The Top 12 Biggest Fish in the World

From the gentle, bus-sized Whale Shark to the powerful Great White, the ocean’s largest fish captivate our imagination. For maritime professionals, these giants are more than wonders; they represent navigational hazards, conservation responsibilities, and indicators of ocean health, directly impacting shipping, fishing, and global marine operations.

In the vast, interconnected world of maritime operations, the sea is both a workplace and a living ecosystem. The largest fish species are not merely biological curiosities but active participants in this shared environment. This article explores the twelve biggest fish in the world, connecting their awe-inspiring biology to practical maritime concerns—from collision risks in busy shipping lanes to their role in sustainable fisheries management and global conservation treaties. For seafarers, shipping companies, and maritime regulators, understanding these creatures is part of ensuring safer, more responsible, and sustainable use of our global oceans.

Why Understanding Marine Giants Matters for Maritime Operations

The presence of the world’s largest fish directly influences several key areas of the maritime industry, turning marine biology into a matter of operational and economic importance. First and foremost is the issue of vessel collisions. Slow-moving, surface-dwelling giants like the Whale Shark and Basking Shark are particularly vulnerable to strikes in congested sea lanes. Such incidents can cause significant damage to vessels, leading to costly repairs, operational downtime, and potential safety incidents. Furthermore, as many of these species are protected under international agreements, collisions can result in regulatory scrutiny and reputational damage. Organizations like the International Maritime Organization (IMO).

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The Top 12 Biggest Fish in the World

1. Whale Shark (Rhincodon typus)

• Maximum Recorded Size: 18.8 meters (62 feet), approximately 21.5 tonnes.

• Maritime Significance: The Whale Shark, the largest fish on Earth, is a flagship species for global marine tourism, supporting economies in regions like the Philippines and Ningaloo Reef, Australia. Its predictable surface-feeding behavior in coastal waters, however, creates a significant collision risk with vessels. To address this, some coastal states implement seasonal speed restrictions or recommend route alterations in known aggregation areas. The International Whaling Commission (IWC) and the IMO have collaborated on guidelines to reduce ship strikes on large marine animals, which are directly applicable to protecting this gentle giant. For shipping, awareness of these zones is crucial for both safety and compliance with emerging environmental, social, and governance (ESG) standards.

2. Basking Shark (Cetorhinus maximus)

• Maximum Recorded Size: 12 meters (40 feet).

• Maritime Significance: This colossal filter-feeder, often seen with its mouth agape at the surface, presents a clear navigational hazard, especially for smaller craft in the productive waters of the North Atlantic and North Pacific. Historically, Basking Sharks were heavily targeted for their liver oil, a chapter in maritime history documented in sources like Lloyd’s List archives. Today, they are protected in many jurisdictions. Their recovery is monitored by marine scientists, and their movement patterns can inform Marine Spatial Planning efforts, helping to balance conservation with shipping and renewable energy development in offshore spaces.

3. Great White Shark (Carcharodon carcharias)

• Maximum Recorded Size: 6.4 meters (21 feet).

• Maritime Significance: As the ocean’s most famous apex predator, the Great White Shark influences safety protocols for coastal and offshore activities, including commercial diving, offshore aquaculture, and tourism. Beyond safety, its role as a top predator makes it a critical indicator of ocean ecosystem health. Research institutions like the Woods Hole Oceanographic Institution (WHOI) conduct satellite tagging studies that reveal migratory “highways.” This data is invaluable for scientists and can also inform broader maritime planning, highlighting areas of high biodiversity that may require special management consideration under instruments like the International Convention for the Prevention of Pollution from Ships (MARPOL).

4. Tiger Shark (Galeocerdo cuvier)

• Maximum Recorded Size: 5.5 meters (18 feet).

• Maritime Significance: Known for its indiscriminate appetite, the Tiger Shark is an unwilling indicator of marine pollution. They are frequently found with ingested marine debris, including plastic waste and other refuse that can originate from illegal discharges from vessels. These findings are often cited in reports by the IMO and the UN Environment Programme (UNEP) on the challenges of enforcing MARPOL Annex V (which regulates garbage at sea). For the maritime industry, the plight of species like the Tiger Shark underscores the tangible consequences of poor waste management practices at sea and reinforces the need for strict compliance and crew training.

