Diss. (sammanfattning) Umeå : Sveriges lanbruksuniv. / Härtill 6 uppsatser.

Sympatric populations of S. malma and S. alpinus from Alaska were compared using a discriminant function analysis. The comparison indicated little or no hybridization. S. malma is, therefore, regarded as a distinct species. S. malma has fewer gill rakers, pyloric caeca and pores along the lateral line than S. alpinus. Five hundred specimens of S. malma from 42 North American localities were examined. Considerable geographic variability was observed. The variation showed no correlation with latitude. Evidence is presented that subspecific distinctions are invalid in S. malma. It is suggested that S. malma evolved in the North Pacific area sometime during the Pliestocene. / Science, Faculty of / Zoology, Department of / Graduate

Abstract The thesis includes two studies of Arctic charr, Salvelinus alpinus, responses to climate variation. In the first chapter, site-specific data from a fishery on the Hornaday River, Northwest Territories (NWT), are used to make inferences about the environmental drivers of observed variation in the mean biological characteristics of the catch. Mean length and weight characteristics of subsistence-fished Arctic charr available from 15 years of monitoring on the Hornaday River, were significantly influenced by among-year differences in local summer temperature and/or precipitation patterns. Environmental influences on mean length were age-specific, with temperature being the most important influence on younger (age-5) fish and precipitation being the most important influence on older (age-8) fish. Mean weight was positively influenced by precipitation only. Significant models of length-temperature relationships further indicated that larger mean sizes occurred in years when average summer air temperatures ranged from 6.7-7.1ºC. The effects of precipitation on nutrient exports to the nearshore marine area appear to trigger many of the observed correlations. Overall, results suggest that the large-scale environmental changes predicted by climate change scenarios will hold significant implications for Arctic charr from the Hornaday River, with population-specific effects likely to be exhibited in other northern Arctic charr populations. The second chapter uses archival biological data on 67 anadromous and lacustrine charr populations from eastern North America to assess variation within and among populations of Arctic charr as a function of latitude. Eastern North America was defined to include areas east of 80° W, including: Maine, the Canadian Maritime Provinces, insular Newfoundland, Labrador, Québec, and the eastern Arctic Islands of Baffin, Devon and Ellesmere. Obtained population data sets contained individual observations on age, length, weight, sex and fecundity of Arctic charr from as many age-classes as possible and included sufficient life-history information to permit grouping populations to life-history types: dwarf lacustrine, normal lacustrine and anadromous. Data were used to determine the significance of latitudinal clines in the biological responses as explanations of variation in age-specific biological characteristics (length and growth rate) among populations and life-history-types. The presence of a gradient in temperature and growing season length across latitudes was significantly related to a latitudinal compensation in the growth rate of all age-classes of normal and dwarf lacustrine Arctic charr populations. No decrease in dwarf length-at-age along the gradient was noted, whereas normal lacustrine length-at-age in the younger ages (age-4 to age-6) declined along the gradient. Results provide evidence of the applicability of the countergradient hypothesis as an explanation of among population differences in length-at-age for normal and dwarf lacustrine Arctic charr. Only weak evidence of the applicability of the countergradient hypothesis to anadromous Arctic charr populations was found. Although a decrease in length-at-age for all age-classes was observed along the gradient, only four age-classes (age-10 to age-13) showed a significant increase in growth rate with an increase in latitude. The similarity of the marine thermal environment across the latitudinal gradient is argued to account for the differential response of anadromous Arctic charr in comparison to lacustrine populations.

