The range of white sharks is shrinking and shifting as a result of climate change, according to a new study from the Monterey Bay Aquarium. The experts report that there have been unprecedented sightings of juvenile white sharks at the northern end of Monterey Bay, which is a major shift in their range.
The researchers have determined that the northward shift of young white sharks indicates that they are struggling to find suitable habitat as water temperatures rise beyond their desirable temperature range.
“Nature has many ways to tell us the status quo is being disrupted, but it’s up to us to listen,” said study co-author Dr. Kyle Van Houtan. “These sharks – by venturing into territory where they have not historically been found – are telling us how the ocean is being affected by climate change.”
Two decades ago, as aquarium scientists were preparing to display young white sharks, they monitored juveniles in southern California to study their behavior.
After the North Pacific was impacted by an extreme marine heatwave between 2014 and 2016, the team noticed unusual sightings of juvenile white sharks off central California. This is outside of their typical grounds off southern California, and the farthest north that young white sharks have ever been spotted.
In an effort to identify their thermal preferences, the team analyzed 22 million electronic data records from 14 sharks and compared these records to 38 years of ocean temperatures.
Between 1982 and 2013, the northernmost edge of the juveniles’ range was located near Santa Barbara. After the marine heatwave, this range shifted dramatically north to Bodega Bay, and currently hovers near Monterey.
“After studying juvenile white shark behavior and movements in southern California for the last 16 years, it is very interesting to see this northerly shift in nursery habitat use,” said study co-author Dr. Chris Lowe. “I think this is what many biologists have expected to see as the result of climate change and rising ocean temperatures. Frankly, I’ll be surprised if we don’t see this northerly shift across more species.”
“This study would not have been possible without contributions from our community scientists and treasured Aquarium volunteers,” said Dr. Van Houtan. “Eric Mailander, a local firefighter, provided a decade of detailed logbook records of shark sightings, and volunteer Carol Galginaitis transcribed those hand-written data into an electronic database.”
The researchers say their findings reinforce what scientists have been saying for years – animals and nature are revealing the impacts of climate change.
“White sharks, otters, kelp, lobsters, corals, redwoods, monarch butterflies – these are all showing us that climate change is happening right here in our backyard,” said Dr. Van Houtan.
“It’s time for us to take notice and listen to this chorus from nature. We know that greenhouse gas emissions are rapidly disrupting our climate and this is taking hold in many ways. Our study showed one example of juvenile white sharks appearing in Monterey Bay. But let’s be clear: The sharks are not the problem. Our emissions are the problem. We need to act on climate change and reduce our reliance on fossil fuels.”
The study is published in the journal Scientific Reports.