Ecosystem models of Lake Victoria (East Africa): Can Ecopath with Ecosim and Atlantis predict similar policy outcomes?
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Date
2019
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Great Lakes Research
Abstract
Ecosystem simulation models are valuable quantitative decision tools for supporting ecosystem-based
fisheries management. However, the application of ecosystem models in fisheries management is still
undermined by the lack of simple procedures to test the effect of model uncertainty on policy outcomes.
The use of multiple ecosystem models is viewed as ‘‘insurance” against the effects of uncertainty emanating
from modelling complex systems, which calls for investigations to ascertain whether models with different
structure and assumptions can give consistent policy evaluations. We compared two structurallydistinct
ecosystem models, Ecopath with Ecosim (EwE) and Atlantis, for Lake Victoria by varying fishing
mortality of the key functional groups: Nile perch (the top predator) and haplochromines (key prey species).
We compared model behaviour at the ecosystem level and at the level of functional groups, by evaluating
changes in biomass of targeted groups and the consequent effects of changes in target groups on
non-target groups. Results showed qualitative similarities (direction of change) for the major harvested
groups; however, the cascading effects on non-target species varied across models, depending on the species
interaction feedbacks. We conclude that: EwE and Atlantis, despite the huge differences in ecological
processes between the models, can give consistent qualitative advice, which is needed for strategic management
decisions; consistency in the representation of trophic interactions may help to minimize variations
in simulated fishery responses due to model structure. This study helps to highlight scenarios that
are robust to model choice, and for which simpler models (such as EwE) could also provide reliable
advice.
Description
Keywords
EBFM, Ecosystem indicators, Lake Victoria Model, comparison, Multispecies models
Citation
Natugonza, V., Ainsworth, C., Sturludóttir, E., Musinguzi, L., Ogutu-Ohwayo, R., Tomasson, T., ... & Stefansson, G. (2019). Ecosystem models of Lake Victoria (East Africa): can Ecopath with Ecosim and Atlantis predict similar policy outcomes?. Journal of Great Lakes Research, 45(6), 1260-1273.