach GHRL mRNA expression was high in late winter, decreased to a nadir in mid-summer and increased again to a high level in early autumn. Liver LEP mRNA remained low during winter, spring and early summer, after which there was a gradual, 7-fold increase until October. The seasonal changes in ghrelin and leptin support a role of these hormones in the long-term regulation of energy homeostasis in the anadromous Arctic charr. It cannot be excluded, however, that the increase in liver leptin expression during autumn is related to sexual maturation. [Copyright &y& Elsevier]

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]

Genetic variation in growth performance was estimated in 26 families from two commercial strains of Arctic charr Salvelinus alpinus. Physiological determinants of growth and metabolic capacities were also assessed through enzymatic assays. A relatedness coefficient was attributed to each family using parental genotypes at seven microsatellite loci. After 15 months of growth, faster growing families had significantly lower relatedness coefficients than slower growing families, suggesting their value as indicators of growth potential. Individual fish that exhibited higher trypsin activity also displayed higher growth rate, suggesting that superior protein digestion capacities can be highly advantageous at early stages. Capacities to use amino acids as expressed by glutamate dehydrogenase (GDH) activities were lower in the liver of fast-growing fish (13–20%), whereas white muscle of fast-growing fish showed higher activities than that of slow-growing fish for amino acid metabolism and aerobic capacity [22–32% increase for citrate synthase (CS), aspartate aminotransferase (AAT) and GDH]. The generally higher glycolytic capacities (PK and LDH) in white muscle of fast-growing fish indicated higher burst swimming capacities and hence better access to food. [ABSTRACT FROM AUTHOR]

Landscape genetics holds promise for the forecasting of spatial patterns of genetic diversity based on key environmental features. Yet, the degree to which inferences based on single species can be extended to whole communities is not fully understood. We used a pristine and spatially structured community of three landlocked salmonids ( Salvelinus fontinalis, Salmo salar, and Salvelinus alpinus) from Gros Morne National Park (Newfoundland, Canada) to test several predictions on the interacting effects of landscape and life history variation on genetic diversity, neutral divergence, and gene flow ( m, migration rate). Landscape factors consistently influenced multispecies genetic patterns: (i) waterfalls created strong dichotomies in genetic diversity and divergence between populations above and below them in all three salmonids; (ii) contemporary m decreased with waterway distance in all three species, while neutral genetic divergence ( θ) increased with waterway distance, albeit in only two taxa; (iii) river flow generally produced downstream-biased m between populations when waterfalls separated these, but not otherwise. In contrast, we expected differential life history to result in a hierarchy of neutral divergence ( S. salar > S. fontinalis > S. alpinus) based on disparities in dispersal abilities and population size from previous mark-recapture studies. Such hierarchy additionally matched varying degrees of spatial genetic structure among species revealed through individual-based analyses. We conclude that, whereas key landscape attributes hold power to predict multispecies genetic patterns in equivalent communities, they are likely to interact with species-specific life history attributes such as dispersal, demography, and ecology, which will in turn affect holistic conservation strategies. [ABSTRACT FROM AUTHOR]

In some polymorphic populations of Arctic charr in Transbaikalia, an individual can transform from a smaller to larger size form during their lifetime as a result of accelerated growth that follows a period of slow growth and reproduction as a small size form. Alternating periods of slow and fast growth are reflected in growth layer patterns visible in fin ray cross sections. Stained microtome fin ray cross sections were used to reveal the incidence of transformations from one form to another. Data were collected from 14 northern Transbaikalian lakes containing two or three sympatric Arctic charr forms (‘dwarf’, ‘small’, and ‘large’) exhibiting varying levels of morphological separation. Individuals recruited from the dwarf or small form were found in varying proportions among the small and/or large form in 12 lakes. Small or large form charr that grew without noticeable acceleration to the adult size typical of the form or experienced accelerated growth as juveniles prior to maturation were also observed. There were no transformations between sympatric forms that differed in the length and number of gill rakers and in some other meristic characters. Results indicate that in the region under study, transformations of sympatric Arctic charr size forms are a widespread, but not a ubiquitous, phenomenon. Such transformations reflect the plasticity of the developmental channels of the forms. In the course of intra-lacustrine form divergence and genetic differentiation, the frequency of the observed transformations decreases to zero. [ABSTRACT FROM AUTHOR]

