Toothy travelers
Sharks are expanding their range as climate change raises sea temperatures
ENVIRONMENT| WILDLIFE
Researchers found rising ocean temperatures are reshaping where sharks live and travel.
Two recent studies offer new insights into how shark behavior and habitats are changing.
Some species expanded their range farther north along the East Coast, while others, such as great white sharks, use the Gulf of Mexico as an important winter habitat.
The oceans experienced historic warming over the past decade, soaking up more than 90% of the surplus heat accumulating in the climate system, according to the National Oceanic and Atmospheric Administration.
Will we see more sharks?
Not necessarily. You may not see more sharks overall, but you could see them in places where they were once less common.
Shannon Barry, a researcher in the Department of Ocean Engineering and Marine Sciences at the Florida Institute of Technology and lead author of a recent study, seems to agree.
"As we see ocean temperatures increasing, especially as you move northward along the U.S. Atlantic coast, these near-shore habitats that bull sharks use for nursery sites are moving into the temperature range preferred by juveniles," she said.
Shark sightings are popping up in regions they don't normally visit as the animals adjust to warming waters, USA Today previously reported.
As ocean conditions change, some species shift their migration routes, feeding grounds and nursery habitats, Barry's study says. These changes can lead to more shark sightings and, in some areas, a greater likelihood of shark-human encounters.
Where are they shifting?
As ocean temperatures rise, bull sharks appear to be moving critical nursery habitats farther north along the East Coast. Barry and her researchers found evidence that a new nursery population became established in North Carolina, signaling a broader shift in the species' behavior.
"The move poleward is driven by climate change," Barry said. "Bull sharks have a specific temperature range they like to maintain," Barry said, with adults typically found between 78.8 and 86 degrees Fahrenheit, and rarely bellow 68 degrees, while juveniles have been found in temperature ranges of 68 to 93.2 degrees Fahrenheit.
Another peer-reviewed study, published in the journal Wildlife Research, challenges previous assumptions about great white shark migration. Researchers found many great whites travel thousands of miles each winter from Canada and the northeastern United States to the Gulf of Mexico.
Using satellite-linked smart position and acoustic tags, researchers tracked 92 white sharks tagged between Nova Scotia, Canada, and Jacksonville, Florida, finding that 57 sharks across all life stages spent significant time in the Gulf or Straits of Florida, primarily from December through May, as part of a long-term OCEARCH-led research eff ort.
"For years we suspected white sharks were using the Gulf more than people realized," Chris Fischer, founder and expedition leader of OCEARCH, posted on the group's site. "This research confirms the Gulf is a regular winter habitat for this population and highlights how connected the ecosystems of the Atlantic Ocean truly are."
Where are bites common?
It's no surprise that Florida leads the nation in unprovoked shark bites. With more than 8,000 miles of coastline and millions of people entering the water each year, the state off ers more opportunities for shark-human encounters than anywhere else in the U.S.
You're far more likely to be struck by lightning than attacked by a shark. Shark attacks are considered extremely rare. The Florida Museum, a state natural history museum, puts the odds of being attacked by a shark at 1 in 11.5 million, while the odds of being struck by lightning in a given year are 1 in 1.2 million, according to NOAA.
TrackingSharks says seven shark bite attacks occurred this year as of July 5 in five states: Florida (2), California (2), Georgia (1), New York (1) and Texas (1).
Bull sharks react to climate change
Once rarely used by juvenile bull sharks, Pamlico Sound in North Carolina now qualifies as a shark nursery habitat. The study offers one of the first genetic examples of a large coastal predator adapting to climate change.
Great white sharks winter in the Gulf
Great white sharks migrate thousands of miles each year from the northeastern U.S. and Atlantic Canada to warmer winter habitats. Researchers found the sharks were commonly located along the edge of the West Florida Shelf, near Pulley Ridge, around the Florida Keys and in offshore waters near DeSoto Canyon and the Florida Panhandle.
How to reduce risk of a shark attack
â– Have a swimming buddy; don't go in the water alone.
â– Don't swim at dawn or dusk, as low light can increase your risk of a shark mistaking you for prey.
â– Don't enter waters where there is fishing activity.
â– Don't wear shiny jewelry, as it can catch the sunlight and glint like fish that sharks prey on.
â– Try to avoid splashing, which generates a sound similar to that of struggling fish, which can attract sharks.
