The extensive phenotypic polymorphism in the European whitefish has triggered evolutionary resear... more The extensive phenotypic polymorphism in the European whitefish has triggered evolutionary research in order to disentangle mechanisms underlying diversification. To illuminate the ecological distinctiveness in polymorphic whitefish, and evaluate taxonomic designations, we studied nine Norwegian lakes in three watercourses, which each har- boured pairs of divergent whitefish morphs. We compared the morphology and life history of these morphs, documented the
Methods and Technologies in Fish Biology and Fisheries, 2007
The production of Atlantic salmon (Salmo salar) dwarfs the wild salmon fishery by two orders of m... more The production of Atlantic salmon (Salmo salar) dwarfs the wild salmon fishery by two orders of magnitude. Throughout the North Atlantic region, large numbers of aquacultured (farm) fish escape and invade rivers that contain native salmon. This causes considerable concern, because interactions between escaped farm fish and native fish can cause a decline in the fitness and productivity of the
Genetic introgression of domesticated to wild conspecifics is of great concern to the genetic int... more Genetic introgression of domesticated to wild conspecifics is of great concern to the genetic integrity and viability of the wild populations. Therefore, we need tools that can be used for monitoring unidirectional gene flow from domesticated to wild populations. A challenge to quantitation of unidirectional gene flow is that both the donor and the recipient population may be genetically substructured and that the subpopulations are subjected to genetic drift and may exchange migrants between one another. We develop a standardized method for quantifying and monitoring domesticated to wild gene flow and demonstrate its usefulness to farm and wild Atlantic salmon as a model species. The challenge of having several wild and farm populations was circumvented by in silico generating one analytical center point for farm and wild salmon, respectively. Distributions for the probability that an individual is wild were generated from individual-based analyses of observed wild and farm genotyp...
HINDAR, K., AND B. Jowsss~. 1982. Habitat and food segregation of dwarf and normal Arctic charr (... more HINDAR, K., AND B. Jowsss~. 1982. Habitat and food segregation of dwarf and normal Arctic charr (Salvelinus alpinus) from Vangsvatnet Lake, western Norway. Can. 3. Fish. Aquat. Sci. 39: 1030-1045.
ABSTRACT Estimates of fish abundance from electrofishing surveys depend on accurate estimation of... more ABSTRACT Estimates of fish abundance from electrofishing surveys depend on accurate estimation of capture probability. We examine in this paper how estimates of capture probability and abundance of Atlantic salmon from multi-pass removal sampling can be improved by comparing the results of an experimental programme of closed electrofishing sites within selected rivers in west-central Norway, and those obtained from open electrofishing sites established for monitoring long-term juvenile Atlantic salmon population abundance within the Burrishoole catchment, western Ireland. We first establish that the Carle & Strub method provides a more robust estimate of population abundance than the Zippin and Seber methods. We then show how prior information on capture probability may be used to improve the accuracy of the abundance estimate in open sites. We also show that the use of prior information with single-pass electrofishing may improve the accuracy of the abundance estimate so that it is comparable with that of multi-pass electrofishing in terms of stock prediction while requiring less sampling effort.
The river-resident Salmo salar ("sm ablank") has been isolated from other Atlantic salmon populat... more The river-resident Salmo salar ("sm ablank") has been isolated from other Atlantic salmon populations for 9,500 years in upper River Namsen, Norway. This is the only European Atlantic salmon population accomplishing its entire life cycle in a river. Hydropower development during the last six decades has introduced movement barriers and changed more than 50% of the river habitat to lentic conditions. Based on microsatellites and SNPs, genetic variation within sm ablank was only about 50% of that in the anadromous Atlantic salmon within the same river. The genetic differentiation (F ST ) between sm ablank and the anadromous population was 0.24. This is similar to the differentiation between anadromous Atlantic salmon in Europe and North America. Microsatellite analyses identified three genetic subpopulations within sm ablank, each with an effective population size N e of a few hundred individuals. There was no evidence of reduced heterozygosity and allelic richness in contemporary samples (2005)(2006)(2007)(2008) compared with historical samples (1955-56 and 1978-79). However, there was a reduction in genetic differentiation between sampling localities over time. SNP data supported the differentiation of sm ablank into subpopulations and revealed downstream asymmetric gene flow between subpopulations. In spite of this, genetic variation was not higher in the lower than in the upper areas. The meta-population structure of sm ablank probably maintains genetic variation better than one panmictic population would do, as long as gene flow among subpopulations is maintained. Sm ablank is a unique endemic island population of Atlantic salmon. It is in a precarious situation due to a variety of anthropogenic impacts on its restricted habitat area. Thus, maintaining population size and avoiding further habitat fragmentation are important.
