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What are the ecosystem-level impacts and economic consequences of prioritizing marine mammal recovery versus fisheries yields, and how can management strategies be optimized to balance these competing objectives?
What are the ecosystem-level impacts and economic consequences of prioritizing marine mammal recovery versus fisheries yields, and how can management strategies be optimized to balance these competing objectives?
Introduction
Introduction
This overarching question can be explored using EwE to model different scenarios and evaluate the inherent trade-offs. The question is particularly relevant as many marine mammal populations in many parts of the world have recovered after protection from exploitation or culling, which has allowed populations to rebuild. This has led to an ongoing challenge of managing (reel or perceived) conflicts and competition with fisheries in complex ecosystems. It also addresses a key aspect of ecosystem-based management: balancing multiple, sometimes conflicting, objectives within the same ecosystem.
Key topics and concepts
Key topics and concepts
Apply EwE for Scenario Modeling: Load, configure, and execute EwE models to simulate ecosystem dynamics under various marine mammal management scenarios.
Design and Implement Management Scenarios: Develop and apply diverse policy scenarios within EwE, including modifications to fishing mortality, introduction of new fleets, and manipulation of time series data for both retrospective and forward-looking analyses.
Analyze Ecological and Economic Trade-offs: Extract and interpret key EwE output data (e.g., biomass, catch, economic value, predation impacts) to quantify the ecological and economic consequences of balancing marine mammal recovery with fisheries yields.
Evaluate Ecosystem-level Impacts: Investigate direct and indirect ecosystem impacts, such as trophic cascades and competition, arising from changes in marine mammal populations on target and non-target fish stocks.
Critically Assess Model Utility and Limitations: Evaluate the strengths, assumptions, and limitations of ecosystem models like EwE when addressing complex, real-world policy questions concerning marine mammal-fisheries interactions.
Inform Management Strategy Development: Utilize model outputs to inform the development and assessment of management strategies aimed at optimizing outcomes for both marine mammals and fisheries within an ecosystem context.
Learning outcomes
Learning outcomes
This session will provide an introduction to and experience with:
Apply EwE for Scenario Modeling: Load, configure, and execute EwE models to simulate ecosystem dynamics under various marine mammal management scenarios.
Design and Implement Management Scenarios: Develop and apply diverse policy scenarios within EwE, including modifications to fishing mortality, introduction of new fleets, and manipulation of time series data for both retrospective and forward-looking analyses.
Analyze Ecological and Economic Trade-offs: Extract and interpret key EwE output data (e.g., biomass, catch, economic value, predation impacts) to quantify the ecological and economic consequences of balancing marine mammal recovery with fisheries yields.
Evaluate Ecosystem-level Impacts: Investigate direct and indirect ecosystem impacts, such as trophic cascades and competition, arising from changes in marine mammal populations on target and non-target fish stocks.
Critically Assess Model Utility and Limitations: Evaluate the strengths, assumptions, and limitations of ecosystem models like EwE when addressing complex, real-world policy questions concerning marine mammal-fisheries interactions.
Inform Management Strategy Development: Utilize model outputs to inform the development and assessment of management strategies aimed at optimizing outcomes for both marine mammals and fisheries within an ecosystem context.
Resources and preparation
Resources and preparation
Please prepare for the session by reading the following.
Marine mammals and fisheries. EwE textbook chapter describing this week's topic. Preferably go through (or at least read through) the chapter's tutorials before class
Woodstock et al. 2025. Marine mammal and seabird population changes have contrasting but limited impacts on fisheries catches in the North Sea. CJFAS. https://doi.org/10.1139/cjfas-2025-0056. We will use the model from this paper for the tutorial.
The Woodstock model includes "multi-stanza" groups, i.e. groups modelled with age structure (instead of biomass dynamics as we've used up to now). Please read about multi-stanza groups in EwE here:
Age-structured dynamics text book chapter
Multi-stanza life histories. Pretty heavy chapter, you're not expected to go into details
Adding multi-stanza groups to models. Tutorial describing how to change a group from biomass dynamics to using an age-structured population dynamics model. It's fine it you just look through this tutorial.
Quick readings for background:
Jog et al. (2022) Marine Mammal Interactions With Fisheries: Review of Research and Management Trends Across Commercial and Small-Scale Fisheries. Front. Mar. Sci. 9:758013. https://doi.org/10.3389/fmars.2022.758013. Review of marine mammal - fisheries interactions.
Jackson et al. The global extent and severity of operational interactions between conflicting pinnipeds and fisheries. Nat Commun 15, 7449 (2024). https://doi.org/10.1038/s41467-024-51298-6
Tutorials
Tutorials
Marine mammals and fisheries. The tutorial is quite extensive, and you are not required to work your way through all of it. But you are encouraged to do enough to get a good sense of the approach and how you work with EBM questions and evaluate potential tradeoffs.
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