| 61. |
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| 62. |
- Palm, Stefan, et al.
(författare)
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Laxing och felvandrad lax i Mörrumsån : En genetisk analys
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med denna studie har varit att DNA-analysera ett större material av laxfisk från Mörrumsån för att: · få en bättre bild av hur stor andel felbedömda arthybrider med öring, s.k. laxingar, som förekommit bland vuxen "lax" från olika år och fångstmånader, · uppskatta den totala andelen laxing bland all vuxen laxfisk i Mörrumsån (lax, laxing, öring), · identifiera genetiskt avvikande lax ("felvandrare"), samt · undersöka hur stora genetiska förändringar som skett i åns laxbestånd sedan 1960-talet och om det finns tecken på genetisk påverkan av felvandrad lax från andra vattendrag. Bakgrund till denna analys är att en tidigare genetisk pilotstudie av vuxen lax från Mörrumsån hösten 2011 gav förvånande och oroväckande resultat. En betydande andel (ca 20%) av den förmodade laxen visade sig då vara arthybrider med öring, s.k. laxingar. Dessutom bar en hög andel (10-20%) av de rena laxarna på genuppsättningar som förväntas vara mycket ovanliga bland lax född i Mörrumsån, vilket indikerade att det handlade om felvandrad lax från andra vattendrag. Resultaten var dock baserade på ett litet antal fiskar från ett enstaka år. I denna utökade studie har vi funnit att den totala andelen arthybrider bland förmodad lax från åren 1961, 1985 och 2004-2012 var klart lägre (ca 6%) än i pilotstudien från 2011 (ca 20 %). Denna skillnad beror i första hand på att det förekommer betydligt färre felbedömda arthybrider i fångster av nystigen blanklax i maj–juni än under de efterföljande fiskemånaderna (då fisken från pilotstudien 2011 var insamlad). En trolig förklaring till att andelen felbedömda laxar ökat under säsongerna är att laxingen i Mörrumsån, i likhet med öringen, uppvisar en senare lekvandringstid än laxen. Baserat på sportfiskestatistik, fiskräkningsdata och DNA-resultat har vi beräknat att andelen laxing bland all vuxen laxfisk i Mörrumsån kan ha varit omkring 10% under de senaste åren. En så hög andel arthybrider i ån kan ge betydande produktionsförluster genom "spolierade lekar" när de i princip sterila laxinghanarna blandar sig i laxens och öringens lek. För en riktig riskanalys behövs dock bättre kunskap om laxingarnas lekbeteende och reproduktiva framgång. Även andelen förmodat felvandrad lax (2-3% under perioden 2004-2012) visade sig vara lägre än i pilotstudien baserad på sent fångad lax från 2011 (10-20 %). De flesta genetiskt avvikande laxar var fångade sent under säsongerna vilket kan förklara den höga andelen i det likaledes sent fångade materialet från 2011. Samtidigt har vi kunnat observera små genetiska förändringar, som tillsammans med en ökad genetisk variationsgrad sedan 1960-talet tyder på att "främmande gener" till viss del har tillförts Mörrumsåns laxbestånd. Det är dock oklart när och hur denna genetiska påverkan har ägt rum.
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| 63. |
- Palm, Stefan, et al.
(författare)
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Microsatellite markers reveal clear geographic structuring among threatened noble crayfish (Astacus astacus) populations in Northern and Central Europe
- 2013
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 14, s. 809-821
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Tidskriftsartikel (refereegranskat)abstract
- Noble crayfish (Astacus astacus L.), the most highly valued freshwater crayfish in Europe, is threatened due to a long-term population decline caused mainly by the spread of crayfish plague. Reintroduction of the noble crayfish into restored waters is a common practice but the geographic and genetic origin of stocking material has rarely been considered, partially because previous genetic studies have been hampered by lack of nuclear gene markers with known inheritance. This study represents the first large scale population genetic survey of the noble crayfish (633 adults from 18 locations) based on 10 newly developed microsatellite markers. We focused primarily on the Baltic Sea area (Estonia, Finland and Sweden) where the largest proportion of the remaining populations exists. To allow comparisons, samples from the Black Sea catchment (the Danube drainage) were also included. Two highly differentiated population groups were identified corresponding to the Baltic Sea and the Black Sea catchments, respectively. The Baltic Sea catchment populations had significantly lower genetic variation and private allele numbers than the Black Sea catchment populations. Within the Baltic Sea area, a clear genetic structure was revealed with population samples corresponding well to their geographic origin, suggesting little impact of long-distance translocations. The clear genetic structure strongly suggests that the choice of stocking material for re-introductions and supplemental releases needs to be based on empirical genetic knowledge.
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| 64. |
- Palm, Stefan
(författare)
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Migratory connectivity of two Baltic Sea salmon populations: retrospective analysis using stable isotopes of scales
- 2014
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 71, s. 336-344
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Tidskriftsartikel (refereegranskat)abstract
- Migratory connectivity refers to the extent to which individuals of a migratory population behave in unison, and has significant consequences for the ecology, evolution and conservation of migratory animals. We made a retrospective assessment of the migratory connectivity of River Simojoki and River Kymijoki populations of Atlantic salmon Salmo salar L. by using stable isotope analysis of archived scales to identify the final feeding areas used before ascending rivers for spawning. We also tested differences in migratory connectivity between wild and hatchery-reared salmon and compared Carlin-tag recoveries with salmon scale stable isotope analysis as methods for studying salmon migrations. Stable isotope (C-13, N-15) values from the last growth region of scales from salmon caught ascending their natal rivers were compared via discriminant analysis with those from scales of salmon caught in different Baltic Sea areas during 19892011. Most River Simojoki salmon had likely fed in the Baltic Proper (mean SD for ascending fish probability 0.59 0.32) with secondary likely feeding areas in the Bothnian Sea (0.21 0.26) and the Gulf of Finland (0.20 0.27). Most River Kymijoki salmon had likely fed in the Gulf of Finland (0.71 0.42) with the Baltic Proper (0.29 0.41) a secondary feeding area. The results did not indicate the Bothnian Sea to be an important feeding area. The two salmon populations showed weak migratory connectivity and rather fixed areal preference throughout the record irrespective of wild or stocked origin. Although the results from the scale stable isotope analyses were broadly consistent with previously reported Carlin-tag recoveries, we argue that the stable isotope approach offers several important advantages in the study of salmon migratory behaviour.
