Eero Niemelä - Academia.edu (original) (raw)
Papers by Eero Niemelä
Background: New sequencing technologies have tremendously increased the number of known molecular... more Background: New sequencing technologies have tremendously increased the number of known molecular markers (single nucleotide polymorphisms; SNPs) in a variety of species. Concurrently, improvements to genotyping technology have now made it possible to efficiently genotype large numbers of genome-wide distributed SNPs enabling genome wide association studies (GWAS). However, genotyping significant numbers of individuals with large number of SNPs remains prohibitively expensive for many research groups. A possible solution to this problem is to determine allele frequencies from pooled DNA samples, such 'allelotyping' has been presented as a cost-effective alternative to individual genotyping and has become popular in human GWAS. In this article we have tested the effectiveness of DNA pooling to obtain accurate allele frequency estimates for Atlantic salmon (Salmo salar L.) populations using an Illumina SNP-chip. Results: In total, 56 Atlantic salmon DNA pools from 14 populations were analyzed on an Atlantic salmon SNP-chip containing probes for 5568 SNP markers, 3928 of which were bi-allelic. We developed an efficient quality control filter which enables exclusion of loci showing high error rate and minor allele frequency (MAF) close to zero. After applying multiple quality control filters we obtained allele frequency estimates for 3631 bi-allelic loci. We observed high concordance (r > 0.99) between allele frequency estimates derived from individual genotyping and DNA pools. Our results also indicate that even relatively small DNA pools (35 individuals) can provide accurate allele frequency estimates for a given sample. Conclusions: Despite of higher level of variation associated with array replicates compared to pool construction, we suggest that both sources of variation should be taken into account. This study demonstrates that DNA pooling allows fast and high-throughput determination of allele frequencies in Atlantic salmon enabling cost-efficient identification of informative markers for discrimination of populations at various geographical scales, as well as identification of loci controlling ecologically and economically important traits.
Global Change Biology
Stable isotope analysis of organic matter in sediment records has long been used to track histori... more Stable isotope analysis of organic matter in sediment records has long been used to track historical changes in productivity and carbon cycling in marine and lacustrine ecosystems. While flow dynamics preclude stratigraphic measurements of riverine sediments, such retrospective analysis is important for understanding biogeochemical cycling in running waters. Unique collections of riverine fish scales were used to analyse δ(15) N and δ(13) C variations in the food web of two European rivers that experience different degrees of anthropogenic pressure. Over the past four decades, dissolved inorganic N loading remained low and constant in the Teno River (70°N, Finland); by contrast, N loading increased four-fold in the Scorff River (47°N, France) over the same period. Archived scales of Atlantic salmon parr, a riverine life-stage that feeds on aquatic invertebrates, revealed high δ(15) N values in the Scorff River reflecting anthropogenic N inputs to that riverine environment. A strong ...
The factors determining the vulnerability of wild Atlantic salmon populations to genetic invasion... more The factors determining the vulnerability of wild Atlantic salmon populations to genetic invasion by aquaculture escapees are poorly understood. The Teno River salmon stock of northern Lapland includes multiple, genetically and demographically distinct wild populations distributed over many tributaries. Scales from >100,000 fish have been collected throughout the Teno for 40 years, generating a long-term genetic dataset with which to monitor changes due to aquaculture influences. Aquaculture escapees have been recorded in the river since the late 1980s. A full understanding of hybridization between wild salmon and aquaculture escapees requires genetic markers to accurately identify early and later-generation hybrids. Although aquaculture fish comprise multiple distinct lines, areas of the genome responding to domestication selection may show parallel changes over lines and thus collectively discriminate them from wild individuals. We utilized a 220K Atlantic salmon SNP chip and t...
