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Climate change is predicted to change not only the temperature of many freshwater systems but also flow dynamics. Understanding how fishes will fare in the future requires knowing how they will respond to both extended variations of temperature and flow. Arctic charr have had their thermal tolerance measured, but never with respect to flow. Additionally, this circumpolar species has multiple populations exhibiting dramatic phenotypic plasticity which may mean that regional differences in thermal tolerance are unaccounted for. In Iceland, Arctic charr populations have experienced highly variable flow and temperature conditions over the past 10,000 years. The Icelandic climate, topography and geothermal activity have created a mosaic of freshwater habitats inhabited by charr that vary substantially in both temperature and flow. Our purpose was to test whether populations from these varied environments had altered thermal tolerance and whether phenotypic plasticity of thermal tolerance in charr depends on flow. We raised cultured Icelandic charr from hatch under a 2 X 2 matrix of flow and temperature and compared them to wild charr captured from matching flow and temperature environments. Wild fish were more thermally tolerant than cultured fish at both acclimation temperatures and were more thermally plastic. Icelandic Arctic charr were more thermally tolerant than comparison charr populations across Europe and North America, but only when acclimated to 13 °C; fish acclimated to 5 °C compared equably with comparison charr populations. Icelandic Arctic charr were also more thermally plastic than all but one other salmonine species. Neither flow of rearing or the flow selected during a thermal tolerance (CT max) test factored into thermal tolerance. Thermal tolerance was also independent of body size, condition factor, heart and gill size. In summary, wild Icelandic Arctic charr have greater thermal tolerance and plasticity than predicted from the literature and their latitude, but artificial selection for properties like growth rate or fecundity may be breeding that increased tolerance out of cultured fish. As the world moves toward a warmer climate and increased dependence on cultured fish, this is a noteworthy result and merits further study. [Display omitted] • Wild Icelandic Arctic charr are more thermally tolerant and possibly more thermally plastic than cultured conspecifics. • Warm acclimated Icelandic Arctic charr are more thermally tolerant than comparison charr populations across Europe and North America. • Icelandic Arctic charr are more thermally plastic than most other salmonines. • Thermal tolerance of Arctic charr is independent of water flow velocity during both rearing and thermal performance testing. [ABSTRACT FROM AUTHOR]

A comparative analysis of the mitochondrial DNA variability in Salvelinus taranetzi (and closely related taxa) from Asia and Salvelinus alpinus erythrinus from the Northwest Territories (NWT), North America, representing the Arctic phylogenetic group of charrs of the genus Salvelinus, has been carried out. The estimated divergence of the combined nucleotide sequences of the mtDNA CoI and Cytb genes and CR region within the discussed phylogroup varies in the range of 0.001–0.003 and does not exceed the intraspecific variability of S. taranetzi. A genealogical analysis confirms the phylogenetic proximity of S. a. erythrinus from NWT and S. taranetzi from Asia. By assuming a common origin of S. taranetzi and S. a. erythrinus, we have shown a significant differentiation between the geographical populations as a result of probable fragmentation of their common ancestor's range. According to the hierarchical analysis of molecular variance (AMOVA), the intergroup component accounts for the major part (83% of variance) of the mtDNA variability (490 bp, CR) with a low genetic diversity within the groups (10%). The region of Anadyr–Kolyma Basin, which determines the heterogeneity of the phylogroups, stands out on a broad geographical scale. [ABSTRACT FROM AUTHOR]

The Arctic char ( Salvelinus alpinus) species 'complex' has fascinated biologists for decades particularly with respect to how many species there are and their geographic distributions. I review recent research on the species complex, focussing on biodiversity within northwestern North America, which indicates (i) what was once considered a single taxon consists of three taxa: S. alpinus (Arctic char), S. malma (Dolly Varden), and S. confluentus (bull trout), (ii) morphological and genetic data indicate that S. alpinus and S. malma, and S. malma and S. confluentus exist as distinct biological species in sympatry, (iii) sympatric forms of S. alpinus exist in Alaska as in other areas of the Holarctic, (iv) Dolly Varden comprises two well-differentiated subspecies, S. m. malma and S. m. lordi, in the eastern Pacific and the northwestern Canadian Arctic that meet at a contact zone on the southern edge of the Alaska Peninsula, and (v) Dolly Varden and bull trout consist of several population assemblages that have legal status as distinct conservation units under US and Canadian law. This research has significantly revised what constitutes the S. alpinus species 'complex', provided insights into the ecology and genetics of co-existence, and promoted conservation assessment that better represents biodiversity within Salvelinus. A geographically and genetically comprehensive analysis of relationships among putative taxa of Pan-Pacific Salvelinus is still required to better quantify the number of taxa and their origins. [ABSTRACT FROM AUTHOR]