The development of skeleton elements was studied in prolarvae, larvae, and fry of two morphologically different forms of the Arctic char Salvelinus alpinus complex—small plankton-eating and dwarf (having a seasonal change of plankton and benthic feeding)—that sympatrically inhabit Lake Davatchan (Transbaikalia). According to genetic data, these forms diverged in this lake from a specialized lacustrine ecotype of char and reached reproductive isolation. Comparative analysis revealed similarity in the shape of anlagen and transitive states of cranial bones. In prolarvae and larvae of the dwarf form, the onset of similar morphological states of skeleton elements occurs at a smaller body length than in fish of the small form. Differences in the development of serial skeleton structures (teeth, gill rakers, fin rays, centra, and scales), heterochronies of timing of appearance and rate of differentiation of skeleton elements were found. It is suggested that these differences resulted from the ecological differentiation of the two forms according to spawning grounds that became local habitats of larvae and fry (sublittoral and hypolimnion). The initial divergence could be caused by the presence in the lake of two (autumn and spring-summer) peaks of numbers of food organisms. [ABSTRACT FROM AUTHOR]

This study investigated the effects of crude rapeseed oil (RO) on lipid content and composition in muscle and liver of Arctic charr Salvelinus alpinus. Triplicate groups were fed diets containing fish oil (FO):RO ratio of 100:0, 75:25, 50:50 and 25:75 until two-fold mass increase. Total lipid content increased significantly in the liver with higher proportion of RO in the diet. Profound effects were seen in the fatty acid composition in the analysed tissues with a reduction in 20:5n-3 and 22:6n-3 and an increase in 18:2n-6 with higher RO content in the diets. A drop in cholesterol content was seen at 25% inclusion of RO in both tissues. Wild-caught fish contained a considerably higher amount of 20:4n-6 in both storage and membrane lipids of white muscle compared with the experimental fish. [ABSTRACT FROM AUTHOR]

The presence of two morphotypes of Arctic charr Salvelinus alpinus was confirmed via morphological variation and otolith strontium (Sr) within three open-lake systems of southern Baffin Island, Nunavut, Canada: Qinngu (LH001), Iqalugaarjuit Lake (PG082) and Qasigiat (PG015). Analysis of otolith Sr indicates that a component of each S. alpinus population within lakes LH001 and PG082 is migratory (large–maturing S. alpinus), whereas another component is lake-resident (small–maturing S. alpinus). Alternatively, small and large maturing S. alpinus may both inhabit tidal habitats during their lifetime in lake PG015. Three morphological characters were identified by principal factor analysis (PFA) as characters that were different between maturity groups for all lakes studied: eye diameter, pectoral fin length and pelvic fin length. As well, upper jaw length (LH001 and PG082) and fork depth (PG015) were identified in PFA as traits that differed between morphs. Univariate tests of morphological characters identified by PFA demonstrated maturity group differences with the exception of eye diameter in Lake PG015 and upper jaw length and pelvic fin length in lake LH001. No difference was found in the MANOVA test of upper and lower gill raker number between small–maturing and undeveloped fish within all lakes studied. Clear morphological variation observed between small–maturing and undeveloped fish in all three lakes of the study suggests ecological niche separation between morphotypes. This is the first documented case of lake-resident S. alpinus use of the tidal habitat in the presence of a migratory large–maturing morphotype. [ABSTRACT FROM AUTHOR]