Molecular Ecology, 2014
Delaying sexual maturation can lead to larger body size and higher reproductive success, but carr... more Delaying sexual maturation can lead to larger body size and higher reproductive success, but carries an increased risk of death before reproducing. Classical life history theory predicts that trade-offs between reproductive success and survival should lead to the evolution of an optimal strategy in a given population. However, variation in mating strategies generally persists, and in general, there remains a poor understanding of genetic and physiological mechanisms underlying this variation. One extreme case of this is in the Atlantic salmon (Salmo salar), which can show variation in the age at which they return from their marine migration to spawn (i.e. their 'sea age'). This results in large size differences between strategies, with direct implications for individual fitness. Here, we used an Illumina Infinium SNP array to identify regions of the genome associated with variation in sea age in a large population of Atlantic salmon in Northern Europe, implementing individual-based genome-wide association studies (GWAS) and population-based F ST outlier analyses. We identified several regions of the genome which vary in association with phenotype and/or selection between sea ages, with nearby genes having functions related to muscle development, metabolism, immune response and mate choice. In addition, we found that individuals of different sea ages belong to different, yet sympatric populations in this system, indicating that reproductive isolation may be driven by divergence between stable strategies. Overall, this study demonstrates how genome-wide methodologies can be integrated with samples collected from wild, structured populations to understand their ecology and evolution in a natural context.
PLoS ONE, 2013
Genetic stock identification (GSI) using molecular markers is an important tool for management of... more Genetic stock identification (GSI) using molecular markers is an important tool for management of migratory species. Here, we tested a cost-effective alternative to individual genotyping, known as allelotyping, for identification of highly informative SNPs for accurate genetic stock identification. We estimated allele frequencies of 2880 SNPs from DNA pools of 23 Atlantic salmon populations using Illumina SNP-chip. We evaluated the performance of four common strategies (global F ST , pairwise F ST , Delta and outlier approach) for selection of the most informative set of SNPs and tested their effectiveness for GSI compared to random sets of SNP and microsatellite markers. For the majority of cases, SNPs selected using the outlier approach performed best followed by pairwise F ST and Delta methods. Overall, the selection procedure reduced the number of SNPs required for accurate GSI by up to 53% compared with randomly chosen SNPs. However, GSI accuracy was more affected by populations in the ascertainment group rather than the ranking method itself. We demonstrated for the first time the compatibility of different large-scale SNP datasets by compiling the largest population genetic dataset for Atlantic salmon to date. Finally, we showed an excellent performance of our top SNPs on an independent set of populations covering the main European distribution range of Atlantic salmon. Taken together, we demonstrate how combination of DNA pooling and SNP arrays can be applied for conservation and management of salmonids as well as other species.
Molecular Ecology, 2007
Defining populations and identifying ecological and life-history characteristics affecting geneti... more Defining populations and identifying ecological and life-history characteristics affecting genetic structure is important for understanding species biology and hence, for managing threatened or endangered species or populations. In this study, populations of the world's largest indigenous Atlantic salmon ( Salmo salar ) stock were first inferred using model-based clustering methods, following which life-history and habitat variables best predicting the genetic diversity of populations were identified. This study revealed that natal homing of Atlantic salmon within the Teno River system is accurate at least to the tributary level. Generally, defining populations by main tributaries was observed to be a reasonable approach in this large river system, whereas in the mainstem of the river, the number of inferred populations was fewer than the number of distinct sampling sites. Mainstem and headwater populations were genetically more diverse and less diverged, while each tributary fostered a distinct population with high genetic differentiation and lower genetic diversity. Population structure and variation in genetic diversity among populations were poorly explained by geographical distance. In contrast, age-structure, as estimated by the proportion of multisea-winter spawners, was the most predictive variable in explaining the variation in the genetic diversity of the populations. This observation, being in agreement with theoretical predictions, emphasizes the essence of large multisea-winter females in maintaining the genetic diversity of populations. In addition, the unique genetic diversity of populations, as estimated by private allele richness, was affected by the ease of accessibility of a site, with more difficult to access sites having lower unique genetic diversity. Our results show that despite this species' high capacity for migration, tributaries foster relatively closed populations with little gene flow which will be important to consider when developing management strategies for the system.