5. Giant Oceanic Manta Ray (Mobula birostris)

• Maximum Recorded Size: 7-meter (23-foot) “wingspan.”

• Maritime Significance: These intelligent rays are a cornerstone of the high-value dive tourism industry worldwide. Their predictable aggregation at cleaning stations makes their habitats economically important but also vulnerable to disturbance from coastal development and ship traffic. Listed under the Convention on Migratory Species (CMS), member states are encouraged to protect critical habitats. This can influence coastal management plans, potentially affecting regulations for inshore shipping traffic and the environmental licensing of new port infrastructure or coastal industrial projects.

6. Greenland Shark (Somniosus microcephalus)

• Maximum Recorded Size: 7.3 meters (24 feet).

• Maritime Significance: This mysterious, long-lived denizen of the deep Arctic is coming under new pressure due to climate change. As Arctic sea ice recedes, new shipping routes like the Northern Sea Route are opening, increasing the risks of disturbance, pollution, and bycatch for this slow-growing species. The International Association of Classification Societies (IACS) develops unified rules for polar vessel operation (the Polar Code), which include provisions for environmental protection. Understanding the habitat of species like the Greenland Shark is essential for conducting the Environmental Impact Assessments (EIAs) required under this regulatory framework.

7. Megamouth Shark (Megachasma pelagios)

• Maximum Recorded Size: 5.5 meters (18 feet).

• Maritime Significance: Since its dramatic discovery in 1976, this rare filter-feeder has been a prized find for science. Most specimens have been caught as bycatch in deep-sea fishing gear or found washed ashore. Its accidental capture highlights the unintended consequences of global fishing operations on poorly understood pelagic species. Data from these rare encounters helps map deep-water biodiversity, which can inform the designation of Particularly Sensitive Sea Areas (PSSAs) by the IMO—a tool that can restrict certain maritime activities in ecologically unique regions.

8. Great Hammerhead Shark (Sphyrna mokarran)

• Maximum Recorded Size: 6 meters (20 feet).

• Maritime Significance: Critically endangered due to the shark fin trade, the Great Hammerhead is at the center of stringent international trade controls under CITES. Many nations and regions enforce strict “Fins Naturally Attached” policies to combat finning. This places a direct enforcement burden on fishing vessel operators and port state control inspectors, who must be able to identify species and verify compliance. Maritime authorities, including the USCG and AMSA, conduct inspections and interdictions at sea, making this species a focal point in the fight against illegal, unreported, and unregulated (IUU) fishing.

9. Ocean Sunfish (Mola mola)

• Maximum Recorded Size: 3.3 meters (11 feet) long, 2,300 kg (5,000 lbs).

• Maritime Significance: The heaviest bony fish, often seen basking on its side at the surface, is a frequent victim of ship strikes and a species highly susceptible to injury from plastic pollution. Their high bycatch rates in certain fisheries are a documented problem. For mariners, the sight of a sunfish—often scarred by propellers or entangled in debris—serves as a powerful, real-time indicator of ocean health. Their plight reinforces the goals of industry initiatives like the IMO’s GloLitter Partnerships, which aim to reduce plastic litter from the maritime sector.

10. Mako Shark (Isurus oxyrinchus)

• Maximum Recorded Size: Up to 4 meters (13 feet).

• Maritime Significance: The shortfin mako is one of the ocean’s fastest swimmers and a prized catch in high-value commercial and recreational fisheries. Its management involves complex international quota systems set by bodies like the International Commission for the Conservation of Atlantic Tunas (ICCAT). The transshipment of its fins and meat at sea is a monitored activity, and combating illegal trade involves tracking vessels that may use flags of convenience. This makes the mako a case study in the enforcement of international agreements like the Port State Measures Agreement (PSMA), designed to prevent illegally caught fish from entering the global market.

