Leverage points

AWAITING REVIEW

Indicator summary

Summary of indicator structure and function

Definition and/or background

The following is from Fulton et al 2004a -

It has been suggested that there is little value in trying to manage marine ecosystems as a whole as species assemblages and dominance may change dramatically without producing any changes in ecosystem function. Instead management should be focused at the level of “leverage points”, which represent points of interaction between people and particular ecosystem components that influence the quality or quantity of valued products (Bax et al. 1999). This is not necessarily the same as simply managing the interactions directly effecting harvest species. For example, Bax et al. (1999) found that predation on commercial species was not a major influence on fisheries production on the southeastern Australian continental shelf, and so was not suitable as a leverage point. The potential leverage points identified by Bax et al. (1999) were: the amount or rate of discarding of commercial species; and the association of fish communities with certain habitat types. This indicates, that as fish are concentrated around their preferred habitats, the strongest forms of management will be those focused on increasing fisher’s effectiveness (ease with which they reach their quota) without increasing habitat impacts (or effort) (Bax et al. 1999). The role of leverage points as ecological indicators stems from the principle that they give some measure of the state of a crucial part of the ecosystem, otherwise they would be useless as a guide for management actions. Thus, they can not only act as “leverage points” for management to focus on, but they can also direct attention to crucial aspects of system state and as such make sound and useful ecological indicators. This may be especially the case where the definition of “valued products” is extended to include species or system attributes that are of high ecological or intrinsic value rather than specifically commercial fisheries value. However, this particular role for leverage points remains untested.

Attribute

Habitat structure and condition, Community structure and function, Trophic structure, Ecosystem structure and function

Purpose

Fisheries

Data required

The following is from Fulton et al 2004a -

Any data that allows for the evaluation of the true level of influence of a hypothesised leverage point, such data could include:

• Estimates of production
• % cover, presence/absence or abundance of sessile biota
• Diet data
• Biomass or abundance of species or groups in the ecosystem (also allows for the identification of community composition)
• Morphological characteristics of species or groups in the ecosystem
• Carbon or nitrogen isotope ratios
• Physical habitat data (depth, temperature, roughness etc)

Ecosystem applicability

The following is from Fulton et al 2004a -

The methodology should be applicable in any system. However, practicably it will be restricted to systems where there is enough available data to allow for the identification of the “leverage points” for that system.

Robustness

The following is from Fulton et al 2004a -

High: by definition the leverage points have been shown to be interactions with a strong influence on products or system components of high value or interest. The biggest limitation is that there must be enough available data to allow for the identification of the “leverage points” in the first place. Comparison of the values for leverage points in fished and unfished systems (or through time) may make the use of leverage more useful as ecological indicators

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:

Bax, N., A. Williams, S. Davenport, and C. Bulman. 1999. Managing the ecosystem by leverage points: a model for a multispecies fishery. In: Ecosystem approaches for fisheries management: proceedings of the Symposium on Ecosystem Considerations in Fisheries Management, pp 283-303. University of Alaska Sea Grant College Program, no. AK-SG-99-01. Fairbanks, Alaska: University of Alaska Sea Grant Program .

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.

Other references that can be used to update this page

Citation

Page created by:Shavawn Donoghue

Last modified on: Apr 11, 2014 15:21

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