Abstract The thesis includes two studies of Arctic charr, Salvelinus alpinus, responses to climate variation. In the first chapter, site-specific data from a fishery on the Hornaday River, Northwest Territories (NWT), are used to make inferences about the environmental drivers of observed variation in the mean biological characteristics of the catch. Mean length and weight characteristics of subsistence-fished Arctic charr available from 15 years of monitoring on the Hornaday River, were significantly influenced by among-year differences in local summer temperature and/or precipitation patterns. Environmental influences on mean length were age-specific, with temperature being the most important influence on younger (age-5) fish and precipitation being the most important influence on older (age-8) fish. Mean weight was positively influenced by precipitation only. Significant models of length-temperature relationships further indicated that larger mean sizes occurred in years when average summer air temperatures ranged from 6.7-7.1ºC. The effects of precipitation on nutrient exports to the nearshore marine area appear to trigger many of the observed correlations. Overall, results suggest that the large-scale environmental changes predicted by climate change scenarios will hold significant implications for Arctic charr from the Hornaday River, with population-specific effects likely to be exhibited in other northern Arctic charr populations. The second chapter uses archival biological data on 67 anadromous and lacustrine charr populations from eastern North America to assess variation within and among populations of Arctic charr as a function of latitude. Eastern North America was defined to include areas east of 80° W, including: Maine, the Canadian Maritime Provinces, insular Newfoundland, Labrador, Québec, and the eastern Arctic Islands of Baffin, Devon and Ellesmere. Obtained population data sets contained individual observations on age, length, weight, sex and fecundity of Arctic charr from as many age-classes as possible and included sufficient life-history information to permit grouping populations to life-history types: dwarf lacustrine, normal lacustrine and anadromous. Data were used to determine the significance of latitudinal clines in the biological responses as explanations of variation in age-specific biological characteristics (length and growth rate) among populations and life-history-types. The presence of a gradient in temperature and growing season length across latitudes was significantly related to a latitudinal compensation in the growth rate of all age-classes of normal and dwarf lacustrine Arctic charr populations. No decrease in dwarf length-at-age along the gradient was noted, whereas normal lacustrine length-at-age in the younger ages (age-4 to age-6) declined along the gradient. Results provide evidence of the applicability of the countergradient hypothesis as an explanation of among population differences in length-at-age for normal and dwarf lacustrine Arctic charr. Only weak evidence of the applicability of the countergradient hypothesis to anadromous Arctic charr populations was found. Although a decrease in length-at-age for all age-classes was observed along the gradient, only four age-classes (age-10 to age-13) showed a significant increase in growth rate with an increase in latitude. The similarity of the marine thermal environment across the latitudinal gradient is argued to account for the differential response of anadromous Arctic charr in comparison to lacustrine populations.

