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 September 2006

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.

Problem Aleutians SEAK Steller sea lion abundance 0 30,000 60,000 90,

Study areas Aleutian Islands Southeast Alaska Shelf east of 140 o W 0 - 1,000m depth 91,000 km o W – 170 o E m depth 57,000 km 2

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.

Aleutians biomass

SE Alaska biomass

Estimate environmental variation Aleutians SE Alaska

Known environmental indices AOI, ALPI, RI NPI Pacific Decadal Oscillation PDO

Environmental variation Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96Jan-99 Jan-02 Inverse PDO PDO

Fitting the models Fitting the models Aleutians - biomass Biomass PDO Relative SS = 1 Environ. variation Relative SS = 0.97 Fishing Relative SS = 0.99

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

Fitting the models Fitting the models SE Alaska - biomass Salmon 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, , , , , Herring 0 100, , , , ,000 Pacific Ocean perch 0 50, , , , , Sablefish 0 20,000 40,000 60,000 80, , Halibut 0 20,000 40,000 60,000 80, ,000

Fitting the models Fitting the models SE Alaska - catch Steller sea lions ,000 30,000 45, ,000 20,000 30,000 40, Relative SS = 1 Environ. variation Relative SS = 0.8 PDO Catch Forced catch Relative SS = 0.63 Fishing

Competitive Interactions Fishing Ocean Climate Change Predation Steller sea liondecline Steller sea lion decline Aleutian Islands Guenette, Heymans, Christensen & Trites (in prep) ,000 20,000 30,000 40,000 Abundance Competitive Interactions Predation

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.

Total systems throughput Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96 Jan-99 Jan-02 Aleutians SEAK

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).

Information theory Ulanowicz 1986 Organization & Specialization Information C Φ A Φ = C - A

Finn cycling index Jan-63Jan-66Jan-69Jan-72 Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93 Jan-96 Jan-99Jan Aleutians SEAK Abs. diff. between value and 5 yr average

Ascendency Aleutians SEAK Jan-63Jan-66Jan-69Jan-72Jan-75Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93Jan-96 Jan-99Jan Abs. diff. between value and 5 yr average

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

Redundancy Jan-63Jan-66Jan-69Jan-72 Jan-75 Jan-78Jan-81Jan-84Jan-87Jan-90Jan-93Jan-96 Jan-99Jan Aleutians SEAK Abs. diff. between value and 5 yr average

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.

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