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Tiger sharks are being spotted off the coast of the New England earlier than usual, and they’re hanging around for longer. What's going on? And are they here to stay.

Tiger sharks are showing up off the coast of New England earlier. What’s going on?

Former Digital Production Assistant at NOVA

Tiger sharks are being spotted off the coast of the New England earlier than usual, and they’re hanging around for longer. What's going on? And are they here to stay.

Sharks Are Showing Up Earlier—and Staying Longer

Tiger sharks are showing up off the coast of New England earlier. What’s going on?

Nature

Sharks Are Showing Up Earlier—and Staying LongerPublished September 29, 2022Narrator: Sharks are turning up at U.S. beaches farther north sooner and staying for longer, ditching their usual hangouts for cooler waters.Michelle Jewell: Now, when white sharks and other sharks like bulls and tigers are moving further north, it's less exploratory and more we're going here to hang out for a while. So it's an incredible change.Narrator: Experts say that historically, many sharks are pretty predictable in their migration patterns.Sora Kim: Most sharks, they have sort of like this set course and this set pattern of like where they go, when they go. Once they're sort of adults, they sort of go back and forth between these places.Narrator: Tiger sharks typically spend the winter in tropical waters around Florida and The Bahamas, but travel north in the summer seeking cooler temperatures. But these days, their summer vacations are starting sooner.Neil Hammerschlag: About for every one degree Celsius above the long term average, we see sharks, our tiger sharks, extending their movements about 250 miles further north. And off like the northeast, like off of like New England, they are starting to come there about two weeks earlier. That has been a big change.Narrator: The water off the U.S. northeastern coast has historically been too cold for tiger sharks to comfortably thrive there. The average sea surface temperature of the Earth's oceans has increased steadily, about 0.14 degrees Fahrenheit per decade from 1901 to 2020. And the Gulf of Maine is one of the fastest warming bodies of water in the world, averaging a record high sea surface temp of 59.9 degrees Fahrenheit in the fall of 2021, more than four degrees more than the long term average. This temperature shift might mean tiger sharks that prefer tropical water temps could start to move in.Neil Hammerschlag: I think tiger sharks to some degree can act kind of like a canary in the coal mine because their movements are so intertwined with water temperatures.Narrator: But it's not just tiger sharks that are affected by changes in water temperature. On the west coast, baby white sharks are being spotted unusually far north in areas like Northern Monterey Bay as a result of a heat wave in 2014. Warmer water temperatures are motivating tiger and great white sharks as well as bull sharks to move to different areas for a couple of reasons. One, is most sharks are considered cold blooded. Their body temperature matches that of their environment. If waters get too warm, they'll seek out cooler spots. Another reason is that what sharks eat is moving. As temperatures get too hot for prey to thrive, they move out, and their predators follow. When apex predators like sharks who are at the top of their food chains move into an area, it directly affects the prey already living there.Michelle Jewell: If you're a striped bass and you're in an area that suddenly sharks start coming through, you're probably gonna leave that area or you're gonna change what time of day you go to those areas to try and avoid that predator, and that can have a huge impact on an ecosystem. So there's potential that sharks are putting in a new predation pressure into these systems that they haven't seen before and it'll take time for them to adjust to it as well.Narrator: Since 1970, the global population of oceanic sharks and rays has decreased by more than 70%, a dramatic decline bringing some species to the brink of extinction. One study found overfishing to be the main driver of the decline. And these new ventures also put sharks in danger, drawing them away from parts of the ocean that are protected from fishing and interference like mining or drilling.Sora Kim: They'll probably have to deal with human encounters more, both in terms of humans being scared, but more importantly of them getting fished or killed advertently and inadvertently.Narrator: And as ocean temperatures continue to trend upwards...Michelle Jewell: Sharks, fish, the plants, the birds, everything that relies on the ocean is sensitive to those temperature changes and they all have thresholds.Narrator:These changes in shark migration tell us that even small changes in temp can have a major impact on life in the ocean, and that we're only just starting to see the effects of those changes and fluctuations and patterns that are likely just beginning.

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Sharks Are Showing Up Earlier—and Staying Longer

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Support Provided By

Explore More

Ocean 'Dead Zones' Have Quadrupled Since 1950

In the race against climate change, many animals may not keep up

Meet the women diversifying shark science