The genetic impact of escaped farm Atlantic salmon on natural populations

Aquaculture ◽  
1995 ◽  
Vol 137 (1-4) ◽  
pp. 55-56 ◽  
Author(s):  
A. Ferguson ◽  
P. McGinnity ◽  
C. Stone ◽  
S. Clifford ◽  
J. Taggart ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Natural Populations ◽  
Farm Atlantic Salmon ◽  
Genetic Impact

Present Status of the Salmonids Atlantic Salmon and Sea-Trout in the Dutch Part of the River Rhine

1994 ◽  
Vol 29 (3) ◽  
pp. 37-41 ◽  
Author(s):  
W. G. Cazemier
Keyword(s):  
Atlantic Salmon ◽  
Salmo Trutta ◽  
Natural Populations ◽  
River Rhine ◽  
Sea Trout ◽  
The Past ◽  
The North ◽  
Trout Population ◽  
The North Sea ◽  
Heavy Pollution

In the past, the anadromous salmonids, Atlantic salmon (Salmo salar) and sea-trout (Salmo trutta), have formed natural populations in the river Rhine. From the beginning of the nineteenth century onwards, the greater part of the drainage area of the river has been gradually altered from a more or less rural and agricultural area, into a highly industrialised one with subsequent industrialisation, river-engineering and heavy pollution. These developments are considered to be the major cause for the disappearance of the populations of anadromous salmonid fish in the 1950s. The water quality has recovered significantly during the past 25 years. From about 1975 onwards, this process gave rise to a recovery of the anadromous trout population. Results of recent studies of the sea-trout migration pattern are presented. They reveal that nowadays these salmonids can complete their up- and downstream migrations from the North Sea to places, situated at hundreds of kilometres upward the river and vica versa. The numbers of recorded Atlantic salmon and catch locations in inland waters are presented. They show a significant increase since 1989. These phenomena can be understood as promising signs of the recovery of the Rhine aquatic ecosystem.

scholarly journals Captive-bred Atlantic salmon released into the wild have fewer offspring than wild-bred fish and decrease population productivity

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201671
Author(s):  
Ronan James O'Sullivan ◽  
Tutku Aykanat ◽  
Susan E. Johnston ◽  
Ger Rogan ◽  
Russell Poole ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Natural Populations ◽  
Mixed Population ◽  
Lifetime Reproductive Success ◽  
Wild Relative ◽  
Offspring Survival ◽  
Wild Populations ◽  
Annual Productivity ◽  
In The Wild ◽  
Analyse Data

The release of captive-bred animals into the wild is commonly practised to restore or supplement wild populations but comes with a suite of ecological and genetic consequences. Vast numbers of hatchery-reared fish are released annually, ostensibly to restore/enhance wild populations or provide greater angling returns. While previous studies have shown that captive-bred fish perform poorly in the wild relative to wild-bred conspecifics, few have measured individual lifetime reproductive success (LRS) and how this affects population productivity. Here, we analyse data on Atlantic salmon from an intensely studied catchment into which varying numbers of captive-bred fish have escaped/been released and potentially bred over several decades. Using a molecular pedigree, we demonstrate that, on average, the LRS of captive-bred individuals was only 36% that of wild-bred individuals. A significant LRS difference remained after excluding individuals that left no surviving offspring, some of which might have simply failed to spawn, consistent with transgenerational effects on offspring survival. The annual productivity of the mixed population (wild-bred plus captive-bred) was lower in years where captive-bred fish comprised a greater fraction of potential spawners. These results bolster previous empirical and theoretical findings that intentional stocking, or non-intentional escapees, threaten, rather than enhance, recipient natural populations.

scholarly journals Natural selection acts on Atlantic salmon major histocompatibility (MH) variability in the wild

2007 ◽  
Vol 274 (1611) ◽  
pp. 861-869 ◽  
Author(s):  
Elvira de Eyto ◽  
Philip McGinnity ◽  
Sofia Consuegra ◽  
Jamie Coughlan ◽  
Jarle Tufto ◽  
...  
Keyword(s):  
Natural Selection ◽  
Atlantic Salmon ◽  
Balancing Selection ◽  
Natural Populations ◽  
Class Ii ◽  
Major Histocompatibility ◽  
Genotype Frequencies ◽  
Fitness Consequences ◽  
In The Wild ◽  
Class Ii Alpha

