Southwest Atlantic Fisheries Face Climate Chaos Without a Governing Body

The Southwest Atlantic Ocean is one of the most productive and politically fragmented stretches of water on Earth, and a new perspective article argues that this combination has become dangerously unstable. Writing in the journal Discover Oceans, an international team of researchers led by Juliano Palacios-Abrantes of the University of British Columbia warns that the region, which spans 17.65 million square kilometers between 5°N and 60°S, remains one of the few large oceanic areas with no dedicated governance body covering all of its shared resources. As climate change reshuffles fish stocks across national borders and distant-water fleets exploit the resulting gaps, the authors call for an integrated, ecosystem-based regional framework before the region’s ecological and economic assets slip beyond coordinated control.

The oceanographic machinery behind the region’s productivity is extraordinary. Powerful western boundary currents, including the North Brazil Current, the Brazil Current and the Malvinas Current, drive intense mixing between subtropical and subantarctic water masses. Frontal zones, eddies, upwelling cells and massive river discharges combine to fertilize shelf ecosystems that rank among the most productive marine regions worldwide. This physical complexity carves the coast into distinct biogeographic provinces and ecoregions with high endemism, sustaining biodiversity hotspots, migratory corridors and critical habitats for fish, sharks, cephalopods and marine mammals such as southern and humpback whales and orcas. Spawning grounds, nurseries and feeding areas are distributed across and beyond national jurisdictions, meaning that no single country can manage the system in isolation.

The economic stakes are enormous. Designated by the Food and Agriculture Organization of the United Nations as Major Fishing Area 41, the Southwest Atlantic hosts more than 32,000 artisanal and industrial vessels employing 896,000 people. In 2021, catches in these multispecies fisheries were estimated at 2 million tonnes with a landed value of roughly 5 billion dollars. Along northern Brazil, continental shelf waters support small-scale multispecies fisheries, often with limited statistical reporting, while further south industrial fleets from Brazil, Uruguay and Argentina target shared stocks of high commercial value. Seasonal connectivity is striking: in winter, fish, shrimp and squid stocks move northward from the Patagonian and Uruguayan shelves onto the southern Brazilian shelf, where they form a substantial component of the national fishing industry. The result is a catch composition dominated by transboundary and straddling stocks that ignore maritime boundaries drawn by treaty.

On paper, the region’s nations are committed collaborators. Brazil, Uruguay and Argentina are signatories of the United Nations Convention on the Law of the Sea, the Convention on Biological Diversity and the new BBNJ Agreement on marine biological diversity in areas beyond national jurisdiction, which Brazil and Uruguay have ratified. All three cooperate within the International Commission for the Conservation of Atlantic Tunas and belong to the Zone of Peace and Cooperation of the South Atlantic. Yet the record of integrated regional management is thin. The most ambitious experiment, the FAO-established Regional Advisory Fisheries Commission known as CARPAS, coordinated fishery statistics, biological research and stock assessments from 1962 until its abolition in 1997. Its successor in spirit, the bilateral Comisión Técnica Mixta del Frente Marítimo, manages the shared Argentine-Uruguayan fishing zone and is recognized by FAO as the only regional fisheries body in the Southwest Atlantic, leaving Brazil largely outside formal regional arrangements since CARPAS dissolved.

The governance vacuum is most visible in the fight against illegal, unreported and unregulated fishing. The Port State Measures Agreement, a key instrument designed to keep vessels engaged in illegal fishing from landing their catches, has so far been ratified only by Uruguay in the region. Because the three countries share borders, vessels can simply divert to ports in non-member states or opportunistically reflag to domestic registries, a practice known as flag domestication. Between 2016 and 2021, port visits by vessels that reflagged to a domestic flag increased by roughly 27 percent in Brazil and 57 percent in Uruguay. Meanwhile, distant-water fleets from Asia and Europe, armed with state-of-the-art technology and subsidized by their home states, compete unequally with domestic industrial and small-scale fleets for squid, tuna and other valuable resources, exploiting institutional gaps on the high seas at the margins of national jurisdictions.

Geopolitics compounds the problem. The sovereignty dispute between Argentina and the United Kingdom over the Islas Malvinas/Falkland Islands, South Georgia and the South Sandwich Islands and their surrounding maritime areas remains a central obstacle, intensified by the potential exploitation of shared marine resources. More than 42 coastal small-scale fisheries operate along the Patagonian coast of Argentina, most managed independently with little joint research or coordinated, inclusive management. South of 45°S, valuable transboundary stocks such as the southern king crab and stone crab fishery in the Beagle Channel are shared between Argentina and Chile but managed unilaterally, and the South Atlantic Fisheries Commission, which once delivered joint measures, has been suspended since 2020. The authors note that diplomacy from Brazil, Uruguay and Argentina has resisted creating a Regional Fisheries Management Organization, partly out of concern that multilateral regulation could hand a legal foothold to extra-regional actors and dilute national sovereignty over strategic fish stocks.

