The answer to that research question could better inform how humans protect sharks and habitats like Crystal River in a future where climate change may alter shark behavior. It also could offer a key to springs restoration and shark conservation in estuaries like Tampa Bay, where bull sharks are known to feed and give birth.

Andres and her team of researchers on the newly minted Crystal River Bull Shark Project started fishing for sharks in August and began tracking their movements two months later.

Since the team began, they have caught 27 baby bulls and are monitoring 10 of them with special acoustic tags that map where in the river a shark has traveled.

“The biggest threat to bull shark survival is loss of nursery habitat, because this is when they’re most vulnerable,” Andres said, pointing to the river around her.

“As their coastal habitat degrades because they rely on rivers and estuaries — which obviously are also heavily influenced by humans — they are losing their ability to shelter their babies.”

At full maturity, bull sharks can grow to 11 feet and are estimated to live more than two decades. Bull sharks are one of the few shark species known to inhabit freshwater ecosystems, and there’s even documentation of them venturing hundreds of miles up rivers, according to Florida’s wildlife commission. Their preference of shallow coastal waters and their ability to thrive in freshwater make their encounters with humans more likely.

In estuaries like Tampa Bay, mother bull sharks will typically leave the nursery right after giving birth, and it’s likely that’s also happening in Crystal River, according to Andres.

In many ways, the bull shark project is personal. Harrison Clark, the project’s lead field technician, is from Crystal River. The team is using his family’s boat for the research fishing trips. And he’s been dating Andres for the past four years.

The idea for the research was born during Thanksgiving dinner in 2021, when Andres was at the Clark family’s house. From inside the waterfront home, Clark saw that anglers a few hundred feet away had hooked into a shark. Soon Andres — who studied sharks for her doctorate in marine science — was outside yelling questions to the anglers about the animal’s size and weight.

Clark remembers telling Andres that night: “I’m from here, and you’ve studied bull sharks. Let’s do a project.”

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