Pathogen-driven balancing selection is thought to maintain polymorphism in major histocompatibility (MH) genes. However, there have been few empirical demonstrations of selection acting on MH loci in natural populations. To determine whether natural selection on MH genes has fitness consequences for wild Atlantic salmon in natural conditions, we compared observed genotype frequencies of Atlantic salmon ( Salmo salar ) surviving in a river six months after their introduction as eggs with frequencies expected from parental crosses. We found significant differences between expected and observed genotype frequencies at the MH class II alpha locus, but not at a MH class I-linked microsatellite or at seven non-MH-linked microsatellite loci. We therefore conclude that selection at the MH class II alpha locus was a result of disease-mediated natural selection, rather than any demographic event. We also show that survival was associated with additive allelic effects at the MH class II alpha locus. Our results have implications for both the conservation of wild salmon stocks and the management of disease in hatchery fish. We conclude that natural or hatchery populations have the best chance of dealing with episodic and variable disease challenges if MH genetic variation is preserved both within and among populations.

Hatchery tank enrichment affects cortisol levels and shelter-seeking in Atlantic salmon (Salmo salar)

2013 ◽  
Vol 70 (4) ◽  
pp. 585-590 ◽  
Author(s):  
Joacim Näslund ◽  
Malin Rosengren ◽  
Diego Del Villar ◽  
Lars Gansel ◽  
Johnny R. Norrgård ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Plasma Cortisol ◽  
Natural Populations ◽  
Fish Welfare ◽  
Plastic Tube ◽  
Atlantic Salmon Salmo Salar ◽  
Basal Plasma ◽  
Cortisol Levels ◽  
The Impact

Stocking programs using hatchery-reared salmon are often implemented for augmenting natural populations. However, survival of these fish is often low compared with wild conspecifics, possibly because of genetic, physiological, and behavioural deficiencies. Here, we compared presmolt Atlantic salmon (Salmo salar) from three different environmental treatments (barren environment, plastic tube enrichment, and plastic shredding enrichment) with regard to plasma cortisol levels, shelter-seeking behaviour, and fin deterioration. Basal plasma cortisol levels were higher in barren-reared fish, indicating higher stress levels, while no differences were found in acute cortisol response after a 30 min confinement test. Shelter-seeking was higher in salmon reared in enriched tanks when tested alone, but not when tested in small groups. Barren-reared fish had higher levels of fin deterioration over winter, potentially owing to higher aggression levels. These results suggest that enrichment can reduce the impact of stressors experienced in the hatchery and thus increase fish welfare. Tank enrichment may also be used to produce salmon better adapted for the more complex environment encountered after release.

scholarly journals Low but significant genetic differentiation underlies biologically meaningful phenotypic divergence in a large Atlantic salmon population

2015 ◽  
Author(s):  
Tutku Aykanat ◽  
Susan E Johnston ◽  
Panu Orell ◽  
Eero Niemelä ◽  
Jaakko Erkinaro ◽  
...  
Keyword(s):  
Life History ◽  
Genetic Differentiation ◽  
Atlantic Salmon ◽  
Genetic Divergence ◽  
Natural Populations ◽  
Structured Populations ◽  
Life History Strategies ◽  
Adaptive Divergence ◽  
Juvenile Growth ◽  
Significant Genetic Differentiation