11. Beluga Sturgeon (Huso huso)

• Maximum Recorded Size: 7 meters (23 feet).

• Maritime Significance: While primarily a freshwater species, the Beluga Sturgeon represents the critical intersection of maritime logistics and wildlife trafficking. It is the source of high-value caviar, and with wild populations collapsed, it is listed on CITES Appendix II. All international trade requires permits, making customs authorities at ports and airports key enforcement agents. The illegal transport of its roe is a classic example of how maritime supply chains can be exploited for wildlife crime, requiring vigilance from freight forwarders, shipping lines, and port officials alike.

12. Goliath Grouper (Epinephelus itajara)

• Maximum Recorded Size: 2.5 meters (8.2 feet), 360 kg (800 lbs).

• Maritime Significance: This massive reef fish plays a vital role in coastal ecosystems, including around offshore artificial structures like oil and gas platforms and purposely sunk ships. Its recovery in places like Florida, where it is protected, demonstrates how maritime infrastructure can sometimes function as artificial reef habitat. This relationship is a key consideration in the Environmental Impact Assessments (EIAs) for offshore decommissioning projects and new installations, guided by standards from classification societies like Bureau Veritas (BV) and ABS.

Summary Table: The Ocean’s Largest Fish and Their Maritime Relevance

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Challenges and Practical Solutions for Coexistence

The shared use of the ocean between maritime commerce and marine megafauna creates inherent challenges, but the industry is responding with innovative and practical solutions. The most direct conflict is the risk of vessel collisions, which can be devastating for wildlife and costly for ship operators. In response, the concept of dynamic vessel management is gaining traction. This involves ships voluntarily slowing down or making slight course alterations when large animals are reported in real-time via platforms like the Whale Alert system. On a regulatory level, the establishment of Seasonal Management Areas (SMAs) with mandatory speed restrictions during known migration periods has proven effective in reducing strikes in regions like the Northwest Atlantic. The IMO has disseminated comprehensive guidance on minimizing underwater noise and collisions, which leading shipping companies are increasingly integrating into their Safety Management Systems (SMS) to meet both safety and environmental objectives.

Another significant challenge is bycatch—the accidental capture of non-target species in fishing gear. Large rays, sharks, and sunfish are particularly vulnerable in global fishing operations. Technological innovation is key to mitigation. The development and testing of modified fishing gear, such as hooks that reduce shark catch rates or nets equipped with acoustic deterrent devices, are ongoing, supported by research from the UN Food and Agriculture Organization (FAO) and non-governmental organizations. For the shipping industry that transports the world’s seafood, the demand for full supply chain transparency is growing. Digital tools like blockchain-based catch documentation schemes can help ensure that cargo originates from fisheries using best practices, allowing carriers to verify the sustainability of their shipments and meet the increasing due diligence requirements of clients and regulators.

Finally, the broader degradation of marine habitats from pollution and underwater noise impacts these species’ survival. The maritime sector’s role in pollution prevention is foundational. Strict adherence to MARPOL regulations is the baseline, but industry leadership is moving beyond compliance. Initiatives for advanced wastewater treatment, zero-discharge operations, and effective ballast water management (as mandated by the IMO’s Ballast Water Management Convention) all contribute to healthier marine ecosystems. Furthermore, when planning new port expansions or offshore wind farms, conducting robust Environmental Impact Assessments (EIAs) that specifically evaluate effects on large marine fauna is now standard practice. These assessments, often conducted according to guidelines from classification societies like DNV and RINA, help design projects that avoid critical habitats and minimize acoustic disturbance during construction, paving the way for more harmonious development.

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Case Studies and Real-World Applications

Real-world incidents and initiatives clearly illustrate the stakes and the pathways to sustainable coexistence. A stark example is the 2019 loss of containers from the MSC Zoe in the North Sea. Beyond the immediate logistical crisis, the resulting debris field of plastics and consumer goods posed a severe, long-term ingestion threat to filter-feeding giants like Basking Sharks and ocean roamers like the Ocean Sunfish. This event triggered not only a large-scale cleanup but also a major review of container securing standards (CSC) and stimulated research into oceanographic debris tracking models. It demonstrated tangibly how a single maritime accident can have prolonged ecological consequences for marine megafauna.

