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Abstract Climate change and fishery impacts modify the spatial distribution of marine species. Understanding and predicting changes in distribution is important for adaptation by fishers and the management of fishery resources and biodiversity. However, identifying such trends is challenging given the variability inherent in trawl survey data. We apply a novel two-step approach to identify fish distribution trends from trawl surveys. First, species-specific average locations (mean latitude and longitude centre of gravity) and extent (effective area occupied) were estimated within a spatio-temporal delta modelling framework. The resulting time series and associated variance estimates were then passed to a multivariate Bayesian state-space model to estimate average trends over the study period. We applied this two-stage approach to three decades (1986–2016) of demersal trawl research survey data from the Agulhas Bank of South Africa to quantify distributional changes in 44 commonly caught fishes (chondrichthyans and teleosts). Across the entire assemblage, average trends showed a westward (alongshore) shift in location and a reduction in the extent of populations. At the species level, six taxa showed a location trend towards the west or south-west, and three shifted towards the east or north-east. The area occupied by species showed two taxa that had a decreasing trend in spatial extent and one species that was expanding. The mean westward and contracting trends of the assemblage were interpreted as likely signals of climate forcing, whereas the eastward shift of three species may be linked to fishing impacts. A lack of knowledge of subsurface oceanographic changes in the region challenges interpretation of the distribution changes and is identified as a research priority. We recommend additional research regarding causal drivers of distribution shifts, specifically to attribute observed changes to climate, fishing, and inter-annual environmental variability. [ABSTRACT FROM AUTHOR]

One of the stated applications of the IUCN Red List of Ecosystems (RLE) is to influence government policy and decision-making. We share 15 years' experience in integrating an independently developed indicator of ecosystem threat status into government policies and practice. South Africa's ecosystem threat status indicator was conceptualised in the early 2000s and progressed from a project-based indicator to listing of threatened ecosystems in terms of national legislation in 2011. We show the range of applications of the indicator, from its use as a headline indicator in the National Biodiversity Assessment to its role as a direct trigger for Environmental Impact Assessment. The strong link between threatened ecosystems and systematic conservation planning in South Africa also enabled ecosystem threat status to inform multi-sectoral development planning and decision-making. We show how bridging products, data availability, persistent mainstreaming and stakeholder engagement have encouraged the use of the indicator in government policy. The advantages and disadvantages of legislative listing are shared. Sound scientific foundations, combined with pragmatism, have provided a policy-relevant tool for focussing management on threatened ecosystems. We make active recommendations that will facilitate the policy uptake of the IUCN RLE in other countries. [ABSTRACT FROM AUTHOR]