Despite decades of research assessing the genetic structure of natural populations, the biological meaning of low yet significant genetic divergence often remains unclear due to a lack of associated phenotypic and ecological information. At the same time, structured populations with low genetic divergence and overlapping boundaries can potentially provide excellent models to study adaptation and reproductive isolation in cases where high resolution genetic markers and relevant phenotypic and life history information are available. Here, we combined SNP-based population inference with extensive phenotypic and life history data to identify potential biological mechanisms driving fine scale sub-population differentiation in Atlantic salmon (Salmo salar) from the Teno River, a major salmon river in Europe. Two sympatrically occurring sub-populations had low but significant genetic differentiation (FST = 0.018) and displayed marked differences in the distribution of life history strategies, including variation in juvenile growth rate, age at maturity and size within age classes. Large, late-maturing individuals were virtually absent from one of the two sub-populations and there were significant differences in juvenile growth rates and size-at-age after oceanic migration between individuals in the respective sub-populations. Our findings suggest that different evolutionary processes affect each sub-population and that hybridization and subsequent selection may maintain low genetic differentiation without hindering adaptive divergence.

Aqueous aluminium eliminates Gyrodactylus salaris (Platyhelminthes, Monogenea) infections in Atlantic salmon

Parasitology ◽  
1999 ◽  
Vol 119 (1) ◽  
pp. 19-25 ◽  
Author(s):  
A. SOLENG ◽  
A. B. S. POLÉO ◽  
N. E. W. ALSTAD ◽  
T. A. BAKKE
Keyword(s):  
Atlantic Salmon ◽  
Natural Populations ◽  
Basic Knowledge ◽  
Limited Extent ◽  
Fish Health ◽  
Acidic Water ◽  
First Time ◽  
Positive Effect ◽  
Control Water ◽  
Abiotic Environmental Factors

This study focuses on the effect of acidic water and aqueous aluminium on the monogenean ectoparasite Gyrodactylus salaris, infecting Atlantic salmon (Salmo salar) parr. G. salaris-infected salmon were exposed to various combinations of acidity and aluminium concentrations. The most pronounced effect was the elimination of parasites after 4 days when 202 μg Al/l was added to the water. The effect of aluminium was concentration dependent, but was relatively independent of pH (5·2, 5·6 and 5·9). At the lowest pH of 5·0 the effect of aluminium was enhanced. Acidic aluminium-poor water had no or minor effects on the G. salaris infections except at pH 5·0 where all parasites were eliminated within 9 days. The G. salaris populations increased exponentially in untreated control water. The results show for the first time that aqueous aluminium can, to a limited extent, have a positive effect on fish health. This study emphasizes that basic knowledge about abiotic environmental factors is of importance in order to understand the population dynamics, range extension and dispersal of ectoparasites such as G. salaris. Finally, our results suggest that aluminium treatment could form an effective disinfection method against ectoparasites in hatcheries and laboratories, as well as complementing the controversial rotenone treatments used against natural populations of G. salaris.

Allozyme variation in natural populations of Atlantic salmon in Asturias (northern Spain)

Aquaculture ◽  
1991 ◽  
Vol 93 (4) ◽  
pp. 291-298 ◽  
Author(s):  
J.A. Sánchez ◽  
G. Blanco ◽  
E. Vazquez ◽  
E. García ◽  
J. Rubio
Keyword(s):  
Atlantic Salmon ◽  
Natural Populations ◽  
Allozyme Variation ◽  
Northern Spain

Large-Scale Escapes of Farmed Atlantic Salmon (Salmo salar) into Norwegian Rivers Threaten Natural Populations

1991 ◽  
Vol 48 (3) ◽  
pp. 426-428 ◽  
Author(s):  
D. Gausen ◽  
V. Moen
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Large Scale ◽  
Natural Populations ◽  
Genetic Introgression ◽  
Fish Farms ◽  
Farmed Salmon ◽  
Atlantic Salmon Salmo Salar ◽  
Farmed Atlantic Salmon ◽  
And Behavior

We present data on Atlantic salmon (Salmo salar) which show that escaped farmed salmon enter Norwegian rivers in great numbers. Escaped farmed salmon comprised a substantial proportion of the mature salmon present on the spawning grounds in autumn. A potential for large-scale genetic introgression thus exists. The sex ratios, length distributions, and times of ascent of wild and farmed salmon differed significantly, reflecting major variations in biology and behavior. High proportions of farmed salmon (> 20%) were found only in rivers having fish farms situated closer than 20 km from the outlet.

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