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Experiences applying Ecosim in the Gulf of Alaska Sheila JJ Heymans, Sylvie Guénette Villy Christensen, Andrew Trites UBC FISHERIES CENTRE INCOFISH WP 4 Meeting Cape Town 11-16 September 2006
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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.
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Problem Aleutians SEAK Steller sea lion abundance 0 30,000 60,000 90,000 195619611966197119761981198619911996
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Study areas Aleutian Islands Southeast Alaska Shelf east of 140 o W 0 - 1,000m depth 91,000 km 2 170 o W – 170 o E 0 - 500m depth 57,000 km 2
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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.
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Aleutians biomass
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SE Alaska biomass
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Estimate environmental variation 0.0 0.5 1.0 1.5 2.0 2.5 19631968197319781983198819931998 Aleutians SE Alaska
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Known environmental indices -3 -2 0 1 2 3 1963196819731978 1983198819931998 10 11 12 13 14 15 AOI, ALPI, RI NPI Pacific Decadal Oscillation PDO
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Environmental variation 0.7 0.8 0.9 1 1.1 1.2 1.3 Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96Jan-99 Jan-02 Inverse PDO PDO
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Fitting the models Fitting the models Aleutians - biomass Biomass PDO Relative SS = 1 Environ. variation Relative SS = 0.97 Fishing Relative SS = 0.99
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Fitting the models Fitting the models Aleutians - catch Catch Relative SS = 0.99 Fishing Relative SS = 0.97 Environ. variation Relative SS = 1 PDO Forced catch
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Fitting the models Fitting the models SE Alaska - biomass Salmon 19631968197319781983198819931998 19631968197319781983198819931998 Biomass Environ. variation Relative SS = 1 PDO Relative SS = 0.8 Fishing Relative SS = 0.63 Steller sea lions 0 1,000 2,000 3,000 4,000 19631968197319781983198819931998 0 50,000 100,000 150,000 200,000 19631968197319781983198819931998 Herring 0 100,000 200,000 300,000 400,000 500,000 Pacific Ocean perch 0 50,000 100,000 150,000 200,000 250,000 19631968197319781983198819931998 Sablefish 0 20,000 40,000 60,000 80,000 100,000 19631968197319781983198819931998 Halibut 0 20,000 40,000 60,000 80,000 100,000
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Fitting the models Fitting the models SE Alaska - catch Steller sea lions 0 1 2 3 4 5 6 7 0 15,000 30,000 45,000 19631968197319781983198819931998 10,000 20,000 30,000 40,000 0 19631968197319781983198819931998 Relative SS = 1 Environ. variation Relative SS = 0.8 PDO Catch Forced catch Relative SS = 0.63 Fishing
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Competitive Interactions Fishing Ocean Climate Change Predation Steller sea liondecline Steller sea lion decline Aleutian Islands Guenette, Heymans, Christensen & Trites (in prep) 196019802000 0 10,000 20,000 30,000 40,000 Abundance Competitive Interactions Predation
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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 3500 4500 5500 6500 Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96 Jan-99 Jan-02 Aleutians SEAK
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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 Ulanowicz 1986 Organization & Specialization Information C Φ A Φ = C - A
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Finn cycling index 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96 Jan-99Jan-02 0.6 0.7 0.8 0.9 1.0 1.1 1.2 Aleutians SEAK Abs. diff. between value and 5 yr average
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Ascendency Aleutians SEAK 50 55 60 65 70 75 80 Jan-63Jan-66Jan-69Jan-72Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93Jan-96 Jan-99Jan-02 24 25 26 27 28 29 30 31 32 Abs. diff. between value and 5 yr average
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0 20 40 60 80 Jan-63Jan-65 Jan-67Jan-69Jan-71Jan-73Jan-75Jan-77Jan-79Jan-81Jan-83Jan-85Jan-87Jan-89Jan-91 Jan-93 Jan-95Jan-97Jan-99Jan-01 Ascendency - Aleutians Flow Export Respiration Abs. diff. between value and 5 yr average
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Redundancy 32 33 34 35 36 37 38 Jan-63Jan-66Jan-69Jan-72 Jan-75 Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93Jan-96 Jan-99Jan-02 44 45 46 47 48 49 Aleutians SEAK Abs. diff. between value and 5 yr average
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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, ADF&G, NMFS, MMU Carl Walters, Steve Martell
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