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Whale shark stranding points to silting of Indonesia’s Kendari Bay

A whale shark sucks water into its mouth in the waters off of Borneo. Image by Rhett A. Butler/Mongabay.

  • Volunteers and officials successfully pushed a whale shark back out to sea after it got stranded in shallow water in Indonesia’s Kendari Bay.
  • The incident, which one rescuer said was a first, has highlighted the consequences of the rapid silting of the bay amid a spate of development projects in the area.
  • The clearing of land allows dirt to run into waterways, with the accumulated sediment halving the depth of Kendari Bay and making flood prevention more difficult.
  • Amid the silting, fishing catches have declined and there are indications of heavy-metal contamination of the water.

On the second day of 2021, a whale shark drifted into Kendari Bay, in eastern Indonesia, and became trapped when the tide quickly turned.

After a 10-hour struggle in murky, shallow water, government officials and local residents managed to push the giant fish 5 kilometers (3 miles) up the inlet that feeds into the bay and back out to sea.

The ultimately successful, ad hoc rescue effort highlights the consequences for marine creatures as the bay gradually fills with silt released by land clearing for development projects. Kendari, the city on the bay, has grown rapidly along with the region’s nickel mining and palm oil industries.

Yahya, a motorcycle taxi driver who lives nearby, heard the bustle early in the morning and joined several residents seeking to help the 3-meter (10-foot) whale shark, an endangered species.

He found a disoriented, squirming animal larger than a car, with a meter-wide (3-foot) mouth, struggling to survive amid sparse mangrove trees and houses on stilts above milky-brown water.

“We were afraid it could attack one of us. But it eventually calmed down, and we pushed it along,” Yahya told Mongabay. “I think this is the first time something like this has happened.”

Locals push the whale shark away from the shoreline. Image courtesy of the Southeast Sulawesi conservation agency.

With the waters just a meter deep at low tide, the animal likely lost its bearings and got stuck. Yahya and others stayed in shallow waters until they reached the deepest part of the bay, at the construction site for a colossal bridge that has become a symbol of development in Southeast Sulawesi province.

The accompanying urban growth has left more land open to the elements, allowing dirt to run into waterways. The accumulated sediment has halved the depth of Kendari Bay and made flood prevention more difficult.

The rescue team included members of the local conservation and fisheries offices, as well as members of the police, the search and rescue agency, and the coastal management agency of the nearby city of Makassar. The team used makeshift equipment or simply their own hands to keep the whale surrounded by water and moving in the right direction.

The whale shark is pushed through a waterway lined with mangrove trees. Image courtesy of the Southeast Sulawesi conservation agency.

The creature’s injuries likely came from contact with mangrove trees or stilt houses, according to Sakrianto, the head of the province’s conservation agency.

Whale sharks can grow to be longer than 18 meters (60 feet), though the average size is fairly smaller. This whale shark, about 3 meters long, was likely a teenager, said Andry Indryasworo Sukmoputro, the head of the Makassar coastal resources management agency.

“Sulawesi’s waters are both habitat and migration route for marine creatures such as whales, dolphins, dugongs and whale sharks,” he said. “The migration process can lead to stranding events.”

Whale sharks are Earth’s biggest fish species. As filter feeders, they need open space to gulp large amounts of water and filter for plankton and small fish.

A snorkeler swims with three juvenile whale sharks in the Sea of Cortez off Baja California, Mexico. Image by Rhett A. Butler/Mongabay.

Sea mammal strandings are a frequent occurrence across Indonesia. The government has sought to establish a network of first responders to deal with such incidents, training hundreds of people in recent years. Yahya, though, was just a bystander who tried to help out.

Officials said they weren’t sure why this whale shark swam so far into the bay, which is busy with boat traffic, and up the river, where the water is opaque a few inches from the surface.

Studies have begun to reveal the extent of the impact of sedimentation on the life of the bay, and some suggest much of the biodiversity is beyond rescue. Fishing used to provide food for families along the bay and river, but catches no longer support incomes, and there is some indication that the bay may be contaminated with heavy metals.

Banner: The whale shark is pushed through a waterway lined with mangrove trees. Image courtesy of the Southeast Sulawesi conservation agency.

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