Journal of Fish Diseases, 1980
Journal of Fish Biology, 2006
The 30 year time series analyses revealed large temporal variation in the return rates and a rece... more The 30 year time series analyses revealed large temporal variation in the return rates and a recent increase in abundance of previous spawning Atlantic salmon Salmo salar in the River Teno, northern Scandinavia. The mean proportion of repeat spawners was 7 and 4% in the total Atlantic salmon catch and 9 and 22% in multi-sea-winter (MSW) catch component for females and males, respectively. Previous spawners constituted on the average 7% of the catch in mass but up to 20% (31 t) and 30% (19 t) in , respectively. In 1975, the proportion of previous spawners varied between 1 and 6% (3-12% of MSW Atlantic salmon), whereas in 2001-2004, they accounted for 8-21% (16-35% of MSW Atlantic salmon) of the total Atlantic salmon catch. The number of previous spawners in the catch correlated significantly with the preceding numbers of respective 1-3 sea-winter (SW) maiden Atlantic salmon 2 years earlier. The recent increase in the numbers of 1S1 and 2S1 (1 or 2 years at sea followed by first spawning and 1 year reconditioning period at sea) alternate spawning Atlantic salmon was a consequence of higher numbers of maiden 1SW and 2SW Atlantic salmon in the catches and increased sea temperatures. Similarly, the return rate of 1SW Atlantic salmon to second spawning has improved in recent years. Most previous spawners ascended and were captured early in the fishing season. The smolt and sea-age combinations of repeat spawners comprised 68 age groups contributing with the annual mean of 15 age groups to the great diversity of the River Teno Atlantic salmon population complex. #
Journal of Fish Biology, 2006
... To enhance the opportunity for previous spawners to contribute to egg deposition within a sto... more ... To enhance the opportunity for previous spawners to contribute to egg deposition within a stock, proper management and knowledge related to the migration ... in the River Teno system for help collecting data on ascending salmon; J. Haantie, P. Aro, J. Ollila, S. Guttorm and M ...
Journal of Fish Biology, 2000
... We thank many fishermen in the River Teno watershed for the samples of ascending salmon and k... more ... We thank many fishermen in the River Teno watershed for the samples of ascending salmon and kelts; J. Haantie, P. Aro, J. Ollila and S. Guttorm for analysing the scale material; J. Kuusela for help with computing; P ... Fleming, IA, Jonsson, B., Gross, MR & Lamberg, A. (1996). ...
Journal of Fish Biology, 2004
... 400409. Chichester: Ellis Horwood. Priede, IG, Solbé, JF, de LG, Nott, JE, O'Grady, KT ... more ... 400409. Chichester: Ellis Horwood. Priede, IG, Solbé, JF, de LG, Nott, JE, O'Grady, KT & Cragg-Hine, D. 1988). Behaviour of adult Atlantic salmon, Salmo salar L., in the estuary of the River Ribble in relation to variations in dissolved oxygen and tidal flow. ...
Journal of Fish Biology, 1995
... Hutchings, JA (1986). Lakeward migrations by juvenile Atlantic salmon, Salmo salar. Canadian ... more ... Hutchings, JA (1986). Lakeward migrations by juvenile Atlantic salmon, Salmo salar. Canadian Journal of Fisheries und Aquatic Sciences 43, 132-741. Jmgensen, L., Kristoffersen, K. & Halvorsen, M. (1993). Laksungers utnyttelse av innsjaer i sml vassdrag i Troms. ...