Arctic charr is the most northerly distributed salmonid and the most abundant fish in high latitude postglacial lakes. Arctic charr lives in oligotrophic water bodies where it has been able to adapt and thrive due, in part, its noted outstanding phenotypic plasticity. Throughout its geographic range, the Arctic charr has had to specialize to get the most of each ecosystem, to the point that Arctic charr were originally described as 56 different species and only later considered as many phenotypic variations of the same group, called the Arctic charr complex. With the aim of using the resources available in areas with very low primary production, Arctic charr often specialize to become different morphotypes within the same water body. Each morphotype can follow different life histories that can be anadromous or non-migratory. In several lakes, the non-migratory stocks may also differentiate further, each form with its own trophic and/or reproductive behavior. Adult sympatric forms may differ in depth distribution, size-at-maturity, time and place of spawning, color and/or other meristic characters that include differential gill raker and vertebrae numbers. The two typical forms that are found in sympatry are a small, profoundal form often termed “dwarf” Arctic charr and a large, littoral or pelagic zone resident often termed “Normal” Arctic charr. The Arctic charr colonized most of its current habitat very recently, after the ice retreat in the late Pleistocene, 10000-15000 years ago. The reproductive isolation of stocks, if it has occurred at all, occurred so recently that the accumulated genetic drift often does not yield enough data to support the genetic separation of the stocks. Since the geographic borders of the stocks tend to be unclear and because the Arctic charr is a migratory species, the management of fisheries can be difficult in light of these issues, this thesis examines the potential for identifying Arctic charr populations using Major Histocompatibility (MH) genes as molecular markers. MH genes are useful because they are not neutral markers, but are subject to selection. MH receptors present peptides to T-lymphocytes and from that interaction the immune system defines what is self or non-self and thus whether or not immune reactions should be initiated. Due to the large variety of potential pathogenic peptides to be presented, the domain of the MH receptor that binds the peptide, the peptide binding region, is the most polymorphic coding region known. Each individual has a limited number of MH alleles. Given the high degree of polymorphism in populations it is virtually impossible that two individuals will share the same set, of MHC alleles with the exception of monozygotic twins. Since MH receptors present peptides derived from pathogens, they are related to disease resistance, and some MH alleles are more effective at presenting certain peptides than others. Therefore, populations settled in a specific niche will interact with a defined variety of pathogens that will select for certain patterns in the MH alleles of the population. The selection of these MH allelic patterns occurs rapidly, since they determine the survival of the individuals during disease outbreaks. Rapid selection means that MH allelic patterns they can be used to differentiate populations that have been separated for relatively short periods of time. The MH genes of Arctic charr had not been characterized before the publication of this thesis, so the first step was their isolation and characterization. We found the MH sequences obtained to have typical characteristics of classical MH receptors, sharing similarities with other salmonids and having most of their variation in the peptide binding region. We next characterized populations of Arctic charr selected from the global distribution using the three polymorphic MH receptors. For all of the receptor we found most of the polymorphisms distributed equally amongst the populations, but the interpopulation diversity was generally enough to differentiate at least some of the studied populations. For the MH Class I we studied three non classical (UCA, UGA, UEA) and one classical (UBA) gene. For UBA and UCA we found a large degree of polymorphism while UGA and UEA were not very polymorphic. Despite the fact that the UGA gene was also not polymorphic in studies of rainbow trout, we found the gene to be the best Class I population marker for Arctic charr because it had the highest relative rates of interpopulation diversity. Thus, UGA may be exhibiting some antigen presentation functions in Arctic charr. The population analysis using MH Class II α and Class II β genes were the most successful. Particularly in the case of Class II β, the analyses arose capable of differentiating all the populations chosen for this study. Both genes showed high levels of polymorphism and high rates of non-synonymous/synonymous substitution in the exon that encodes the peptide binding region. Lastly, we used MHC Class II α and Class II β to differentiate two separate sets of morphotypes living in sympatry in Lake Kiryalta in Russia and Gander Lake in Canada. The morphotypes in Gander Lake were successfully differentiated using both MH Class II α and β allele data, while the morphotypes in Lake Kiryalta were separated only with the MH Class II β allele data. Given that the use of one or more MH genes used allowed us to differentiate the populations studied, MH genes seem to be extremely useful as population markers for Arctic charr. Since MH genes not only characterize populations according to their phylogenetic relationships, but also according to their specific adaptation to inhabited niches, we concluded that all the Arctic charr populations studied are independent evolutionary significant units of the Arctic charr species. The conclusion implies that although different stocks might be living in sympatry, they should be considered as separate species for fishery and other management purposes, because their specific adaptations to the pathogens in their ecological niche might not allow them to cross-repopulate the other stock if it were removed by over-fishing or other anthropogenic stresses.

