When a hurricane or tropical storm barrels toward eastern North Carolina, humans board up windows and evacuate—but what do sharks do? Thanks to acoustic tagging and long-term monitoring, we now know that sharks don’t just passively endure storms. They have strategies for survival, and some are surprisingly sophisticated.
Sensing the Storm: Barometric Pressure
Sharks, especially coastal species like blacktips and bulls, appear to respond less to wind and waves than to rapid drops in barometric pressure. Research shows that blacktip juveniles in Florida left shallow nursery bays when pressure plummeted during Tropical Storm Gabrielle (2001). They returned after the storm once pressure stabilized. This suggests sharks aren’t reacting to turbulence itself but to the atmospheric signal that precedes it (Heupel et al., 2003). For blacktips, studies suggest that a drop of ~10 millibars in less than 24 hours is enough to trigger evacuation. Bulls show similar patterns, though individual responses vary (Boucek et al., 2019). In general, it’s not an exact “preferred” pressure number but rather the rate of change that matters.
Shark Species and Storm Behavior
Blacktip Sharks (Carcharhinus limbatus)
- Known responders to pressure drops. Juveniles flee shallow estuaries and head for deeper water as storms approach.
- Return quickly. They often reappear in their nurseries within a day or two after conditions settle.
- Key study: Blacktip sharks respond to falling barometric pressure associated with Tropical Storm Gabrielle. (Heupel et al., 2003).
Bull Sharks (Carcharhinus leucas)
- Juveniles in Florida’s Everglades left estuaries before Hurricane Irma (2017). Some moved out days ahead of landfall, suggesting pressure cues were critical.
- More variability. Some left immediately, others lingered, highlighting differences in individual thresholds.
- Key study: Ecological responses of estuarine organisms to Hurricane Irma. (Boucek et al. 2019).
Sandbar Sharks (Carcharhinus plumbeus)
- Nursery dependence. Juveniles use very shallow nurseries in Chesapeake Bay and Pamlico Sound (Grubbs et al., 2007).
- Storm strategy (inferred). While direct hurricane data are lacking, their reliance on shallow estuaries suggests they likely mirror blacktip behavior—seeking deeper channels when pressure plummets.
Spinner Sharks (Carcharhinus brevipinna)
- Less direct data. Telemetry studies document their presence on the Mid-Atlantic shelf (NOAA, 2019), but no hurricane-event tracking exists yet.
- Probable pattern. Like their blacktip relatives, they are expected to move offshore or deeper in response to rapid barometric drops.
Eastern North Carolina: Local Implications
NC Marine and Estuary Map | Credit: ESRI
- Pamlico Sound Bull Shark Nursery. Since 2011, juveniles have been recorded here each summer, tracked with acousti: c tags. Seasonal exits toward deeper water (Cape Lookout to Hatteras, even Cape Canaveral in winter) suggest a built-in escape route when storms loom (Bangley et al., 2018).
- Sandbars off Cape Hatteras. Juveniles overwinter just offshore in <20 m depths—safer refuge during storm surge compared to shallow estuaries (Musick & Colvocoresses, 1988).
- Barrier Islands & Inlets. When storms surge into the sounds, sharks likely use inlets to escape into the continental shelf’s deeper, more stable waters.
Why This Matters
Hurricanes don’t just rearrange coastlines—they reshape the ecology of estuaries and nurseries. Storm-driven freshening of Pamlico Sound (as seen after Hurricanes Dennis, Floyd, and Irene) can cause hypoxia (low dissolved oxygen levels that make it difficult for aquatic life to breathe) and prey shifts (Paerl et al., 2001). For sharks, evacuating shallow water isn’t just about avoiding turbulence—it’s survival against collapsing water quality.
Key Takeaways for NC Shark Ecology
- Sharks sense storms primarily via barometric pressure drops, not turbulence.
- Blacktips: textbook responders; evacuate at ~10 mb drops in 24 hrs.
- Bulls: similar, but with more individual variation.
- Sandbars & Spinners: less direct data, but likely respond in kind.
- Eastern NC: Pamlico Sound, Core/Bogue, and Chesapeake Bay nurseries mean juvenile sharks face real storm risks—and escaping to the shelf is a proven strategy.
Sharks and Storms: A Take-Home Message
Next time a hurricane approaches Topsail, Surf City, or anywhere along our NC coastline, remember: the sharks know it’s coming too. Long before the first raindrops fall, many have already slipped into deeper waters, riding out the storm in safety—only to return once the skies clear and the estuaries calm.
References
Bangley, C. W., Paramore, L., Shiffman, D. S., & Rulifson, R. A. (2018). Increased abundance and nursery habitat use of the bull shark (Carcharhinus leucas) in Pamlico Sound, North Carolina. Ecology and Evolution, 8(11), 5195–5205. https://doi.org/10.1002/ece3.3760
Boucek, R. E., Rehage, J. S., Adams, A. J., Santos, R., Blewett, D. A., & Lowerre-Barbieri, S. K. (2019). Ecological responses of estuarine organisms to Hurricane Irma. Ecology and Evolution, 9(21), 11979–11991. https://doi.org/10.1002/ece3.5209
Grubbs, R. D., Musick, J. A., Conrath, C. L., & Romine, J. G. (2007). Long-term movements, habitat fidelity, and seasonal occurrence of juvenile sandbar sharks in the Chesapeake Bay region. Marine Ecology Progress Series, 333, 287–301. https://doi.org/10.3354/meps333287
Heupel, M. R., Simpfendorfer, C. A., & Hueter, R. E. (2003). Running before the storm: Blacktip sharks respond to falling barometric pressure associated with Tropical Storm Gabrielle. Fisheries Research, 63(2), 193–196. https://doi.org/10.1016/S0165-7836(02)00211-7
Musick, J. A., & Colvocoresses, J. A. (1988). Distribution and abundance of sharks from the central U.S. Atlantic continental shelf. Transactions of the American Fisheries Society, 117(1), 44–55. https://doi.org/10.1577/1548-8659(1988)117<0044:DOOS>2.3.CO;2
National Oceanic and Atmospheric Administration. (2019). Spinner shark (Carcharhinus brevipinna) presence in Mid-Atlantic waters. NOAA Technical Report. https://repository.library.noaa.gov/view/noaa/22487
Paerl, H. W., Bales, J. D., Ausley, L. W., Buzzelli, C. P., Crowder, L. B., Eby, L. A., Fear, J. M., Go, M., Peierls, B. L., Richardson, T. L., & Ramus, J. S. (2001). Ecosystem impacts of three sequential hurricanes (Dennis, Floyd, and Irene) on the United States’ largest lagoonal estuary, Pamlico Sound, NC. Proceedings of the National Academy of Sciences, 98(10), 5655–5660. https://doi.org/10.1073/pnas.171093598