On the proactive side, the “Protecting Blue Corridors” initiative led by the World Wide Fund for Nature (WWF), in collaboration with shipping companies and research bodies, exemplifies a partnership approach. This project uses satellite telemetry data from tagged whales, sharks, and rays to map critical oceanic migratory corridors. This scientific data is then shared directly with the commercial shipping community to inform voluntary vessel speed reductions or course adjustments outside of formal regulatory zones. It is a powerful model of how applied marine science, conducted by institutions like the Scripps Institution of Oceanography, can directly feed into practical maritime risk management and conservation strategy.

In the regulatory domain, the management of Atlantic Highly Migratory Species by U.S. authorities offers a comprehensive case study in balancing conservation with use. The management plan includes strict quotas, gear modifications (such as requiring circle hooks to reduce bycatch mortality), and 100% electronic monitoring on certain commercial vessels. This integrated approach, enforced by NOAA Fisheries and the US Coast Guard, aims to rebuild populations of species like the Shortfin Mako while allowing sustainable fisheries to operate. It showcases the complex, science-based governance required to manage shared oceanic resources, a model relevant to regional fisheries management organizations (RFMOs) worldwide.

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Future Outlook and Maritime Trends

The future relationship between the maritime industry and ocean giants will be shaped by technological advancement, stricter regulation, and the overarching challenge of climate change. Enhanced surveillance and monitoring technologies will play a pivotal role. The use of drones, autonomous underwater vehicles (AUVs), and AI-powered analysis of satellite data will allow for near real-time tracking of marine animal aggregations. This information could eventually be integrated directly into bridge navigation systems (ECDIS) as a standard overlay, providing officers of the watch with dynamic, data-driven alerts—a potential future class notation from societies like Lloyd’s Register for “wildlife-aware” navigation.

Regulatory frameworks will continue to evolve and tighten. The IMO is likely to progress from guidelines to more binding measures concerning underwater radiated noise and ship strike mitigation. Concurrently, the financial sector’s focus on sustainable finance will grow. Concepts like “Ocean Accounting,” which quantifies the economic value of ecosystem services, may begin to influence maritime insurance premiums and loan conditions from institutions like the World Bank. Vessels and companies that demonstrably lead in biodiversity protection may secure favorable financial terms, making environmental stewardship a core business advantage.

Finally, the industry’s green transition presents a profound opportunity. The shift toward decarbonization and alternative fuels promises to reduce not only emissions but also underwater noise pollution. Quieter ships will lessen the acoustic disturbance that disrupts the communication, feeding, and migration of large marine life. The development of “Green Shipping Corridors”—zero-emission routes between major hub ports—could be strategically planned to also function as protected migratory pathways, aligning climate action with biodiversity conservation. This holistic approach, supported by research from groups like the International Council on Clean Transportation (ICCT), represents the most promising vision for a future where global trade and the ocean’s majestic giants thrive together.

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Frequently Asked Questions (FAQ)

Q1: What should a deck officer do immediately upon spotting a very large fish or shark near the vessel?
A1: The priority is to ensure the safety of both the vessel and the animal. The officer should immediately notify the bridge team, reduce speed if safe to do so, and consider making a slight course alteration to pass at a safe distance. Reporting the sighting (species, location, direction) to a relevant wildlife sighting network contributes valuable data for scientific and conservation efforts.

Q2: How can a shipping company proactively reduce its risk of colliding with large marine animals?
A2: Companies can adopt several proactive measures: implement crew training programs on species identification and reporting procedures, establish voluntary slow-speed policies in known high-risk areas, subscribe to real-time whale alert services for dynamic voyage planning, and support or participate in research initiatives that map marine animal movements.

