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Comparative Analysis of Salmon and Cod: the role of population dynamics in environmental forcing

Comparative Analysis of Salmon and Cod: the role of population dynamics in environmental forcing. Loo Botsford, UCD Lee Worden, UCB Francis Juanes, U Mass Alan Hastings, UCD Mike Fogarty, NMFS, WH Matt Holland, UCD Steve Teo, UCD Hui-Yu Wang, U Mass. US GLOBEC, 1990s-present.

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Comparative Analysis of Salmon and Cod: the role of population dynamics in environmental forcing

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  1. Comparative Analysis of Salmon and Cod: the role of population dynamics in environmental forcing Loo Botsford, UCD Lee Worden, UCB Francis Juanes, U Mass Alan Hastings, UCD Mike Fogarty, NMFS, WH Matt Holland, UCD Steve Teo, UCD Hui-Yu Wang, U Mass

  2. US GLOBEC, 1990s-present The effects of environmental change on global ocean ecosystems A mechanistic approach But typical scenario: physics Fish population time time Correlated -> causal influence Modeling: physics, NPZ…. What’s missing? Population dynamics of higher trophic levels

  3. Example: CCS salmon Coho salmon collapse coastwide mid-1970s Chinook salmon does not Same time as change in new index = PDO

  4. CCS coho salmon Change in zooplankton composition Coho abundance PDO But how (point of action)? Coho growth rate Coho survival year 1 Coho survival year 2 Also, why didn’t chinook salmon respond in the same way? Different population dynamics? Different physics?

  5. semelparous (die after spawning)

  6. Recent findings in population dynamics 1. Point of action (e.g., survival at age 3, juvenile growth rate) makes a difference in response 2. Age distribution of reproduction and mortality also determine response. 3. Fishing changes that response Worden, et al. 2009 - coho and chinook salmon Myers, et al. (1998) - sockeye salmon Bjornstadt, et al. (2004) - Atlantic cod

  7. From Worden, et al. Several dominant modes of response: 1. Geometric decay 2. A cycle with period = dominant age of reproduction Nequil N time Nequil N 0 2 4 6 Effects of environment? time Varying survival rate geometric decay mode Varying maturation/age schedule cyclic mode.

  8. Example: CCS coho salmon Variable growth rate Variable survival rate

  9. Example: cyclic salmon populations Fraser River sockeye salmon spawning runs, major streams (Myers, et al. 1998)

  10. View of response depends on method of observation: 1. Recruitment 2. Spawners 3. Catch (constant fishing) Less variability on short time scales Example: CCS chinook salmon, variable growth rate Catch Recruitment

  11. Results of fishing or long-term decline in survival: Increase in resonance Decline, then collapse Example: CCS coho salmon

  12. CCS coho salmon Variable growth rate

  13. Relevance to climate change 1. Sensitivities to slow change 2. Sensitivity to change in time scales of variability, e.g., ENSO. ENSO

  14. Our plans: Synthesis of what is known re: Pacific and Atlantic salmon, Pacific and Atlantic cod response to environmental variability How much of the differences in response are due to differences in life histories vs. differences in physical forcing? Interact with physicists regarding current and likely future time scales of environmental variability Determine population response to variability on these different time scales from data and modeling results.

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