Some migratory shark species are lingering longer on the Atlantic northeast coast each year — an unusual delay that's becoming the norm, a Stony Brook University study found. 

What's happening?

Researchers at the School of Marine and Atmospheric Sciences at Stony Brook University spent five years tracking the movement patterns of migratory shark species in the Atlantic Ocean, according to a summary posted on Phys.org. 

Between 2018 and 2022, the researchers tagged and tracked 155 sharks across six migratory shark species — blacktip, dusky, sand tiger, sandbar, thresher, and white sharks — observing their latest migration dates. 

The scientists found that ocean warming delayed the southward migration journeys of five out of six shark species by between 1 and 29 days. Two key factors — sea surface temperatures and photoperiod, or the duration of sunlight in a 24-hour period — were found to influence shark migration patterns. 

Based on their findings and the projection of rising global temperatures in the coming decades, the study authors predict a "delay [in] southern autumn migrations of coastal sharks with many species remaining in northern habitats for longer durations," per the Phys.org summary. "Our findings are consistent with previous work showing that both temperature and photoperiod govern shark migratory timing."

Warmer waters are also causing deoxygenation in deeper sea sections, pushing sharks and similar fish closer to the coastlines, increasing human-shark encounters, and causing an imbalance in ocean food chains. 

Why are shark migration patterns important?

This change in shark migration patterns disrupts the balance of ecosystems in the Atlantic Ocean. 

Sharks are apex predators, meaning they are predators at the top of the food chain in the ocean. 

The delays in shark migration patterns mean that these sharks are hanging out in the northern region of the ocean for longer. This means prey species in the region could be overhunted beyond their ability to repopulate, disrupting the balance of the ecosystems. 

With rising global temperatures and sea surface temperatures, migratory shark species will further delay their migration journeys, inducing a ripple effect on food availability and balance of food webs in the ocean. 

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Fisheries that depend on the continued abundance of targeted fish species in the ocean may also experience disruptions and uncertainty in their fish supply. 

What's being done about changing shark migration patterns?

The Global Shark Movement is an international scientific research project of more than 40 shark research teams across the world that focuses on tracking shark movements over time. The data is integrated with real-time potential threats, such as active fishing efforts by commercial fisheries, to improve shark conservation efforts. 

Rising temperatures impact oxygen levels in the ocean, pushing sharks closer to the coastline, and they delay shark migration patterns. 

To support a healthier ocean and habitat for sharks and other marine life, reduce plastic waste, which often ends up as litter in the ocean, and choose healthier and more sustainable food options. 

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