Researchers are developing a model system to evaluate the effectiveness of shark sanctuaries

Researchers from Virginia Tech’s College of Natural Resources and Environment are evaluating the effectiveness of shark sanctuaries by developing a modeling system that uses publicly available catch data to determine shark catch rates and mortality rates. Published in the magazine advance science, Their findings represent an important step in using data science to address ocean conservation challenges.

“Shark sanctuaries are coastal areas designated by states as places where targeted shark fishing is prohibited,” said Brendan Shea, Ph.D. student in the Department of Fish and Wildlife Conservation and lead author of the paper. “My initial ambition was to use publicly available data to look at these reserves from a high-level perspective, understanding the scale of fishing that occurs in these areas and what the potential risks are to sharks.”

This goal led to Shea collaborating with Assistant Professor Francesco Ferretti, who encouraged Shea to move forward with the research. Ferretti suggested that shark sanctuary data could be used to develop a model that could provide numbers on how many sharks have been caught while fishing in the sanctuary’s waters, and how many sharks will die as a result of the experience.

“Unlike some other marine protected areas that prohibit commercial fishing completely, shark sanctuaries still allow fishing to occur, and any time you fish, you are going to catch sharks,” Shea said. “The stress of being caught and released means that you are going to have some unintended deaths of sharks in these reserves, even if all the sharks are released.”

Using fisheries data to better model conservation challenges

To estimate catch and mortality rates for oceanic shark species, the research team used fishing vessel positioning data from Global Fishing Watch, an open-access website that provides a global view of commercial fishing activities around the world to enhance ocean management. The group also collected publicly available data from regional fisheries management organizations to create a model that would estimate the impacts of longline fishing on seven open-ocean shark species.

The team’s models estimate that 286,820 large sharks were caught within the eight protected areas the group focused on in 2019, with 109,729 sharks dying as a result of fishing pressure. Researchers learned that blue and silky sharks account for more than 70% of sharks caught, with thresher sharks and oceanic white sharks also seeing significant numbers of catches and deaths.

“There is always a debate about the impact of conserving marine protected areas and shark sanctuaries on species populations,” said Ferretti, a member of the Center for Global Change and the Center for Coastal Studies. “What this paper does, for the first time, is provide clear numbers on how many sharks are being caught and how many sharks are dying as a result of fishing in these waters.”

Using multiple streams of data to address a specific conservation issue represents an important step forward in fisheries research, said Shea, who collaborated with research partner Beneath the Waves, a non-profit marine research organization.

“We have traditionally relied on a lot of outdated fisheries management measures, such as direct monitoring and having people sit on boats with records to monitor the catch,” Shea said. “We are now in an era where absolutely everything has a data point associated with it all the time. We need to start trying to leverage all these data streams to tell a clearer story about what is happening in our oceans.”

Verity stresses that research like this represents important progress toward considering new approaches to understanding fish populations, as well as the impacts humans are having on open ocean species.

“This is an example of how we are moving from fisheries science to fisheries data science,” Ferretti said. “In the age of big data, we have demonstrated that we can conduct applied research in conservation and management, work that applies to many other aspects of fisheries management on a large and even global scale.”

Next steps in integrating data with conservation research

Shea’s upcoming research efforts will continue to use data. It aims to better understand the local ranges of large marine predators, in order to more accurately evaluate the benefits of conservation strategies such as shark sanctuaries.

“For spatial conservation to be effective in the conservation of large pelagic species, we need a better understanding of their home ranges, or the amount of space they need and use throughout their lives,” Shea said. “This is not well studied for many wide-ranging species, and the knowledge gained will build on our initial work to better evaluate the conservation and management roles of marine protected areas.”