Study suggests warming oceans are changing tiger shark migrations

A recent study suggested that warming oceans are changing shark migrations.

Scientists tracked the migration patterns of 47 tiger sharks and found a gradual shift of when and where they go following rising ocean temperatures tied to long-term climate change or short-term variables like marine heatwaves.

"The goal of this was to evaluate the effects of ocean warming on their movements, their distributions, their migratory timing and ultimately what it meant for their protection within marine protected areas," says Neil Hammerschlag, director at the University of Miami Shark Research and Conservation Program.

They started by tagging sharks to track their location.

"The tag is really important for understanding shark location. This is really important for understanding the depth and temperature preferences," Hammerschlag says.

Hammerschlag and his team also used satellites to transmit information and data.

"We obtained from NOAA's data on where tiger sharks have been captured and released by anglers and scientists over the last 40 years within the western North Atlantic Ocean," he said.

They found that sharks like temperatures around 80 degrees Fahrenheit. With tagging data, they found that tiger sharks altered their movements during periods when water temperatures spiked.

For every three to four degree Fahrenheit increase in the ocean, the sharks migrated about 270 miles farther north.

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They also found that the sharks arrived there two weeks earlier than average.

Comparing data with the 1980s, the areas of peak tiger shark catches over the past decade are about 250 miles farther north and about a month earlier off the New England coast.

"What was kind of concerning is that these climate-driven changes in shark movements have actually increased their vulnerability to fishing," Hammerschlag says.

He says the sharks are well protected from commercial fishing between their home range and zones, prohibiting long-line fishing.

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"During periods of anonymously warm water tiger sharks, their movements were extending beyond these. They're shipping their movements outside and essentially becoming vulnerable now to this type of fishing," Hammerschlag said.

These earlier migrations could also put additional prey and people at risk, but he says there's no need for worry.

"Thankfully, humans aren't on the menu. But you know, tiger sharks are large predators and shifts in where they go might change their encounter rates of people," he said.

Scientists are now researching what these changes mean for shark conservation, the ecosystem and humans in the long run.