Upstream Salmon and Society in the Pacific Northwest (1996) / Chapter Skim
Currently Skimming:
6 Genetics and Conservation
6 Genetics and Conservation
Pages 145-163
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From page 145... ...
provided the first modern description of the importance of local populations and genetic diversity for the management of Pacific salmon. They pointed out that each local population was genetically adapted to its own environment ("home-stream colony")
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From page 146... ...
Genetic differences between individuals within a local breeding population are the basis for natural selection and adaptive evolution, and genetic differences between breeding populations reflect local adaptation to past environments and random events. The genetic differences between breeding populations represent the broadest pool of genetic variation and are a valuable component of diversity.
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From page 147... ...
Inverted triangle emphasizes that locally adapted and largely reproductively isolated, local breeding populations are basic unit of diversity. Varied operational definitions of stock would place this term in the range identified by dashed lines.
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From page 148... ...
Thousands of local breeding populations make up the West Coast salmon fishery, and many of these are likely to be intermingled in any particular catch. Nevertheless, the result of regulating fishing on a stock basis and ignoring the reproductive units that together constitute a stock is the disappearance or extirpation of some of the local breeding populations (Clark 1984~.
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From page 149... ...
However, analysis of genetic variation in a network of local breeding populations can provide insight into the pattern and amount of straying among local breeding populations. The chinook of the Klamath River drainage show a complex pattern of genetic differentiation at 36 variable protein loci detected electrophoretically; Bartley et al.
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From page 150... ...
Therefore, the estimated rate of straying among these local breeding populations is about one stray per year within each reproductive population. LOCAL ADAPTATION One important reason to protect local populations is that they are locally adapted to the streams that support them.
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151 o o o o o ~ o oo o o o o ~ o oo o ~ C~ _ _ o o V Cq o 2 o C)
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From page 152... ...
-0.30 it G -0.45 UPSTREA SALMON AND SOCIETY IN THE PACIFIC NORTHWEST 5 _ W' (\ · 1; ,' 4 .
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From page 153... ...
Some anadromous salmon have spectacularly complex life histories. For example, Snake River sockeye emerge in freshwater at an elevation of 2,000 meters, migrate to a nursery lake, and generally spend 2 years growing in the lake.
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From page 154... ...
In some cases, arrival in the freshwater habitat can precede actual spawning by many months. A number of studies have demonstrated that nearly all those aspects of life history are influenced to some degree by genetic differences among individuals and populations (reviewed in Taylor 1991 and Levings 1993~.
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From page 155... ...
METAPOPULATION STRUCTURE The individual local breeding populations within a drainage basin or other geographical area are usually connected in a higher level of organization by exchange of individuals through "straying." The set of local breeding populations connected by exchange of individuals is a metapopulation or a "population of populations" (Hanski and Gilpin 19911; an example of a metapopulation is the fall-run chinook of the lower Columbia River (Pascual and Quinn 19941.
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From page 156... ...
The geographical arrangement of salmon into discrete spawning populations where environmental conditions are appropriate for successful reproduction makes the metapopulation model appropriate for salmon. Local breeding populations of salmon are small enough and exist in such variable environments that they are likely to have relatively short persistence times.
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From page 157... ...
A, metapopulation of chinook in Klamath River drainage (Source: Utter et al.
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From page 158... ...
Studies of biochemical variation do not permit any interpretation of the adaptive significance of genetic differences among local breeding populations, because we do not completely understand the relationship between biochemically detected genetic variation and phenotypic vanation. It is likely that the pattern of o.o~o O.~ o.oos UJ ~ 0.007 cn it 0.006 o.oos 0.004 0.003 0 002 _ O.W1 0.000 o 100 200 300 400 500 600 7= 800 900 1000 GEOGRAPHIC DISTANCE (km)
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From page 159... ...
genetic divergence at protein loci among chinook populations largely reflects the operation of genetic exchange and genetic drift on selectively neutral, or nearly neutral, genetic variation. However, as gene flow decreases and genetic divergence increases, the probability that populations will acquire adaptations to their local environment increases.
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From page 160... ...
The unifying theme of the ESU concept is conservation of the evolutionary legacy and potential of the biological species that is, the genetic variability that is a product of past evolutionary events and that represents the reservoir on which future evolutionary potential depends. The goal is thus to ensure viability of the biological species by conserving enough of its basic components to allow the dynamic processes of evolution to proceed.
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From page 161... ...
EFFECTS OF HUMAN ACTIVITIES ON GENETIC DIVERSITY The genetic structure of salmon populations in the Pacific Northwest has been modified drastically over the last 100 years. Many locally adapted populations have been lost because of dams and loss of habitat.
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From page 162... ...
In summary, a large array of human activities have affected salmon genetics in such a way as to reduce genetic diversity at all levels of population structure. CONCLUSIONS Sustained productivity of anadromous salmon in the Pacific Northwest is possible only if the genetic resources that are the basis of such productivity are
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From page 163... ...
An adequate number of returning adults for every local breeding population is needed to ensure persistence of all the reproductive units. The result of regulating fishing on a metapopulation basis and ignoring the reproductive units that make up a metapopulation is the disappearance or extirpation of some of the local breeding populations and the eventual collapse of the ~netapopulation's production.
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