Indicator summary

Summary of indicator structure and function

Definition and/or background

The following is from Fulton et al 2004a -

Ecological studies have suggested that ecosystems evolve in a succession of stages of maturity (Odum 1969) so as to increase control system feedback, internalise flows and increase the specialisation and number of constituent components (Christensen 1992). It is believed that fisheries reduce the maturity of an ecosystem, by destroying its physical structure and shifting community composition to r-selected species. The ratio of total primary production to total biomass is a model-derived indicator thought to be a function of the “maturity” of the system (Christensen et al. 2000). This is because, in immature systems production exceeds respiration and this allows the system to evolve by accumulation biomass (and thus the ratio decreases as the system moves from an immature to a mature state). By tracking the value of this ratio through time or by comparing the value at fished and unfished sites, it may be possible to detect large-scale ecological effects of fishing (via changes in the value of the ratio).

Attribute

Ecosystem structure and function

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: by itself P/B can be confounded by other maturity altering forces on the system and may not show only the effects of fishing. Further, as a model-derived indicator it is reliant on the assumptions used to construct the underlying model and the data used to parameterise and initialise the model. This makes it unsuitable as a predictive indicator, but this does not prevent it from being an informative indicator, especially if it is part of a larger suite of indicators. Thus, as one of a set of indicators it may be useful for characterising ecosystems and how they change.

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. 1992. Network analysis of trophic interaction in aquatic ecosystems.  55 p . ICLARM Contribution, 835ICLARM.

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.

Odum, E. P. 1969. The strategy of ecosystem development. Science 164, no. 18 April: pp 262-70.

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.

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