To reduce the likelihood of sharks and humans crossing paths, scientists need to know where sharks go and when.
To find out, Cape Cod scientists created a catalog, or logbook, of sharks identified through both tagging and photographic documentation of their pigmentation patterns and dorsal fin profiles between 2015 and 2018.
The team then conducted a three-year study to compare the number of newly recorded individuals with those previously recorded, reconstructing these encounters through statistical modeling to estimate the population. Unlike previous studies in South Africa, California and elsewhere, Winton’s model takes into account the movements of individuals.
Old models assumed that “all individuals act and exploit these areas in the same way, and this can affect the quality of the estimates obtained,” Winton explains. “We’ve created a new model that takes into account that sharks can move in and out of the area, and takes into account places along the coast where individuals like to ‘hang out.’ »
The advent of high-resolution handheld underwater cameras, used by the Cape Cod team, has also made it easier and more accurate to identify sharks, says Taylor Chapple, an assistant professor at the state university. of Oregon, which did not participate in the study.
“This type of study is innovative for species like the white shark because we can identify a very large part of the population, which tends to confirm our results,” explains Taylor Chapple, who has studied white shark populations in California. . White sharks generally live up to 70 years.
Additionally, researchers at the Center for Coastal Studies, based on Cape Cod, are using sonar to map shark movements. This method revealed that Cape Cod sharks have a hunting strategy that is completely unique to the region.