We compared mitochondrial DNA and gill-raker number variation in populations of the European whit... more We compared mitochondrial DNA and gill-raker number variation in populations of the European whitefish Coregonus lavaretus (L.) species complex to illuminate their evolutionary history, and discuss mechanisms behind diversification. Using single-strand conformation polymorphism (SSCP) and sequencing 528 bp of combined parts of the cytochrome oxidase b (cyt b ) and NADH dehydrogenase subunit 3 (ND3) mithochondrial DNA (mtDNA) regions, we
Proceedings of the Royal Society B: Biological Sciences, 2000
Farm Atlantic salmon escape and invade rivers throughout the North Atlantic annually, which has g... more Farm Atlantic salmon escape and invade rivers throughout the North Atlantic annually, which has generated growing concern about their impacts on native salmon populations. A large-scale experiment was therefore undertaken in order to quantify the lifetime success and interactions of farm salmon invading a Norwegian river. Sexually mature farm and native salmon were genetically screened, radio tagged and released into the River Imsa where no other salmon had been allowed to ascend. The farm ¢shes were competitively and reproductively inferior, achieving less than one-third the breeding success of the native ¢shes. Moreover, this inferiority was sex biased, being more pronounced in farm males than females, resulting in the principal route of gene £ow involving native males mating with farm females. There were also indications of selection against farm genotypes during early survival but not thereafter. However, evidence of resource competition and competitive displacement existed as the productivity of the native population was depressed by more than 30%. Ultimately, the lifetime reproductive success (adult to adult) of the farm ¢shes was 16% that of the native salmon. Our results indicate that such annual invasions have the potential for impacting on population productivity, disrupting local adaptations and reducing the genetic diversity of wild salmon populations.
Proceedings of the Royal Society B: Biological Sciences, 2009
Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female ... more Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female differential sperm selection. Here, we examined the influence of variation in major histocompatibility (MH) class I allelic composition upon sperm competition dynamics in Atlantic salmon. We ran in vitro fertilization competitions that mimicked the gametic microenvironment, and replicated a paired-male experimental design that allowed us to compare differences in sperm competition success among males when their sperm compete for eggs from females that were genetically either similar or dissimilar at the MH class I locus. Concurrently, we measured variation in spermatozoal traits that are known to influence relative fertilization success under these conditions. Contrary to the findings demonstrating mechanisms that promote MH complex heterozygosity, our results showed that males won significantly greater relative fertilization success when competing for eggs from genetically similar females at the MH class I. This result also showed covariation with the known influences of sperm velocity on relative fertilization success. We discuss these unexpected findings in relation to sperm-egg recognition and hybridization avoidance mechanisms based upon immunogenetic variation.
Reproductive potentials of transplanted cutthroat trout (Salmo clarki) and Dolly Varden charr (Sa... more Reproductive potentials of transplanted cutthroat trout (Salmo clarki) and Dolly Varden charr (Salvelinus malma) and of their donor stocks were estimated from life history data. We found good agreement between observed and predicted age at maturity in all populations, and cannot reject the hypothesis that the fish matured at the age maximizing the overall lifetime reproductive potential (R= ~ Ixf xe-rx). Our estimates were insensitive to x probable variations in female fecundity, adult mortalityrate and maximum body length. Small changes in either juvenile mortality-rate or individual growth-rate had marked effects on the estimations, as did changes in the Malthusian parameter (r). Three alternative mechanistic explanations of how age at maturity is determined could be rejected. We suggest that fish are able to adjust the maturity age non-genetically to changes in growth-rate, and that temporal variations in juvenile survival-rate allow coexistence of genotypes coding for different ages at maturity at the same growth-rate.
Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in ... more Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in many species including the Atlantic salmon Salmo salar, one of the most culturally and economically important fish species of the North Atlantic region. Since 1966, >350 scientific papers on protein variation have been published encompassing 25 000þ salmon from over 400 locations in >200 river systems across the species' distribution. Variation has been detected at 30% of the 110 protein loci screened, though most studies examine <40. The method has been applied largely to the investigation of population structure and differentiation, but work has also led to the systematic revision of the genus Salmo and remains the primary source of insight into hybridization in the wild with brown trout Salmo trutta. Spatial patterns of differentiation show temporal stability, both within and among river systems, and strongly support structuring of the species into river and tributary specific populations and the designation of European and North American populations as distinct sub-species. They also show widespread regional differentiation within both continents, beyond the marked subcontinental differences between Baltic Sea and Atlantic Ocean populations in Europe. Most of the differentiation probably reflects gene flow and founder events associated with colonization following the retreat of the glaciers from much of the species' modern range. However, variation at MEP-2* shows strong correlations with environmental temperature, both within and among rivers, and associations with phenotypic performance. This suggests selection is acting on the locus and provides †Author to whom correspondence should be addressed. Tel.: þ44 (0) 796 472060; fax: þ44 (0) 1796 473523; # 2005 Crown copyright compelling evidence for the local adaptation of populations. Protein studies have led to more population centred management of the species and have been exploited in the discrimination of regional stocks in mixed stock analysis in high seas fisheries, particularly in the Baltic Sea, and as markers for the assessment of stocking success. They have also advanced insight into how the genetic character of populations can be changed in cultivation and the potential impact of salmon aquaculture and stocking on wild populations. The method has been largely superseded by DNA based analyses, but the results remain highly relevant to Atlantic salmon management and conservation and are an irreplaceable data set for studying genetic stability of populations over time. # 2005 Crown copyright
Atlantic salmon (Salmo salar) juveniles were electrofished along a 300-m stretch of a river to te... more Atlantic salmon (Salmo salar) juveniles were electrofished along a 300-m stretch of a river to test for possible associations between genetic similarity and geographical distance between individuals. Multilocus DNA fingerprinting showed that genetically similar juveniles (1-4 years old) were found closer together in the river than less related individuals. However, the association between genetic similarity and geographical distance, although significant, was not strong. This may indicate that factors other than genetic relatedness influence the positioning in the river. A sex bias in the relationship between genetic similarity and geographical distance was caused by a difference between sexually mature and immature males. The study shows that sampling of salmon juveniles should be spread over a wide stretch of the river in order to avoid sampling relatives. Moreover, by including several year classes, the overall degree of genetic similarity is effectively reduced compared with sampling individuals of similar age.
Combining morphological and genetic analysis, we compared patterns of diversification within and ... more Combining morphological and genetic analysis, we compared patterns of diversification within and between morphs among sympatric European whitefish (Coregonus lavaretus L.) populations in Lake Femund, Norway. Seven external populations, from potential colonization routes into Lake Femund were included. We found that deep-, shallow-, river-and bay spawning populations are distinct morphs in Lake Femund. Within morphs, populations range from being similar genetically (Fst ¼ 0-0.005) among deep-spawning populations to being highly differentiated (Fst ¼ 0.153) between bay-spawning populations. Between morphs, genetic differences ranged from a low (Fst ¼ 0.008-0.022) between deep-and shallow-spawning populations to high difference (Fst ¼ 0.125-0.143) between shallow-and bay-spawning populations. A higher proportion of molecular variance was seen among (3.9%) than within morphs (2.8%). The adaptive gene combinations behind the four morphs seem to have originated within the lake, although the lake could have been colonized from more than one source population.
. Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental re... more . Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental results. À ICES Journal of Marine Science, 63: 1234e1247. Cultured salmonids are released or escape into the wild in large numbers and may make up significant proportions of wild salmonid populations in fresh-and saltwater, causing considerable concern for the fitness and productivity of these populations. This paper focuses on the effects of escaped farmed Atlantic salmon (Salmo salar) on wild salmon. Farmed salmon have been under artificial selection for growth and other economically important traits for 30 years and are genetically different in their origin at the molecular and quantitative genetic levels. Escaped farmed salmon spawn in the wild with limited success. Their offspring outgrow those of wild origin but suffer higher mortality. Whole-river experiments in Ireland and Norway have shown that the lifetime success of farmed salmon is reduced relative to wild salmon. Based on data from these experiments, we model the future of wild salmon populations experiencing invasions of escaped farmed salmon. Simulations with a fixed intrusion rate of 20% escaped farmed salmon at spawning suggest that substantial changes take place in wild salmon populations within ten salmon generations (w40 years). Low-invasion scenarios suggest that farmed offspring are unlikely to become established in the population, whereas high-invasion scenarios suggest that populations are eventually mixtures of hybrid and farmed descendants. Recovery of the wild population is not likely under all circumstances, even after many decades without further intrusion. Managers of wild salmon will have difficulty in obtaining broodstock of the original wild population after a few generations of high intrusion. We conclude that further measures to reduce escapes of farmed salmon and their spawning in wild populations are urgently needed.
