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Genetic assessment of a summer chum salmon metapopulation in recovery.

Small MP, Johnson TH, Bowman C, Martinez E - Evol Appl (2013)

Bottom Line: Following supplementation, differentiation among subpopulations decreased (but not significantly) and isolation by distance patterns remained unchanged.There was no decline in genetic diversity in wild-born fish, but hatchery-born fish sampled in the same spawning areas had significantly lower genetic diversity and unequal family representation.Despite potential for negative effects from supplementation programs, few were detected in wild-born fish.

View Article: PubMed Central - PubMed

Affiliation: Washington Department of Fish and Wildlife, Molecular Genetics Laboratory Olympia, WA, USA.

ABSTRACT
Programs to rebuild imperiled wild fish populations often include hatchery-born fish derived from wild populations to supplement natural spawner abundance. These programs require monitoring to determine their demographic, biological, and genetic effects. In 1990s in Washington State, the Summer Chum Salmon Conservation Initiative developed a recovery program for the threatened Hood Canal summer chum salmon Evolutionarily Significant Unit (ESU) (the metapopulation) that used in-river spawners (wild fish) for each respective supplementation broodstock in six tributaries. Returning spawners (wild-born and hatchery-born) composed subsequent broodstocks, and tributary-specific supplementation was limited to three generations. We assessed impacts of the programs on neutral genetic diversity in this metapopulation using 16 microsatellite loci and a thirty-year dataset spanning before and after supplementation, roughly eight generations. Following supplementation, differentiation among subpopulations decreased (but not significantly) and isolation by distance patterns remained unchanged. There was no decline in genetic diversity in wild-born fish, but hatchery-born fish sampled in the same spawning areas had significantly lower genetic diversity and unequal family representation. Despite potential for negative effects from supplementation programs, few were detected in wild-born fish. We hypothesize that chum salmon natural history makes them less vulnerable to negative impacts from hatchery supplementation.

No MeSH data available.


Neighbor-joining dendrogram of Cavalli-Sforza and Edwards chord distances among samples. Bootstrap values over 70% are plotted on the tree nodes.
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fig04: Neighbor-joining dendrogram of Cavalli-Sforza and Edwards chord distances among samples. Bootstrap values over 70% are plotted on the tree nodes.

Mentions: Population centers formed two major clusters in the principle coordinates analysis plot (Fig. 3), and there was no distinction detected between hatchery and wild samples from the same tributaries. The first axis explained 45% of the genetic variance: SJF samples clustered on the left, and HC samples clustered on the right. The second axis explained 12% of the variance: The HC populations divided loosely into two to three clusters along the second axis. The lowest cluster included samples from Dosewallips, Duckabush, Hamma Hamma, and Quilcene rivers as well as the 2004 collection from Big Beef Creek. The topmost cluster included the original samples from Big Beef Creek (these separated along the third axis; the 1979 collection was missing most of one locus and plotted distantly from the 1978 collection), Union River samples, and the older samples from Lilliwaup Creek. The more recent Lilliwaup samples clustered mainly in the center, supporting high genetic drift in this population. The placement of the original Big Beef samples indicated that before reintroduction, summer chum salmon in Big Beef Creek were genetically more similar to other subpopulations from low-elevation tributaries on the east side of HC rather than the geographically closer subpopulations in tributaries originating in the Olympic Mountains (Dosewallips and Duckabush) on the west side of HC. A dendrogram of genetic distances among samples (Fig. 4) displayed similar overall structure. The SJF and HC clusters separated with 100% bootstrap support, with JCL forming a supported sub-branch. The Dosewallips, Duckabush, Hamma Hamma, and Quilcene samples formed an unsupported cluster, and the original samples from Lilliwaup Creek clustered with 79% bootstrap support on a branch with Union River and the original Big Beef Creek samples. The remaining Lilliwaup Creek samples clustered on three unsupported branches. There were no distinctions evident between hatchery-born and wild-born samples collected in the same tributaries.


