Potential ecosystem indicators for th

1) Ecosystem indicators are a way of reducing ecosystem complexity into a form that is most informative and useful to management. As a means of turning data into information, indicators are ultimately a communication tool facilitating science-based governance, i.e. the sustainable use of WCPO tuna resources and the conservation of associated species. 2) One framework suggested for the development of quantitative ecosystem indicators is PSR: Pressure-State-Response. This approach attempts to identify key forcing variables (e.g. oceanographic indices, fishing mortality), measures of system state, for the ecosystem and for individual components (e.g. stock status for target species) and indicators of system response to the pressures identified and to management action. 3) Appropriate methodologies for the derivation of indicators include univariate, bivariate and multivariate data analysis. These allow the investigation of single properties, the comparison of two or more properties (usually to investigate cause and effect), and the derivation of single indicators describing multiple series collectively representing the ecosystem as a whole. 4) In developing ecosystem indicators we must bear in mind the divisions of responsibility between ecosystem science and resource management. Scientists can suggest what analyses are feasible and sensible to do while resource managers must determine what scientific information they want, alongside other information concerning stakeholder priorities, how to reconcile different interests and decide on appropriate action. This is particularly so under an ecosystem approach to fisheries management, which requires value judgements based on economic, ecological and social trade-offs. 5) In conclusion, indicators will be important to identify ecosystem fluctuations affecting fisheries performance (e.g. potential changes in yields) and ecological impacts of fishing. The development of ecosystem indicators should allow all stakeholders (managers, investors, fishers, conservationists and other communities) to identify and better understand natural and fishery induced changes in marine ecosystems.