Q3: Are there specific international maritime laws that protect these giant fish?
A3: While no single law protects all species, a network of agreements applies. Many are listed under CITES, regulating international trade. Regional Fisheries Management Organizations (RFMOs) set catch limits for commercially targeted species like Mako sharks. Additionally, the IMO’s MARPOL Convention and guidelines on PSSAs help protect critical habitats from pollution and other shipping impacts.

Q4: Why is the issue of large fish relevant to the container or bulk shipping sector, which doesn’t engage in fishing?
A4: All vessels share the ocean and face operational risks like collisions. Furthermore, the maritime industry is under increasing pressure from investors, banks, and charterers to demonstrate strong ESG performance. Showing proactive measures to protect marine biodiversity is becoming a component of corporate reputation, access to green financing, and compliance with the environmental expectations of clients and the public.

Q5: What role do classification societies play in addressing human impacts on large marine species?
A5: Classification societies like DNV and ABS develop voluntary class notations for quiet ship design and other environmentally friendly technologies. They also set the procedural standards for how Environmental Impact Assessments (EIAs) are conducted for offshore projects, ensuring potential effects on marine megafauna are properly evaluated, mitigated, and monitored.

Q6: How is climate change affecting the relationship between these fish and maritime operations?
A6: Climate change is altering ocean temperatures and currents, which shifts the migration patterns and feeding grounds of large fish. This creates uncertainty for seasonal management zones. Simultaneously, melting Arctic ice is opening new shipping routes, bringing vessel traffic and potential pollution into previously undisturbed habitats of species like the Greenland Shark, necessitating new risk assessments and adaptive regulations.

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Conclusion

The twelve biggest fish in the world are living icons of the ocean’s scale and mystery. For the maritime community, they are also dynamic components of the working seascape, presenting challenges and responsibilities that intersect with safety, regulation, and sustainability. From mitigating ship strikes on gentle Whale Sharks to enforcing international trade bans on endangered hammerheads, the industry’s engagement with these species is a measure of its commitment to true ocean stewardship. By embracing accurate knowledge, innovative technology, and proactive planning, the global maritime sector can navigate a course that ensures its operations support, rather than diminish, the health of the marine ecosystems we all depend on. The future of shipping is inextricably linked to the future of the ocean, and protecting its most magnificent inhabitants is a responsibility we all share.

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References

1. International Maritime Organization (IMO). (n.d.). Guidelines for the reduction of underwater noise from commercial shipping to address adverse impacts on marine life. Retrieved from https://www.imo.org

2. International Maritime Organization (IMO). (n.d.). Particularly Sensitive Sea Areas (PSSAs). Retrieved from https://www.imo.org

3. DNV. (2023). Maritime Impact Report: Navigating the future of ocean sustainability. Retrieved from https://www.dnv.com

4. Lloyd’s Register. (2022). Ship Strike Prevention: Technologies and Operational Practices. Retrieved from https://www.lr.org

5. United Nations Food and Agriculture Organization (FAO). (2022). The State of World Fisheries and Aquaculture (SOFIA). Rome. Retrieved from https://www.fao.org

6. Woods Hole Oceanographic Institution (WHOI). (2023). Shark Research and Conservation. Retrieved from https://www.whoi.edu

7. Marine Pollution Bulletin. (Various). Studies on marine debris ingestion and vessel interactions. Elsevier.

8. International Council on Clean Transportation (ICCT). (2023). The climate and environmental impacts of Arctic shipping. Retrieved from https://theicct.org

9. World Wide Fund for Nature (WWF). (2023). Protecting Blue Corridors: A global network for migratory species. Retrieved from https://www.worldwildlife.org

10. U.S. Coast Guard (USCG). (n.d.). Living Marine Resources: Enforcement. Retrieved from https://www.uscg.mil

11. Australian Maritime Safety Authority (AMSA). (n.d.). Marine environment protection. Retrieved from https://www.amsa.gov.au

12. Scripps Institution of Oceanography. (2023). Ocean Animal Tracking. Retrieved from https://scripps.ucsd.edu