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- Guban, Peter, et al.
(författare)
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Genetic diversity in Monoporeia affinis at polluted and reference sites of the Baltic Bothnian Bay
- 2015
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Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 93:1-2, s. 245-249
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Tidskriftsartikel (refereegranskat)abstract
- The amphipod Monoporeia affinis plays an important role in the Baltic Sea ecosystem as prey and as detritivore. The species is monitored for contaminant effects, but almost nothing is known about its genetics in this region. A pilot screening for genetic variation at the mitochondrial COI gene was performed in 113 individuals collected at six sites in the northern Baltic. Three coastal sites were polluted by pulp mill effluents, PAHs, and trace metals, and two coastal reference sites were without obvious connection to pollution sources. An off-coastal reference site was also included. Contaminated sites showed lower levels of genetic diversity than the coastal reference ones although the difference was not statistically significant. Divergence patterns measured as Phi(ST) showed no significant differentiation within reference and polluted groups, but there was significant genetic divergence between them. The off-coastal sample differed significantly from all coastal sites and also showed lower genetic variation.
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| 2. |
- Palmé, Anna, et al.
(författare)
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Compromising Baltic salmon genetic diversity : conservation genetic risks associated with compensatory releases of salmon in the Baltic Sea
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Many aspects need to be considered when evaluating the consequences of halting compensatory releases of salmon in the Baltic area. The present report focuses strictly on genetic concerns associated with large scale salmon releases. A majority of the original wild Baltic salmon populations, i.e. populations of Atlantic salmon (Salmo salar) in the Baltic Sea, has gone extinct. Historically, 84 rivers flowing into the Baltic Sea have harbored Atlantic salmon, but currently only 10 of these maintain self sustaining wild natural populations in safe numbers (CCB 2012). Large scale releases of salmon are carried out in the Baltic region to increase productivity of separate populations and to compensate for natural reproduction that has been lost due to hydroelectric power plants that are blocking previous migratory routes. Already in the 1980s observations of pronounced genetic differentiation between populations inhabiting different rivers, coupled with indications that salmon hatchery stocks are genetically divergent from the wild populations they were meant to represent, have warranted conservation genetics researchers to warn against potential negative effects of large scale releases (Ståhl 1981, 1983, 1987). In brief, current large scale releases can cause the following four types of genetic risks for native populations: 1) loss of genetic variation, 2) loss of adaptations, 3) change of population composition, and 4) change of population structure (Laikre et al. 2010). These adverse genetic impacts have been recognized and documented for salmonid fishes for decades (Ryman 1981; Ryman & Utter 1987; Hindar et al.1991; Waples 1999; Naish et al. 2008; Nielsen & Hansen 2008). In 2011 these potential risks of large scale releases gained attention when the European Commission put forward a proposal of phasing out all compensatory releases of salmon in the Baltic area (European Commission 2011). We have compiled and reviewed information regarding compensatory releases of salmon in Swedish rivers including spatio-temporal genetic variability patterns of wild and hatchery salmon populations in the Baltic region. We review and synthesize scientific information from both peer-review and “gray” literature, and have used available genetic data from both published and unpublished studies to address the following main questions: What is currently known regarding the spatio-temporal genetic variability patterns of Atlantic salmon in the Baltic Sea? How has the loss of salmon populations affected the overall capacity for Baltic salmon to maintain genetic variation? What are the effects of releases on genetic variation between and within wild salmon populations? How much of the overall genetic variability of Baltic salmon exists exclusively in hatcheries or is maintained only through breedingrelease operations?Based on current genetic knowledge, what recommendations can be provided with respect to the proposal from the European Commission to halt compensatory releases of salmon in the Baltic? A total of 37 scientific studies on Baltic salmon genetic diversity have been identified. "Gray" genetic literature on Swedish salmon populations comprises seven additional reports. Together they cover genetic information from populations representing 35 Baltic river systems (Rivers Umeälven and Vindelälven counted separately) and c. 23 000 genotyped individuals. The main conclusions from these studies are that the Baltic salmon is genetically divergent from other Atlantic salmon populations and that there is a high degree of genetic structuring between populations in different rivers within the Baltic area. Further, there is a hierarchical grouping of populations in the Baltic, and three larger genetic groups, corresponding to populations in the north, east and south Baltic Sea have been found. In Sweden, compensatory releases of salmon are performed in eight rivers flowing into the Baltic Sea and a total of more than 1.8 million salmon smolt are released annually in Sweden. Despite the hydropower companies’ policy to use local strains, fish of non-local origin is sometimes released. Further, in some hatcheries relatively few spawners are used, which may lead to an increased loss of genetic variation. Information regarding the number of released salmon, number of females and males used in rearing, and strains used for stocking is not easily accessible, and therefore assessment of genetic effects of large scale releases is not straightforward Our analyses of published and unpublished genetic data indicate that a large part of the original genetic variation in Baltic salmon has already been lost due to extinction of individual populations and reduction in population sizes. There is a clear pattern of isolation-by-distance among wild populations, whereas no such pattern is found among hatchery stocks. Further, hatchery stocks typically exhibit lower genetic variation and are less divergent from each other than wild populations. However, hatchery stocks can harbor unique genetic variation and may thus be important to conserve. The genetic effects of releases have not been monitored in the Baltic, but one scientific study indicates strong genetic homogenization of wild populations. Many of the changes of Baltic salmon gene pools occurred prior to the time when molecular genetic studies were possible. Thus, we are not likely to ever clarify exactly the changes that have occurred. Studies of salmonid releases in other parts of the world have in several cases documented altered genetic composition and reduced variability and viability. The extent of this threat needs further investigation. Until such data is available large scale releases should be stopped in line with the precautionary principle, provided that essential actions are implemented to protect remaining wild stocks from e.g. overharvest. Likewise, as many previous spawning areas as possible need to be restored, to safeguard the continued existence of Baltic salmon.
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