'Bukang-i' confirmed as female dusky shark, scientists say

The shark known as "Bukang-i" that has been lingering in the waterfront park near Busan's North Port has been confirmed as a dusky shark (Carcharhinus obscurus), scientists said Tuesday.

The National Institute of Fisheries Science said it made the final determination after analyzing close-up footage of the animal. "We confirmed the external characteristics of a dusky shark, including a clearly developed ridge between the first and second dorsal fins," the institute said.

The dusky shark is a large species with a broad, rounded snout, a ridge running between its two dorsal fins, and triangular, serrated teeth on the upper jaw. Pups measure 70 to 100 centimeters at birth, and adults can grow to about 4.2 meters.

The species is widely distributed from coastal to offshore waters across tropical, subtropical and temperate zones worldwide, including waters off the Korean Peninsula. It prefers water temperatures of 18 to 26 degrees Celsius and undertakes long-distance migrations as temperatures shift, feeding on fish and squid.

No research has yet been conducted on the diet of dusky sharks in the North Pacific, though populations off Australia are known to prey on mackerel, jack and sardines. The species gives birth to live young and reproduces slowly, and the International Union for Conservation of Nature (IUCN) lists it as Endangered on its Red List due to declining population numbers.

The dusky shark and the sandbar shark are closely related and difficult to tell apart with the naked eye. The key distinguishing feature is the presence of a ridge between the first and second dorsal fins — present in the dusky shark and absent in the sandbar shark.

In South Korea, the dusky shark had long been treated as the same species as the sandbar shark until 2019, when it was reported to the academic community as a previously unrecorded species in the country. Since then, sightings have been confirmed along the entire Korean coastline, including waters off Namhae in South Gyeongsang Province, Samcheok in Gangwon Province, Sinan in South Jeolla Province, Jeju and seas near Busan.

Bukang-i was first spotted at the North Port waterfront park on Sept. 18. Initial morphological assessments suggested it was either a sandbar shark or a dusky shark of the genus Carcharhinus. Comparison with nearby landmarks of known dimensions put the shark's body length at approximately 3 meters, and the shape of its ventral reproductive organs confirmed it as female.

The institute said it will continue to monitor Bukang-i's swimming behavior and health, and plans to coordinate with Busan city and other relevant authorities should any abnormal signs emerge.