Genetic assessment of a summer chum salmon metapopulation in recovery.

Small MP, Johnson TH, Bowman C, Martinez E - Evol Appl (2013)

Neighbor-joining dendrogram of Cavalli-Sforza and Edwards chord distances among samples. Bootstrap values over 70% are plotted on the tree nodes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927888&req=5

fig04: Neighbor-joining dendrogram of Cavalli-Sforza and Edwards chord distances among samples. Bootstrap values over 70% are plotted on the tree nodes.
Mentions: Population centers formed two major clusters in the principle coordinates analysis plot (Fig. 3), and there was no distinction detected between hatchery and wild samples from the same tributaries. The first axis explained 45% of the genetic variance: SJF samples clustered on the left, and HC samples clustered on the right. The second axis explained 12% of the variance: The HC populations divided loosely into two to three clusters along the second axis. The lowest cluster included samples from Dosewallips, Duckabush, Hamma Hamma, and Quilcene rivers as well as the 2004 collection from Big Beef Creek. The topmost cluster included the original samples from Big Beef Creek (these separated along the third axis; the 1979 collection was missing most of one locus and plotted distantly from the 1978 collection), Union River samples, and the older samples from Lilliwaup Creek. The more recent Lilliwaup samples clustered mainly in the center, supporting high genetic drift in this population. The placement of the original Big Beef samples indicated that before reintroduction, summer chum salmon in Big Beef Creek were genetically more similar to other subpopulations from low-elevation tributaries on the east side of HC rather than the geographically closer subpopulations in tributaries originating in the Olympic Mountains (Dosewallips and Duckabush) on the west side of HC. A dendrogram of genetic distances among samples (Fig. 4) displayed similar overall structure. The SJF and HC clusters separated with 100% bootstrap support, with JCL forming a supported sub-branch. The Dosewallips, Duckabush, Hamma Hamma, and Quilcene samples formed an unsupported cluster, and the original samples from Lilliwaup Creek clustered with 79% bootstrap support on a branch with Union River and the original Big Beef Creek samples. The remaining Lilliwaup Creek samples clustered on three unsupported branches. There were no distinctions evident between hatchery-born and wild-born samples collected in the same tributaries.

Bottom Line: Following supplementation, differentiation among subpopulations decreased (but not significantly) and isolation by distance patterns remained unchanged.There was no decline in genetic diversity in wild-born fish, but hatchery-born fish sampled in the same spawning areas had significantly lower genetic diversity and unequal family representation.Despite potential for negative effects from supplementation programs, few were detected in wild-born fish.

View Article: PubMed Central - PubMed

Affiliation: Washington Department of Fish and Wildlife, Molecular Genetics Laboratory Olympia, WA, USA.

ABSTRACT
Programs to rebuild imperiled wild fish populations often include hatchery-born fish derived from wild populations to supplement natural spawner abundance. These programs require monitoring to determine their demographic, biological, and genetic effects. In 1990s in Washington State, the Summer Chum Salmon Conservation Initiative developed a recovery program for the threatened Hood Canal summer chum salmon Evolutionarily Significant Unit (ESU) (the metapopulation) that used in-river spawners (wild fish) for each respective supplementation broodstock in six tributaries. Returning spawners (wild-born and hatchery-born) composed subsequent broodstocks, and tributary-specific supplementation was limited to three generations. We assessed impacts of the programs on neutral genetic diversity in this metapopulation using 16 microsatellite loci and a thirty-year dataset spanning before and after supplementation, roughly eight generations. Following supplementation, differentiation among subpopulations decreased (but not significantly) and isolation by distance patterns remained unchanged. There was no decline in genetic diversity in wild-born fish, but hatchery-born fish sampled in the same spawning areas had significantly lower genetic diversity and unequal family representation. Despite potential for negative effects from supplementation programs, few were detected in wild-born fish. We hypothesize that chum salmon natural history makes them less vulnerable to negative impacts from hatchery supplementation.

No MeSH data available.