Journal of Fish Biology, 1997
Juvenile and adult scale characteristics were used to compare two juvenile groups of Atlantic sal... more Juvenile and adult scale characteristics were used to compare two juvenile groups of Atlantic salmon in a large subarctic river in northern Scandinavia: individuals that have migrated from the main stem into small tributaries and those which remain in the main stem. Body size and scale measurements indicated enhanced growth in migratory parr as compared to their resident main stem counterparts. Analysis of adult salmon scale characteristics using maximum likelihood estimators revealed that 20% of the adults had been in the tributaries before the end of their second year of life, and more than 30% more had moved into the tributaries in the third year. Tributary fish matured at a smaller size and younger age (one-sea-winter salmon) than those rearing in the main stem which included a higher proportion of multi-sea-winter salmon. In addition, when smolt ages and ages at maturity were compared, older female smolts often resulted in smaller spawners and younger smolts, larger spawners. Small female spawners were more likely to survive to become repeat spawners. 1997 The Fisheries Society of the British Isles 1997 The Fisheries Society of the British Isles
Journal of Fish Biology, 2001
ABSTRACT
Journal of Fish Biology, 1994
ABSTRACT
Journal of Fish Biology, 1999
Multi-sea-winter Atlantic salmon (75-115 cm fork length L F , 2-4-winter fish) were radio-tagged ... more Multi-sea-winter Atlantic salmon (75-115 cm fork length L F , 2-4-winter fish) were radio-tagged in the Tanafjord (70 N), Norway, in 1992Norway, in -1993, and 130 fish entered the large subarctic River Tana (Teno). They entered the fresh water at any time of the tidal cycle but more so during the high and ebbing tides. No diel rhythm was detected in river entry under polar day conditions. There were no differences in the change of flow between days when salmon moved and when they did not, but during active migration increasing discharge was associated with increased swimming activity of salmon, especially later in the summer. Increasing air temperature was also associated with enhanced migration activity. Low river flow was associated with increasing delay in salmon passing the first riffle area of the river, 35 km from the sea. 1999 The Fisheries Society of the British Isles
Journal of Fish Biology, 2007
ABSTRACT Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults... more ABSTRACT Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001–2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300–0900 hours) and high sun (0900–1500 hours), while adults favoured the period of low sun (2100–0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2–3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups.
Background: New sequencing technologies have tremendously increased the number of known molecular... more Background: New sequencing technologies have tremendously increased the number of known molecular markers (single nucleotide polymorphisms; SNPs) in a variety of species. Concurrently, improvements to genotyping technology have now made it possible to efficiently genotype large numbers of genome-wide distributed SNPs enabling genome wide association studies (GWAS). However, genotyping significant numbers of individuals with large number of SNPs remains prohibitively expensive for many research groups. A possible solution to this problem is to determine allele frequencies from pooled DNA samples, such 'allelotyping' has been presented as a cost-effective alternative to individual genotyping and has become popular in human GWAS. In this article we have tested the effectiveness of DNA pooling to obtain accurate allele frequency estimates for Atlantic salmon (Salmo salar L.) populations using an Illumina SNP-chip. Results: In total, 56 Atlantic salmon DNA pools from 14 populations were analyzed on an Atlantic salmon SNP-chip containing probes for 5568 SNP markers, 3928 of which were bi-allelic. We developed an efficient quality control filter which enables exclusion of loci showing high error rate and minor allele frequency (MAF) close to zero. After applying multiple quality control filters we obtained allele frequency estimates for 3631 bi-allelic loci. We observed high concordance (r > 0.99) between allele frequency estimates derived from individual genotyping and DNA pools. Our results also indicate that even relatively small DNA pools (35 individuals) can provide accurate allele frequency estimates for a given sample. Conclusions: Despite of higher level of variation associated with array replicates compared to pool construction, we suggest that both sources of variation should be taken into account. This study demonstrates that DNA pooling allows fast and high-throughput determination of allele frequencies in Atlantic salmon enabling cost-efficient identification of informative markers for discrimination of populations at various geographical scales, as well as identification of loci controlling ecologically and economically important traits.
Global Change Biology
Stable isotope analysis of organic matter in sediment records has long been used to track histori... more Stable isotope analysis of organic matter in sediment records has long been used to track historical changes in productivity and carbon cycling in marine and lacustrine ecosystems. While flow dynamics preclude stratigraphic measurements of riverine sediments, such retrospective analysis is important for understanding biogeochemical cycling in running waters. Unique collections of riverine fish scales were used to analyse δ(15) N and δ(13) C variations in the food web of two European rivers that experience different degrees of anthropogenic pressure. Over the past four decades, dissolved inorganic N loading remained low and constant in the Teno River (70°N, Finland); by contrast, N loading increased four-fold in the Scorff River (47°N, France) over the same period. Archived scales of Atlantic salmon parr, a riverine life-stage that feeds on aquatic invertebrates, revealed high δ(15) N values in the Scorff River reflecting anthropogenic N inputs to that riverine environment. A strong ...
