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Arctic charr (Salvelinus alpinus) is a niche‐market high‐value species for Nordic aquaculture. Similar to other salmonids, both anadromous and landlocked populations are encountered. Whole‐genome re‐sequencing (22X coverage) was performed on two farmed populations of anadromous (Sigerfjord; n = 24) and landlocked (Arctic Superior; n = 24) origin from Norway and Sweden respectively. More than 5 million SNPs were used to study their genetic diversity and to scan for selection signatures. The two populations were clearly distinguished through principal component analysis, with the mean fixation index being ~0.12. Furthermore, the levels of genomic inbreeding estimated from runs of homozygosity were 6.23% and 8.66% for the Norwegian and the Swedish population respectively. Biological processes that could be linked to selection pressure associated primarily with the anadromous background and/or secondarily with domestication were suggested. Overall, our study provided insights regarding the genetic composition of two main strains of farmed Arctic charr from Scandinavia. At the same time, ample genomic resources were produced in the magnitude of millions of SNPs that could assist the transition of Nordic Arctic charr farming in the genomics era. [ABSTRACT FROM AUTHOR]

Arctic charr, Salvelinus alpinus (L.), occur as anadromous, resident, and landlocked populations within their circumpolar distribution. While resident Arctic charr reside in freshwater their entire life, anadromous Arctic charr migrate to sea in the summer due to the increased resource availability, but return to freshwater to overwinter and/or spawn. The migratory behaviour in Arctic charr is generally restricted to the northern range of their distribution area. The objective of this study was to estimate the amount of straying and contemporary gene flow among anadromous Arctic charr from eight river systems in northern Norway to illuminate the role of straying for the contemporary genetic stability of the populations. The results revealed that Arctic charr frequently stray among watercourses, especially among those in close geographical proximity, although strays were found nearly 500 km from their river of origin. While straying was revealed among six river systems, the results also revealed limited or no contemporary gene flow among the nine populations identified in the eight sampled river systems. The study also shows that Arctic charr may be a potential host for spreading diseases and parasites among watercourses. [ABSTRACT FROM AUTHOR]

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

The influence of different climate variables on the first four years of otolith growth in Salangen Arctic charr, Salvelinus alpinus, was studied over the period 1939-2005. Salangen is a coastal, low altitude, subarctic lake system located in northern Norway. Climate data, including water temperature, air temperature, ice-cover and precipitation, were available for most of the 67 year period. Water temperatures in May and June had a significant effect on otolith growth during the second growth year, while no relationship between otolith growth and climate variables was found for the first, third and fourth years of otolith growth. Otolith increment size during the third and fourth growth year was autocorrelated with growth during the previous year. Spring snow fall and timing of ice break-up had an indirect effect on growth, as these variables were highly correlated with spring water temperatures. High variation in otolith growth within years and among individuals suggests that individual and age-specific variations in spatial habitat use may confound the direct effects of changing air temperatures and time of ice break-up. [ABSTRACT FROM AUTHOR]

The article presents information on a study which determined the morphological variability of the Arctic charr representing anadromous, landlocked and stationary fluviatile populations occurring in the region of the Hornsund fjord in SW Spitsbergen, Norway in relation to their trophic preferences. It estimates the food preferences of the examined fish based on the contents of their alimentary tracts. It reveals the ersults of single-factor ANOVA testing differences in fork length of the Arctic charr from the region.

The article presents information on a study which examined the summer dynamics of density and biomass of the Arctic charr, Salvelinus alpinus, in a polar stream in Spitsbergen, Norway. It determines the basic population parameters of the freshwater fish species and their changes in the summer period. It describes the changes in the fish size structure of the Salvelinus alpinus population from the Ariebekken stream in the successive electrofishings in summer 2004. It also reveals the results of one-way ANOVA and t-test testing the difference in fish length in different seazones in 2004 and 2005.

The effects of induced water level fluctuations and introduction of the mysid Mysis relicta Lovén on population structure of brown trout, Salmo trutta L., and Arctic charr, Salvelinus alpinus (L.), were studied during 1953–1995 in Limingen hydroelectric reservoir, Norway. The main response was a marked reduction in catch-per-unit-effort (CPUE) for trout and charr, probably caused by reduced recruitment following increased variation in water level. For both species, mean length decreased until 1967 and increased thereafter, whereas mean mass-at-length increased for the whole period. Both length and mass-at-length were negatively correlated with CPUE. The increases in mean length and mass-at-length were probably because of reduced competition following the reduced recruitment. Mysis relicta has become an important food item for charr but not for brown trout, but the increases in mean length and mass-at-length of charr started prior to the appearance of M. relicta in the charr diet. [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]