Are trends in species occupancy or an index of biotic integrity more useful for guiding fish conservation planning?

Numerous ecological indicators are used in environmental assessment, but these indicators often fail to yield the information managers require. There is a need for analyses of how well ecological indicators capture information required for effective environmental management. We analysed the information content of New Zealand's Fish Index of Biotic Integrity ( FIBI ). National policy directs the monitoring of FIBI trends to determine the magnitude and direction of change in fish communities, to support state-dependent decisions and reporting of progress towards policy objectives. We compared multi-decadal, national trends in FIBI with trends in the occupancy of species comprising the FIBI . FIBI exhibited only a ‘ small decline’ over four decades. In contrast, we infer ‘ very large’ and ‘ large declines’ in the occupancy of over 50 % of the species analysed. Trends in FIBI obscured evidence for increases in the occupancy of some species. We explain how the tendency of FIBI to obscure and underrepresent species trends impedes catchment management. These impediments are unlikely to be fixed through refinements to the statistical framework of FIBI . Rather than argue for adjustments to the index, we argue for analysis and reporting of species trends. We demonstrate how species trends can be reported to stakeholders in a simple, uncomplicated way, overcoming limitations of the FIBI with no extra cost and with minimal trade-offs. Although it is difficult to recommend FIBI for reporting species trends, it retains utility as an assessment tool, and we argue that complementary use of an improved FIBI alongside species trends best facilitates assessment. • Fish Index of Biotic Integrity ( FIBI ) underrepresents and obscures species trends. • Factors eroding FIBI 's sensitivity to species trends are highlighted. • Trends in species occupancy better facilitate catchment management. • Species trends can be reported in simple, informative ways, at no extra cost.