The factors determining the vulnerability of wild Atlantic salmon populations to genetic invasion... more The factors determining the vulnerability of wild Atlantic salmon populations to genetic invasion by aquaculture escapees are poorly understood. The Teno River salmon stock of northern Lapland includes multiple, genetically and demographically distinct wild populations distributed over many tributaries. Scales from >100,000 fish have been collected throughout the Teno for 40 years, generating a long-term genetic dataset with which to monitor changes due to aquaculture influences. Aquaculture escapees have been recorded in the river since the late 1980s. A full understanding of hybridization between wild salmon and aquaculture escapees requires genetic markers to accurately identify early and later-generation hybrids. Although aquaculture fish comprise multiple distinct lines, areas of the genome responding to domestication selection may show parallel changes over lines and thus collectively discriminate them from wild individuals. We utilized a 220K Atlantic salmon SNP chip and t...
Molecular Ecology, 2014
Delaying sexual maturation can lead to larger body size and higher reproductive success, but carr... more Delaying sexual maturation can lead to larger body size and higher reproductive success, but carries an increased risk of death before reproducing. Classical life history theory predicts that trade-offs between reproductive success and survival should lead to the evolution of an optimal strategy in a given population. However, variation in mating strategies generally persists, and in general, there remains a poor understanding of genetic and physiological mechanisms underlying this variation. One extreme case of this is in the Atlantic salmon (Salmo salar), which can show variation in the age at which they return from their marine migration to spawn (i.e. their 'sea age'). This results in large size differences between strategies, with direct implications for individual fitness. Here, we used an Illumina Infinium SNP array to identify regions of the genome associated with variation in sea age in a large population of Atlantic salmon in Northern Europe, implementing individual-based genome-wide association studies (GWAS) and population-based F ST outlier analyses. We identified several regions of the genome which vary in association with phenotype and/or selection between sea ages, with nearby genes having functions related to muscle development, metabolism, immune response and mate choice. In addition, we found that individuals of different sea ages belong to different, yet sympatric populations in this system, indicating that reproductive isolation may be driven by divergence between stable strategies. Overall, this study demonstrates how genome-wide methodologies can be integrated with samples collected from wild, structured populations to understand their ecology and evolution in a natural context.
PLoS ONE, 2013
Genetic stock identification (GSI) using molecular markers is an important tool for management of... more Genetic stock identification (GSI) using molecular markers is an important tool for management of migratory species. Here, we tested a cost-effective alternative to individual genotyping, known as allelotyping, for identification of highly informative SNPs for accurate genetic stock identification. We estimated allele frequencies of 2880 SNPs from DNA pools of 23 Atlantic salmon populations using Illumina SNP-chip. We evaluated the performance of four common strategies (global F ST , pairwise F ST , Delta and outlier approach) for selection of the most informative set of SNPs and tested their effectiveness for GSI compared to random sets of SNP and microsatellite markers. For the majority of cases, SNPs selected using the outlier approach performed best followed by pairwise F ST and Delta methods. Overall, the selection procedure reduced the number of SNPs required for accurate GSI by up to 53% compared with randomly chosen SNPs. However, GSI accuracy was more affected by populations in the ascertainment group rather than the ranking method itself. We demonstrated for the first time the compatibility of different large-scale SNP datasets by compiling the largest population genetic dataset for Atlantic salmon to date. Finally, we showed an excellent performance of our top SNPs on an independent set of populations covering the main European distribution range of Atlantic salmon. Taken together, we demonstrate how combination of DNA pooling and SNP arrays can be applied for conservation and management of salmonids as well as other species.
