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Reef fish are faring fine in eastern Indonesia, study suggests

A bluestreak fusilier fish in Indonesia. Image by Rickard Zerpe/Flickr.

  • A new study examines the health of reef fish populations in the lesser Sunda-Banda seascape, a part of the Coral Triangle, which overlaps with Indonesian waters in the western Pacific.
  • In remote areas far from large human populations, reef fish are generally doing well, the researchers found.
  • The researchers propose turning one area in Southwest Maluku, Indonesia, into a marine protected area.

The coral reefs of the lesser Sunda-Banda seascape in southeastern Indonesia host some of the planet’s most biodiverse marine ecosystems, which remain relatively untouched even as overfishing ravages sea life to the country’s west and all over the world. New research suggests reef fish inhabiting understudied sections of the lesser Sunda-Banda are doing well overall in terms of species present and total numbers.

“This study seems to be the first assessment ever of all species of consumable reef fishes for this area in the peer-reviewed scientific literature,” said Hawis Madduppa, head of the Marine Biodiversity and Biosystematics Lab at the Bogor Institute of Agriculture (IPB), who was not affiliated with the study.

“It’s not all bad news for Indonesian marine conservation. We still have hope for good, sustainable reef fisheries.”

The paper, published in IOP Conference Series: Earth and Environmental Science, intends to inform reef management in the far-flung lesser Sunda-Banda seascape, which lies in the Coral Triangle, a vast region of the western Pacific that’s home to the highest diversity of corals and reef fishes anywhere on the planet.

From 2014 to 2015, the researchers conducted three expeditions involving underwater surveys of reef fish communities in the Indonesian districts of East Flores, Alor and Southwest Maluku, where people catch a vast variety of fish to feed their families or sell at markets. The census covered 1,800 square kilometers (695 square miles) throughout 62 spots at a depth of 10 meters (33 feet). Divers collected and classified exploitable reef fish into 5-centimeter (2-inch) intervals of length, from 3 to more than 50 centimeters (1 to 20 inches). Then the scientists derived fish biomass figures by means of known relationships between the size and weight of the species they observed.

In this way, lead author Fakhrizal Setiawan and his colleagues recorded 176 reef fish species that support the livelihoods of hundreds of thousands of Indonesians. More than half the fish the team encountered were plankton-eating dark-banded fusiliers (Pterocaesio tile), but they concluded that the ranges and counts of species in the reef systems were generally sound and balanced.

“Southwest Maluku has the highest biomass and quite a lot of abundance, very different from Alor and East Flores because pressure in fisheries is very low there,” said Fakhrizal, who at the time of the research was working as a reef fish ecologist for the Wildlife Conservation Society. Fakhrizal collaborated on the study with researchers from WWF-Indonesia and the Fisheries Diving Club at IPB.

“Many islands in Southwest Maluku are very remote, so fish live happy and healthy with little contact with humans,” he said.

A school of dark-banded fusilier of the coast of northern Sulawesi, Indonesia. Image by Bernard Dupont/Flickr.

The lowest stocks occurred in East Flores, which has been subject to intensive reef fishing associated with a larger human presence. The harvested fish community in Alor looked stressed as well, a condition possibly resulting from harmful extraction methods, including potassium cyanide poisoning.

The wealth of reef fish in Southwest Maluku, where fishers typically practice old-style, low-impact handlining, makes this place ecologically significant, so Fakhrizal proposed turning it into a marine protected area (MPA) to bolster biodiversity throughout the lesser Sunda-Banda. Because diversity is comparable across the three regions, he said, Southwest Maluku can “give fish to the areas with high-pressure fishing and supply spillover fish to sustain the ecosystem.” Hawis added that with MPA designation, “the important spawning and nursery area can be protected, and the degraded area can have a chance to recover.”

There are, however, limits to reef fish resilience that could devastate the local fishing industry and national economy dependent on it, Fakhrizal noted.

“When one area is open to more and more destructive fishing, at some point, it cannot recover from pressure,” he said. “Fishermen get more money using poison or bombing to get a lot of reef fish, but maybe their children cannot get fish from the area, move far away, then need money for fuel. An area like Southwest Maluku with small fisheries may not be high-value, but it’s economically sustainable enough for long-term opportunity. In Alor and East Flores, there could be a decrease in fisheries in a few years.”

A scorpionfish in Alor, Indonesia. Image by prilfish/Flickr.

Fakhrizal’s paper echoes monitoring work completed in 2017 by Reef Check Indonesia, a nonprofit based in Bali. It also determined that fusilier fish were the most abundant ones in East Flores and Alor, since upwelling transported plentiful nutrients to this species there.

Altogether the current findings provide reason for optimism, said Hawis. “In Indonesia, the farther east you go, the higher the abundance and biomass due to the remoteness,” he said. “I’m very glad we still have an area with a high abundance of natural fish stock, more than 2,000 kilograms per hectare,” or about 1,800 pounds per acre.

To maintain stocks, strong multi-scale laws should be established and enforced to prohibit damaging fishing equipment and the removal of breeding or developing fish, said Sila Sari, data and knowledge coordinator with Reef Check Indonesia. Alongside intensifying surveillance to reduce offenses in Southwest Maluku, she recommended enhancing rules with traditional knowledge that has for millennia moderated fishing and preserved Indonesian reefs.

“Eastern Indonesia is rich with different local wisdoms that can be engaged through management and protected area regulation,” said Sari, who was not involved in the study. “It’ll be great to see changes between each area and between inside or outside the MPA and assess how effectively it works by assessing fish stocks. Each year or two, we need to repeat the same survey at the same sites.”

Hawis emphasized the broad research on lesser Sunda-Banda marine biodiversity required to safeguard the target reef fish, too. To create an MPA, he said, biologists must investigate connectivity across islands or populations by harnessing molecular mechanisms, such as environmental DNA and population genetics, and evaluate the relatedness of organisms in reef ecosystems.

“Mostly, people in Indonesia want faster, easier reef restoration,” Fakhrizal said. “But to be conserved effectively, coral reefs need time to recover without human disorder. We should give reefs in the lesser Sunda-Banda time to rebuild with MPAs.”

Setiawan, F., Muhidin, Agustina, S., Pingkan, J., Estradivari, Tarigan, S. A., . . . Sadewa, S. (2019). Stock estimation, species composition and biodiversity of target reef fishes in the lesser Sunda-Banda Seascape (East Flores, Alor and South West Maluku regencies), Indonesia. IOP Conference Series: Earth and Environmental Science, 278, 012070. doi:10.1088/1755-1315/278/1/012070

Banner: A bluestreak fusilier fish. Image by Rickard Zerpe/Flickr

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