Arctic charr is the most northerly distributed salmonid and the most abundant fish in high latitude postglacial lakes. Arctic charr lives in oligotrophic water bodies where it has been able to adapt and thrive due, in part, its noted outstanding phenotypic plasticity. Throughout its geographic range, the Arctic charr has had to specialize to get the most of each ecosystem, to the point that Arctic charr were originally described as 56 different species and only later considered as many phenotypic variations of the same group, called the Arctic charr complex. With the aim of using the resources available in areas with very low primary production, Arctic charr often specialize to become different morphotypes within the same water body. Each morphotype can follow different life histories that can be anadromous or non-migratory. In several lakes, the non-migratory stocks may also differentiate further, each form with its own trophic and/or reproductive behavior. Adult sympatric forms may differ in depth distribution, size-at-maturity, time and place of spawning, color and/or other meristic characters that include differential gill raker and vertebrae numbers. The two typical forms that are found in sympatry are a small, profoundal form often termed “dwarf” Arctic charr and a large, littoral or pelagic zone resident often termed “Normal” Arctic charr. The Arctic charr colonized most of its current habitat very recently, after the ice retreat in the late Pleistocene, 10000-15000 years ago. The reproductive isolation of stocks, if it has occurred at all, occurred so recently that the accumulated genetic drift often does not yield enough data to support the genetic separation of the stocks. Since the geographic borders of the stocks tend to be unclear and because the Arctic charr is a migratory species, the management of fisheries can be difficult in light of these issues, this thesis examines the potential for identifying Arctic charr populations using Major Histocompatibility (MH) genes as molecular markers. MH genes are useful because they are not neutral markers, but are subject to selection. MH receptors present peptides to T-lymphocytes and from that interaction the immune system defines what is self or non-self and thus whether or not immune reactions should be initiated. Due to the large variety of potential pathogenic peptides to be presented, the domain of the MH receptor that binds the peptide, the peptide binding region, is the most polymorphic coding region known. Each individual has a limited number of MH alleles. Given the high degree of polymorphism in populations it is virtually impossible that two individuals will share the same set, of MHC alleles with the exception of monozygotic twins. Since MH receptors present peptides derived from pathogens, they are related to disease resistance, and some MH alleles are more effective at presenting certain peptides than others. Therefore, populations settled in a specific niche will interact with a defined variety of pathogens that will select for certain patterns in the MH alleles of the population. The selection of these MH allelic patterns occurs rapidly, since they determine the survival of the individuals during disease outbreaks. Rapid selection means that MH allelic patterns they can be used to differentiate populations that have been separated for relatively short periods of time. The MH genes of Arctic charr had not been characterized before the publication of this thesis, so the first step was their isolation and characterization. We found the MH sequences obtained to have typical characteristics of classical MH receptors, sharing similarities with other salmonids and having most of their variation in the peptide binding region. We next characterized populations of Arctic charr selected from the global distribution using the three polymorphic MH receptors. For all of the receptor we found most of the polymorphisms distributed equally amongst the populations, but the interpopulation diversity was generally enough to differentiate at least some of the studied populations. For the MH Class I we studied three non classical (UCA, UGA, UEA) and one classical (UBA) gene. For UBA and UCA we found a large degree of polymorphism while UGA and UEA were not very polymorphic. Despite the fact that the UGA gene was also not polymorphic in studies of rainbow trout, we found the gene to be the best Class I population marker for Arctic charr because it had the highest relative rates of interpopulation diversity. Thus, UGA may be exhibiting some antigen presentation functions in Arctic charr. The population analysis using MH Class II α and Class II β genes were the most successful. Particularly in the case of Class II β, the analyses arose capable of differentiating all the populations chosen for this study. Both genes showed high levels of polymorphism and high rates of non-synonymous/synonymous substitution in the exon that encodes the peptide binding region. Lastly, we used MHC Class II α and Class II β to differentiate two separate sets of morphotypes living in sympatry in Lake Kiryalta in Russia and Gander Lake in Canada. The morphotypes in Gander Lake were successfully differentiated using both MH Class II α and β allele data, while the morphotypes in Lake Kiryalta were separated only with the MH Class II β allele data. Given that the use of one or more MH genes used allowed us to differentiate the populations studied, MH genes seem to be extremely useful as population markers for Arctic charr. Since MH genes not only characterize populations according to their phylogenetic relationships, but also according to their specific adaptation to inhabited niches, we concluded that all the Arctic charr populations studied are independent evolutionary significant units of the Arctic charr species. The conclusion implies that although different stocks might be living in sympatry, they should be considered as separate species for fishery and other management purposes, because their specific adaptations to the pathogens in their ecological niche might not allow them to cross-repopulate the other stock if it were removed by over-fishing or other anthropogenic stresses.

Economic viability of Fraser River, Labrador Arctic charr (Salvelinus alpinus) aquaculture in Atlantic Canada may be greatly improved if grow-out could be completed in seawater (30 ppt), while having a low incidence of sexual maturation before harvesting. Growth and survival in seawater was investigated among individually PIT-tagged Arctic charr reared in tanks in the laboratory. Direct transfer from freshwater to brackish water (20 ppt), and then acclimation to 30 ppt was successful. The manipulation of photoperiod, temperature, and food ration can be used as practical applications in aquaculture to arrest maturation; this was investigated in two additional experiments. The most effective photoperiod was LD18:6 for 6 weeks starting December 21, which reduced maturation to 43% compared to 78% in controls. Restricted ration from December 21 through March 15 had no effect on maturation, however, rearing females in 5°C compared to 10°C reduced maturation to 15% compared to >80% in controls.