Abstract: Sperm velocity has been shown to be a major determinant of fertilization success of external fertilizers. Yet, sperm velocity varies both within and between ejaculates and only a small number of fast sperm cells within an ejaculate are likely to have the potential of fertilizing the eggs. Having such fast cells should be of special importance during sperm competition, particularly for subordinate males that may release their sperm later or further away from eggs, than dominants. We examined ejaculates of dominant and subordinate male Arctic charr (Salvelinus alpinus), a species with sperm competition. Yet, rather than examining just average sperm velocity values, the aim was to examine whether the fastest fraction of sperm cell from dominant and subordinate males differed in velocity. While there was no difference in the average sperm velocity between dominant and subordinate males, analysis of the fastest swimming sperm cells show that subordinate males have significantly higher initial sperm velocity than dominant males within the 10, 5 and 1% fastest sperm cells. That is, the difference in sperm velocity between dominant and subordinate charr is most predominant among the fastest sperm cells. In sum, this study emphasizes the importance of studying the fastest sperm cells in the ejaculates, as status-dependent differences in sperm velocity may not be detected using average values. [Copyright &y& Elsevier]

Abstract: Shelter is of major importance in many species of fish both in the wild and in aquaculture. Sheltering behaviour of Arctic charr has been poorly studied in aquaculture. A new type of shelter made of PVC agricultural drain cut in half was tested on culture performance and behaviour during the endogenous feeding period. This device offered grooves where alevins could position themselves and lie in a vertical position. A first experiment compared fish with and without shelter in incubator compartments. All fish were measured at 122, 158, and 190days post fertilization (dpf) and observed at 126, 139 and 157dpf. Fish provided with shelter showed better growth performances, lower mortality and started first exogenous feeding about six days later compared to fish without shelter. These effects from shelter provision were also associated with much less mobility in fish provided with shelter. At 126dpf, all fish provided with shelter were immobile while other fish displayed horizontal stationary body movement (86%) or swam against the water current (7%). At 157dpf, 85% of fish without shelter were immobile compared to 95% in fish provided with shelter. Both categories displayed stationary body movements. In most cases, there was one single fish per groove and a stable average value of 2.4 grooves was maintained between two successive fish throughout the study. The second experiment was a preference test where the fish were placed in similar compartments but occupied by a half shelter. We found that 61% of the fish were located under the shelter at 122dpf while at 157dpf, 58% were on the shelter and 42% out of the shelter. The present results revealed Arctic charr behavioural characteristics in the presence of a new type of artificial shelter at very early stages of development. This shelter enables the fish to stabilize in a vertical position without producing any movement and to choose by itself its favorite location throughout development. This device could be used to improve Arctic charr growth, performance and fish welfare during the endogenous feeding period. [Copyright &y& Elsevier]

The major histocompatibility complex (MHC) contains the most variable genes in vertebrates, but despite extensive research, the mechanisms maintaining this polymorphism are still unresolved. One hypothesis is that MHC polymorphism is a result of balancing selection operating by overdominance, but convincing evidence for overdominant selection in natural populations has been lacking. We present strong evidence consistent with MHC-specific overdominance in a free-living population of Arctic charr (Salvelinus alpinus) in northernmost Europe. In this population, where just two MHC alleles were observed, MHC heterozygous fish had a lower parasite load, were in better condition (as estimated by a fatness indicator) and had higher survival under stress than either of the homozygotes. Conversely, there was no consistent association between these fitness measures and assumedly neutral microsatellite variability, indicating an MHC-specific effect. Our results provide convincing empirical evidence consistent with the notion that overdominance can be an important evolutionary mechanism contributing to MHC polymorphism in wild animal populations. They also support a recent simulation study indicating that the number of alleles expected to be maintained at an MHC loci can be low, even under strong heterozygote advantage. [ABSTRACT FROM AUTHOR]

This article discusses a study which examined an ulcerative and hemorrhagic disease in Arctic char Salvelinus alpinus caused by Aeromonas salmonicida subsp, smithia. The study performed routine pathological examination of dead and euthanized moribund fish. It submitted the field strains to a phylogenetic analysis to confirm the phenotypic identification of the species. In addition, the study showed the presence of a Type III secretion system and several related virulence effector genes in the species.