and Saettem, L. M. 2003. Setting biological reference points for Atlantic salmon stocks: transfer... more and Saettem, L. M. 2003. Setting biological reference points for Atlantic salmon stocks: transfer of information from data-rich to sparse-data situations by Bayesian hierarchical modelling. e ICES Journal of Marine Science, 60: 1177e1193.
Rapid growth is often associated with several fitness-related benefits. However, in most organism... more Rapid growth is often associated with several fitness-related benefits. However, in most organisms growth rates are rarely maximized, suggesting that trade-offs limit the benefits of rapid growth. To enable sustained high growth, behavioural modifications incurring costs may be required, and these may be responsible for evolution of sub-maximal growth rates. 2. In a field experiment it was tested whether rapid growth in brown trout is achieved by increasing potentially costly movement activity. Causal relations were obtained by manipulating the growth rate using bovine growth hormone (GH) implants and monitoring movement activity of stream-dwelling brown trout for two months using radiotelemetry. 3. GH-treated trout grew significantly faster than sham-treated trout both in terms of body mass and length. The GH-treated trout also had a significantly larger absolute movement during the experiment, moving about 68% more than the sham-treated trout. There were no GH effects on diel movement or home range between the two treatments. Plasma GH levels were lower in the GHtreated fish, indicating negative feedback inhibition of native GH secretion, and that the bovine GH implant was still functioning at the end of the study. 4. This is the first study to show increased movement activity in GH-enhanced fish in the wild. Because increased movement is expected to lead to increased metabolic costs, the higher movement activity in the GH-treated trout was likely associated with increased foraging activity. The results demonstrate that increased movement activity is associated with rapid growth in brown trout. Such movement activity may be unfavourable under certain ecological conditions or life stages (i.e. high risk of predation or low resource levels), and may thus represent one component of the cost limiting evolution of maximum growth rates.
The genetic diversity of metapopulations is influenced not only by the effective sizes (N e ) of ... more The genetic diversity of metapopulations is influenced not only by the effective sizes (N e ) of individual subpopulations, but also by the total effective size of the metapopulation (meta-N e ). We estimated meta-N e of four neighbouring Atlantic salmon populations connected by gene flow using genetic estimates of subpopulation N e s and migration rates derived from capture-recapture data. The meta-N e was lower than the sum ofN e s of the subpopulations, suggesting that genetic diversity harboured by the four river salmon metapopulation is lower than what would have been expected by viewing individual subpopulations separately. In addition, meta-N e was found to be sensitive to changes inN e of the subpopulation from which net emigration rate was largest, so as that the genetic diversity of the metapopulation would be best preserved by avoiding any reductions in N e of this subpopulation. Yet, this subpopulation is the one that has historically-and still isexperiencing the highest exploitation rate in the metapopulation system.