Mercury concentrations in freshwater and marine biota are an ongoing concern, even in areas remote from local point sources, such as in the Canadian Arctic and sub-Arctic. Anadromous Arctic charr, which feed in the marine environment, have lower mercury concentrations than non-anadromous Arctic charr, which feed strictly in freshwater, but the two life-history forms have rarely been studied together, and the mechanisms driving the difference are unclear. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual total mercury concentration ([THg]) across a range of latitudes (49 – 81° N) in eastern Canada. From six of these sampling locations, additional samples of lower trophic level biota (i.e., algae, invertebrates, and forage fishes) were obtained in order to investigate patterns of total mercury (THg) and methylmercury (MeHg) biomagnification in the marine and lacustrine foodwebs supporting Arctic charr. Arctic charr mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations (all p < 0.01), ranging from 111 to 227 ng/g ww. Within-population variations in Arctic charr [THg] were best explained by fish age, and were also positively related to fork-length and δ15N-inferred trophic level. Across all sampling sites, the relationship between Arctic charr [THg] and fish age was significant and statistically similar in both life-history types, but only the non-anadromous fish demonstrated a significant relationship with trophic level. Fork-length and site latitude did not explain significant additional variation in Arctic charr [THg] across sampling locations. Trophic magnification factors were 1.98 – 5.19 for THg and 3.02 – 6.69 for MeHg in lacustrine foodwebs, and 1.59 – 2.82 for THg and 2.72 – 5.70 for MeHg in marine foodwebs, and did not differ significantly between the two feeding habitats for either THg or MeHg. The biomagnification rate of MeHg exceeded that of THg in both habitats. Mercury concentrations at the base of the foodweb were higher in the lacustrine environment (estimated at 17 – 139 ng/g dw for THg and 5 – 42 ng/g dw for MeHg) than in the marine environment (8 – 39 ng/g dw for THg and 1 – 11 ng/g dw for MeHg). The proportion of mercury in the methylated form was related to trophic level, and the relationship was statistically similar in the lacustrine and marine habitats. There was no effect of site latitude on mercury concentrations in marine or lacustrine biota, thus the difference between feeding habitats was consistent across a range of latitudes (56 – 72°N) in eastern Canada. We conclude that a difference in prey mercury concentration, driven by differential mercury concentrations at of the base of the lacustrine and marine foodwebs, is important for explaining the difference in mercury concentration between anadromous and non-anadromous in Arctic charr.

The brook trout <i>Salvelinus fontinalis</i> is the only salmonid native to the southern Appalachian Mountains, and is distributed across eastern North America from Canada to Georgia. This species was once abundant in coldwater lakes and streams throughout its range, but environmental disturbances and the introduction of non-native species have drastically reduced the number and sizes of wild populations. Genetic evidence suggests a division at the subspecies level between southern- and northern-derived brook trout populations, with the break between the two forms occurring roughly at the New River watershed. Before the subspecies structure was recognized, brook trout of northern origin were widely stocked throughout the Southeast. The primary objective of this study was to determine the phylogenetic origin of all wild brook trout populations in southwestern Virginia using allozyme markers. Seventy-eight streams believed to contain brook trout in the New, James, Holston, and Yadkin river drainages were sampled by backpack electrofishing. Muscle tissue samples were collected from 916 individuals from 56 populations using a non-lethal biopsy technique. The samples were analyzed by cellulose acetate gel electrophoresis and histochemical staining techniques. Variation at four polymorphic loci, including the diagnostic creatine kinase (<i>CK-A2*</i>) locus, was quantified in terms of genetic diversity and population genetic differentiation. Allele frequencies indicated that 19 populations were of putative southern origin, 5 of northern origin, and 32 of mixed genetic origin. The secondary objective was to determine the geographic distribution of southern- and northern-form brook trout populations throughout the native range using data compiled from all known genetic studies. A map of these data showed that the break between the southern and northern form is sharp, occurring at the New/Roanoke-James watershed divide. Populations from the New River drainage expressed the southern allele at a frequency of 85%, suggesting that their historic native character is southern, and that the presence of northern alleles is due to stocking or stream-capture events. The persistence of the southern form, despite the heavy stocking of northern-derived individuals, may be evidence of an adaptive advantage for the southern form of the species. Existence of adaptive genetic differentiation supports the case for conservation of the southern form of the species in future management of brook trout. / Master of Science

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