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Second Irrawaddy dolphin death in Borneo linked to fishing nets

A couple of Irrawaddy dolphins swim. Photo courtesy of Seang Y Teng/Flickr. (https://www.flickr.com/photos/tengseangy/34162446942/)

  • A second rare Irrawaddy dolphin has washed up dead on a beach in eastern Borneo this year.
  • Injuries believed to have been inflicted by a fishing net are the most likely cause of death, a biologist says.
  • An NGO has called on authorities to educate fishermen about minimizing bycatch and to map out dolphin migratory paths and habitats in the area.

SAMARINDA, Indonesia — Activists in eastern Borneo suspect that an Irrawaddy dolphin found dead on a local beach last month had probably been snagged in a fishing net.

This is the second documented death of the endangered species from suspected net entanglement in the waters of East Kalimantan province this year.

News of the discovery, which occurred in the province’s North Penajam Paser district on Sept. 13, first broke after a resident posted pictures online of the dead animal.

A team of local authorities and environmental experts were deployed the following day to investigate.

The decomposing body of an Irrawaddy dolphin (Orcaella brevirostris) was found in eastern Borneo last month. Photo courtesy of Rare Aquatic Species of Indonesia (RASI).

The dolphin (Orcaella brevirostris) is believed to have died several days earlier, according to Maulana, an activist from the conservation group Rare Aquatic Species of Indonesia (RASI) who was part of the investigation team.

“We buried the animal not too far from where it was found,” he said.

RASI marine biologist Danielle Kreb said injuries on the dolphin’s body appeared to be consistent with entanglement in a fishing net, which most likely caused its death.

She said local fishermen sometimes ignored their bycatch — other animals ensnared in their nets — which could include this threatened species.

Getting caught in fishing nets is among the major threats to the species, whose population is estimated at fewer than 100 individuals per river in a few Southeast Asian rivers, including the Irrawaddy in Myanmar and the Mahakam in East Kalimantan. Two-thirds of the 48 dolphin deaths recorded by Kreb from 1995-2005 in the Mahakam occurred as a result of entanglement in large gillnets, according to a 2007 paper.

Last month’s discovery was the second such find this year in East Kalimantan, on the Indonesian portion of the island of Borneo. In March, the body of another dolphin washed up on the shore of the Mahakam with similar injuries attributed to a fishing net.

The dolphin’s carcass found last month appeared to show injuries consistent with entanglement in a fishing net. Photo courtesy of Rare Aquatic Species of Indonesia (RASI).

Local environmental group the Balikpapan Bay Concerned Forum (FPTB) called on local authorities to educate fishermen about minimizing dolphin bycatch.

“The government should also work with experts to draw up a map indicating migration paths and feeding zones of the Irrawaddy dolphin, and then integrate it into the regional policy planning as a local protected area,” said Hamsuri, an activist with the FPTB.

The dolphin found last month is believed to have been part of a group migrating upriver from Balikpapan Bay, northeast of the beach where the body washed up, according to Hery Seputro, another FPTB member.

The Irrawaddy dolphin is classified as Vulnerable by the IUCN, along with the dugong (Dugong dugon), another marine mammal that inhabits Balikpapan Bay, where industrial and urban expansion has recently taken a toll on the water quality.

Seputro called on the government to carry out a new survey of the bay and surrounding areas to assess the threats to native species, including the Irrawaddy dolphin, and find ways to protect them.

He said pollution from the dumping of waste was a major problem in the area. “We once did an autopsy on a dead marine animal and found it had died from eating trash,” Seputro said.

This story was reported by Mongabay’s Indonesia team and was first published on our Indonesian site on Sept. 28, 2017.

Banner image: A couple of Irrawaddy dolphins are swimming. Photo courtesy of Seang Y Teng/Flickr.

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