A first-of-its-kind study, led by Atlantic Shark Expeditions President Dr. Neil Hammerschlag and published in 2022, has confirmed what scientists have long suspected: tiger shark migration patterns in the western North Atlantic are changing in response to ocean warming. This peer-reviewed research integrated nearly 40 years of capture records, 9 years of satellite tracking data, long-term temperature records, and statistical modeling to reveal the pace and scale of climate-driven shifts in a large marine predator’s behavior.
Tiger sharks (Galeocerdo cuvier) are vital apex predators that play a critical role in ocean ecosystems. Their seasonal movements help regulate marine food webs, and their presence often reflects ecosystem health. Dr. Hammerschlag’s research revealed that tiger shark migration was happening both earlier in the year and extending farther north than previously documented. These changes were closely tied to rising sea surface temperatures, particularly in the waters off New England and Nova Scotia.
The study found that for every 1 °C increase in sea surface temperature, tiger sharks shifted their range approximately 440 kilometers northward. In some years, they arrived on the northeast shelf up to two weeks earlier than historical averages. Regions that were once too cold for tiger sharks, such as the northern edge of their range near Nova Scotia, are now within their temperature tolerance zone.
This work drew on a robust dataset spanning four decades. Dr. Hammerschlag’s team analyzed thousands of individual location and temperature records from tiger sharks captured and tagged between 1980 and 2020. These were paired with historical climate data and interpreted using mathematical models, allowing the researchers to evaluate the effects of temperature on the sharks. The results showed a consistent trend: both the timing and location of tiger shark occurrences shifted in lockstep with ocean warming.
Long-term datasets like this are rare in marine predator science and offer a powerful lens into how climate variability translates into real ecological change. By spanning multiple decades and combining multiple data sources, the research provides a more complete picture than short-term or localized studies. This breadth strengthens the reliability of the findings and reinforces the importance of sustained monitoring programs to detect and respond to changes in apex predator behavior and distribution over time.
These shifts in tiger shark migration have direct implications for conservation planning and ecosystem management in warming waters.
The implications of changing tiger shark migration extend beyond scientific interest. As these large predators move into new areas, they may encounter higher fishing pressures, increased overlap with human activity, and ecosystems unaccustomed to their presence.
Of particular concern was the documented decline in overlap between tiger shark movements and static marine protected areas. As sharks expanded into unprotected waters, they faced increased risk of bycatch and targeted fishing. According to the study, the probability of a shark being inside a protected zone significantly decreased with warmer temperatures, potentially undermining decades of conservation gains.
Dr. Hammerschlag is an experienced marine ecologist with over 160 peer-reviewed publications exploring the movement, behavior, and conservation of large marine predators. His research has helped fill a critical knowledge gap in understanding how climate change impacts apex predator behavior and habitat use.
While this study was completed before Atlantic Shark Expeditions and the Shark Research Foundation were formally active, its insights continue to shape science-based education and conservation initiatives today.
Atlantic Shark Expeditions invites citizen scientists and shark enthusiasts to participate in data-driven fieldwork. On select expeditions, guests assist with environmental monitoring and photo documentation of sharks for identification. It’s a rare opportunity to be part of conservation science right on the water.
Please note that while tiger sharks have reached waters off Nova Scotia, sightings remain highly uncommon. We do not expect to encounter or view tiger sharks on our cage diving expeditions. During our summer season you are most likely to see blue sharks, mako sharks, and porbeagle sharks. In September and October, we offer great white expeditions which have an increased chance of great white viewings.
Tiger shark migration is shifting. The science is clear. Now it’s up to us to follow the data and protect these apex predators in a changing world.
This Shark Week, take your fascination even deeper. While millions tune in to Discovery Channel for thrilling footage of the ocean’s top predators, we’re celebrating
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