Shark pups (babies) and human babies aren’t that too different: both tend to start their lives out in the confines of a nursery.
Great white sharks aren’t exclusive to California waters — they are found globally in cool, coastal … [+]
The nurseries look different, however. While a human’s might be adorned in pastel colors and fluffy stuffed toys, shark nurseries are sheltered areas away from bigger animals that might make them a quick meal. Many species of tropical sharks use semi-enclosed bodies of shallow water such as bays and estuaries as a nursery. Mangrove environments and seagrass meadows are the preferred habitat for some while other coastal sharks are adapted to use open systems such as bays, river deltas, shallow beaches, and other coastal fringe habitats. The time young sharks spend in nurseries depends on both biotic and abiotic factors that aren’t fully understood. But eventually they do leave…
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Yup, even sharks must grow into being an adult!
For young great white sharks (Carcharodon carcharias) off California, the southern sandy beaches off the Eureka state often act as a nursery ground. It’s here where they can feed, grow, and congregate as they largely terrify beachgoers and delight scientists at the up-close research opportunity. Great white sharks aren’t exclusive to California waters — they are found globally in cool, coastal waters. The largest predatory fish on Earth, they are probably the most feared and misunderstood animal in the USA (the movie “Jaws” probably didn’t help). Yet despite being one of the best-known sharks, relatively little is known about its biology.
The presence of so many sharks near people is an opportunity for shark researchers like Dr. Chris … [+]
While some species of sharks can reach lengths of 40 feet or more, the vastness of the ocean dwarfs their size. The presence of so many sharks near people is an opportunity for shark researchers like Dr. Chris Lowe at California State University. “There’s so many people and so many sharks, that we have the capacity to gather huge amounts of data, to look at how they interact and behave around people. And that’s primarily for juveniles up to maybe nine feet long,” Lowe told ABC7 News. His team is studying what seems to be a nursery much closer to the Bay Area, seeking to understand what is attracting more young juveniles hundreds of miles north to Monterey Bay. “So what are the sharks doing close to the shoreline? How long are they going to be there? How close might they get to people? What depths do they prefer? Those sorts of questions,” Professor Lowe explained. “And of course, what we want to know is when it gets cold up there in the winter, where do they go?”
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One reason behind this shift? Researchers point to climate change. Oceans worldwide are being affected by climate change in a variety of ways and will continue to do so in the future. The University of Miami has found that over the past 40-ish years, shark distributions have expanded northward, paralleling rising temperatures.The coast of California has experienced a number of incidents of extreme ocean temperatures (commonly referred to as marine heat waves) over the last decade. Starting in 2014, a marine heat wave in the North Pacific nicknamed “the blob” encroached on the Pacific Coast and caused major havoc to coastal environments that is still being seen today. However, this shark migration seems to have continued even in cooler oceanic cycles.
Unfortunately, there probably doesn’t exist a single answer wrapped up in a pretty bow. Marine … [+]
Perhaps it’s prey? Scientists are already finding evidence that fish are moving polewards… so their predators will have to follow them in order to survive. Or is it coastal degradation from development that is ruining nurseries and forcing sharks to move up north?
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Unfortunately, there probably doesn’t exist a single answer wrapped up in a pretty bow. Marine forces are complicated and not fully understood, as Dr. Sammy Andrzejaczek of Stanford’s Hopkins Marine Station points out. “The ocean is so dynamic, we don’t know why they’re here,” Andrzejaczek told ABC7 News. “Yeah, it could be temperature, it could be their prey shifting.” At Hopkins Marine Station, Dr. Andrzejaczek and her colleagues are using a three-dimensional, vertical models of the ocean to understand how sharks and other marine creatures behave and use it at different depths to figure out what is happening. As a result, feeding patterns, preferred temperatures, and oxygen levels could be revealed. “We really need to understand that additional dimension to understand how they move and why they’re moving and how that may change in the future,” says Andrzejaczek.
While their projects are separate, the questions on habitat use certainly overlap. And both teams … [+]
While Andrzejaczek focuses on the water column, Lowe takes to the skies using drones to locate sharks off Monterey. Unmanned aerial vehicles, often known as drones, are providing scientists with real-time information about sharks’ presence near beaches, as well as insight into their unique behaviours. Drones being sent up by civilians are spotting more interactions between humans and sharks than ever before, giving researchers a better understanding of how we co-exist with them when they aren’t biting. Lowe also uses tags to study their movement within the water column, agreeing an understanding of their vertical habitat use is key to their behavior. “If [the great whites are] going to those beaches, [that’s] because that’s a safe place for them,” Lowe explains. “Then when you have that heavily stratified water column with warm water at the surface, and cooler water down deep, that gives them options. So, we’re just starting to analyze the datasets that we have over the last couple of years to look at how that might affect where they spend their time.”
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While their projects are separate, the questions on habitat use certainly overlap. And both teams hope their work will lead to better-informed and effective management practices – both on the surface as well as at depth.
