Country scale assessments of coastal fish communities and drivers for sustainable socio-ecosystem management

Tropical coastal marine ecosystems, such as coral reefs, mangroves, and seagrass beds, harbor a significant portion of marine biodiversity and productivity, providing essential ecosystem services to human societies, including food and fisheries resources. However, global changes are causing rapid degradation of these ecosystems, resulting in the loss of ecological functions, habitats, and resources, which threaten both ecosystems and human societies. Successful examples of localized ecosystem and resource management exist, but generalizing these at larger, country and regional scales, which are relevant to strategic decisions, remains challenging. Identifying appropriate management measures is often difficult because ecosystem resilience is driven by various ecological processes that can be disrupted by a multitude of environmental stressors, including local pressures from fishing, habitat degradation and destruction, and global climate change, whose prevalence can vary across sites and species. We use a country-scale collaborative science approach to quantify long-term changes in fish communities, assess the efficiency of current management, and identify critical stress thresholds for sustainable management in the broad and biodiverse coastal system of New Caledonia. Our analyses characterize the distribution, composition, and abundance-biomass trajectories of key fish communities at various scales around the archipelago to shed light on local management successes and failures, as well as the mechanisms underlying resilience, to advise management decisions. Carried out in close collaboration with local communities, this work contributes to the development of sustainable management and conservation plans for New Caledonia’s exceptional coastal marine ecosystems and fish resources, which are listed as a UNESCO World Heritage site.