Data deficits make every one of these challenges harder. Sharks of conservation concern have limited observational coverage, reef fish assemblage structure is understood only in specific sub-regions, deep-sea ecosystems remain virtually unexplored by visual surveys, and fisheries statistics are chronically incomplete, particularly for small-scale fleets across Latin America and the Caribbean. Brazil’s experience is emblematic: from 1990 to 2007 the national environmental institute IBAMA coordinated broad fisheries statistics, but successive institutional reforms disrupted data compilation, producing a near-complete national halt. No sustained national program has been restored, leaving the North and Northeast, where small-scale catches surpass industrial ones and underpin local food security, severely under-monitored. Without systematic monitoring, the status of shared stocks such as seabob shrimp and acoupa weakfish on the Brazil-Guianas shelf remains poorly resolved, impeding any coordinated, climate-ready management.

Climate change is now amplifying every existing pressure. Most of the region has undergone substantial surface warming over the past four decades, and compound events combining marine heatwaves, high acidity and low chlorophyll have increased rapidly in the equatorial and South Atlantic. An intensifying Brazil Current is shifting fish and shellfish assemblages along the Brazilian and northern Argentine-Uruguayan shelves, and catch records reveal a tropicalization of fisheries, with warm-water species becoming more prevalent as cold-water species decline and distributions shift poleward. Under high-emission projections, a weakened Atlantic Meridional Overturning Circulation would warm the South Atlantic further, while changing wind patterns could alter nutrient fluxes, biological connectivity and species distributions. Ecosystem models project that commercially important transboundary species will shift southward, new shared stocks will emerge across exclusive economic zones, and straddling stocks will move proportionally onto the high seas, where unilateral management loses effectiveness and exposure to distant-water fleets and governance conflict rises.

The authors argue that the moment for action is unusually favorable. Brazil is at the center of the global environmental agenda, hosting the UNFCCC COP30 in Belém in November 2025, the third BBNJ Agreement symposium in March 2026 and the UN Ocean Decade Conference in Rio de Janeiro in 2027. At the third UN Ocean Conference in Nice, Brazil helped launch the Blue Nationally Determined Contributions Challenge, a global call to embed the ocean in national climate plans, with climate-resilient fisheries grounded in ecosystem-based management as a key strategy. Existing instruments such as the Port State Measures Agreement and the BBNJ Agreement offer ready-made platforms that can be adapted to regional realities, and the revitalized ZOPACAS, along with scientific networks like ALICMAR, whose members met in 2024 to discuss exactly these themes, could provide neutral arenas where science diplomacy builds trust, shared monitoring systems and joint assessments even amid geopolitical tension.

Ultimately, the researchers contend that a flexible, polycentric regional framework anchored in science-based adaptive management, strengthened data sharing and inclusive participation of fishers, industry, academia and civil society is both feasible and necessary. Far from threatening sovereignty, they argue, a regional organization for cooperative governance could strengthen it, giving Argentina, Brazil and Uruguay a united front to defend shared resources against governance gaps and the advance of distant-water fleets, while negotiated engagement with extra-regional actors proceeds through instruments like the BBNJ Agreement. Bioregionalization of coastal and shelf areas offers a macroscale template for aligning institutions with ecological reality, and a network of transboundary marine protected areas, connected to the high seas and to designated Ecologically and Biologically Significant Areas such as the Atlantic Equatorial Fracture Zone and the heavily fished Blue Hole off Argentina, could boost biodiversity protection, stock recovery and climate resilience. The transformation will take time and political will, the authors acknowledge, but the alternative, remaining reactive while the ocean warms and stocks move, is a future in which one of the world’s great marine regions is managed by no one at all.

Subject of Research: Integrated ocean governance, fisheries management and climate resilience in the Southwest Atlantic Ocean

Article Title: Integrated ocean governance is needed in the Southwest Atlantic Ocean to foster fisheries, conservation and resilience to climate change

Article References: Palacios-Abrantes, J., Llompart, F., Cardoso, L. G., Defeo, O., Gianelli, I., Jaureguizar, A. J., Lopes, P. F. M., Perez, J. A. A., Piccolo, N. I. P., Piola, A. R., Polejack, A., Prado, L. F., & Saraceno, M. (2026). Integrated ocean governance is needed in the Southwest Atlantic Ocean to foster fisheries, conservation and resilience to climate change. Discover Oceans, 3(1), Article 19. https://doi.org/10.1007/s44289-026-00134-4

Image Credits: AI Generated

DOI: 10.1007/s44289-026-00134-4

Keywords: ocean governance, Southwest Atlantic Ocean, fisheries management, climate change, BBNJ Agreement, IUU fishing, marine conservation, transboundary fish stocks, ocean science diplomacy, marine protected areas, ecosystem-based management, small-scale fisheries