Multi-model approaches to understanding food web impacts of low sardine abundance

California Current Project

 

Multiple models strengthen our understanding of California Current food webs

In the California Current, sardine recently declined to less than 10% of their recent peak abundances, and anchovy populations have also been depressed. Through collaboration with the Ocean Modeling forum, IEA scientists contributed to a multi-model approach to explore how sardine abundance impacts the ecosystem and predators.

As part of the Ocean Modeling Forum, we have applied three ecosystem modeling approaches: Ecopath (Koehn et al. 2016), MICE (Punt et al. 2016), and Atlantis (Kaplan et al. 2017). We also used static Ecopath diets to predict impacts to predators using a statistical generalization of the dynamic Ecosim model (PREP, (Pikitch et al. 2012)).

Comparison of multiple models strengthened final conclusions and yielded various methods to force the three models into a common currency for comparison. Results from both ecosystem models for which brown pelicans are modeled at the species level (MICE and Ecopath/PREP) emphasize the vulnerability of brown pelicans to low sardine abundance due to diets that are high in sardines and anchovy, another species with high variability. Two ecosystem models (MICE and Atlantis) suggest that California sea lions should exhibit relatively minor responses to sardine depletion, due to having broader diets and lower reliance on anchovy. On the other hand, Ecopath/PREP models suggest that sardine declines will have a strong impact on California sea lions. This discrepancy reflects structural differences in the models: weaker responses in Atlantis and MICE are likely attributable to the explicit representation of density dependence and age-structure.

The work has been presented to a subcommittee of the Pacific Fishery Management Council.

Collaborators:

Isaac C Kaplan 1, Tessa B Francis 2, André E Punt 3, Laura E Koehn 3, Enrique Curchitser 4, Felipe Hurtado-Ferro 4, Kelli F Johnson 3, Salvador E. Lluch.Cota 5, William J Sydeman 6, Timothy E Essington 3, Nathan Taylor 7, Kirstin Holsman 8, Alec D MacCall 6, and Phillip S Levin 9*

* Ocean Modeling Forum Leads

Partners

  • Conservation Biology Division, Northwest Fisheries Science Center, NOAA

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  • University of Washington Tacoma, Puget Sound Institute

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  • School of Aquatic and Fishery Sciences, University of Washington

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  • Rutgers University, Department of Environmental Sciences

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  • Centro de Investigaciones Biológicas del Noroeste, Mexico

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  • Farallon Institute

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  • Pacific Biological Station, Fisheries and Oceans Canada, Canada

    FOC logo
  • Alaska Fisheries Science Center NOAA Fisheries

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  • University of Washington School of Environmental & Forest Sciences

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    Primary:

    1. Kaplan et al. 2017

    Supporting:

    1. 1. Kaplan, Isaac C., Laura E. Koehn, Emma E. Hodgson, Kristin N. Marshall, and Timothy E. Essington. 2017. “Modeling Food Web Effects of Low Sardine and Anchovy Abundance in the California Current.” Ecological Modelling 359 (September): 1–24.

    2. 2. Koehn, Laura E., Timothy E. Essington, Kristin N. Marshall, Isaac C. Kaplan, William J. Sydeman, Amber I. Szoboszlai, and Julie A. Thayer. 2016. “Developing a High Taxonomic Resolution Food Web Model to Assess the Functional Role of Forage Fish in the California Current Ecosystem.” Ecological Modelling 335 (September): 87–100.

    3. 3. Pikitch, Ellen, Patricia Dee Boersma, Ian Boyd, David Conover, Philippe Cury, Timothy Essington, Selina Heppell, et al. 2012. “Little Fish, Big Impact: Managing a Crucial Link in Ocean Food Webs.” Lenfest Ocean Program. .

    4. 4. Punt, André E., Alec D. MacCall, Timothy E. Essington, Tessa B. Francis, Felipe Hurtado-Ferro, Kelli F. Johnson, Isaac C. Kaplan, Laura E. Koehn, Phillip S. Levin, and William J. Sydeman. 2016. “Exploring the Implications of the Harvest Control Rule for Pacific Sardine, Accounting for Predator Dynamics: A MICE Model.” Ecological Modelling 337 (October): 79–95.

Underwater photo of a school of sardines

Fig. 1. Sardines schooling near giant kelp (Macrocystis pyrifera)

Seabirds diving for fish at sea

Fig. 2. California brown pelicans diving for prey (photo credit: Crew and Officers of NOAA Ship FAIRWEATHER)

California Current