System Omnivory Index

AWAITING REVIEW

Indicator summary

Summary of indicator structure and function

Definition and/or background

The following is from Fulton et al 2004a -

The System Omnivory Index (SOI) is a measure of how feeding interactions are distributed in relation to trophic levels (Christensen et al. 2000). The index is the average omnivory index of all consumers weighted by the logarithm of each consumer’s food intake. As a value of SOI close to zero indicates specialist feeders and increases as feeding interactions become more complex, the index characterises the extent to which a system displays web-like features and as such can be used as an indicator of the effects of fishing, which is expected to affect system complexity. SOI has been used in places such as the Eastern Bering Sea (Trites et al. 1999) to identify changes in system structure through time as a result of fishing pressure and environmental change. As with many proposed indicators, trends in the value of SOI (or the comparison of values from fished and unfished areas) will be more informative, with regard to characterising the effects of fishing, than single snapshot values.

Attribute

Ecosystem structure and function, community structure, trophic structure

Purpose

Fisheries

Data required

The following is from Fulton et al 2004a -

• Biomass per species (or group) recorded (preferably at least for the main components of the ecosystem and through time or vs. some reference area)
• Taxonomic data (or at least categorisation of the main components of the system)
• Catch data of species in fishery
• Mortality estimates for each group
• Consumption / Biomass estimates for each group
• Diet data

Ecosystem applicability

The following is from Fulton et al 2004a -

Should be applicable in all ecosystems.

Robustness

The following is from Fulton et al 2004a -

Medium to high: assuming taxonomic resolution and diet composition data is reliable, trends in SOI could be very informative. However, diet composition and sufficient taxonomic resolution of the data are not always present and thus the trophic structure of the models used to derive SOI can have a large influence on the resulting values. Once the true magnitude of this model structure issue has been investigated, or data resolution is of a sufficient grade, SOI should be a useful indicator.

References

Fulton, E.A., Smith, A.D.M., Webb, H., and Slater, J. (2004a) Ecological indicators for the impacts of fishing on non-target species, communities and ecosystems: Review of potential indicators. AFMA Final Research Report, report Number R99/1546.

References that Fulton et al uses for this indicator:

Christensen, V., C.J. Walters, and D. Pauly. 2000. ECTOPATH with ECOSIM: a user’s guide. October 2000 edition. Fisheries Centre, University of British Columbia, Vanouver, Canada and International Centre for Living Aquatic Resources Management, Penang, Malaysia.

Trites, A. W., P. A. Livingston, S. Mackinson, M. C. Vasconcellos, A. M. Springer, and D. Pauly. 1999. Ecosystem change and the decline of marine mammals in the Eastern Bering Sea: testing the ecosystem shift and commercial whaling hypotheses, Fisheries Centre, University of British Columbia, Vancouver, B.C., Canada.

Background reading

Fulton, E.A., Fuller,M., Smith, A.D.M., and Punt, A. (2004) Ecological indicators of the ecosystem effects of fishing: Final report. AFMA Final Research Report, report Number R99/1546.

Citation

Page created by:Shavawn Donoghue

Last modified on: Apr 11, 2014 15:38

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