Sharks undertake remarkable long-distance journeys across the world’s oceans. These extensive travels, sometimes spanning thousands of miles, are not random movements, highlighting the adaptability and navigational abilities of these marine predators. Understanding these movements is important for marine conservation efforts.
Following Prey
The availability of food sources drives many shark migrations. Sharks frequently follow the movements of their prey, which often migrate seasonally or aggregate in specific areas. This ensures a consistent food supply, allowing sharks to maintain their energy needs.
Great white sharks, for example, follow seal populations, congregating at locations like Seal Island in South Africa where seals are abundant. When seals become scarce, these sharks may shift their feeding strategies to target fish or smaller sharks. Individual great white sharks have been tracked covering vast distances, such as “Nicole’s” journey from South Africa to Australia, likely in pursuit of food. Whale sharks, the largest fish in the ocean, undertake extensive migrations to areas rich in plankton blooms and fish or coral spawning events, gathering in hotspots like the waters off the Yucatán Peninsula.
Tiger sharks also exhibit migratory patterns linked to prey, following schools of fish, squid, and marine mammals. In Hawaii, tiger sharks migrate between islands to coincide with seasonal prey concentrations. Similarly, Galapagos sharks frequent areas where baitfish are abundant, reflecting their reliance on shifting prey populations. These movements underscore how shark survival is connected to marine food webs.
Reproductive Migration
Reproduction is another reason many shark species embark on long-distance travels. These migrations often lead them to specific, protected areas for mating, giving birth, or to utilize nursery grounds where their young can develop safely.
Sandbar sharks migrate to breeding grounds, such as the East Coast of Florida in the spring. Pregnant females then move into shallow bays and estuaries, like Delaware Bay or Chesapeake Bay, which serve as crucial pupping grounds. Juvenile sandbar sharks remain in these protected nursery habitats. Great white shark females also migrate to coastal areas for pupping, seeking shallow waters to enhance their pups’ chances of survival. Some research indicates that mature female great white sharks may operate on a two-year reproductive cycle, visiting aggregation sites every two years.
Nurse sharks demonstrate site fidelity, returning to the same breeding grounds, such as the Dry Tortugas in Florida. Females may mate biennially or triennially, showing a strong attachment to these specific locations. Other species, like scalloped hammerheads, migrate to reach their natal nursery grounds for birthing. Lemon sharks also give birth in particular lagoons, such as those found in the Bahamas, highlighting the diverse strategies sharks employ to ensure their species’ continuation.
Responding to Environmental Changes
Sharks also migrate to adapt to changing environmental conditions, including variations in water temperature, salinity, and ocean currents. Most shark species are cold-blooded, influencing their body temperature and prompting them to seek optimal ranges. Migrating to suitable habitats helps reduce physiological stress and ensures comfortable living conditions.
Great white sharks, for example, prefer water temperatures between 10 and 27°C, and their migrations reflect this preference. As autumn progresses and water temperatures drop, they move southward from their summer feeding grounds off the northeastern United States, heading to warmer waters off the southeastern U.S. or into the Gulf of Mexico for winter. Sandbar sharks also exhibit temperature-driven movements, migrating north in spring as water temperatures rise to around 16°C and returning south in fall or winter when temperatures fall below 17°C.
Ocean currents can also influence shark movements, as some species utilize them to conserve energy. Warming ocean temperatures, linked to climate change, are altering traditional shark migration patterns. Tiger sharks in the Western North Atlantic, for instance, are now migrating earlier and extending their ranges farther north; for every 1°C increase in sea surface temperature, they shift their range approximately 440 kilometers northward. These shifts can lead to mismatches between predator arrival and prey availability, posing new challenges for these migratory species.