Aims We investigated post-glacial recolonization of the North American Arctic by Arctic char ( Salvelinus alpinus) and examined potential hybridization between different glacial lineages upon secondary contact. Location North American Arctic and adjacent areas. Methods We collected mt DNA sequence data from 1355 individuals from 110 sampling locations and data from nine microsatellite loci from 931 individuals from 37 locations. We assessed the phylogenetic relationships and geographical distribution of mt DNA haplotypes and conducted historical demographic analyses. We used a Bayesian clustering analysis method to detect potential hybridization between glacial lineages. Results Two highly divergent mt DNA lineages were identified in the Arctic region with distinct but overlapping geographic distributions: one in Beringia and the other over the entire Arctic Archipelago and coastal mainland east of Alaska. The microsatellite data also implied the existence of these two lineages. Evidence of hybridization was detected between the Arctic lineage and an Atlantic lineage in eastern North America. Main conclusions Our data suggested survival and recolonization from two northern glacial refugia: one in Beringia and another in a smaller refugium, perhaps in the Arctic Archipelago itself or a separate refugium within Beringia. Patterns of hybridization detected supported the presence of a secondary contact zone between glacial lineages in the eastern Canadian Arctic. [ABSTRACT FROM AUTHOR]

Contact zones between divergent lineages of aquatic taxa have been described from the northeastern Pacific Ocean. We surveyed samples of Dolly Varden ( Salvelinus malma) from their North American range for variation at 14 microsatellite DNA loci. After accounting for hybridization between Dolly Varden and co-occurring bull trout ( Salvelinus confluentus) and Arctic char ( Salvelinus alpinus), we found evidence for two genetic lineages of Dolly Varden consistent with the previously recognized subspecies, northern Dolly Varden ( S. m. malma) and southern Dolly Varden ( S. m. lordii). We documented a contact zone between the two subspecies from the eastern Alaska Peninsula to Cook Inlet, Alaska, where admixture values (i.e., the proportion of the genome estimated to be composed of northern Dolly Varden, QNDV) ranged between QNDV = 0.245 and 0.754 across about 700 ocean kilometres. Populations of Dolly Varden showing low admixture (i.e., less than 5%) were located a minimum of 346 km to the west to 1200 km to the southeast, respectively, from the contact zone. The two lineages of Dolly Varden probably stem from isolation and subsequent divergence in, and dispersal from, distinct northern and southern Pleistocene glacial refugia and substantiate the treatment of S. malma as two subspecies and as at least two designatable units under Canada's Species at Risk Act. [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]

Variation in fecundity was examined from 32 populations of Arctic charr Salvelinus alpinus in eastern North America covering a range of 37° latitude and extending from Maine, U.S.A., to northern Ellesmere Island in the Canadian Arctic. Populations were classed as dwarf, normal or anadromous and covered a suite of different habitat and climatic regimes. Fecundity varied with fork length ( LF), with LF adjusted fecundity differing significantly among populations within each of the morphotypes implying that fecundity was a continuously responsive trait influenced by local environmental factors. Latitudinal variation in fecundity was also evident among morphotypes when the simultaneous effects of both latitude and LF were controlled. There was a significant trade-off between fecundity and egg size in two of five populations of anadromous Arctic charr, but no evidence in limited data from either normal or dwarf populations. In contrast with some other studies of fecundity in salmonids, there was no evidence for a latitudinal cline in egg size. [ABSTRACT FROM AUTHOR]

Arctic char (Salvelinus alpinus) tolerate high-density culture conditions, have an excellent fillet yield, are amenable to niche marketing, and are suitable for production within super-intensive recirculating systems. Much of the North American production of Arctic char has been within recirculating systems, which can provide more optimum water temperatures for fish growth and can also overcome limitations created by a lack of high-quality water resources or strict pollution discharge limits. This paper describes some of the developments that have been made in recirculating systems used to produce Arctic char and examines several North American facilities that have used recirculating systems to produce Arctic char. This description includes several state-of-the-art recirculating systems that are now being used to commercially produce Arctic char and another that has just been built and is about to come on-line. This paper also describes several areas where advances have been made in cold-water recirculating system design in order to improve the water quality that they maintain at high feed loadings and to increase the production capacity of these systems. Several critical process improvements include: increased hydraulic exchange rates through the culture tank, superior culture tank designs, better oxygen control strategies and ozonation, improved design of forced-ventilated cascade aeration columns, full flow drum filtration, and better pipe and sump cleanout designs. Several of the strengths and weaknesses of Arctic char production within land-based recirculating systems are also discussed. [Copyright &y& Elsevier]