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Importance of trophic information, simplification and aggregation error in ecosystem models

Metcalf, SJ, Dambacher, JM, Hobday, AJ and Lyle, JM 2008 , 'Importance of trophic information, simplification and aggregation error in ecosystem models' , Marine Ecology - Progress Series, vol. 360 , pp. 25-36 , doi:

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Ecosystem models are becoming increasingly important as pressure from fisheries
intensifies and ecosystem-based fisheries management becomes more widely used. Trophic webs
often form the basis of ecosystem models and ecosystem-specific dietary information is crucial for
optimal model performance. This is particularly the case if model predictions are used in management
decisions. The Tasmanian live fish fishery for banded morwong was used as a case study to
investigate the importance of trophic information, model simplification and aggregation error on
ecosystem model results. Dietary analysis of 6 commonly captured reef fish was undertaken. Significant
trophic overlap was found between blue throat wrasse Notolabrus tetricus and purple wrasse
N. fucicola, and banded morwong Cheilodactylus spectabilis and bastard trumpeter Latridopsis
forsteri. Marblefish Aplodactylus arctidens and long-snouted boarfish Pentaceropsis recurvirostris
had significantly different diets from other species studied. Using this information, a detailed qualitative
model was produced and then simplified through the aggregation of variables. Variables were
aggregated using 3 methods: Euclidean distance, Bray-Curtis similarity, and regular equivalence for
inclusion in 3 simplified models. Variable aggregation is undertaken in many studies and may create
aggregation error. Each aggregation method produced a different proportion of incorrect model
predictions as a result of aggregation error. The model simplified using regular equivalence produced
the least aggregation error and a web structure aligned with the dietary analysis. More widespread
use of these methods in fisheries management should be considered.

Item Type: Article
Authors/Creators:Metcalf, SJ and Dambacher, JM and Hobday, AJ and Lyle, JM
Keywords: Diet · Qualitative modelling · Model structure · Regular equivalence
Journal or Publication Title: Marine Ecology - Progress Series
ISSN: 0171-8630
DOI / ID Number:
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