Two modal size groups of sexually mature Arctic charr ( Salvelinus alpinus) differing in shape and found at different depths in Lake Aigneau in the Canadian sub-Arctic are described and tested for genetic and ecological differentiation. Forms consisted of a small littoral resident, mean size 21.7 cm, and a large profundal resident, mean size 53.9 cm. Mitochondrial DNA analysis indicated that seven of eight haplotypes were diagnostic for either the littoral or profundal fish, with 66.6% of the variation being found within form groupings. Pairwise tests of microsatellite data indicated significant differences in nine of 12 loci and a significant difference between the forms across all tested loci. Molecular variation was partitioned to 84.1% within and 15.9% between forms and suggestive of either restricted interbreeding over time or different allopatric origins. Stable isotope signatures were also significantly different, with the profundal fish having higher δ13C and δ15N values than the littoral fish. Overlap and separation, respectively, in the range of form δ13C and δ15N signatures indicated that carbon was obtained from similar sources, but that forms fed at different trophic levels. Littoral fish relied on aquatic insects, predominantly chironomids. Profundal fish were largely piscivorous, including cannibalism. Predominantly empty stomachs and low per cent nitrogen muscle-tissue composition among profundal fish further indicated that the feeding activity was limited to the winter when ice-cover increases the density of available prey at depth. Results provide evidence of significant differences between the modal groups, with origins in both genetics and ecology. [ABSTRACT FROM AUTHOR]

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

Sequence variation in the mtDNA control region of Arctic charr Salvelinus alpinus and Dolly Varden Salvelinus malma from 56 Siberian and North American populations was analysed to assess their phylogeographic relationships and the origins of sympatric forms. Phylogenetic trees confirm the integrity of phylogroups reported in previous mtDNA studies except that the Siberian group does not separate as a single cluster. Haplotype network analysis indicates the proximity of Siberian and Atlantic haplotypes. These are considered as one Eurasian group represented by the Atlantic, east Siberian (interior Siberia including Transbaikalia, Taimyr) and Eurosiberian (Finland, Spitsbergen, Taimyr) sub-groups. Salvelinus alpinus with presumably introgressed Bering group (malma) haplotypes were found along eastern Siberian coasts up to the Olenek Bay and the Lena Delta region, where they overlap with the Eurasian group and in the easternmost interior region. It is proposed that Siberia was colonized by S. alpinus in two stages: from the west by the Eurasian group and later from the east by the Bering group. The high diversity of Eurasian group haplotypes in Siberia indicates its earlier colonization by S. alpinus as compared with the European Alps. This colonization was rapid, proceeded from a diverse gene pool, and was followed by differential survival of ancestral mtDNA lineages in different basins and regions, and local mutational events in isolated populations. The results presented here support a northern origin of Transbaikalian S. alpinus, the dispersion of S. alpinus to the Lake Baikal Basin from the Lena Basin, segregation of S. alpinus between Lena tributaries and their restricted migration over the divides between sub-basins. These results also support sympatric origin of intralacustrine forms of S. alpinus. [ABSTRACT FROM AUTHOR]

