Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Population diversity and the portfolio effect in an exploited species

Subjects

Abstract

One of the most pervasive themes in ecology is that biological diversity stabilizes ecosystem processes and the services they provide to society1,2,3,4, a concept that has become a common argument for biodiversity conservation5. Species-rich communities are thought to produce more temporally stable ecosystem services because of the complementary or independent dynamics among species that perform similar ecosystem functions6. Such variance dampening within communities is referred to as a portfolio effect7 and is analogous to the effects of asset diversity on the stability of financial portfolios8. In ecology, these arguments have focused on the effects of species diversity on ecosystem stability but have not considered the importance of biologically relevant diversity within individual species9. Current rates of population extirpation are probably at least three orders of magnitude higher than species extinction rates10, so there is a pressing need to clarify how population and life history diversity affect the performance of individual species in providing important ecosystem services. Here we use five decades of data from Oncorhynchus nerka (sockeye salmon) in Bristol Bay, Alaska, to provide the first quantification of portfolio effects that derive from population and life history diversity in an important and heavily exploited species. Variability in annual Bristol Bay salmon returns is 2.2 times lower than it would be if the system consisted of a single homogenous population rather than the several hundred discrete populations it currently consists of. Furthermore, if it were a single homogeneous population, such increased variability would lead to ten times more frequent fisheries closures. Portfolio effects are also evident in watershed food webs, where they stabilize and extend predator access to salmon resources. Our results demonstrate the critical importance of maintaining population diversity for stabilizing ecosystem services and securing the economies and livelihoods that depend on them. The reliability of ecosystem services will erode faster than indicated by species loss alone.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Bristol Bay sockeye habitat and associated change in variability of returns at different spatial scales and levels of life history aggregation.
Figure 2: Effect of interannual variability on the probability of fishery closures or capacity-swamping returns.
Figure 3: Annual run timing to fishing districts and streams.

References

  1. MacArthur, R. H. Fluctuations of animal populations, and a measure of community stability. Ecology 36, 533–536 (1955)

    Article  Google Scholar 

  2. Elton, C. S. The Ecology of Invasions by Animals and Plants (Chapman & Hall, 1958)

    Book  Google Scholar 

  3. Hooper, D. U. et al. Effects of biodiversity on ecosystem functioning: a consensus of current knowledge. Ecol. Monogr. 75, 3–35 (2005)

    Article  Google Scholar 

  4. Chapin, F. S. et al. Consequences of changing biodiversity. Nature 405, 234–242 (2000)

    CAS  Article  Google Scholar 

  5. Duffy, J. E. Why biodiversity is important to the functioning of real-world ecosystems. Front. Ecol. Environ 7, 437–444 (2009)

    Article  Google Scholar 

  6. Tilman, D. Biodiversity: population versus ecosystem stability. Ecology 77, 350–363 (1996)

    Article  Google Scholar 

  7. Figge, F. Bio-folio: applying portfolio theory to biodiversity. Biodivers. Conserv. 13, 827–849 (2004)

    Article  Google Scholar 

  8. Markowitz, H. Portfolio selection. J. Finance 7, 77–91 (1952)

    Google Scholar 

  9. Luck, G. W., Daily, G. C. & Ehrlich, P. R. Population diversity and ecosystem services. Trends Ecol. Evol. 18, 331–336 (2003)

    Article  Google Scholar 

  10. Hughes, J. B., Daily, G. C. & Ehrlich, P. R. Population diversity: its extent and extinction. Science 278, 689–692 (1997)

    ADS  CAS  Article  Google Scholar 

  11. Hilborn, R., Quinn, T. P., Schindler, D. E. & Rogers, D. E. Biocomplexity and fisheries sustainability. Proc. Natl Acad. Sci. USA 100, 6564–6568 (2003)

    ADS  CAS  Article  Google Scholar 

  12. Hutchinson, W. F. The dangers of ignoring stock complexity in fishery management: the case of the North Sea cod. Biol. Lett. 4, 693–695 (2008)

    Article  Google Scholar 

  13. Quinn, T. P. The Behavior and Ecology of Pacific Salmon and Trout (Univ. Washington Press, 2005)

    Google Scholar 

  14. Doak, D. F. et al. The statistical inevitability of stability-diversity relationships in community ecology. Am. Nat. 151, 264–276 (1998)

    CAS  PubMed  Google Scholar 

  15. Mantua, N. J. & Hare, S. R. The Pacific decadal oscillation. J. Oceanogr. 58, 35–44 (2002)

    Article  Google Scholar 

  16. Schindler, D. E. et al. Climate change, ecosystem impacts, and management for Pacific salmon. Fisheries 33, 502–506 (2008)