Molecular Ecology, 2007
Defining populations and identifying ecological and life-history characteristics affecting geneti... more Defining populations and identifying ecological and life-history characteristics affecting genetic structure is important for understanding species biology and hence, for managing threatened or endangered species or populations. In this study, populations of the world's largest indigenous Atlantic salmon ( Salmo salar ) stock were first inferred using model-based clustering methods, following which life-history and habitat variables best predicting the genetic diversity of populations were identified. This study revealed that natal homing of Atlantic salmon within the Teno River system is accurate at least to the tributary level. Generally, defining populations by main tributaries was observed to be a reasonable approach in this large river system, whereas in the mainstem of the river, the number of inferred populations was fewer than the number of distinct sampling sites. Mainstem and headwater populations were genetically more diverse and less diverged, while each tributary fostered a distinct population with high genetic differentiation and lower genetic diversity. Population structure and variation in genetic diversity among populations were poorly explained by geographical distance. In contrast, age-structure, as estimated by the proportion of multisea-winter spawners, was the most predictive variable in explaining the variation in the genetic diversity of the populations. This observation, being in agreement with theoretical predictions, emphasizes the essence of large multisea-winter females in maintaining the genetic diversity of populations. In addition, the unique genetic diversity of populations, as estimated by private allele richness, was affected by the ease of accessibility of a site, with more difficult to access sites having lower unique genetic diversity. Our results show that despite this species' high capacity for migration, tributaries foster relatively closed populations with little gene flow which will be important to consider when developing management strategies for the system.
Journal of Fish Diseases, 1980
Journal of Fish Biology, 2006
The 30 year time series analyses revealed large temporal variation in the return rates and a rece... more The 30 year time series analyses revealed large temporal variation in the return rates and a recent increase in abundance of previous spawning Atlantic salmon Salmo salar in the River Teno, northern Scandinavia. The mean proportion of repeat spawners was 7 and 4% in the total Atlantic salmon catch and 9 and 22% in multi-sea-winter (MSW) catch component for females and males, respectively. Previous spawners constituted on the average 7% of the catch in mass but up to 20% (31 t) and 30% (19 t) in , respectively. In 1975, the proportion of previous spawners varied between 1 and 6% (3-12% of MSW Atlantic salmon), whereas in 2001-2004, they accounted for 8-21% (16-35% of MSW Atlantic salmon) of the total Atlantic salmon catch. The number of previous spawners in the catch correlated significantly with the preceding numbers of respective 1-3 sea-winter (SW) maiden Atlantic salmon 2 years earlier. The recent increase in the numbers of 1S1 and 2S1 (1 or 2 years at sea followed by first spawning and 1 year reconditioning period at sea) alternate spawning Atlantic salmon was a consequence of higher numbers of maiden 1SW and 2SW Atlantic salmon in the catches and increased sea temperatures. Similarly, the return rate of 1SW Atlantic salmon to second spawning has improved in recent years. Most previous spawners ascended and were captured early in the fishing season. The smolt and sea-age combinations of repeat spawners comprised 68 age groups contributing with the annual mean of 15 age groups to the great diversity of the River Teno Atlantic salmon population complex. #
Journal of Fish Biology, 2006
... To enhance the opportunity for previous spawners to contribute to egg deposition within a sto... more ... To enhance the opportunity for previous spawners to contribute to egg deposition within a stock, proper management and knowledge related to the migration ... in the River Teno system for help collecting data on ascending salmon; J. Haantie, P. Aro, J. Ollila, S. Guttorm and M ...
Journal of Fish Biology, 2000
... We thank many fishermen in the River Teno watershed for the samples of ascending salmon and k... more ... We thank many fishermen in the River Teno watershed for the samples of ascending salmon and kelts; J. Haantie, P. Aro, J. Ollila and S. Guttorm for analysing the scale material; J. Kuusela for help with computing; P ... Fleming, IA, Jonsson, B., Gross, MR & Lamberg, A. (1996). ...
Journal of Fish Biology, 2004
... 400409. Chichester: Ellis Horwood. Priede, IG, Solbé, JF, de LG, Nott, JE, O'Grady, KT ... more ... 400409. Chichester: Ellis Horwood. Priede, IG, Solbé, JF, de LG, Nott, JE, O'Grady, KT & Cragg-Hine, D. 1988). Behaviour of adult Atlantic salmon, Salmo salar L., in the estuary of the River Ribble in relation to variations in dissolved oxygen and tidal flow. ...
Journal of Fish Biology, 1995
... Hutchings, JA (1986). Lakeward migrations by juvenile Atlantic salmon, Salmo salar. Canadian ... more ... Hutchings, JA (1986). Lakeward migrations by juvenile Atlantic salmon, Salmo salar. Canadian Journal of Fisheries und Aquatic Sciences 43, 132-741. Jmgensen, L., Kristoffersen, K. & Halvorsen, M. (1993). Laksungers utnyttelse av innsjaer i sml vassdrag i Troms. ...
Journal of Fish Biology, 1997
Juvenile and adult scale characteristics were used to compare two juvenile groups of Atlantic sal... more Juvenile and adult scale characteristics were used to compare two juvenile groups of Atlantic salmon in a large subarctic river in northern Scandinavia: individuals that have migrated from the main stem into small tributaries and those which remain in the main stem. Body size and scale measurements indicated enhanced growth in migratory parr as compared to their resident main stem counterparts. Analysis of adult salmon scale characteristics using maximum likelihood estimators revealed that 20% of the adults had been in the tributaries before the end of their second year of life, and more than 30% more had moved into the tributaries in the third year. Tributary fish matured at a smaller size and younger age (one-sea-winter salmon) than those rearing in the main stem which included a higher proportion of multi-sea-winter salmon. In addition, when smolt ages and ages at maturity were compared, older female smolts often resulted in smaller spawners and younger smolts, larger spawners. Small female spawners were more likely to survive to become repeat spawners. 1997 The Fisheries Society of the British Isles 1997 The Fisheries Society of the British Isles
Journal of Fish Biology, 2001
ABSTRACT
Journal of Fish Biology, 1994
ABSTRACT
Journal of Fish Biology, 1999
Multi-sea-winter Atlantic salmon (75-115 cm fork length L F , 2-4-winter fish) were radio-tagged ... more Multi-sea-winter Atlantic salmon (75-115 cm fork length L F , 2-4-winter fish) were radio-tagged in the Tanafjord (70 N), Norway, in 1992Norway, in -1993, and 130 fish entered the large subarctic River Tana (Teno). They entered the fresh water at any time of the tidal cycle but more so during the high and ebbing tides. No diel rhythm was detected in river entry under polar day conditions. There were no differences in the change of flow between days when salmon moved and when they did not, but during active migration increasing discharge was associated with increased swimming activity of salmon, especially later in the summer. Increasing air temperature was also associated with enhanced migration activity. Low river flow was associated with increasing delay in salmon passing the first riffle area of the river, 35 km from the sea. 1999 The Fisheries Society of the British Isles
Journal of Fish Biology, 2007
ABSTRACT Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults... more ABSTRACT Seasonal and diel migration timing of wild Atlantic salmon Salmo salar smolts and adults were investigated annually (2001–2004) in the subarctic River Utsjoki, a tributary of the large River Teno (70° N), using underwater video monitoring. Submerged video cameras provided information on the exact timing and intensity of both migrations in a natural river channel, without disturbing the fish. In contrast to the mainly nocturnal migration pattern described from temperate rivers, the River Utsjoki smolts and adults migrated throughout the day. Smolts migrated most intensively during hours of rising (0300–0900 hours) and high sun (0900–1500 hours), while adults favoured the period of low sun (2100–0300 hours). Smolt migrations started in June and lasted on average 42 days. Adults usually ascended the site 2–3 weeks before the first descending smolts were observed and the adult migrations extended to the end of August. Seasonal synchrony was observed between smolt and adult migrations in years of slowly warming water, whereas in a year of exceptionally warm early summer (2002), smolts migrated earlier than adults. Thus, water temperature seemed to be an important environmental factor triggering the smolt migration, while the migration of adults was probably more fixed to a certain season. Weak positive correlations between fish counts and water temperature were observed, indicating that increasing water temperature may have promoted both smolt and adult migrations. The influence of discharge was negligible, although increasing discharge late in the season may have activated the remaining individuals in both groups.