Levels of genetic variability at 12 microsatellite loci and 19 single nucleotide polymorphisms in... more Levels of genetic variability at 12 microsatellite loci and 19 single nucleotide polymorphisms in mitochondrial DNA were studied in four farm strains and four wild populations of Atlantic salmon. Within populations, the farm strains showed significantly lower allelic richness and expected heterozygosity than wild populations at the 12 microsatellite loci, but a significantly higher genetic variability with respect to observed
A total of 6,324 base pairs, distributed on eight different regions of the mitochondrial DNA (mtD... more A total of 6,324 base pairs, distributed on eight different regions of the mitochondrial DNA (mtDNA) were re-sequenced for 32 specimens of Norwegian farmed and wild Atlantic salmon. A total of 16 new and three previously reported single nucleotide polymorphisms (SNPs) were detected. These SNPs were validated using 240 farm and 119 wild Norwegian salmon. Alignments of sequences obtained in
The extensive phenotypic polymorphism in the European whitefish has triggered evolutionary resear... more The extensive phenotypic polymorphism in the European whitefish has triggered evolutionary research in order to disentangle mechanisms underlying diversification. To illuminate the ecological distinctiveness in polymorphic whitefish, and evaluate taxonomic designations, we studied nine Norwegian lakes in three watercourses, which each har- boured pairs of divergent whitefish morphs. We compared the morphology and life history of these morphs, documented the
Methods and Technologies in Fish Biology and Fisheries, 2007
The production of Atlantic salmon (Salmo salar) dwarfs the wild salmon fishery by two orders of m... more The production of Atlantic salmon (Salmo salar) dwarfs the wild salmon fishery by two orders of magnitude. Throughout the North Atlantic region, large numbers of aquacultured (farm) fish escape and invade rivers that contain native salmon. This causes considerable concern, because interactions between escaped farm fish and native fish can cause a decline in the fitness and productivity of the
Genetic introgression of domesticated to wild conspecifics is of great concern to the genetic int... more Genetic introgression of domesticated to wild conspecifics is of great concern to the genetic integrity and viability of the wild populations. Therefore, we need tools that can be used for monitoring unidirectional gene flow from domesticated to wild populations. A challenge to quantitation of unidirectional gene flow is that both the donor and the recipient population may be genetically substructured and that the subpopulations are subjected to genetic drift and may exchange migrants between one another. We develop a standardized method for quantifying and monitoring domesticated to wild gene flow and demonstrate its usefulness to farm and wild Atlantic salmon as a model species. The challenge of having several wild and farm populations was circumvented by in silico generating one analytical center point for farm and wild salmon, respectively. Distributions for the probability that an individual is wild were generated from individual-based analyses of observed wild and farm genotyp...
HINDAR, K., AND B. Jowsss~. 1982. Habitat and food segregation of dwarf and normal Arctic charr (... more HINDAR, K., AND B. Jowsss~. 1982. Habitat and food segregation of dwarf and normal Arctic charr (Salvelinus alpinus) from Vangsvatnet Lake, western Norway. Can. 3. Fish. Aquat. Sci. 39: 1030-1045.
ABSTRACT Estimates of fish abundance from electrofishing surveys depend on accurate estimation of... more ABSTRACT Estimates of fish abundance from electrofishing surveys depend on accurate estimation of capture probability. We examine in this paper how estimates of capture probability and abundance of Atlantic salmon from multi-pass removal sampling can be improved by comparing the results of an experimental programme of closed electrofishing sites within selected rivers in west-central Norway, and those obtained from open electrofishing sites established for monitoring long-term juvenile Atlantic salmon population abundance within the Burrishoole catchment, western Ireland. We first establish that the Carle &amp; Strub method provides a more robust estimate of population abundance than the Zippin and Seber methods. We then show how prior information on capture probability may be used to improve the accuracy of the abundance estimate in open sites. We also show that the use of prior information with single-pass electrofishing may improve the accuracy of the abundance estimate so that it is comparable with that of multi-pass electrofishing in terms of stock prediction while requiring less sampling effort.
The river-resident Salmo salar ("sm ablank") has been isolated from other Atlantic salmon populat... more The river-resident Salmo salar ("sm ablank") has been isolated from other Atlantic salmon populations for 9,500 years in upper River Namsen, Norway. This is the only European Atlantic salmon population accomplishing its entire life cycle in a river. Hydropower development during the last six decades has introduced movement barriers and changed more than 50% of the river habitat to lentic conditions. Based on microsatellites and SNPs, genetic variation within sm ablank was only about 50% of that in the anadromous Atlantic salmon within the same river. The genetic differentiation (F ST ) between sm ablank and the anadromous population was 0.24. This is similar to the differentiation between anadromous Atlantic salmon in Europe and North America. Microsatellite analyses identified three genetic subpopulations within sm ablank, each with an effective population size N e of a few hundred individuals. There was no evidence of reduced heterozygosity and allelic richness in contemporary samples (2005)(2006)(2007)(2008) compared with historical samples (1955-56 and 1978-79). However, there was a reduction in genetic differentiation between sampling localities over time. SNP data supported the differentiation of sm ablank into subpopulations and revealed downstream asymmetric gene flow between subpopulations. In spite of this, genetic variation was not higher in the lower than in the upper areas. The meta-population structure of sm ablank probably maintains genetic variation better than one panmictic population would do, as long as gene flow among subpopulations is maintained. Sm ablank is a unique endemic island population of Atlantic salmon. It is in a precarious situation due to a variety of anthropogenic impacts on its restricted habitat area. Thus, maintaining population size and avoiding further habitat fragmentation are important.
