Downscaling global reference points to assess the sustainability of local fisheries

Abstract

Multispecies coral reef fisheries are typically managed by local communities who often lack research and monitoring capacity, which prevents estimation of well-defined sustainable reference points to perform locally relevant fishery assessments. Recent global advances in modelling coral reef fisheries have developed pathways to use environmental indicators to estimate multispecies sustainable reference points. These global reference points are a promising tool for assessing data-poor reef fisheries but need to be downscaled to be relevant to resource practitioners. Here, using a small-scale multispecies reef fishery from Papua New Guinea, we estimate sustainable reference points and assess the sustainability of the fishery by integrating global-scale analyses with local-scale environmental conditions, fish catch, reef area, standing biomass estimates, and fishers perceptions. We found that assessment results from global models applied to the local context of our study location provided results consistent with local fishers perceptions. Specifically, our downscaled results suggest that the fishing community is overfishing their reef fish stocks (i.e., catching more than can be sustained) and stocks are below BMMSY (i.e., below biomass levels that maximize production), making the overall reef fishery unsustainable. These results were consistent with fisher perceptions that reef fish stocks were declining in abundance and mean fish length, and that they had to spend more time finding fish. Our downscaled site-level assessment reveals severe local resource exploitation, whose dynamics are masked in national-scale assessments, emphasizing the importance of matching assessments to the scale of management. More broadly, our study shows how global reference points can be applied locally when long-term data are not available, providing baseline assessments for sustainably managing previously un-assessed multispecies reef fisheries around the globe.