• Rocky Mountain Research Station
• 240 West Prospect
• Fort Collins, CO 80526
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Patterns of Finescale Genetic Variation in Chinook Salmon

Although patterns of genetic variation have been studied in many salmon species, most studies have been conducted across very broad areas. Much less is known about the fine-scale genetic variation across individual river basins, but this knowledge may help answer questions about which habitat features are most important, how much habitat a species needs, and how local management can be effectively implemented.

To address these questions, the Boise Laboratory studied Chinook salmon populations across the Middle Fork Salmon River located in central Idaho. Tissue samples for genetic analysis were obtained from fish that had died after spawning. Exact locations of the carcasses were recorded to allow determination of spatial patterns in genetic variation.

Our results show that despite extended population declines, these Chinook salmon populations retain high levels of genetic variation. Genetic variation gives these fish the ability to adapt to future changes in the environment, so there is still hope of maintaining these populations for some time. Distinct differences in genetic structure were apparent across relatively small areas, often less than 6 miles of stream, and suggest that salmon home not just to the stream where they were born, but to specific areas within streams. It also appears that males and females act differently on the spawning grounds. Females tend to home more strongly and often show distinct genetic differences between areas, whereas males stray more frequently and show weaker genetic patterns. Finally, differences in geology among streams also influence patterns in genetic variation and indicate that different basins may face different issues.

Results of this research are helping state and federal agencies responsible for protection of threatened and endangered salmon species design more effective conservation strategies. Managers now have a better understanding of the resilience of Chinook salmon populations and can make better informed decisions about the amount of stream habitat that needs to be protected and how these habitats should be arranged across a river basin. As growing human populations throughout the Pacific Northwest place increasing pressure on salmon populations and stream environments begin to experience rapid alterations driven by climate change, these insights may be key to preserving many salmon populations.

References

Neville, H., D.J. Isaak, R.F. Thurow, J.B. Dunham, and B.E. Rieman. 2006. Individual-based genetic autocorrelation analysis uncovers fine-scale genetic structure related to geomorphic context and sex in Chinook salmon. Molecular Genetics 0:000-000.

Neville, H., D.J. Isaak, R.F. Thurow, J.B. Dunham, and B.E. Rieman. 2006. Microsatellite variation reveals weak genetic structure and retention of genetic variability in threatened Chinook salmon (Oncorhynchus tshawytcha) within a Snake River watershed. Conservation Genetics DOI 10.1007/s10592-006-9155-4.