Small population of sharks survive by eating fish, not mammals, in area of heavy fishing.
A team of scientists has discovered one of the last remaining white shark populations in the Sicilian Channel, of the western Mediterranean Sea.
Between 2021 and 2023, Dr. Francesco Ferretti, an assistant professor at Virginia Tech and his team conducted three pilot expeditions to locate and document the sharks. Using eDNA, or environmental DNA sampling to find traces of the animals in the water. The team covered four major sites, collecting 159 eDNA samples, and carrying out 359 hrs of pelagic mid-water baited video surveys, 43 hours of deep-water benthic baited video surveys, and 111 hrs of fishing. Although no white sharks were observed or tagged, the DNA detection in 5 samples confirmed the shark’s presence.
This research, published this month in the journal Frontiers of Marine Science, is an important first step in understanding this vanishing population of white sharks, and conservation efforts needed to prevent this population of white sharks from going extinct.
Unlike other regions like South Africa, South Australia, California and Mexico, the Mediterranean’s sharks have no known aggregation spots. They are extremely rare, and this makes them very hard to locate and study. White sharks are pan-global in temperate and sub tropical regions with migratory behavior over wide ranges, but typically aggregate in feeding concentrations.
Although they were historically abundant and widely distributed in the Mediterranean, impacted by centuries of coastal fishing and more recently, industrial fishing, white sharks have declined to dangerously low abundance levels. The IUCN lists this species as Critically Endangered in the region.
White Shark Chase
Called the ‘White Shark Chase’, by Ferreti et. al., the initiative plans to tag and study these rare sharks to better understand their movements and population. During the expeditions, the researchers also journeyed from the north-west tip of Sicily, to other islands including Lampedusa and Pantelleria, as well as Tunisia and Malta, deploying cameras and collecting eDNA samples. Bluefin tuna have been identified by other researchers i.e. (Moro et al.2020) as a potentially major white shark prey in the Mediterranean, attracting white sharks and other predators during their migration through the Sicilian channel.
Co-researcher, Dr. Taylor Chapple, an assistant professor at Oregon State University and expert on white shark movements and behavior on the West Coast of California, believes the diet of this population is composed of tuna and small fish. This is different from that of other white sharks around the world which are primarily seals.
During their field studies, the team detected white sharks on five occasions, confirming the southern Sicilian Channel, particularly near northern Africa, is an area of conservation significance for these sharks. Overfished and caught as bycatch, this population of white sharks is considered critically endangered by the IUCN.