Experiences applying Ecosim in the Gulf of Alaska

1
Experiences applying Ecosimin the Gulf of Alaska

• Sheila JJ Heymans, Sylvie Guénette
• Villy Christensen, Andrew Trites

INCOFISH WP 4 Meeting Cape Town 11-16 September
2006
2
Aims

• To evaluate how fishing and climate change have
  impacted the ecosystem resources of the Northeast
  Pacific
• Used two systems Aleutians and SE Alaska
  species, notably Steller sea lions and other
  mammals, have different trajectories.

3
Problem
Aleutians
SEAK
4
Study areas
Southeast Alaska
Aleutian Islands

• Shelf east of 140oW
• 0 - 1,000m depth
• 91,000 km2

170oW 170oE 0 - 500m depth 57,000 km2
5
Methodology

• Construct models of both ecosystems (1963)
• Driven by fisheries (i.e. using C/B)
• Fitting change vulnerabilities, feeding time,
  P/B, etc.
• Estimate forcing function
• Correlate to environmental parameters
• Enter environmental function to fit model.

6
Aleutians biomass
7
SE Alaska biomass
8
Estimate environmental variation
2.5
2.0
1.5
1.0
0.5
0.0
1963
1968
1973
1978
1983
1988
1993
1998
9
Known environmental indices
3
15
2
14
1
13
0
12
-1
11
-2
-3
10
1963
1968
1973
1978
1983
1988
1993
1998
10
Environmental variation
1.3
1.2
1.1
1
0.9
0.8
0.7
Jan-63
Jan-66
Jan-69
Jan-72
Jan-75
Jan-78
Jan-81
Jan-84
Jan-87
Jan-90
Jan-93
Jan-96
Jan-99
Jan-02
11
Fitting the models Aleutians - biomass
Biomass
12
Fitting the models Aleutians - catch
Catch
13
Fitting the modelsSE Alaska - biomass
Salmon
Steller sea lions
4,000
200,000
3,000
150,000
2,000
100,000
50,000
1,000
0
0
1963
1968
1973
1978
1983
1988
1993
1998
1963
1968
1973
1978
1983
1988
1993
1998
Pacific Ocean perch
Sablefish
250,000
100,000
200,000
80,000
150,000
60,000
100,000
40,000
50,000
20,000
0
0
1963
1968
1973
1978
1983
1988
1993
1998
1963
1968
1973
1978
1983
1988
1993
1998
Halibut
Herring
100,000
500,000
80,000
400,000
300,000
60,000
200,000
40,000
100,000
20,000
0
0
1963
1968
1973
1978
1983
1988
1993
1998
1963
1968
1973
1978
1983
1988
1993
1998
14
Fitting the modelsSE Alaska - catch
Catch
Steller sea lions
7
6
5
4
3
2
1
0
40,000
30,000
20,000
10,000
45,000
30,000
15,000
0
0
1963
1968
1973
1978
1983
1988
1993
1998
1963
1968
1973
1978
1983
1988
1993
1998
15
Steller sea lion decline
Aleutian Islands
Guenette, Heymans, Christensen Trites (in prep)
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Conclusions

• Both external forces (fishing climate change)
  have caused the changes in these two ecosystems
• Fishing important for POP, herring and sablefish
• Environmental forces such as PDO combined with
  fishing important for Steller sea lions, halibut
  and pollock
• Sea lion decline explained by climate and
  predation
• Unable to fit salmon as effects are larger scale
  than these models.

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Total systems throughput
6500
Aleutians
5500
4500
SEAK
3500
Jan-63
Jan-66
Jan-69
Jan-72
Jan-75
Jan-78
Jan-81
Jan-84
Jan-87
Jan-90
Jan-93
Jan-96
Jan-99
Jan-02
18
Network Analysis Indices

• Finn cycling index relative amount of cycling in
  the ecosystem as a percentage of the total
  systems throughput (Finn 1976).
• Ascendency indicator of the specialization and
  organization in the ecosystem (Ulanowicz, 1986).
• Redundancy Internal flow overhead is an
  indication of the internal redundancy in the
  system (Mageau et al. 1998).

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Information theory
Organization Specialization
F C - A
Ulanowicz 1986
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Finn cycling index
3.5
1.2
3.0
1.1
2.5
1.0
SEAK
Aleutians
0.9
2.0
1.5
0.8
1.0
0.7
0.5
0.6
Jan-75
Jan-78
Jan-81
Jan-84
Jan-87
Jan-90
Jan-93
Jan-96
Jan-63
Jan-66
Jan-69
Jan-72
Jan-99
Jan-02
21
Ascendency
80
32
31
75
30
70
29
SEAK
Aleutians
65
28
27
60
26
55
25
50
24
Jan-63
Jan-66
Jan-69
Jan-72
Jan-75
Jan-78
Jan-81
Jan-84
Jan-87
Jan-90
Jan-93
Jan-96
Jan-99
Jan-02
22
Ascendency - Aleutians
80
60
40
20
0
Jan-63
Jan-65
Jan-67
Jan-69
Jan-71
Jan-73
Jan-75
Jan-77
Jan-79
Jan-81
Jan-83
Jan-85
Jan-87
Jan-89
Jan-91
Jan-93
Jan-95
Jan-97
Jan-99
Jan-01
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Redundancy
38
49
37
48
36
47
35
46
Aleutians
SEAK
34
45
33
32
44
Jan-63
Jan-66
Jan-69
Jan-72
Jan-75
Jan-78
Jan-81
Jan-84
Jan-87
Jan-90
Jan-93
Jan-96
Jan-99
Jan-02
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Conclusions

• Effects of environmental variation is seen in the
  total systems throughput, ascendency and
  redundancy
• Finn cycling index shows less direct effects and
  might be more useful as index of emergent
  effects
• Change from the running average increased after
  regime shift in most indices
• Difference less in SEAK than in AI
• AI largest fluctuations in respiration for both
  ascendency and overhead.

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Acknowledgements

• Support from NOAA through the North Pacific
  Universities Marine Mammal Research Consortium
  and the North Pacific Marine Science Foundation
• Colleagues from DFO, ADFG, NMFS, MMU
• Carl Walters, Steve Martell