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| 65. |
- Palm, Stefan, et al.
(författare)
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No indications of Atlantic salmon (Salmo salar) shoaling with kin in the Baltic Sea
- 2008
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X .- 1205-7533. ; 65, s. 1738-1748
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have shown that fish shoals may consist of closely related individuals. It has been found. for example, that released out-migrating salmon smolts tend to aggregate with kin. including when sibling groups have been reared separately. We used genetic microsatellite markers to test whether "shoals" of adult Atlantic salmon (Salmo salar) during the marine phase (i.e., aggregations of fish Caught in drift nets at offshore feeding areas in the Baltic Sea) consisted of closely related individuals (full-siblings, half-siblings). We found no evidence of kin cohesiveness related to shoals, however. Despite a weak overall tendency for individuals assigned to the same population (river or stock) to Occur tooether, estimates of genetic relatedness in combination with consistent heterozygote deficiencies. and results from mixed-stock analyses and assignment tests collectively indicated that shoals consisted of unrelated fish from multiple populations.
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| 66. |
- Palm, Stefan, et al.
(författare)
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Populationsgenetisk kartläggning av Vänerlax.
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In Lake Vänern, Sweden, two of the world's few land-locked and large-sized Atlantic salmon (Salmo salar) populations exist. The lake also is home for fast growing, lake-migrating populations of brown trout (Salmo trutta). Since the 1800s, widespread human exploitation of spawning and nursery areas in rivers has severely affected the migratory salmonids in the Lake Vänern area, and a large number of local populations have gone extinct. To compensate for lost natural production caused by the hydropower development, extensive compensatory stocking has been going on for many decades using local salmon and trout originating from Rivers Klarälven and Gullspångsälven. In these two rivers wild production of salmon still exists, and they are also the most important reproduction and nursery areas for the wild lake-migratory trout. The salmon and trout from Klarälven and Gullspångsälven are considered unique with a high conservation value. At the same time, they constitute valuable biological resources for the fishery. A prolonged history of weak populations in the wild, use of few parental fish in hatchery production, stock-crosses, and interbreeding of farmed and wild fish has undoubtedly altered the genetic population structure. So far, however, it has remained largely unclear how large genetic changes that have taken place. This report contains a comprehensive population genetic survey of salmon and trout (wild and hatchery produced) originating from Gullspångsälven and Klarälven. By comparing contemporary genetic data with historic material (microsatellite DNA) extracted from scale samples collected during past decades, it has been possible to assess levels of genetic change since the 1960s. It has also been possible to estimate genetically effective population sizes, levels of gene flow and population admixture. Our results show that clear genetic changes have occurred due to a combination of genetic admixture and random allele frequency fluctuations in small populations (genetic drift). Despite significant genetic changes in several cases, current levels of genetic differentiation among the stocks are nevertheless marked. Hence, it is still justified to regard these as genetically unique and worthy of protection. At the same time there are reasons for serious concern. For example, the estimated proportion of "native genes" in current Gullspångsälven salmon (both wild and hatchery) is only about 70 %, corresponding to a gene flow from Klarälven salmon since the 1960s of about 6-9 % per generation - an alarmingly high level. To prevent continued erosion of the genetic population structure, a set of recommendations is provided. A more successful genetic conservation work will be needed to safeguard long-term survival and productivity of the Lake Vänern (wild and hatchery) stocks, and is a basic condition for a sustainable salmonid fishery.
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| 67. |
- Palm, Stefan, et al.
(författare)
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Reduced genetic diversity and low effective size in peripheral northern European catfish Silurus glanis populations
- 2019
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Ingår i: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 95:6, s. 1407-1421
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Tidskriftsartikel (refereegranskat)abstract
- Using 10 polymorphic microsatellites and 1251 individual samples (some dating back to the early 1980s), genetic structure and effective population size in all native and introduced Swedish populations of the European wels catfish or Silurus glanis were studied. Levels of genetic variability and phylogeographic relationships were compared with data from a previous study of populations in other parts of Europe. The genetically distinct Swedish populations displayed comparably low levels of genetic variability and according to one-sample estimates based on linkage disequilibrium and sib ship-reconstruction, current local effective population sizes were lower than minimum levels recommended for short-term genetic conservation. In line with a previous suggestion of postglacial colonisation from a single refugium, all Swedish populations were assembled on a common branch in a star-shaped dendrogram together with other European populations. Two distinct subpopulations were detected in upper and lower habitats of River Emån, indicating that even minor dispersal barriers may restrict gene flow for wels in running waters. Genetic assignment of specimens encountered in the brackish Baltic Sea and in lakes where the species does not occur naturally indicated presence of long-distance sea dispersal and confirmed unauthorised translocations, respectively.
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| 68. |
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| 69. |
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| 70. |
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