The ocean’s vast expanse is home to incredible journeys, with many marine species embarking on epic migrations across international borders and even entire ocean basins. These highly migratory marine species, including fish, marine mammals, reptiles, and seabirds, travel thousands of miles in search of food, breeding grounds, or optimal temperatures. While these journeys showcase their resilience and adaptability, they also make these species particularly vulnerable to threats like overfishing and habitat degradation.
Dive in as we explore eight remarkable examples of highly migratory marine species and the challenges they face in today’s oceans.
Sooty Shearwater
Habitat: Open ocean between sub-tropical and sub-antarctic waters.
Distance covered each year: Up to 40,000 miles (64, 400 km).
The Sooty Shearwater is the most highly migratory marine species on Earth. This seabird species undertakes an annual figure-eight migration, likely facilitated by global wind circulation and the Coriolis effect. During migration, they can cover an impressive 620 miles (1,000 km) daily. They travel from breeding sites in the Southern Hemisphere to abundant feeding grounds in the North Pacific Ocean. Upon reaching cooler northern waters, they settle in one of three wintering grounds, where they stay for the remainder of the cycle.
Sooty Shearwaters typically stay far from land, except during breeding season when millions gather in nesting colonies on islands near New Zealand, Australia and Chile. The return journey involves utilizing easterly trade winds again, with a highly synchronized crossing of the equator. This migration allows Sooty Shearwaters to experience a perpetual cycle of spring, summer and autumn. This allows them to capitalize on peak marine resources in both hemispheres throughout the year and may have evolved as a strategy to cope with fluctuations in food availability, particularly during El Niño events.
Blue Whale
Habitat: Across all the world’s oceans except the Arctic Ocean.
Distance covered each year: 18,000 miles.
The Blue Whale is the largest migratory marine species on Earth. They generally migrate seasonally, spending summers in feeding grounds and winters in breeding grounds. For example, the timing of their migration is influenced by both prey availability and environmental factors, particularly sea surface temperature. Blue Whales appear to use the memory of previous years’ temperature patterns to anticipate krill abundance and time their arrival at feeding grounds. However, some individuals may not migrate at all, depending on local conditions.
Interestingly, their vocalizations also change with their migratory and reproductive cycles. Male Blue Whales sing at night during the summer feeding season but switch to daytime singing during their southward migration to breeding grounds. Further research is needed to confirm the direct link between singing and migration. However, if established, Blue Whale song could serve as an “acoustic signature of migration,” aiding conservation efforts by predicting migration timing and reducing the risk of ship strikes.
Humpback Whale
Habitat: Across the world’s oceans.
Distance covered each year: Up to 16, 000 miles (25,750 km).
Humpback Whales are arguably the champions of long-distance migration among mammals. These marine mammals journey between cold-water feeding grounds in the summer and warm-water breeding grounds in the winter. They travel at a leisurely pace of three to five miles per hour and can cover up to 100 miles in a single day.
During their three-week to two-month seasonal migrations, Humpback Whales rarely eat. Instead, they rely on the blubber reserves they accumulated before their journey. Their primary food source is krill, tiny shrimp found in the icy Arctic and Antarctic waters.
The reasons behind these extensive journeys are still debated, but scientists suggest that warmer waters might help this migratory species conserve energy during the winter. Another possibility is that migration serves as a defense against Killer Whale predation, as shallow, warm waters offer Humpback Whales a better chance of fending off attacks.
Leatherback Turtles
Habitat: Across the Atlantic, Pacific and Indian Oceans.
Distance covered each year: Over 12,000 miles (19,300 km).
The Leatherback Turtle is one of the most highly migratory marine species in the world. These sea turtles navigate using the Earth’s magnetic field, and a unique pink spot on their heads may aid in this process by allowing light to reach their pineal gland, which influences their perception of day length and seasons. This, combined with temperature changes, might signal migration time.
Atlantic populations journey from Caribbean nesting beaches to Canadian foraging grounds, while Pacific populations travel from Southeast Asia to California and even Alaskan waters. Contrary to previous assumptions, male and female Leatherbacks migrate together. This shared journey exposes them to the same threats such as plastic pollution and entanglement in fishing gear.
Blue Marlin
Habitat: Tropical and sub-tropical waters of the Pacific, Atlantic and Indian Oceans.
Distance covered each year: Over 9,200 miles (14, 800 km).
Blue Marlin undertake extensive migrations across the Atlantic Ocean, highlighting the marine connectivity between populations in the eastern and western Atlantic. Their migrations are influenced by seasonal changes in environmental conditions and prey distribution. While some individuals make trans-Atlantic journeys, others exhibit strong site fidelity, returning to specific locations year after year.
Blue Marlins shift their season range towards offshore areas and lower latitudes during winter months. This movement is closely linked to their preference for warm surface waters, typically exceeding 22.9℃. The warmth not only encourages them to venture further offshore but also appears to correlate with deeper daytime dives, suggesting a potential influence on their physiology or prey distribution.
Atlantic Salmon
Habitat: Across the Arctic and Atlantic Ocean, spawning in European and North American rivers.
Distance covered each year: Over 6,000 miles (9,600 km).
