Aim To present an updated database of fish species recorded on south‐western Atlantic reef environments and to explore the ecological drivers of the structure, the latitudinal gradient of biodiversity and the centre of endemism in this peripheral province. Location South‐western Atlantic (SWA): Brazilian and Argentinian Provinces. Methods A database composed of 733 fish species along 23 locations in the SWA (00°55′ N to 43°00′ S) was compiled based on primary data, literature and museum records. Cluster and beta diversity analyses were carried out to evaluate faunal overlaps among locations and subprovinces. “Target‐area‐distance effect” and “stepping stones dispersal” hypotheses for assemblage composition were tested through Mantel tests. Relationships between the distribution patterns and ecological traits of reef fish species were investigated through generalized linear mixed‐effect models. Results Out of the 733 fish species, 405 are SWA resident reef fishes, of which 111 (27%) are endemics and 78 are threatened with extinction. Cluster analysis detected six subprovinces in the SWA structured following the target‐area‐distance model, and with no evidence for a latitudinal gradient in diversity. The greatest overall richness and endemic species richness were found in the east–south‐eastern region. Depth range, habitat use and body size were the main drivers of SWA reef fish assemblage structure. Main conclusions The Brazilian and Argentinian coasts constitute different provinces structured by oceanographic barriers and environmental filters. Similarities among oceanic islands indicate connectivity driven by stochastic and ecological factors. Species richness and endemism indicate that peripheral provinces may also bear centres of origin and biodiversity, patterns driven by parapatric/ecological speciation and the overlap between tropical and subtropical reef fish species. Ecological drivers of reef fish distribution, such as habitat specialization and body size, support hypotheses of speciation in the periphery. New approaches for spatial planning, marine protected areas and off‐reserve marine management are essential for the conservation and sustainability of SWA reef fishes.

HIGHLIGHTS• The Anthropocene compels unlocking of ocean-related network capabilities.• Orchestration of local, regional, and global knowledge networks can augment transformative capacity.• Transdisciplinary network diagnostics are promising social learning tools.• Strategic advice for transformational research in ocean territories are provided. This paper dedicates to understanding of what is needed to achieve the transformation of ocean governance. Based on the theory of transformative agency conceptualized in a multi-level governance context, we build on recent novel inter-and transdisciplinary research in Brazil to explore the opportunities for transformation in the dynamic, complex, and multi-level field of ocean governance. We focus this analysis on three transformation processes toward developing a socially and ecologically coherent marine protected area network as the core of a marine spatial planning process for enhanced ecosystem-based polycentric governance of the country's Exclusive Economic Zone. The findings illuminate leverage points for achieving (much needed) transformation in Brazilian ocean governance and potentially beyond. These include: connecting transformative actions into coherent narratives and testing strategic advice derived from theories of transformative agency to promote regime shifts in ocean governance systems; setting of more ambitious social mobilization targets; fostering orchestration of knowledge-networks considering multiple issues, territorial and institutional levels; implementing institutional learning experiments; supporting transformational trajectories toward co-evolutionary, polycentric, ecosystem-and area-based ocean governance systems; and pursuing gradual, incremental structural understanding of Gerhardinger et al. Healing the Blue Amazon with Knowledge-Action Networks a given knowledge network field as a major driver of catalyzing transformative change. Hereby, this article advances understanding of how to better navigate the transformation toward enhanced sustainability in an important part of the Atlantic and hence of our global ocean.

Global biodiversity declines and increasing rates of extinction necessitate the assessment and prediction of the vulnerability of species to extinction. Here, we examine the relationships between conservation status and ecological traits of reef fish species of the Brazilian biogeographical province. We used binomial tests and a logistic regression to address two questions. Do biological attributes differ between threatened and non-threatened fishes? Which combination of traits and impacts exerts greater influence on species threat status? Of the 559 species, 36 are categorized as threatened (compiled from global, national and local Red Lists). Three species are categorized as Critically Endangered, seven as Endangered and 26 as Vulnerable. Our analyses revealed that Elasmobranchii, sexchanging bony fishes and endemic species are the most vulnerable reef fishes in Brazilian waters. Body size and trophic category were identified as good predictors of the vulnerability of a species to extinction. Small-bodied species that are exploited by the ornamental trade and have complex reproductive strategies are also of concern. Such combinations of attributes could be of value in predicting which reef fish species elsewhere have a high risk of extinction.

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Decision-makers focus on representing biodiversity pattern, maintaining connectivity, and strengthening resilience to global warming when designing marine protected area (MPA) systems, especially in coral reef ecosystems. The achievement of these broad conservation objectives will likely require large areas, and stretch limited funds for MPA implementation. We undertook a spatial prioritisation of Brazilian coral reefs that considered two types of conservation zones (i.e. no-take and multiple use areas) and integrated multiple conservation objectives into MPA planning, while assessing the potential impact of different sets of objectives on implementation costs. We devised objectives for biodiversity, connectivity, and resilience to global warming, determined the extent to which existing MPAs achieved them, and designed complementary zoning to achieve all objectives combined in expanded MPA systems. In doing so, we explored interactions between different sets of objectives, determined whether refinements to the existing spatial arrangement of MPAs were necessary, and tested the utility of existing MPAs by comparing their cost effectiveness with an MPA system designed from scratch. We found that MPAs in Brazil protect some aspects of coral reef biodiversity pattern (e.g. threatened fauna and ecosystem types) more effectively than connectivity or resilience to global warming. Expanding the existing MPA system was as cost-effective as designing one from scratch only when multiple objectives were considered and management costs were accounted for. Our approach provides a comprehensive assessment of the benefits of integrating multiple objectives in the initial stages of conservation planning, and yields insights for planners of MPAs tackling multiple objectives in other regions