Abstract: The present study was conducted to establish a homologous radioimmunoassay (RIA) for quantifying plasma leptin (Lep) levels in salmonid species, and to study Lep levels in relation to nutritional status. A part of the Lep peptide, a 14 amino acid long sequence, identical between a Salmo and an Oncorhynchus species was synthesised. Polyclonal antibodies were raised in rabbit against this antigen and both were subsequently used in the development of a RIA protocol for assessing plasma Lep levels. The limit of detection of the assay was 0.3nM, and intra- and interassay coefficient of variation (CV) were 8.4% and 13%, respectively. Apart from Atlantic salmon and rainbow trout, the assay exhibits measuring parallelism for a range of fish species, including arctic char, Atlantic cod and turbot, suggesting that the established RIA is useful for quantifying Lep levels in several fish species. The RIA indicates that Lep is found in salmonid plasma at levels of 0.5–5nM, which is comparable with other peptide hormones, and well within the measuring range of the RIA. A study of fed and fasted rainbow trout showed elevated plasma Lep levels during fasting. In addition there was no correlation between Lep levels and condition factor. These data suggest that the relation between circulating Lep levels and energy status differs from that in mammals. While Lep is linked to energy balance, it may not act as an adiposity signal in salmonids, possibly pointing to functional divergence among ectothermic and endothermic vertebrates. [Copyright &y& Elsevier]

Abstract: The timing of ovulation and LH plasma levels were investigated in Arctic charr reared at 5°C and 10°C, exposed to the ambient photoperiod, or short or long-day photoperiod regimes during the prespawning period. The effectiveness of sGnRHa alone, or sGnRHa combined with a dopamine antagonist, in stimulating LH secretion and inducing ovulation was also investigated. With the natural photoperiod, ovulation occurred spontaneously at 5°C, but was inhibited at 10°C. A transition from 10 to 5°C soon resulted in suppression of the inhibition. At 5°C, the effectiveness of sGnRHa was similar to that of sGnRHa combined with pimozide in stimulating LH secretion and inducing ovulation. At 10°C, sGnRHa+pimozide was more effective that sGnRHa alone in stimulating LH secretion and inducing a high rate of ovulation, suggesting that dopamine-induced inhibition of LH secretion could occur naturally in Arctic charr at 10°C. Exposure of Arctic charr to a long day (LD) photoperiod regime in fall and winter did not completely inhibit ovulation, but markedly delayed it and prolonged the ensuing ovulation period. The LD photoperiod also reduced LH plasma levels in females while they were ovulating, but did not modify the responsiveness of the pituitary to GnRHa stimulation compared to a control group exposed to a short-day (SD) photoperiod. There was an interval of several weeks after a transition from LD to SD before LH secretion and ovulation were stimulated. [Copyright &y& Elsevier]

Abstract: Several studies have shown that prolonged moderate exercise improve conditions for the farming of salmonids, by reducing aggressive interactions and resulting in enhanced growth and reduced size variation. The present study focuses on the effect of forced moderate exercise on growth and aggression depending on the individual social rank, compared to non-exercised controls in groups of Arctic charr (Salvelinus alpinus L.). Social screening was done prior to the trial in each of 24 groups with five charr, where every fish was ranked into one of five social ranks by successive removal of individuals displaying a dominant or aggressive behaviour. Four ranking groups (=20 fish) were then merged into one experimental group (=6 groups), each with four tagged individuals of ranks 1–5. After 62 days with or without forced exercise, no significant difference in mean Daily Growth Coefficient (DGC) in the exercised (DGC=1.25±0.46) and non-exercised (DGC=1.39±0.47) groups were found. A significant relationship between rank and size at the start remained significant in the non-exercised groups but became insignificant in the exercised groups. It was the highest ranked fish that gained by not being forced to exercise. They had a significantly higher weight gain than the highest ranked fish in the exercised groups and all lower ranked fish independent of treatment. The observed aggression was significantly higher in the non-exercised groups and higher in between than during feeding sessions. [Copyright &y& Elsevier]