We compared mitochondrial DNA and gill-raker number variation in populations of the European whit... more We compared mitochondrial DNA and gill-raker number variation in populations of the European whitefish Coregonus lavaretus (L.) species complex to illuminate their evolutionary history, and discuss mechanisms behind diversification. Using single-strand conformation polymorphism (SSCP) and sequencing 528 bp of combined parts of the cytochrome oxidase b (cyt b ) and NADH dehydrogenase subunit 3 (ND3) mithochondrial DNA (mtDNA) regions, we
Proceedings of the Royal Society B: Biological Sciences, 2000
Farm Atlantic salmon escape and invade rivers throughout the North Atlantic annually, which has g... more Farm Atlantic salmon escape and invade rivers throughout the North Atlantic annually, which has generated growing concern about their impacts on native salmon populations. A large-scale experiment was therefore undertaken in order to quantify the lifetime success and interactions of farm salmon invading a Norwegian river. Sexually mature farm and native salmon were genetically screened, radio tagged and released into the River Imsa where no other salmon had been allowed to ascend. The farm ¢shes were competitively and reproductively inferior, achieving less than one-third the breeding success of the native ¢shes. Moreover, this inferiority was sex biased, being more pronounced in farm males than females, resulting in the principal route of gene £ow involving native males mating with farm females. There were also indications of selection against farm genotypes during early survival but not thereafter. However, evidence of resource competition and competitive displacement existed as the productivity of the native population was depressed by more than 30%. Ultimately, the lifetime reproductive success (adult to adult) of the farm ¢shes was 16% that of the native salmon. Our results indicate that such annual invasions have the potential for impacting on population productivity, disrupting local adaptations and reducing the genetic diversity of wild salmon populations.
Proceedings of the Royal Society B: Biological Sciences, 2009
Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female ... more Polyandry and post-copulatory sexual selection provide opportunities for the evolution of female differential sperm selection. Here, we examined the influence of variation in major histocompatibility (MH) class I allelic composition upon sperm competition dynamics in Atlantic salmon. We ran in vitro fertilization competitions that mimicked the gametic microenvironment, and replicated a paired-male experimental design that allowed us to compare differences in sperm competition success among males when their sperm compete for eggs from females that were genetically either similar or dissimilar at the MH class I locus. Concurrently, we measured variation in spermatozoal traits that are known to influence relative fertilization success under these conditions. Contrary to the findings demonstrating mechanisms that promote MH complex heterozygosity, our results showed that males won significantly greater relative fertilization success when competing for eggs from genetically similar females at the MH class I. This result also showed covariation with the known influences of sperm velocity on relative fertilization success. We discuss these unexpected findings in relation to sperm-egg recognition and hybridization avoidance mechanisms based upon immunogenetic variation.
Reproductive potentials of transplanted cutthroat trout (Salmo clarki) and Dolly Varden charr (Sa... more Reproductive potentials of transplanted cutthroat trout (Salmo clarki) and Dolly Varden charr (Salvelinus malma) and of their donor stocks were estimated from life history data. We found good agreement between observed and predicted age at maturity in all populations, and cannot reject the hypothesis that the fish matured at the age maximizing the overall lifetime reproductive potential (R= ~ Ixf xe-rx). Our estimates were insensitive to x probable variations in female fecundity, adult mortalityrate and maximum body length. Small changes in either juvenile mortality-rate or individual growth-rate had marked effects on the estimations, as did changes in the Malthusian parameter (r). Three alternative mechanistic explanations of how age at maturity is determined could be rejected. We suggest that fish are able to adjust the maturity age non-genetically to changes in growth-rate, and that temporal variations in juvenile survival-rate allow coexistence of genotypes coding for different ages at maturity at the same growth-rate.
Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in ... more Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in many species including the Atlantic salmon Salmo salar, one of the most culturally and economically important fish species of the North Atlantic region. Since 1966, >350 scientific papers on protein variation have been published encompassing 25 000þ salmon from over 400 locations in >200 river systems across the species' distribution. Variation has been detected at 30% of the 110 protein loci screened, though most studies examine <40. The method has been applied largely to the investigation of population structure and differentiation, but work has also led to the systematic revision of the genus Salmo and remains the primary source of insight into hybridization in the wild with brown trout Salmo trutta. Spatial patterns of differentiation show temporal stability, both within and among river systems, and strongly support structuring of the species into river and tributary specific populations and the designation of European and North American populations as distinct sub-species. They also show widespread regional differentiation within both continents, beyond the marked subcontinental differences between Baltic Sea and Atlantic Ocean populations in Europe. Most of the differentiation probably reflects gene flow and founder events associated with colonization following the retreat of the glaciers from much of the species' modern range. However, variation at MEP-2* shows strong correlations with environmental temperature, both within and among rivers, and associations with phenotypic performance. This suggests selection is acting on the locus and provides †Author to whom correspondence should be addressed. Tel.: þ44 (0) 796 472060; fax: þ44 (0) 1796 473523; # 2005 Crown copyright compelling evidence for the local adaptation of populations. Protein studies have led to more population centred management of the species and have been exploited in the discrimination of regional stocks in mixed stock analysis in high seas fisheries, particularly in the Baltic Sea, and as markers for the assessment of stocking success. They have also advanced insight into how the genetic character of populations can be changed in cultivation and the potential impact of salmon aquaculture and stocking on wild populations. The method has been largely superseded by DNA based analyses, but the results remain highly relevant to Atlantic salmon management and conservation and are an irreplaceable data set for studying genetic stability of populations over time. # 2005 Crown copyright
Atlantic salmon (Salmo salar) juveniles were electrofished along a 300-m stretch of a river to te... more Atlantic salmon (Salmo salar) juveniles were electrofished along a 300-m stretch of a river to test for possible associations between genetic similarity and geographical distance between individuals. Multilocus DNA fingerprinting showed that genetically similar juveniles (1-4 years old) were found closer together in the river than less related individuals. However, the association between genetic similarity and geographical distance, although significant, was not strong. This may indicate that factors other than genetic relatedness influence the positioning in the river. A sex bias in the relationship between genetic similarity and geographical distance was caused by a difference between sexually mature and immature males. The study shows that sampling of salmon juveniles should be spread over a wide stretch of the river in order to avoid sampling relatives. Moreover, by including several year classes, the overall degree of genetic similarity is effectively reduced compared with sampling individuals of similar age.
Combining morphological and genetic analysis, we compared patterns of diversification within and ... more Combining morphological and genetic analysis, we compared patterns of diversification within and between morphs among sympatric European whitefish (Coregonus lavaretus L.) populations in Lake Femund, Norway. Seven external populations, from potential colonization routes into Lake Femund were included. We found that deep-, shallow-, river-and bay spawning populations are distinct morphs in Lake Femund. Within morphs, populations range from being similar genetically (Fst ¼ 0-0.005) among deep-spawning populations to being highly differentiated (Fst ¼ 0.153) between bay-spawning populations. Between morphs, genetic differences ranged from a low (Fst ¼ 0.008-0.022) between deep-and shallow-spawning populations to high difference (Fst ¼ 0.125-0.143) between shallow-and bay-spawning populations. A higher proportion of molecular variance was seen among (3.9%) than within morphs (2.8%). The adaptive gene combinations behind the four morphs seem to have originated within the lake, although the lake could have been colonized from more than one source population.
. Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental re... more . Genetic and ecological effects of salmon farming on wild salmon: modelling from experimental results. À ICES Journal of Marine Science, 63: 1234e1247. Cultured salmonids are released or escape into the wild in large numbers and may make up significant proportions of wild salmonid populations in fresh-and saltwater, causing considerable concern for the fitness and productivity of these populations. This paper focuses on the effects of escaped farmed Atlantic salmon (Salmo salar) on wild salmon. Farmed salmon have been under artificial selection for growth and other economically important traits for 30 years and are genetically different in their origin at the molecular and quantitative genetic levels. Escaped farmed salmon spawn in the wild with limited success. Their offspring outgrow those of wild origin but suffer higher mortality. Whole-river experiments in Ireland and Norway have shown that the lifetime success of farmed salmon is reduced relative to wild salmon. Based on data from these experiments, we model the future of wild salmon populations experiencing invasions of escaped farmed salmon. Simulations with a fixed intrusion rate of 20% escaped farmed salmon at spawning suggest that substantial changes take place in wild salmon populations within ten salmon generations (w40 years). Low-invasion scenarios suggest that farmed offspring are unlikely to become established in the population, whereas high-invasion scenarios suggest that populations are eventually mixtures of hybrid and farmed descendants. Recovery of the wild population is not likely under all circumstances, even after many decades without further intrusion. Managers of wild salmon will have difficulty in obtaining broodstock of the original wild population after a few generations of high intrusion. We conclude that further measures to reduce escapes of farmed salmon and their spawning in wild populations are urgently needed.