The Atlantic Salmon undertakes an epic journey that spans hundreds, even thousands, of miles. Their journey begins in freshwater streams, where they hatch and spend their early years. Driven by navigation cues, they then migrate downstream to the ocean, providing a rich source of food that allows them to grow rapidly. Larger fish have a better chance of survival and reproduction, with females producing more eggs. This abundance of offspring is vital for sustaining the population.
After several years at sea, this highly migratory marine species embarks upon a return journey to their natal streams to spawn. This homing instinct is guided by a combination of the Earth’s magnetic field and their keen sense of smell. This migration isn’t without its challenges. Dams, hydroelectric plants, and poorly designed culverts compromise migratory connectivity, preventing them from reaching essential habitats. To aid their passage, fish ladders and bypass structures are often constructed to help them navigate these obstacles. Unlike other salmon species, the Atlantic Salmon can survive spawning and return to the ocean to repeat the cycle.
Pacific Bluefin Tuna
Habitat: Across the Pacific Ocean.
Distance covered each year: 5,000 miles (8,050 km).
Young Pacific Bluefin Tuna embark on a remarkable journey known as the “Trans-Pacific Migration,” which can take as little as 55 days. Their exceptional swimming speeds, reaching 12 to 18 miles per hour, are attributed to their streamlined bodies and powerful muscles. These marine fish travel from their spawning grounds off the coast of Japan to the shores of California, spending several years traveling up and down the coast, from Mexico to as far north as Washington State. After several years of feeding and growing, this migratory marine species makes the same journey in reverse to spawn.
This migration takes them through Arctic waters where their specialized blood vessel network, a counter-current heat exchange system, helps to keep them warm. The fact that more Pacific Bluefin Tuna migrate across the Pacific than previously thought has significant implications for effective management of the fishery. Any catch limits imposed by the United States and Mexico will directly affect the number of Pacifc Bluefin Tuna that survive to reproduce in Japan.
Great White Shark
Habitat: Temperate to tropical waters across the world’s oceans.
Distance covered each year: Over 2,500 miles (4,025 km).
Great White Sharks are known for their seasonal migrations, often traveling vast distances at speeds of up to 35 miles per hour. These wide-ranging migrations are driven by various factors, including food availability, mating opportunities and temperature preferences. Their habitat preferences shift with age: younger sharks favor warmer, shallower coastal areas, while adults venture further offshore and into pelagic zones, often targeting seal and sea lion colonies.
DNA and tracking data from this highly migratory marine species suggest distinct migration patterns. Males tend to roam more widely, whereas females appear to stay closer to specific locations. Great White Sharks also migrate between Australia and South Africa, however, these populations are distinct and don’t interbreed. Atlantic Ocean Great White Sharks have predictable annual migrations between the northern and southern parts of their range. They spend summer and fall in coastal waters off New England and Atlantic Canada, feeding on seals, before moving to warmer winter waters off the southeastern U.S.
Ocean Insights: Hear From Our Experts
By Dr. Rabiah Ryklief
Principal Scientist and Lecturer of Marine Science, with a PhD in Zoology
Migratory marine species often undertake extensive journeys, sometimes spanning hundreds of kilometers across multiple exclusive economic zones (EEZs) and even into the high seas. This transboundary movement, especially prevalent in pelagic-oceanic species, poses a significant challenge for fisheries management and nature conservation. Traditional area-based management tools, such as Marine Protected Areas (MPAs), are often confined within national EEZs, making it difficult to effectively protect species that move beyond these boundaries.
This mismatch between regulatory boundaries and species distributions necessitates international collaboration to ensure the long-term ecological, social, and economic benefits of shared marine species. Understanding how these species use different areas throughout their life cycle is crucial for effective conservation. Telemetry data, gathered from tracking animal movements, provides valuable connectivity information, highlighting critical habitats and migration corridors that may require coordinated management across different jurisdictions.
The need for such collaborative action is underscored by the fact that a significant proportion of migratory marine species face threats. Sea turtles are the most endangered group (85%), followed by seabirds (27%), cartilaginous fish (26%), marine mammals (15%), and bony fish (11%). By integrating telemetry data and connectivity information into transboundary conservation strategies, we can better protect these species and ensure the health of our oceans.
FAQs
What is a migratory species?
Migratory species are animals that relocate between habitats at different times of the year, often in response to seasonal changes in resources like food and sunlight, or to find suitable breeding grounds. These journeys can range from short distances to transcontinental voyages, with some species, known as highly migratory species (HMS), crossing international borders.
What challenges do marine species face while migrating?
There are many challenges that marine species face during migration. These challenges include overfishing, bycatch, and being hit by ships. On top of that, another challenge is climate change. With changes in water temperature, their migration patterns are affected.
How do marine animals migrate?
Marine animals have diverse migration strategies. Some, like powerful swimmers such as tuna, embark on long journeys across vast stretches of open water, following temperature gradients and food sources. Others, like jellyfish, may utilize ocean currents to travel considerable distances with minimal effort. Vertical migration is another common strategy, with many species, including small fish and jellyfish, moving up and down the water column daily. This diel vertical migration often involves ascending to the surface at night to feed and descending to deeper waters during the day.