The diplostomid flukes, Diplostomum spp., infect fish and cause cataract opacities in the eye lens. The effect of exposure dose on abundance of Diplostomum spp. eye flukes in fish is known, but the effect of the duration of cercariae exposure has not been studied. However, under natural conditions, the temporal window for a successful cercaria attachment on fish is very short and, consequently, differences in infectivity of eye fluke cercariae, in the short-exposure durations of a few seconds, are probably biologically the most meaningful. We investigated infectivity of Diplostomum spp. cercariae originating from snail hosts in 3 lakes (3 Lymnaea stagnalis populations and 1 Radix balthica population) in 6 exposure times, ranging from 5 sec to 15 min, in young-of-the-year Arctic charr Salvelinus alpinus. In addition, we compared the infectivity to the cross-morphology of the cercariae. In the long-exposure duration, i.e., ≥5 min, infectivity of Diplostomum spp. did not vary between the snail host species (L. stagnalis and R. balthica) of the same lake or across the L. stagnalis populations of 3 different lakes. However, in the short-exposure duration, i.e., ≤60 sec, Diplostomum spp. cercariae shed from L. stagnalis had higher infectivity than did cercariae from R. balthica of the same lake. This indicates that that there is an interaction between length of cercariae exposure and origin of Diplostomum spp., and that the duration of exposure may influence the results when fish are experimentally infected. Within a lake, cercariae shed from L. stagnalis were also smaller than cercariae shed from R. balthica. [ABSTRACT FROM AUTHOR]

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

This study revealed that progeny of sympatric Salangen Arctic char, omitted from any kind of imprinting to home water, returned with high precision to the home river and parental locality upon releases in their native marine environments. Fish did not select river randomly, and the homing precision was the same for progeny whether fertilized in home stream or in foreign water. The progeny studied originate from the lake Øvervatnet and the Salangen River population and were hatched and reared at a hatchery at Voss in southern Norway. Experimental material comprised freshwater resident and smolt released from parr directly. The freshwater resident is partly anadromous exhibiting about 74% smolt when released directly into the sea. Char at all stages (resident, transformed resident, and smolt released from parr directly) returned in significant numbers to the home river system and the site of the specific parental population. [ABSTRACT FROM AUTHOR]

Winter growth and survival of wild individually tagged juvenile Arctic charr (1+ age) from a riverine anadromous stock, were studied in a small ice-covered (∼6 months) ground water brook (temperature ∼1 °C) connected to Skibotnelva in subarctic northern Norway. The overall winter survival was estimated to be 68% from late October 2005 to early May 2006. The recaptured charr were not significantly different in initial length or weight compared with the nonrecaptured fish suggesting low size-dependent mortality. The majority (98%) of the recaptured charr showed significant increase in size, with a mean increment of 62% from their initial bodyweight and 12% of the charr parr had more than doubled their weight. The mean specific growth rate was calculated to be slightly lower (0.27) than estimated values from a growth model (∼0.35). In addition, the condition factor increased significantly during the field experiment. These results are the first individual growth data on riverine anadromous Arctic charr parr under natural winter conditions, and indicate that charr can grow relatively fast during periods with low temperature and also that ground water brooks can be good over-wintering habitat for juvenile Arctic charr. These results suggest that the winter period is perhaps a less severe bottleneck than previously recognised for the cold-adapted Arctic charr. [ABSTRACT FROM AUTHOR]

Acoustic technologies were applied to describe how landlocked Arctic char from Iqalugaajuruluit Lake, Baffin Island, interact with its lacustrine habitat. Acoustic data from the lake bottom was collected using sonar equipment and substrate types were verified with benthic grabs and mapped in a geographic information system. Arctic char movements during the open water period were recorded from char fitted with acoustic tags. The distribution of the tagged Arctic char in Iqalugaajuruluit Lake was dependent on fish size and related to abiotic factors such as depth, substrate type and depth/temperature, temporally. The volume of water with temperatures below 6 °C during the open water period may be a limiting factor for large char (>400 mm) in small Arctic lakes. The large piscivorous char are found most often in the deepest water over soft substrates and the smaller char which feed on varying proportions of invertebrates and fish were found most often over the more complex substrates such as boulders, pebbles and gravel. [ABSTRACT FROM AUTHOR]