    Article  Google Scholar 

  17. Gende, S. M., Edwards, R. T., Willson, M. F. & Wipfli, M. S. Pacific salmon in aquatic and terrestrial ecosystems. Bioscience 52, 917–928 (2002)

    Article  Google Scholar 

  18. Naiman, R. J., Bilby, R. E., Schindler, D. E. & Helfield, J. M. Pacific salmon, nutrients, and the dynamics of freshwater and riparian ecosystems. Ecosystems (NY, Print) 5, 399–417 (2002)

    Article  Google Scholar 

  19. Schindler, D. E., Leavitt, P. R., Brock, C. S., Johnson, S. P. & Quay, P. D. Marine-derived nutrients, commercial fisheries, and production of salmon and lake algae in Alaska. Ecology 86, 3225–3231 (2005)

    Article  Google Scholar 

  20. Helfield, J. M. & Naiman, R. J. Keystone interactions: salmon and bear in riparian forests of Alaska. Ecosystems (NY, Print) 9, 167–180 (2006)

    Article  Google Scholar 

  21. Payne, L. X. & Moore, J. M. Mobile scavengers create hotspots of freshwater productivity. Oikos 115, 69–80 (2006)

    CAS  Article  Google Scholar 

  22. Olsen, E. M. et al. Small-scale biocomplexity in coastal Atlantic cod supporting a Darwinian perspective on fisheries management. Evol. Appl. 1, 524–533 (2008)

    Article  Google Scholar 

  23. Dixson, D. L. et al. Coral reef fish smell leaves to find island homes. Proc. R. Soc. Lond. B 275, 2831–2839 (2008)

    Article  Google Scholar 

  24. Rooker, J. R. et al. Natal homing and connectivity in Atlantic bluefin tuna populations. Science 322, 742–744 (2008)

    ADS  CAS  Article  Google Scholar 

  25. Gustafson, R. G. et al. Pacific salmon extinctions: quantifying lost and remaining diversity. Conserv. Biol. 21, 1009–1020 (2007)

    Article  Google Scholar 

  26. Lindley, S. T. et al. What Caused the Sacramento River Fall Chinook Stock Collapse? Pre-publication report (Pacific Fishery Management Council, 2009); available at 〈http://swr.nmfs.noaa.gov/media/salmondeclinereport.pdf〉.

  27. Moore, J. W., McClure, M., Rogers, L. A. & Schindler, D. E. Synchronization and portfolio performance of threatened salmon. Conserv. Lett. 10.1111/j.1755-263X.2010.00119.x. (in the press)

  28. Folke, C. et al. Regime shifts, resilience, and biodiversity in ecosystem management. Annu. Rev. Ecol. Syst. 35, 557–581 (2004)

    Article  Google Scholar 

  29. West, F. W. & Fair, L. F. Abundance, Age, Sex, and Size Statistics for Pacific Salmon in Bristol Bay, 2003. Fishery Data Series No. 06–47 (Alaska Department of Fish and Game, 2006)

    Google Scholar 

  30. Rogers, L. A. & Schindler, D. E. Asynchrony in population dynamics in sockeye salmon of southwest Alaska. Oikos 117, 1578–1586 (2008)

    Article  Google Scholar 

  31. Pyper, B. J. & Peterman, R. M. Comparison of methods to account for autocorrelation in correlation analyses of fish data. Can. J. Fish. Aquat. Sci. 55, 2127–2140 (1998)

    Article  Google Scholar 

Download references

Acknowledgements

We thank the Gordon and Betty Moore Foundation, the US National Science Foundation, the University of Washington, the Alaska salmon processing industry and the H. Mason Keeler Professorship for support for this work. N. Baron, L. Neeley and S. Sethi provided feedback and comments on the manuscript, and P. Lisi and G. Holtgrieve helped prepare the figures.

Author information

Authors and Affiliations

Authors

Contributions

D.E.S. designed and coordinated the project; R.H., B.C. and L.A.R contributed to the analyses; M.S.W. helped design the project; and all authors contributed to the writing.

Corresponding author

Correspondence to Daniel E. Schindler.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Information comprising: Value of sockeye salmon resources in Bristol Bay and Variance scaling in data, Supplementary Figures 1-3 with legends and References. (PDF 273 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Schindler, D., Hilborn, R., Chasco, B. et al. Population diversity and the portfolio effect in an exploited species. Nature 465, 609–612 (2010). https://doi.org/10.1038/nature09060

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature09060

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing