Pilot expeditions work to preserve the white shark in the Mediterranean Sea

The Mediterranean Sea is a paradise. Crystal clear waters and incredible coastline spanning multiple continents are renowned around the world. Below these picturesque and sometimes crowded waters swims a legendary creature facing a dangerous and uncertain future: the white shark.

Francesco Ferretti, an assistant professor in the College of Natural Resources and Environment, is working to save one of the most endangered white shark populations on the planet. The research team located signs of remaining white sharks in the Sicilian Channel.

The research was published in Frontiers of marine science on October 22, 2024.

“We decided to take on the challenge of locating the last remaining white sharks in the Mediterranean and saving them,” Ferretti said. “One of the most critical steps was tagging individuals so we could learn more about their abundance and distribution. This led to the ‘White Shark Hunt,’ an initiative under which we began “Identifying the areas of the Mediterranean where these animals could be found is not easy because these sharks are rare.”

Incredibly rare, in fact.

Unlike places like California, where sharks congregate near seal colonies, they have no known concentration areas in the Mediterranean. Finding them was like looking for a needle in a haystack or, more accurately, a grain of sand in the sea.

Taylor Chapple, an assistant professor at Oregon State University at the Coastal Oregon Marine Experiment Station and a technical expert on white sharks on the project, was a postdoctoral fellow with Ferretti at Stanford and they have continued to work together since.

“These animals likely have a very different ecology than white sharks in other global populations,” Chapple said.

“These appear to be more likely based on tuna and smaller fish. This almost overturns our understanding of white sharks. This allows these animals which weigh a few tonnes – larger than any land predator – to exist on a resource that is very surprising. The seals are very fat, and these sharks feed on tuna and continue to get just as big.

This research is the first step toward establishing a shark monitoring program in the region, as part of ongoing efforts to prevent the animal from becoming extinct in the region.

The research was carried out in collaboration with Jeremy Jenrette and Brendan Shea of ​​the Department of Fish and Wildlife; Shea and Austin Gallagher with Beneath the Waves; Chiara Gambardella from the Polytechnic University of Marche; Gambardella and Stefano Moro with the Stazione Zoologica Anton Dohrn; Khaled Echvikhi from the University of Gabès and the Higher Institute of Applied Biology of Médenine; Robert Schallert and Barbara Block of Stanford University; Schallert with Tag-a-Giant; and Chapple with the Oregon State University Coastal Marine Experiment Station.

Ferretti has organized three pilot expeditions in 2021, 2022 and 2023, focusing on what we consider to be hotspots for the species: the Sicily Channel. These expeditions used improved methods and technologies over previous efforts, such as environmental DNA (eDNA) sampling, which detects traces of animal DNA in water, similar to using a dog to detect the presence of an animal.

Researchers also used surface and deep-water cameras with bait to attract sharks, as well as bait to try to lure them closer.

During the expeditions, they detected the presence of white sharks five times at the four sites. The team was correct in their choice of location and timing, from May to June, but did not interact directly with the sharks.

“They are extremely rare and we realized that even with our efforts, we were not working on a large enough scale,” Ferretti said.

“We need to recalibrate our approach and develop new strategies. Despite these challenges, we have been able to identify a stronghold of this population, particularly in the south of the Sicilian Channel, off the coast of North Africa. This area is strongly impacted by the fishing, and this is where we are now focusing our efforts. The pilot expeditions have allowed us to recalibrate for a larger program and have provided valuable information on where to focus future efforts.

Rough sea

The research team, which included Virginia Tech graduate students, used recreational boats that, while suitable, were far from ideal because they were not dedicated research vessels. They lacked space, speed and the equipment needed to properly store chum material, primarily bluefin tuna, which is highly regulated in the Mediterranean and difficult to continuously supply.

“We were able to conduct our research, collecting vital data that will guide future expeditions,” Ferretti said. “This was a demanding but crucial part of our ongoing efforts to protect this endangered population.”

The trips took the team from Marsala, on the northwest tip of Sicily, to various islands like Lampedusa and Pantelleria, as well as Tunisia and Malta, deploying long-line cameras and collecting eDNA samples along the way. However, heavy commercial and fishing boat traffic in the Sicilian Channel made things difficult, and researchers had to closely monitor their equipment to avoid collisions with ships.

In 2023, the team used an 87-foot tall ship to conduct open-water research and had a film crew document the mission.

Although they did not directly see any white sharks, they managed to tag a Mako shark for the first time in the area as part of another research project.

And, Ferretti said, the path for future research missions has been set.

The next horizon

Today, the research team is planning and fundraising for several future expeditions to the Sicilian Canal and beyond.

“We know there is a hotspot, but there could also be other important areas in the eastern Mediterranean harboring critical habitat such as a nursery,” Ferretti said.

Researchers are implementing a range of approaches, including monitoring ports in North Africa to track interactions between fishermen and sharks and collect biological material. This allows them to gather genetic and isotopic samples for analysis. Through isotope analysis, they can learn about population structure, diet, and changes in habitat as the sharks grow.

“We don’t do research in a vacuum,” Chapple said.

“The research we are doing now is so multidisciplinary and the questions we can ask now are not feasible as a single entity. This white shark hunt – there is so much knowledge held by local communities and stakeholders that as a scientist we cannot step in and say this is what we should be doing. These multi-institutional collaborations are essential to understanding the animals, systems and culture surrounding the research.

These collaborations between universities, but also regions, add additional tools to researchers’ toolbox to improve efficiency.

“We are expanding our network of local and international collaborators to maximize the value of the data we collect and establish an appropriate monitoring program for the Mediterranean,” Ferretti said.

“Currently, there are no formal monitoring or conservation programs for this population. We now want to continue monitoring this population because we don’t want to lose it.”