PROTECTING

marine Megafauna

Global Tracking of Marine Megafauna Reveal Critical Insights for their Conservation

We are pleased to have contributed to the global tracking study on marine megafauna, published in June 2025 in Science. Led by Ana Sequeira (Australian National University) and an international team of 376 co-authors, including CORDIO Director Melita Samoilys, the study analysed movements of over 15,000 individuals from 121 species across three decades. The findings reveal that despite their vital ecological roles, marine megafauna face widespread exposure to threats such as overfishing, shipping, plastic pollution and climate change. Alarmingly, even ambitious targets to protect 30% of the ocean will leave many critical habitats unprotected. The study underscores the urgent need for integrated conservation strategies that combine expanded marine protected areas with stronger global mitigation measures.

The Study

Marine megafauna—large, highly mobile ocean animals like sharks, whales, turtles, seabirds and seals—play vital roles as ecosystem engineers and climate sentinels. They regulate food webs, support nutrient cycling, and contribute to the health and resilience of ocean ecosystems. However, many of these species are threatened with extinction, facing pressures from overfishing, ship strikes, pollution and climate change.

To inform more effective conservation strategies, a robust global telemetry dataset was assembled, tracking 15,845 individuals from 121 species across over three decades. This MegaMove project effort revealed that about 66% of the space used by these animals serves as crucial migratory corridors or residence areas, collectively termed Important Marine Megafauna Areas (IMMegAs). 

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Findings

To address data gaps on large-bodied fish populations in the WIO, the researchers developed a rapid survey method using underwater visual census (UVC) techniques. They conducted timed long swims on SCUBA to estimate fish densities and biomass across seven regions, including protected and unprotected sites. Survey locations spanned 27 sites in seven countries, covering areas with various levels of marine protected area (MPA) enforcement, from unmanaged sites to those with strong protection and restricted access, such as the Chagos Archipelago and Iles Glorieuses. The team assessed population densities of ten targeted fish groups—both pelagic, demersal and large bodied single species—focusing on those over 55 cm in length. They also compared data across protection levels using zero-inflated negative binomial (ZINB) modeling and other statistical analyses to evaluate the effectiveness of the protection index on fish densities.

Key Highlights

An illustration of global space use of marine megafauna and time spent in different behaviors.

Recommendations

Humpback whale (Megaptera novaeangliae) in the waters of Tonga (Stock Photo |Envato Elements).

The study clearly shows that increasing area-based protections alone, even to the ambitious 30% target, will not be sufficient to safeguard marine megafauna. Instead, an integrated approach combining spatial protection with comprehensive mitigation strategies is urgently needed. Key recommendations include:

  • Enhanced fisheries management: Reduce direct mortality by enforcing fishing thresholds and gear modifications, strengthening standards, and increasing oversight and enforcement of fishing practices.
  • Shipping mitigation: Implement wildlife-ship traffic separation schemes and vessel slow-down areas to lower the risk of collisions and reduce noise pollution, especially in critical migratory corridors and residency areas.
  • Strengthened national action in EEZs: Take advantage of the fact that most marine megafauna spend significant time within national waters, enabling individual countries to introduce targeted management and mitigation measures under their jurisdiction.
  • Improved high seas governance: Integrate Important Marine Megafauna Areas (IMMegAs) into global agreements, such as the United Nations Convention on the Law of the Sea (UNCLOS), to ensure better regulation of biodiversity beyond national jurisdictions.
  • Private sector engagement: Engage and better regulate industry actors, recognizing that private sector policies (e.g., shipping safety standards or whaling moratoriums) can play critical roles in reducing threats and enabling species recovery.
  • Systematic conservation planning: Design future networks of Marine Protected Areas (MPAs) using a systematic framework that complements existing protections, incorporates IMMegAs, and accounts for ecological representativeness, equity, and environmental justice.
  • Comprehensive threat mitigation beyond spatial protection: Address pervasive threats like plastic pollution and climate change through global and national policies, recognizing that these cannot be resolved solely through area-based conservation measures

Learn more about the marine megefauna movement, MegaMove, at www.megamove.org.

Article DOI: https://doi.org/10.1126/science.adl0239