and Saettem, L. M. 2003. Setting biological reference points for Atlantic salmon stocks: transfer... more and Saettem, L. M. 2003. Setting biological reference points for Atlantic salmon stocks: transfer of information from data-rich to sparse-data situations by Bayesian hierarchical modelling. e ICES Journal of Marine Science, 60: 1177e1193.
Rapid growth is often associated with several fitness-related benefits. However, in most organism... more Rapid growth is often associated with several fitness-related benefits. However, in most organisms growth rates are rarely maximized, suggesting that trade-offs limit the benefits of rapid growth. To enable sustained high growth, behavioural modifications incurring costs may be required, and these may be responsible for evolution of sub-maximal growth rates. 2. In a field experiment it was tested whether rapid growth in brown trout is achieved by increasing potentially costly movement activity. Causal relations were obtained by manipulating the growth rate using bovine growth hormone (GH) implants and monitoring movement activity of stream-dwelling brown trout for two months using radiotelemetry. 3. GH-treated trout grew significantly faster than sham-treated trout both in terms of body mass and length. The GH-treated trout also had a significantly larger absolute movement during the experiment, moving about 68% more than the sham-treated trout. There were no GH effects on diel movement or home range between the two treatments. Plasma GH levels were lower in the GHtreated fish, indicating negative feedback inhibition of native GH secretion, and that the bovine GH implant was still functioning at the end of the study. 4. This is the first study to show increased movement activity in GH-enhanced fish in the wild. Because increased movement is expected to lead to increased metabolic costs, the higher movement activity in the GH-treated trout was likely associated with increased foraging activity. The results demonstrate that increased movement activity is associated with rapid growth in brown trout. Such movement activity may be unfavourable under certain ecological conditions or life stages (i.e. high risk of predation or low resource levels), and may thus represent one component of the cost limiting evolution of maximum growth rates.
The genetic diversity of metapopulations is influenced not only by the effective sizes (N e ) of ... more The genetic diversity of metapopulations is influenced not only by the effective sizes (N e ) of individual subpopulations, but also by the total effective size of the metapopulation (meta-N e ). We estimated meta-N e of four neighbouring Atlantic salmon populations connected by gene flow using genetic estimates of subpopulation N e s and migration rates derived from capture-recapture data. The meta-N e was lower than the sum ofN e s of the subpopulations, suggesting that genetic diversity harboured by the four river salmon metapopulation is lower than what would have been expected by viewing individual subpopulations separately. In addition, meta-N e was found to be sensitive to changes inN e of the subpopulation from which net emigration rate was largest, so as that the genetic diversity of the metapopulation would be best preserved by avoiding any reductions in N e of this subpopulation. Yet, this subpopulation is the one that has historically-and still isexperiencing the highest exploitation rate in the metapopulation system.
Levels of genetic variability at 12 microsatellite loci and 19 single nucleotide polymorphisms in... more Levels of genetic variability at 12 microsatellite loci and 19 single nucleotide polymorphisms in mitochondrial DNA were studied in four farm strains and four wild populations of Atlantic salmon. Within populations, the farm strains showed significantly lower allelic richness and expected heterozygosity than wild populations at the 12 microsatellite loci, but a significantly higher genetic variability with respect to observed
A total of 6,324 base pairs, distributed on eight different regions of the mitochondrial DNA (mtD... more A total of 6,324 base pairs, distributed on eight different regions of the mitochondrial DNA (mtDNA) were re-sequenced for 32 specimens of Norwegian farmed and wild Atlantic salmon. A total of 16 new and three previously reported single nucleotide polymorphisms (SNPs) were detected. These SNPs were validated using 240 farm and 119 wild Norwegian salmon. Alignments of sequences obtained in
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Papers by Kjetil Hindar