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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

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

slide2

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

slide3

Example: CCS salmon

Coho salmon collapse coastwide mid-1970s

Chinook salmon does not

Same time as change in new index = PDO

slide4

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?

slide6

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

slide7

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.

slide8

Example: CCS coho salmon

Variable growth rate

Variable survival rate

slide9

Example: cyclic salmon populations

Fraser River sockeye salmon spawning runs, major streams (Myers, et al. 1998)

slide10

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

slide11

Results of fishing or long-term decline in survival:

Increase in resonance

Decline, then collapse

Example: CCS coho salmon

slide12

CCS coho salmon

Variable growth rate

slide13

Relevance to climate change

1. Sensitivities to slow change

2. Sensitivity to change in time scales of variability, e.g., ENSO.

ENSO

slide14

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.