Measuring change in fish communities: from monitoring to metrics to management Report of a workshop and recommendations for research

Ecological monitoring programs are often designed to provide information on the status and/or trends of populations, communities, and ecosystems that are of interest to natural resource managers. The information these programs provide is then used by managers to make management decisions (i.e. increase or decrease extraction levels, allow or restrict access), and at the same time can be used to evaluate the effectiveness of such actions. To be most useful, monitoring programs need clear and meaningful response metrics, which can be complex for ecosystem or community monitoring programs. In recent years, a number of peer-reviewed studies have used biomass as the primary response metric for reef fish community monitoring programs, and this metric is currently being considered as a response or performance measure for National Coral Reef Monitoring Program of NOAA’s Coral Reef Conservation Program. However, to date there has been no critical evaluation of the utility of biomass-based metrics or comparison with possible alternative or complementary metrics to describe the status of these complex communities. To address this need, we have initiated a project to evaluate the utility of biomass-based metrics and their relationship to other population and community response variables and determine the relative strengths and weaknesses of different metrics for different questions and situations. For this preliminary report, we outline the results of a workshop that included NOAA and academic scientists. The goals were (1) to clearly frame the difficulties of creating appropriate response metrics for complex monitoring programs, (2) identify a range of potential metrics, (3) develop a conceptual analytical framework to evaluate candidate metrics, and (4) outline a workplan for a future project designed to address this research question. In addition, we allocated resources before and after the workshop to assemble datasets from three major NOAA coral reef fish monitoring programs. We found that biomass is only one of many potential responses that may have utility for understanding changes in fish communities, and that the outcomes are likely to be highly context dependent. Other potentially useful responses include abundance and biomass of key subsets of the community, as well as more derived metrics such as size spectra. We also include the major management uses for monitoring programs, the specific information they require, as well as a list of the important attributes for all potential metrics, their links to management, and the key challenges to using each metric. We outline the required next steps to determine which metric, or likely collection of metrics, will be most useful in describing the status and changes of reef fish communities worldwide.