File photo of a young humpback dolphin swimmin in Kualuh River in North Labuhan Batu regency in North Sumatra. - Courtesy of JAAN
JAKARTA: An Indo-Pacific humpback dolphin (Sousa chinensis) that recently went viral after its unusual appearance in the Batang Lubuh River in Riau’s Rokan Hulu regency has been found dead, raising concerns over habitat degradation and environmental pollution.
Authorities said the carcass of the dolphin 1.40am on Monday (Dec 15) by local fishermen. The fishermen reportedly planned to check again after sunrise, but could not find the animal when they returned to the location.
Later on Monday, the dolphin carcass was discovered washed ashore in Kepenuhan Hulu village, around 5km downstream from where it was first spotted. The animal’s remains were apparently in an advanced state of decomposition.
Zulfikar, acting head of the Rokan Hulu Fisheries and Food Security Agency, said tissue, skin and tooth samples were collected for laboratory testing to determine the cause of death.
“After the samples were collected, the dolphin’s carcass was immediately buried near the site of discovery to prevent the spread of disease and environmental contamination. Prompt burial was essential, as freshwater dolphins are known to carry a high parasite load,” Zulkifar said on Tuesday.
The Indo-Pacific humpback dolphin is an oceanic species that primarily inhabits shallow, coastal waters and has a tropical and subtropical range, though it also ventures into estuarine areas.
He added that officials from the Pekanbaru branch of the national marine conservation area office (LKKPN) would exhume the carcass within two months to perform a necropsy.
The dolphin was first sighted on Dec 8 in the Rokan River near Air Hitam village, Pujud district. It then swam upstream into the Batang Lubuh River, a tributary of the Rokan River, where it was spotted the following day by a farmer as he was returning home.
The farmer used his mobile phone to record a video of the dolphin, which quickly went viral on social media.
This prompted hundreds of curious residents to gather on the Surau Munai Bridge, which crosses the Batang Lubuh River in Surau Munai village, from afternoon until late at night for days, hoping to catch a glimpse of the marine mammal.
Zulfikar said the fisheries agency’s personnel attempted to track the dolphin over two days following the viral video but were unable to locate it.
“We only managed to find it after it had died,” he said, expressing deep regret over the dolphin’s death, as its appearance had been initially seen as a potential indicator of the Rokan River’s health.
“The dolphin’s sighting could also serve as an opportunity to raise awareness about environmental conservation and the importance of keeping the river free from pollution,” he added.
LKKPN Pekanbaru head Rahmat Hidayat, said Indo-Pacific dolphins typically inhabited waters along the coast, in river deltas and near islands, so it was unusual to see one so far upstream.
“Such movement far from their natural habitat can be caused by several factors, including disturbances in downstream waters, health threats or limited food availability, which might force dolphins to move upstream,” said Rahmat.
He suggested the unfamiliar environment might have contributed to the dolphin’s death, though he stressed that the exact cause could be confirmed only by laboratory analysis.
The Indo-Pacific humpback dolphin can be distinguished by its long, thin beak, rounded fins and a small dorsal hump, hence its common name. It also has distinctive coloUring that can range from pink to a mottled pattern of pink, white and gray, though mature adults are generally gray.
S. chinensis is classified as vulnerable on the Red List of the International Union for Conservation of Nature due to severely fragmented populations and continuing decline of mature individuals.
Major threats include commercial and residential developments, shipping lanes and water pollution from domestic, industrial and agricultural waste.
The species is protected under Indonesian law. - The Jakarta Post/ANN
